Following on from the "PentaBoost" (http://www.diystompboxes.com/smfforum/index.php?topic=70524.0), I cascaded two pentodes using two 5672 submini pentodes to create the "PentaDriver". Warm pentode distortion/overdrive is the result.
I'll be playing about with resistor values over the next few days to see what else it can do!
5672 tubes require a 1.25 volt heater voltage (at only 50ma), I used a LM317 to provide that.
(http://i210.photobucket.com/albums/bb292/frequencycentral/PentaDriver.jpg)
Great, 50mA only! How's the headroom under 9V? If that sounds right, that could lead to a pedal easy to put in a pedalboard (not that big, consuming not much, and under a common voltage)
Quote from: Franky on September 04, 2008, 06:37:15 PM
Great, 50mA only! How's the headroom under 9V? If that sounds right, that could lead to a pedal easy to put in a pedalboard (not that big, consuming not much, and under a common voltage)
I haven't tried it at 9 volts yet - I would guess it will be fine. The two tubes together consume 100ma.
It's getting late here at Castle Analogue, I'm sure the local peasants are trying to sleep - so I have to power down the lab before they show up with pitchforks and flaming torches.
More experiments tomorrow Igor......................
Lol, yes master Frankency Centralstein.. Same issue here..
(anyway: IT'S ALIIIIVE!!! ;) )
Hi Rick,
Interesting little circuit!
So you have been busy again.
I was looking on the web, to see if there are other solutions for the heather supply.
And I found this, just a resistor and two diodes:
(http://img246.imageshack.us/img246/9081/vca1yr3.jpg)
Quote from: Jimmy-H on September 05, 2008, 04:20:22 AM
Hi Rick,
Interesting little circuit!
So you have been busy again.
I was looking on the web, to see if there are other solutions for the heather supply.
And I found this, just a resistor and two diodes:
(http://img246.imageshack.us/img246/9081/vca1yr3.jpg)
Yeah the same guy did a 5672 VCF - but it's not pure tube, also having a BC547 and BS107 in the audio path.
The following concerns the 6088, but might also be useful in this thread since the 5672 and 6088 have much in common.
I just bought some 6088 subminis. I haven't done anything with them yet but have searched for info and projects on the internet. Here's some links, showing a few more possibilities to supply a 1.25V direct heater.
http://www.shinjo.info/frank/sheets/127/6/6088.pdf
http://www.shinjo.info/frank/sheets/138/6/6088.pdf
http://townsendtubeworks.com/6088.htm
http://members.aol.com/sbench101/BatteryPoweredAmps/submin.html
http://members.aol.com/sbench/6088pre1.html
http://www.prodigy-pro.com/forum/viewtopic.php?t=1195&postdays=0&postorder=asc&start=0
http://users.adelphia.net/~thomasholley/Guitar/Mini%20Tube%20DI.gif
http://uk.youtube.com/watch?v=_uPP5crUOPo
http://uk.youtube.com/watch?v=W1Kiz8DW02M
http://uk.youtube.com/watch?v=Py1m7XBL7N8
http://uk.youtube.com/watch?v=uH7dhpFhm-A
http://uk.youtube.com/watch?v=Ed09l7VAS0w
http://uk.youtube.com/watch?v=B9uJYl-sonY
http://uk.youtube.com/watch?v=YhQqV5WU8eo
Btw, Rick, did you hear any hum (from the direct heated cathode) or microphonics from the 5672?
"5672 tubes require a 1.25 volt heater voltage (at only 50ma), I used a LM317 to provide that."
I don't understand how this could work. Your running 12 volts to your heaters. Your tubes would last about ten seconds. Is there something I'm missing here? As the schem is now I can't see it working.
Quote from: Jered on September 05, 2008, 08:35:13 AM
"5672 tubes require a 1.25 volt heater voltage (at only 50ma), I used a LM317 to provide that."
I don't understand how this could work. Your running 12 volts to your heaters. Your tubes would last about ten seconds. Is there something I'm missing here? As the schem is now I can't see it working.
.....so I have had it running for hours. The heater is provided with 1.25 volts at pin 3.
Do you think it's my "magic tubes".....................or a gap in your knowledge?
How are you adjusting your voltage?
Quote from: Jered on September 05, 2008, 09:31:22 AM
How are you adjusting your voltage?
The LM317 minimum output voltage is 1.25 volts - by coincidence just what the 5672 heater requires.
Quote from: Jered on September 05, 2008, 08:35:13 AM
I don't understand how this could work. Your running 12 volts to your heaters. Your tubes would last about ten seconds. Is there something I'm missing here? As the schem is now I can't see it working.
The LM317 provides its minimum output voltage of 1.25 volts if you connect pin 1 directly to earth and run a 100R resistor between pins 1 and 2, as shown on my schematic. By coincidence 1.25 volts is just what the 5672 heater requires, so it's just a case of powering the 5672 heater at pin 3 with 1.25 volts.
Take a look at the 5672 VCA schematic which Jimmy H posted in this thread. This schematic takes a different approach, using a 275R resistor and two 4007 (1 amp) diodes to drop the 12 volt supply to something that the heater can cope with, again powering the 5672 heater at pin 3. The VCA schematic (and it's sister 5672 VCF schematic which powers the heater identically) has been built by a number of people successfully, check it out: http://electro-music.com/forum/viewtopic.php?highlight=tube+vcf&t=23067
I don't happen to have any 4007 diodes lying around (only 1N4148 which are not suitable), so I used what I did have - the LM317.
It's a little hard for me to accept on your say-so that this circuit won't work for a number of reasons:
- I did the research.
- I asked questions of knowledgable people on this and other forums.
- I experimented on my breadboard.
- I have the working circuit sitting in front of me, which I tested and tweaked for considerably longer than your estimated 'tube survival time' of 10 seconds. Hours in fact.
I would suggest that you get hold of a 5672 tube and a LM317, build the circuit on your breadboard and post your results.
Jered, you said basically the same thing in the Subcaster thread regarding my idea of running two 6111 submini tube heaters in series from 12 volts: "
If you do that they will glow like a lightbulb and die. 5.7 V min-6.9 V max on the heaters." I checked it out, did some reseach asked some questions, got some answers: http://www.diystompboxes.com/smfforum/index.php?topic=69736.msg559547#msg559547 I know from experiment and experience (I have the working pedal to prove it) that this method of powering 6111 heaters works perfectly and is within the quoted tolerance.
The Earth is not flat. Evolution did happen.
Hey, if you say its working, then its working, not here to argue with anybody. Its just, looking at the schem, there is nothing to attenuate the voltage. Its directly connected from the 317 out, to the tube filament. So if your filament is not getting 12 volts, then for some reason, electricity is NOT taking the path of least resistance, in this instance. I'm very intrigued. Can't wait to try this on the breadboard when I get home. Oh and the heater V. min/max for the 6021, 6111, 6112 tubes is 6.2 min to 6.6 max. Anything outside of that and your killing your tube. Its on the datasheet.
If you need any 1N4001 to 4007 diodes PM me your address and I'll get a bunch in the mail to you. You wouldn't believe how many I have.
Peace, Jered
Quote from: Jered on September 05, 2008, 02:52:58 PM
Hey, if you say its working, then its working, not here to argue with anybody. Its just, looking at the schem, there is nothing to attenuate the voltage. Its directly connected from the 317 out, to the tube filament. So if your filament is not getting 12 volts, then for some reason, electricity is NOT taking the path of least resistance, in this instance. I'm very intrigued. Can't wait to try this on the breadboard when I get home. Oh and the heater V. min/max for the 6021, 6111, 6112 tubes is 6.2 min to 6.6 max. Anything outside of that and your killing your tube. Its on the datasheet.
If you need any 1N4001 to 4007 diodes PM me your address and I'll get a bunch in the mail to you. You wouldn't believe how many I have.
Peace, Jered
Hi Jered, no offence meant, and I hope none taken. ;)
The first thing to do is to just try running an LM317 with the adjust tab (pin 1) grounded so that you get the minimum output voltage... which happens to be around 1.25v. You will need to add the 100R resistor across pins 1 and 2, or the LM317 will put out about 7 volts. When you are satisfied you are getting a stable supply around 1.25 volts - apply it to the tube. Maybe add a filtering cap after regulator too - something i should have done, and will add. Then you're in business.
If you do put one together when you get home, maybe experiment with the caps - 470pF, .001uF or .0022uF will change the low cutoff, I have yet to try this. Also, maybe try changing the two 100K resistors at pins 4 and 5 of the first pentode for higher values - 220K or 470K perhaps. I've an idea this might increase the gain and drive the second pentode harder.
The 6111 data sheet I have quotes 6.3 volts +/- 5%, therefore:
Minimum = 5.985 volts
Maximum = 6.615 volts
Yeah, I need to get some 4001 and 4007..........
Happy breadboarding !!
Rick
I realised that the 100k resistor from pin 3 of the pentode to earth is completely pointless - don't know how that got there! So i have removed it from the schematic.
Rick
(http://i210.photobucket.com/albums/bb292/frequencycentral/PentaDriver-1.jpg)
Just use a freakin' "C" or (better) "D" cell battery for the heaters and it will last for a decade!
Use a 9 volt for the other stuff and you'll be 100% battery powered! Those little tubes with the 1.25 heaters are made for generic battery power.... that's the whole point of the puny votages and currents!
Quote from: soulsonic on September 06, 2008, 05:06:51 AM
Just use a freakin' "C" or (better) "D" cell battery for the heaters and it will last for a decade!
Use a 9 volt for the other stuff and you'll be 100% battery powered! Those little tubes with the 1.25 heaters are made for generic battery power.... that's the whole point of the puny votages and currents!
Yeah you're right- these tubes are particularly suited to battery power, or even throwing onto a pedal board without worrying about the massive current draw that some other tube designs require. I think this circuit would probably work equally well from a 9 volt battery and a 'C' or 'D' cell for the heater.
I guess I didn't take that route because I'm building for my own requirements first and foremost. I don't use battery clips in any of my builds. One thing I regret about the learning process that is electronics is that I've built some tube pedals with pretty high current draw requirements - now I'm thinking that if I had used these 'little tubes with puny voltages and currents' from the start I would have a more power-efficient set of pedals. One case in point is my 'Vibracaster' - I used a 6111 drawing 300ma to build mine - I should redesign it using a 5672 really. Heyho - live and learn.
Is there a best source for these tubes? Or is it an Ebay situation...
thanks
-chris
Quote from: cpnyc23 on September 06, 2008, 01:32:15 PM
Is there a best source for these tubes? Or is it an Ebay situation...
thanks
-chris
I got mine from a Dutch Ebay seller.
I just changed the gain pot from 1M Lin to 1M Log for a more even sweep across the range.
Quote from: cpnyc23 on September 06, 2008, 01:32:15 PM
Is there a best source for these tubes? Or is it an Ebay situation...
thanks
-chris
You come from America right?
Just google, and you will find some.
Some examples:
http://www.radiodaze.com/tubes-09.htm
http://www.vacuumtubes.com/price10.html
http://www.vacuumtubes.net/p5.pdf
I'm pretty sure that a CV4092 (only 20ma current draw!) or VX9184 are equivalents - you should check the datasheets beforehand though. An Ebay seller I looked at was offering them both as equivalents to the 5672.
A Note About The Heater Voltage and the LM317 It would appear that not all LM317's are equal.
Forumite
Jered PM'ed me:
Quote from: Jered on September 06, 2008, 09:38:17 PM
The minimum resistor I could use to get 1.254 volts to the heater was 237 ohms. If I use 100 ohm resistor I get .965 volts.
I did some checking on the
LM317 datasheet - and Jered is right, the datasheet quotes 240 ohms.
BUT....................
I'm using an
LM317T - which only requires a 100 ohm to achieve 1.25 volts.
SO......................
What I would suggest is this:
Build the voltage regulator first - test the output voltage before applying it to the tube heaters. If its not 1.25 volts (or thereabouts) tweak the resistor value until it is. The resistor could even be replaced with a 1K trimpot I guess.
:icon_biggrin:
I wasn't aware of this variance with different versions of the LM317.......Heyho - you learn something new every day !!
Circuit board populated. Enclosure drilled. Graphic printed.
It's on the way!
(http://i210.photobucket.com/albums/bb292/frequencycentral/moto_0397.jpg)
Quote from: frequencycentral on September 07, 2008, 10:50:50 AM
A Note About The Heater Voltage and the LM317
It would appear that not all LM317's are equal.
Forumite Jered PM'ed me:
Quote from: Jered on September 06, 2008, 09:38:17 PM
The minimum resistor I could use to get 1.254 volts to the heater was 237 ohms. If I use 100 ohm resistor I get .965 volts.
I did some checking on the LM317 datasheet - and Jered is right, the datasheet quotes 240 ohms.
BUT....................
I'm using an LM317T - which only requires a 100 ohm to achieve 1.25 volts.
SO......................
What I would suggest is this:
Build the voltage regulator first - test the output voltage before applying it to the tube heaters. If its not 1.25 volts (or thereabouts) tweak the resistor value until it is. The resistor could even be replaced with a 1K trimpot I guess.
:icon_biggrin:
I wasn't aware of this variance with different versions of the LM317.......Heyho - you learn something new every day !!
I've got an LM7812 that I'm going to use to drop an 18v laptop computer supply down to 12v (for my PepperShredder) - the main difference between the LM7812 and LM317 is that the 317 is "adjustable" correct ?
Thanks, Dan
Quote from: danielzink on September 07, 2008, 09:17:29 PM
I've got an LM7812 that I'm going to use to drop an 18v laptop computer supply down to 12v (for my PepperShredder) - the main difference between the LM7812 and LM317 is that the 317 is "adjustable" correct ?
Thanks, Dan
Hi Dan, yup that's correct. Have a look at the Subcaster schematic in the Valvecaster thread for how to set it up for a variable voltage: http://www.diystompboxes.com/smfforum/index.php?topic=63479.0
The LM317 data sheet is worth reading.
Handy to have one on your breadboard too, for dialing in different voltages.
Quote from: frequencycentral on September 08, 2008, 04:34:53 AM
Quote from: danielzink on September 07, 2008, 09:17:29 PM
I've got an LM7812 that I'm going to use to drop an 18v laptop computer supply down to 12v (for my PepperShredder) - the main difference between the LM7812 and LM317 is that the 317 is "adjustable" correct ?
Thanks, Dan
Hi Dan, yup that's correct. Have a look at the Subcaster schematic in the Valvecaster thread for how to set it up for a variable voltage: http://www.diystompboxes.com/smfforum/index.php?topic=63479.0
The LM317 data sheet is worth reading.
Handy to have one on your breadboard too, for dialing in different voltages.
I guess my question is more along the lines of - do I have to use the 317 or will my 7812 suufice ?
Thanks, Dan
You mean for the Pepper?? It works at 12v, so yes the 7812 works good.
Quote from: Renegadrian on September 08, 2008, 07:13:26 AM
You mean for the Pepper?? It works at 12v, so yes the 7812 works good.
Thank you sir.
Dan
Ah, this looks cool!
Good timing as well, I'm in the planning/experimentation phase of building an 18V pentode pre-amp for my bass.
Quote from: Isaiah on September 08, 2008, 07:25:55 AM
Ah, this looks cool!
Good timing as well, I'm in the planning/experimentation phase of building an 18V pentode pre-amp for my bass.
Hey
Isaiah, I'm in Coventry myself!
Hey Rick,
do I read this correct on the package: march '38? :o
Quote from: Steben on September 08, 2008, 07:48:30 AM
Hey Rick,
do I read this correct on the package: march '38? :o
No - they are from February and March 1958 - 'Valvo' - made in Hamburg.
I'm in the final stages of building this circuit into a pedal and I would like some advice from you guys.
I'm using a 100K pot for the volume control at the moment. With the gain full up, the output of the circuit is MASSIVE.
I tried a 10K* volume pot, and with the gain at minimum (clean sound) and the volume at maximum there is unity between the bypassed and effected signals.
I still have to add a Valvecaster-like tone control, which will cut the volume a bit - but not that much.
What I'm thinking is this:
Do I keep the 100K volume control, so with the gain at minimum the pedal can be used as a clean boost (versatile) ?
or
Do I attenuate the overall output volume a little by using a 47K* or 22K*, which would make tweaking more meaningful with higher gain settings (but losing the clean boost ability) ?
At the moment, when using higher gain settings, the volume control has to be pretty low down (using the 100K pot) so it's quite sensitive. Lowering the pot value would make it less sensitive but also less versatile.
I'm erring towards just leaving as is (100K) - what do you guys think?
* Actually I'm just bridging lugs 1 and 3 of the 100K pot with a resistor of that value to make a 10K, 47K or 22K pot or whatever.
Hi Rick,
Maybe it's an option, to make a signal divider before the volume pot.
And make this switchable.
Low gain -----> OFF
High gain -----> ON
Just experiment with the values of the two resistors for the divider.
Ok thanks Jimmy. I've reconsidered the matter and decided to use a 22K volume pot instead of the 100K.
Here's why:
The versatility of having the choice between clean boost or heavy overdrive would be nice, but I'll be using the pedal mostly for overdrive, not clean boost. So, if I were to use a 100K pot I would have it turned right down most of the time. As a friend (also a member here - thanks AletheianAlex) on the AX84 forum said: "So let's say 100k output pot set at 25% output... thta makes 75k series resistance... and I just measured a cheap guitar cable that was sitting on the ground and measured 800pF, and we'll say 150pF for the grid... that means that your treble response will be down -3dB around 2.2kHz (not counting the grid stopper)."
The only other change I'm gonna make is to add a small resistor between the gain pot and ground, so it can't be turned fully down - just mostly down. There is a point just before the end of the travel where it cuts off, I'll measure it and add a resistor of that value.
Hey Rick!
Good to know there are other Coventrians into DIY audio electronics.
I have a few questions -
Is the cap on the input just due to personal preference, or do you find the bass frequencies actually need limiting to some extent?
Have you tried wiring the second Pentode as a Triode? I believe you could install a switch to flick between.
Add a 1K resistor onto pin 2 and connect it to the same junction of the R/C network like your schematic for Pentode mode, or
connect the the 1K resistor to pin 1 for Triode mode.
I might have that completely wrong though, so take it with a large pinch of salt.
I'd try it myself, but my Pentodes haven't arrived yet.
I'm pretty new to tubes.
As far as post-clipping filtering goes, do you find there are as many harsh frequencies needing to be removed as in, say, a similar JFET circuit?
Do you have any soundclips please?
Cheers!
Hi Isaiah,
First thing I would say it that I have more enthusiasm than EE knowledge or maths. I grab what information I can and experiment on my breadboard until I get good results. I post schematics in the hope that greater minds that mine will suggest improvements. So, feel free to tweak away, please post any good results you find. I'll be finishing my PentaDriver pedal build tonight, and will live with it for a few weeks before I consider any changes - it's one thing using it at home with my VJ clone, quite another using it through my rehearsal/gig rig.
The input cap worked well in my Valvecaster, so I used it here too.
A triode/pentode switch is a good idea - I'll try it on the breadboard. As I already have a Valvecaster and a Pepper Shredder I have triode overdrive/distortion well covered, so I was more thinking about doing the pentode thing here.
I've never built a JFET circuit, so I can't comment - but I'm not finding any harshness with this design.
I'll get round to posting some soundclips here once I've finished my build - hopefully tonight!
Yo
I would love to hear an audio sample! I have some mini tubes I've been meaning to stick in a pedal...
--Brad
Quote from: Solidhex on September 11, 2008, 02:22:13 PM
Yo
I would love to hear an audio sample! I have some mini tubes I've been meaning to stick in a pedal...
--Brad
Just finished the build, worked first time, no debugging needed.....................cool! 8)
Perfect build - the best I've done - really pleased - I only designed it this time last week! I've so proud!
I have to eat and sleep now, so soundclips and photos tomorrow.... :icon_smile:
Man I dont think I can wait until tomorrow. I think I'll skip all my classes hitting the refresh button every few minutes.
be waiting for those soundclips :)
One of my friday night's beers is for you, Rick!!! :icon_wink:
Ok, here's a soundclip: http://www.aronnelson.com/DIYFiles/up/PentaDiver.mp3
Squier Telecaster Custom (HB) bridge pickup > PentaDriver > soundcard (Event Echo Gina 24) > Wavelab
PentaDriver set with 'Gain' and 'Tone' full up. No processing other than the PentaDriver (it's kinda weird playing so 'dry'!)
..........and some photos:
(http://i210.photobucket.com/albums/bb292/frequencycentral/000_0003.jpg)
(http://i210.photobucket.com/albums/bb292/frequencycentral/000_0001.jpg)
(http://i210.photobucket.com/albums/bb292/frequencycentral/000_0002.jpg)
(http://i210.photobucket.com/albums/bb292/frequencycentral/000_0004.jpg)
(http://i210.photobucket.com/albums/bb292/frequencycentral/000_0006.jpg)
Would you be able to play with that through a miced amp and record it? Really hard to tell what it can do like that.
Quote from: comfortably_numb on September 12, 2008, 03:33:38 PM
Would you be able to play with that through a miced amp and record it? Really hard to tell what it can do like that.
Yeah, I'll do that on Monday - I don't have a microphone here at the moment. I thought I should record it straight into the PC so there was nothing else 'colouring' the sound. You could play the soundclip through your favourite guitar amp though....................isn't that called 'reamping'? Or process it through a cab sim???
That sounds really nice (dry). I'll bet it will be even better hooked up to an amp or amp sim. I like the tone, not harsh and the distortion cleans up nice when you hold the note. Well, add this one on my to do list! :D
-bK
was that dont shake me lucifer?
Quote from: tranceracer on September 12, 2008, 05:16:36 PM
That sounds really nice (dry). I'll bet it will be even better hooked up to an amp or amp sim. I like the tone, not harsh and the distortion cleans up nice when you hold the note. Well, add this one on my to do list! :D
-bK
Thanks bK - I'm looking for a cab sim to process it right now.
Quote from: doug deeper on September 12, 2008, 05:56:09 PM
was that dont shake me lucifer?
'Don't Shake Me Lucifer' by H.I.M. ?? No - great song though. Its the rhythm part to a song by my band....the song is called 'Stupid'.
A really great build again Rick!
I really like it.
And for the sound, It's very different compared to the Valvecaster.
I got a small tube amp (10 Watt).
And I can place two light bulbs of 5 Watt each in series with the speaker (with a switch).
They light up when I crank the amp .
But with those bulbs, I can get power tube distortion while the loudness is reasonable.
The sound I get is similar to the pentadrive.
Love to hear more of your clips. ;)
Quote from: doug deeper on September 12, 2008, 05:56:09 PM
was that dont shake me lucifer?
I thought it was meant to be Anarchy in the UK :icon_redface:.
Quote from: Jimmy-H on September 12, 2008, 06:31:48 PM
A really great build again Rick!
I really like it.
And for the sound, It's very different compared to the Valvecaster.
I got a small tube amp (10 Watt).
And I can place two light bulbs of 5 Watt each in series with the speaker (with a switch).
They light up when I crank the amp .
But with those bulbs, I can get power tube distortion while the loudness is reasonable.
The sound I get is similar to the pentadrive.
Love to hear more of your clips. ;)
Thanks Jimmy, I'll definately do some miced-up too.
Your light bulb thing is intriguing !! Light bulb mojo fuzz ??
I'm just completely fired up with this build - my own design !!! I think is sounds great - and the guts are my best yet too!
Quote from: GREEN FUZ on September 12, 2008, 06:34:30 PM
Quote from: doug deeper on September 12, 2008, 05:56:09 PM
was that dont shake me lucifer?
I thought it was meant to be Anarchy in the UK :icon_redface:.
Hahaha! The song is kind of a 'homage' - a bit like 'Anarchy' crossed with 'Virginia Plain'.......
Quote from: frequencycentral on September 12, 2008, 06:43:09 PM
I'm just completely fired up with this build - my own design !!!
Yeah that's really something to be proud of!!
Quote from: frequencycentral on September 12, 2008, 06:43:09 PM
I think is sounds great - and the guts are my best yet too!
That's for sure :icon_wink:
I've updated the schematic on page 1.
I added a 8K2 resistor between the gain pot and earth - maybe it should have been 10K though.
I added a Subcaster-like tone control.
I didn't change the volume pot in the end - it's still 100K.
Project complete! And on to the next submini tube pedal - what will it be ??
roky erikson and the aliens.
Hey Rick,
Super Nice Build! Very clean!
I was wondering what my next build might be.... looks like I found it.....
Thanks for sharing with the rest of us!
Mick
That was really great. It sounds like a good digital distortion pedal through the sound card, so I can only imagine what it sounds like through an amp :icon_twisted:
Very nice
Jimmy H - when you say it sounds very different to a valve caster, how do you mean? More/less gain? Brighter? Muddier? Do go on ^^
Either this guy has HUGE HANDS or these 5672's are really small!!
(http://i210.photobucket.com/albums/bb292/frequencycentral/closeup-6088a.jpg)
Just a bump to publish the final schematic. I've been deleting and re-uploading the schematic in Photobucket when I have made changes - but it occurs to me that 'cookies' might prevent the viewing unless you click 'refresh'.
(http://i210.photobucket.com/albums/bb292/frequencycentral/PentaDriver-2.jpg)
I just added another soundclip (http://www.aronnelson.com/DIYFiles/up/PentaDriver_plus_Cab_Sim.mp3) - it's the same clip but processed through this Cab Sim: http://www.hitsquad.com/smm/programs/CrunchDude/download/
I just used the default setting and added just a touch of NaturalVerb in Wavelab. It shows the pedal in a different light I think!
If you have been following the "PentaBoost thread (http://www.diystompboxes.com/smfforum/index.php?topic=70524.0), you will have noted that Jasper Oosthoek has implemented an interesting idea for even more gain with his redesign of the "Red Star Drive" (http://www.diystompboxes.com/smfforum/index.php?topic=71350.0), which I have now integrated into the "PentaBoost MkII".
I had to try this idea with the PentaDriver too - who doesn't want more gain???
So I just breadboarded the mod around the anode of the first stage, which results in the signal hitting the second stage even harder. Nice - a massive amount more saturation!
Fortunately, I left enough room on the board of my PentaDriver build to incorporate the mod, which consists of just one PNP transistor and three resistors.
For those of you who are wondering about a transistor been present in what is essentially an all tube circuit - don't worry, the transistor is not in the audio path, it is just there to allow the plate of the first stage to receive a higher voltage, rather than the significant voltage drop casued by the 100K anode resistor in the MkI schematic. The transistor addition gives the first stage an output equivalent to if it had been run at 22 volts - cool!
I've tried a bunch of different PNP transistors, all with good results:
Si: BC212, BC557C, 2n3906
Ge: 2n2000, 2n404, SFT353, GT403
What you do have to be aware of is that the Ge I tried required the 68K resistor to be replaced with a 27K. If in doubt use a trimpot in place of the 68K and dial in the 'sweet spot'
The PNP is also sensitive to changes in power supply voltage, and may have to be rebiased, so a good filtered/regulated wall wart is recommended. For the same reason, battery power is a no no - as the battery loses charge the biasing will go out.
I'll be updating the Red Star Drive thread with a MkII schematic soon, I have to breadboard and verify the mods first, and add a few extra ideas of my own.
(http://i210.photobucket.com/albums/bb292/frequencycentral/54a7a415.jpg)
My God! The PentaDriver MkII just doesn't clean up! It's the highest gain tube pedal I have, beats the Pepper Shredder hands down, and the Valvecaster isn't even in the running.
I've modded my build now - no going back, but I think I need to fit a 'Turbo' switch to switch the extra gain in or out. Damn, I'm loving this pedal!
Here's how I'm going to implement the 'Turbo' switch:
(http://i210.photobucket.com/albums/bb292/frequencycentral/2908594e.jpg)
I just NEED to comment on the beautiful skill of assembly in your gut shots!
Truly a work of art in the most aesthetic manner I have seen.
Kudos!
Well, there go the plans for the Pepper Shredder then!
How are the experiments into other uses for the 5672s coming along?
Quote from: sweetwilly on October 23, 2008, 07:18:03 PM
Well, there go the plans for the Pepper Shredder then!
You could breadboard this in no time at all....... :icon_biggrin:
Quote from: sweetwilly on October 23, 2008, 07:18:03 PM
How are the experiments into other uses for the 5672s coming along?
Somewhat hijacked by Jasper this week! I have a week off though next week............tile the bathroom or breadboard?
Quote from: frequencycentral on October 24, 2008, 02:36:50 AM
You could breadboard this in no time at all....... :icon_biggrin:
Sorry Mother, I know you've travelled half way across the world to visit me, but Rick has just outdone himself and I must breadboard it immediately!
Well I built this as per the last schematic but with no switch (full on turbo). But I used 6088's. So far, no good. It has less output then my guitar plugged strait into the amp. Does anyone have any ideas? is the 6088 really that far off?
Quote from: forsakenrider on October 26, 2008, 11:00:30 PM
Well I built this as per the last schematic but with no switch (full on turbo). But I used 6088's. So far, no good. It has less output then my guitar plugged strait into the amp. Does anyone have any ideas? is the 6088 really that far off?
The 5672 and 6088 are both power amplifier pentodes BUT according the the datasheets, the 6088 has a power output of 0.010 milliwatts, whereas the 5672 has a power output of 0.065 milliwatts.
That's quite a difference - like comparing a 10 watt amp to a 65 watt amp. So maybe the 6088 isn't quite a like for like replacement.
To boost up the output you could try adding another turbo mod to the second stage too.
Is the first stage overdriving the second stage by the way? I guess not. What PNP transistor did you use? Are you running on 12 volts?
Yeah, I noticed the output there too. Just after i posted that I did a datasheet comparison.
Im using a 2n3906 for the Transistor. I really know nothing about Transistors so I just used the 68k like you showed.
Yes I am using a 12v supply, same one i use for my valvecaster (but not at the same time).
It seems to over drive it just a tiny bit but the output is really not there. Im thinking the 6088 is not powerful enough.
I am really looking for something with more gain then my valvecaster so this really turned the light on. I guess I will have to search the bay for some 5672's.....
..... or maybe a turbo valvecaster?? is it posible?
I tried the 'turbo' trick with a 6111 dual triode. It didn't work. :(
You're best bet is to source some 5672, there are loads on Ebay. Once you have those fitted in place of your 6088 you will have a throbbing monster that eats Valvecasters for breakfast. ;D
Now if I could just find a supplier for 6999 or 6526 submini pentodes - those MFs have power outputs of 135mW and 375mW respectively. If I can source either of those I will design a "Bad Mutha"!
Quote from: forsakenrider on October 27, 2008, 02:41:53 PM
..... or maybe a turbo valvecaster?? is it posible?
If you just don't want to be "TRUE" to tubes (using only tubes) you could enjoy a tillman before the valvecaster...not so powerful, but enough to juice up the valvy!
Actually, the turbo DOES work on the the valvecaster. I just tried it.
It DOESNT work on the first stage, and i think it has something to do with the way the "gain" is adjusted on a 'caster. Im guessing that if one implimented a regular style gain then it would work.
but i tried it on the second stage and we get a bit more Ooomph.
But then again, this is not a 'caster thread.
I will get some 5672's and re build my turbo driver.
Only problem is, I have lotsa 6088's and i need something to build with them.....
Quote from: forsakenrider on October 27, 2008, 04:49:32 PM
Actually, the turbo DOES work on the the valvecaster. I just tried it.
It DOESNT work on the first stage, and i think it has something to do with the way the "gain" is adjusted on a 'caster. Im guessing that if one implimented a regular style gain then it would work.
but i tried it on the second stage and we get a bit more Ooomph.
But then again, this is not a 'caster thread.
I will get some 5672's and re build my turbo driver.
Only problem is, I have lotsa 6088's and i need something to build with them.....
Wow that's interesting! I only tried it on the first stage.......I guess i should have perservered with the second - I'll experiment with that.
As for the 6088's you have, maybe not so good for a drive but good as buffers. Your PentaDriver would probably work well by just replacing the first stage 6088 with a 5672.
You should be able to use them to make a tremolo with a 6088, have a look at the 'Tube Stereo Panner' in my schematics section - it's basically just a stereo trem. The downside of the 5672 in that design is the gain increase which needs taming, so 6088 might be even better.
..........or you could send them to me!
hmmm, 2 failed attempts at breadboarding this & no joy. >:( the first was just extending the Pentaboost I had on there already and the 2nd was from scratch. the best I can get is controlling the volume of the microphonics of the 2nd 5672 and a bit of radio interference when I fiddle with the gain. one of 2 possibilites, probably both. 1 - i'm misreading the schematic or 2 - my very very basic breadboard isn't big enough! time for breadboard expansion and lucky number 3 in the next few days.
Is there any way you could post the stripboard layout you used? I could probably work something up, but it would be chock full of errors and I would go insane trying to get those three pots mounted on the board like you have...
Quote from: svstee on January 31, 2009, 10:01:18 PM
Is there any way you could post the stripboard layout you used? I could probably work something up, but it would be chock full of errors and I would go insane trying to get those three pots mounted on the board like you have...
I built mine on Tripad, which is not quite perf, not quite stripboard.
(http://i210.photobucket.com/albums/bb292/frequencycentral/jp52g.jpg)
http://www.maplin.co.uk/module.aspx?C=SO&U=strat310&T=Chester&ModuleNo=1922&ma=Chester+-+Tripad+Board
I kinda make up my layouts as I go - so i don't have a plan as such. The board with the pots on isnt the main board - I just like to mount my pots on a board as it keeps them in line and saves in flying wires. I just had room for the LM317 on there too. The layout would depend on your enclosure anyway. You should give your own layout a go - I'll check it for you.
OK, I really can't get enough of your submini stuff. Built the Red Star Drive, drew up a modified layout for your pentaboost, now I think I'll take a crack at this one. Not really in need of anything high gain, but the non-turbo (all tube) pentadriver looks good. My question is, how useful is the tone control? With the Valvecaster I always left it maxed, wound up taking it out of the circuit. Is this one like the Valvecasters? I can fit these things in RACO boxes better with only two knobs, anyways.
Here it is:
(http://s301.photobucket.com/albums/nn71/svsguitarhero/th_pentadrivernotone9v10.gif)
I'd actually never done a vero layout before today. Hope it doesn't show too much, this is only my third.
Thanks!
The 5672 and 6088 are both power amplifier pentodes BUT according the the datasheets, the 6088 has a power output of 0.010 milliwatts, whereas the 5672 has a power output of 0.065 milliwatts. That's quite a difference - like comparing a 10 watt amp to a 65 watt amp. So maybe the 6088 isn't quite a like for like replacement
Could be the sound is different in a good way because the 6088 is shooting for low power output when using low power input?
A more complex 'pre-amp with a greater #of tubes...
Stupid photobucket!
(http://i301.photobucket.com/albums/nn71/svsguitarhero/pentadrivernotone9v10.gif?t=1233761313)
Any errors?
Quote from: svstee on February 03, 2009, 09:18:52 PM
My question is, how useful is the tone control? With the Valvecaster I always left it maxed, wound up taking it out of the circuit. Is this one like the Valvecasters? I can fit these things in RACO boxes better with only two knobs, anyways.
Hmm, not that useful I have to say. It was a last minute thing. I tend to keep it maxed. Since I got more gain out of mine by doing the Turbo mod, I've been thinking about adding a Big Muff tonestack between the two tubes instead of the existing tone control. I didn't do that in the original design because the BM tonestack is lossy on gain, with the Turbo mod there is more than enough gain.
Your layout looks good, just a couple of things:
- you can lose C6 altogether, thats the tone cap, you don't need it.
- as you are running two tubes, R2 needs to change from
150 ohm / 1 watt to
77.5 ohm / 1 watt (or as close as you can get to that value). This is because two tubes draw twice the
ma of one tube. You could just parallel two 150 ohm, or feed each pin3 from 9 volts with it's own 150 ohm.
- you need to cut the track at n7 or n8. At the moment the wiper of P1 is grounded. Unless there is a cut under C3 at n6?
Good luck!
(http://s301.photobucket.com/albums/nn71/svsguitarhero/th_pentadrivernotone9v11.gif)
Updated version. I'll build it on Friday, if anyone wants to try it please do so and let me know the results. I made up these layouts for aa couple of reasons, I need more practice at vero layouts, and I think most beginners might find the LM317/heatsink/heater voltage thing a little complicated, and the resistor makes things less intimidating as well as a lower/cheaper part count. I think people are more likly to have 1 watt resistors in stock than lm317's, and you don't have to deal with all the variants like lm317, lm317t, all that.
Quote from: svstee on February 05, 2009, 01:03:25 AM
(http://s301.photobucket.com/albums/nn71/svsguitarhero/th_pentadrivernotone9v11.gif)
Updated version. I'll build it on Friday, if anyone wants to try it please do so and let me know the results. I made up these layouts for aa couple of reasons, I need more practice at vero layouts, and I think most beginners might find the LM317/heatsink/heater voltage thing a little complicated, and the resistor makes things less intimidating as well as a lower/cheaper part count. I think people are more likly to have 1 watt resistors in stock than lm317's, and you don't have to deal with all the variants like lm317, lm317t, all that.
I know this is a submini tube project - but I'm having trouble reading your submini layout!
:icon_lol: :icon_lol: :icon_lol:
I really hate photobucket
(http://i301.photobucket.com/albums/nn71/svsguitarhero/pentadrivernotone9v11.gif?t=1233849128)
I didn't do anything different this time, no idea what was going on.
Hre's a slightly neater version of yours, the pots are a bit further apart.
(http://i210.photobucket.com/albums/bb292/frequencycentral/PDnT.jpg)
Thanks a lot, You have been a huge help in my submini questing. ;D
I'll try to build it tonight. I just picked up a shipment of 40 6111 tubes and I have 18 5672's left, so I won't run out of glass bottles any time soon. I'll be drawing up some layouts for you Murder One, and when I get my caps in I'll build it.
Built it, but ran int some problems.
P2 is acting like an inefficient gain control.
P1 is acting like a volume/treble control, but is working backward (getting louder with more bite as pot is turned left), and when turned all the way backward kills all sound.
I used your layout, frequencycentral.
Quote from: svstee on February 06, 2009, 03:01:21 PM
Built it, but ran int some problems.
P2 is acting like an inefficient gain control.
P1 is acting like a volume/treble control, but is working backward (getting louder with more bite as pot is turned left), and when turned all the way backward kills all sound.
I used your layout, frequencycentral.
Ok, can you post some voltages at all pins of each 5672?
Are you getting about 1.25v at pin 3 of each tube?
Did you remember all the (4) jumpers?
And all the cut tracks (5) ?
Are all the resistor/cap values correct?
Both tubes in the right was around?
My layout seems correct. The differences between my build and yours are:
- voltage, mine is 12v
- 1uf cap, mine are polarised
- heater power, I used LM317
Quote from: frequencycentral on February 06, 2009, 08:04:16 PM
My layout seems correct. The differences between my build and yours are:
- voltage, mine is 12v
- 1uf cap, mine are polarised
- heater power, I used LM317
I did all these differences on my pentaboost build and it works great.
Quote from: frequencycentral on February 06, 2009, 08:04:16 PM
Ok, can you post some voltages at all pins of each 5672?
Are you getting about 1.25v at pin 3 of each tube?
Did you remember all the (4) jumpers?
And all the cut tracks (5) ?
Are all the resistor/cap values correct?
Both tubes in the right was around?
I'll get voltages soon, but Pin 3's are about 1.40v each, pretty close.
Got all the jumpers and cuts for sure, I'll go over the resistors with an ohmeter to double check values when I get the voltages. Caps are correct, I used multilayers for the 1 uf and poly for the .047's.
Tubes are in correct, grounding is good.
Hmm. Frustrating. I've checked my layout again and it looks OK. Maybe check for shorts/solder bridges? It also occurs to me that at 9 volts this circuit will have less drive than at 12 volts, as the first stage will not be driving the second stage quite as hard. Whereas with the 'Red Star Drive' there should be more drive at 9 volts because the clipping diodes will have more effect.
Are you sure you have the jumper between g5 and f5?
I'm sure about the jumper. checked for solder bridges as well as shorts. I even ran the pentaboost in front of this and it didn't have much effect, same problems.
Quote from: svstee on February 07, 2009, 02:23:08 PM
I'm sure about the jumper. checked for solder bridges as well as shorts. I even ran the pentaboost in front of this and it didn't have much effect, same problems.
Ok, post your voltages, I'll replicate you circuit on breadboard at 9 volts and see what voltages I come up with.
Quote from: frequencycentral on February 07, 2009, 02:25:33 PM
Quote from: svstee on February 07, 2009, 02:23:08 PM
I'm sure about the jumper. checked for solder bridges as well as shorts. I even ran the pentaboost in front of this and it didn't have much effect, same problems.
Ok, post your voltages, I'll replicate you circuit on breadboard at 9 volts and see what voltages I come up with.
I've replicated your circuit as close as I can on breadboard, running a 9 volts (9.08v actually). I still used an LM317 for the heaters as I dont have the correct value cap. For the 1uf caps I used non-polarised as you did, and you're right there, it doesnt make any difference.
5672 #1
1. 5.81
2. 7.28
3. 1.26
4. -0.012
5. 0.103
5672 #2
1. 5.78
2. 7.36
3. 1.26
4. -0.065
5. 0.101
As I suspected there would be, there is much less gain at 9v than at 12v. It did work really nicely once I added the 'turbo mod' though - makes it a very useable effect at 9 volts.
Turbo Mod: While I was breadboarding I decided to add a 10uf cap between the base of the BC557 and ground, this gets rid of some hiss you may experience. It also seems that the 68K resistor should maybe be a 100K trimpot, to take account of which BC557 you use, some need a lower resistor value than 68K, I measured 57K on the trimpot with one BC557 I tried.
Seeing as I breadboarded the PentaDriver again to get voltages at 9 volts for svstee, I thought I'd have a little tweak too.
- I added a 10uf cap between the base of the BC557 and ground (as mentioned above), which gets rid of some hiss and improves sustain.
- I added a Big Muff style tonestack with values tweaked to suit the impedance of this circuit. The tone control goes from nicely muffled through to ear piercingly tinny!
When I originally designed the PentaDriver I was thinking of added a Big Muff tonestack - what stopped me was that this tonestack is pretty lossy, and I didn't want to compromise the effect. So I went with a simple treble cut tone control. Since I added the Turbo Mod to my pedal I rarely have the volume above 2 on the dial, so it probably has too much boost available - hence the addition of the Big Muff tonestack, which tames the volume without sacrificing any gain. I wouldn't recommend the addition of this tonestack to an 'un-Turbo modded Pentadriver' though.
(http://i210.photobucket.com/albums/bb292/frequencycentral/PentaDriverTurboPlus.jpg)
There! It's actually nice to see this design gradually improving and rounding out. It's certainly a lot different now to the pedal it was when I first built it. And it's quite easy to mod the old tonestack into the new one. Let me know if you build it!
*****************************************************************************************************************************************
EDIT: Just finished modding my pedal to this new spec - it's a lot more fun now, lots of different tones available than with the original tonestack - I'm really pleased!
Quote from: forsakenrider on October 27, 2008, 04:49:32 PM
Actually, the turbo DOES work on the the valvecaster. I just tried it.
It DOESNT work on the first stage, and i think it has something to do with the way the "gain" is adjusted on a 'caster. Im guessing that if one implimented a regular style gain then it would work.
but i tried it on the second stage and we get a bit more Ooomph.
I made a small layout and followed that indication, I connected it to pin 6 - it is boomy and loud, but not in a good way...too noisy, it isn't a keeper for sure...BTW how is it supposed to work?! thx
(http://www.aronnelson.com/gallery/main.php?g2_view=core.DownloadItem&g2_itemId=38714&g2_serialNumber=1)
Adriano - I don't quite understand your layout - what's the component under the word 'Mod'? It is the collector of the transistor that should be directly connected to pin 6.
It works in place of the plate resistor, it's a constant current source (CCS) which has a high impedance (of about 1 meg), but with a resistance of less then 1K so you do not use up your B+ across the plate resistor. So the voltage at the plate is much higher than if you used the 100K resistor instead.
Rick, the one on the left is a switch.
Basically you have 12V going right to the 100k res that goes at the pin 6 of our valve (so to be stock Valvy) - the other way of the switch is the 12V going thru the tranny - I just followed your schem on the page before.
PS I measured 11.98V on both OUT points of the circuit (right side, first and last tracks)...
Ah, a switch - of course! I should have realised. Maybe instead of the 68K you should try a 100K trimpot. The mod in the V2 thread might work better though: http://www.diystompboxes.com/smfforum/index.php?topic=71864.0
Nope my friend, do you remember I tried to build the V2 some months ago with a 12au7, and a trimmer, but no that didn't work... :icon_frown:
Quote from: Renegadrian on February 13, 2009, 01:09:16 PM
Nope my friend, do you remember I tried to build the V2 some months ago with a 12au7, and a trimmer, but no that didn't work... :icon_frown:
Yeah - I didn't continue with the V2 because the extra gain wasn't really enough to make it a 'different' circuit to the Valvy - and that was before I started messing with voltage multipliers. I think you will have more luck with the voltage multiplier that you posted last week than with the PNP CCS. Higher voltage is good. :icon_biggrin:
Yeah, it's great to have 50V from a wall wart... :icon_cool:
BTW you did use the turbo mod on the schem on page 5, so I guess you have it working...Maybe is the Valvy to blame?!
Does the mod work good on pentadriver but not in a Valvy?! And why forsakenrider reported a good use for it in a Valvy?!
Both my turbo experiments on the 12au7 V2 and on a valvy went south... :icon_frown:
Quote from: Renegadrian on February 13, 2009, 01:26:48 PM
Yeah, it's great to have 50V from a wall wart... :icon_cool:
BTW you did use the turbo mod on the schem on page 5, so I guess you have it working...Maybe is the Valvy to blame?!
Does the mod work good on pentadriver but not in a Valvy?! And why forsakenrider reported a good use for it in a Valvy?!
Both my turbo experiments on the 12au7 V2 and on a valvy went south... :icon_frown:
I think the mod depends on the output impedance of the tube (or its mu?). It would have to be a similar but different mod for 12au7 than 6111 than 5672, as each tube has its own output impedance. Better stay with voltage multipliers - maybe more predictable?
Yup - my Pentadriver is as in the schematic on page 5 - I just keep on modding it!
ok, it works if you put a 100k trimmer (actually it was at almost its max position) but it gave the valvy a really baaad sound...so turbo and valvy = not good...Altough my layout in page 5 is verified, don't try to build one and put it in a valvy.
What about using that turbo mod with a dpdt stomp and LED on the pentadriver?
Quote from: svstee on February 13, 2009, 03:06:50 PM
What about using that turbo mod with a dpdt stomp and LED on the pentadriver?
You could try it but my guess it that there would be an audible 'thunk' when you hit the switch.
____ ____
|_1_| |_2_|
____ ____
|_3_| |_4_|
____ ____
|_5_| |_6_|
Should be that way...
1 12V straight
3 V to the circuit
5 V coming from the turbo circuit
2 is linked to 1
4 + leg of the LED (thru its resistor)
Am I right?!
I have no doubt that you guys are now sick to the teeth of me and my submini tube obsession! Anyway, I recorded a couple of new soundclips of my modded PentaDriver, which is now at the spec of the schematic on page 5 - with the turbo mod and Big Muff style tonestack.
Here's a couple of soundclips, nothing special playing wise, just trying to show what the pedal can do in terms of it's tonal variations.
Signal path:
Squier Telecaster Custom (HB) > PentaDriver > Roland Bolt 60 watt tube combo > Shure SM58 > Event Echo Gina 24 soundcard > Wavelab
This clip is with gain at half, just running through some different tone control settings: http://www.aronnelson.com/DIYFiles/up/PentaDriver_Half_Gain.mp3
This clip is with gain at full, again running through some different tone control settings: http://www.aronnelson.com/DIYFiles/up/PentaDriver_Full_Gain.mp3
Quote from: frequencycentral on February 21, 2009, 10:13:00 AM
I have no doubt that you guys are now sick to the teeth of me and my submini tube obsession!
Negative, keep 'em coming!
Just wondering, how much volume boost do you get with this when you set both pots to 10? mine is barely bypassed level, and I don't think it should be.
Quote from: svstee on February 21, 2009, 11:44:57 AM
Just wondering, how much volume boost do you get with this when you set both pots to 10? mine is barely bypassed level, and I don't think it should be.
With the Gain on full I have to set the Volume to between 9 o'clock and 10 o'clock for unity. The both Gain and Volume maxed out it's just massive gain, massive crunch and massive boost. But mine has the Turbo Boost Mod - yours doesn't if I remember. It makes a big difference. You should do it.
Quote from: frequencycentral on February 21, 2009, 10:13:00 AM
I have no doubt that you guys are now sick to the teeth of me and my submini tube obsession!
HECK NO! These are one of the first threads I look for every day, hoping for an interesting update! :D
Quote from: frequencycentral on February 21, 2009, 10:13:00 AM
Signal path:
Squier Telecaster Custom (HB) > PentaDriver > Roland Bolt 60 watt tube combo > Shure SM58 > Event Echo Gina 24 soundcard > Wavelab
This clip is with gain at half, just running through some different tone control settings: http://www.aronnelson.com/DIYFiles/up/PentaDriver_Half_Gain.mp3
This clip is with gain at full, again running through some different tone control settings: http://www.aronnelson.com/DIYFiles/up/PentaDriver_Full_Gain.mp3
Sounds really good! I like that "muddy" "dark" tone. If you're getting that tone from a tele, I bet it sounds nasty w/ a humbucker. Another one added to my "to-do" list! ;)
Keep up the great work!
-bK
Quote from: tranceracer on February 21, 2009, 01:19:08 PM
Quote from: frequencycentral on February 21, 2009, 10:13:00 AM
I have no doubt that you guys are now sick to the teeth of me and my submini tube obsession!
HECK NO! These are one of the first threads I look for every day, hoping for an interesting update! :D
Aw shucks! :icon_redface:
Quote from: tranceracer on February 21, 2009, 01:19:08 PM
Sounds really good! I like that "muddy" "dark" tone. If you're getting that tone from a tele, I bet it sounds nasty w/ a humbucker. Another one added to my "to-do" list! ;)
Actually my Tele is equipped with humbuckers: http://www.squierguitars.com/products/search.php?partno=0327502506
I also have the Squier Telecaster Custom II, which is equipped with P90's.
OK, I dug up my old pentadriver that I built a few months ago. I was never really happy with it but I moved on to other things without tweaking or troubleshooting it much. Anyway it is too quiet, with everything maxed it is about the same volume as bypassed. The distortion doesn't sound great, and the 1M gain pot isn't working right. I used this layout:
(http://i210.photobucket.com/albums/bb292/frequencycentral/PDnT.jpg)
And now for some voltages
IC 1 (Tube One)
1: 3.51
2: 4.43
3: 0.98
4: 0.02
5: 0.00
IC 2 (tube two)
1: 3.12
2: 4.46
3: 1.13
4: 0.00
5: 0.00
I should probably look up the pinouts on this tube. I guess pin 3 is the heater? if so that could be the problem. Doesn't it need 1.25v?
Quote from: svstee on February 28, 2009, 01:55:20 PM
IC 1 (Tube One)
1: 3.51
2: 4.43
3: 0.98
4: 0.02
5: 0.00
IC 2 (tube two)
1: 3.12
2: 4.46
3: 1.13
4: 0.00
5: 0.00
I should probably look up the pinouts on this tube. I guess pin 3 is the heater? if so that could be the problem. Doesn't it need 1.25v?
Here's mine again:
5672 #1
1. 5.81
2. 7.28
3. 1.26
4. -0.012
5. 0.103
5672 #2
1. 5.78
2. 7.36
3. 1.26
4. -0.065
5. 0.101
Yes the heaters requires 1.25v. Strange that your two heaters are reading different voltages, although being fed from the same resistor. In fact, there is a jumper from pin 3 of tube 1 to pin 3 of tube 2, so logic says they should read identical voltages - if not there is something amiss there. Are you sure that the 75R resistor is 75R? Can you use a LM317 to power the heaters instead? Or try a seperate 150R resistor from +ve to each heater.
Quote from: frequencycentral on February 08, 2009, 01:18:40 PM
- I added a Big Muff style tonestack with values tweaked to suit the impedance of this circuit. The tone control goes from nicely muffled through to ear piercingly tinny!
I've got some tubes on order and was trying to play with the tone values in the Tone Stack Calculator before they got here. What is the source impedance for the tubes? Is it determined by the 100k resistor? I thought in the "Valvecaster Head" thread you mentioned that it matched the 20k impedance of the transformer used. Googling returns references to it being 40k as well.
Also, should that 1uF coupling cap be on the other side of the tonestack? In an actual muff the tonestack is connected to the collector of the preceding transistor and coupled at the output. As I understand it this is because it doesn't work without being directly driven by a (relatively) low impedance source.
Quote from: decc on March 01, 2009, 11:31:20 AM
Quote from: frequencycentral on February 08, 2009, 01:18:40 PM
- I added a Big Muff style tonestack with values tweaked to suit the impedance of this circuit. The tone control goes from nicely muffled through to ear piercingly tinny!
I've got some tubes on order and was trying to play with the tone values in the Tone Stack Calculator before they got here. What is the source impedance for the tubes? Is it determined by the 100k resistor? I thought in the "Valvecaster Head" thread you mentioned that it matched the 20k impedance of the transformer used. Googling returns references to it being 40k as well.
Also, should that 1uF coupling cap be on the other side of the tonestack? In an actual muff the tonestack is connected to the collector of the preceding transistor and coupled at the output. As I understand it this is because it doesn't work without being directly driven by a (relatively) low impedance source.
The data sheet mentions 20k load resistance: http://frank.pocnet.net/sheets/127/5/5672.pdf
I messed about with Duncan's Tonestack calculator, but ultimately breadboarding gave me the correct combination. http://www.duncanamps.com/tsc/
That 1uf coupling cap neds to be where it is to stop DC entering the tonestack (I think, though I may be wrong, but it works for me). http://www.diystompboxes.com/pedals/tubedummy.html
Thanks for the datasheet link. The one I had was pretty light on the details. I think it was just the first page of the Philips one.
As for the coupling cap, obviously you know what works since you built it. I thought maybe it was just a mistake in the schematic. Does having the cap there change the source impedance as seen by the tonestack? With it set to 20k the calculator shows a typical muff curve, but raising it (as I would expect would be the result of the cap) degrades things quickly.
Edit: Just looked at a couple Marshall/Fender amp schematics and they have the tube connected directly to their lossy tone stacks, then coupled after.
Quote from: decc on March 01, 2009, 01:12:00 PM
Does having the cap there change the source impedance as seen by the tonestack? With it set to 20k the calculator shows a typical muff curve, but raising it (as I would expect would be the result of the cap) degrades things quickly.
I don't know if the cap changes the impedance - I'm not clever enough to work that out. I just fiddle with stuff on my breadboard until good stuff comes out! Just looking at my tonestack in Duncan's, it's got more mid scoop than a BM. Lowering the input impedance to 10k and then 5k just gives slightly more tops, raising it loses the tops.
Quote from: decc on March 01, 2009, 01:12:00 PM
Edit: Just looked at a couple Marshall/Fender amp schematics and they have the tube connected directly to their lossy tone stacks, then coupled after.
Maybe you should try it both ways and see what happens!
Quote from: frequencycentral on March 01, 2009, 01:23:53 PM
Maybe you should try it both ways and see what happens!
Indeed I will! I'll get back with the results as soon as the tubes arrive...
Finally got to putting this together. Verdict: DC coupling the tonestack and then having the blocking cap after sounds great! There is a some volume and tone loss with the cap in before the tonestack (at least with my setup with slightly different values.) So while the latter still works, I think I'm sticking to the former.
Here's to my new favorite pedal.
Quote from: decc on March 19, 2009, 06:23:24 PM
Finally got to putting this together. Verdict: DC coupling the tonestack and then having the blocking cap after sounds great! There is a some volume and tone loss with the cap in before the tonestack (at least with my setup with slightly different values.) So while the latter still works, I think I'm sticking to the former.
Glad you got it working - how much of a difference did you find between the possible positions of that cap? Is it worth me moving mine?
Quote from: decc on March 19, 2009, 06:23:24 PM
Here's to my new favorite pedal.
Until your next build? :icon_lol:
If you like the way it sounds I wouldn't bother. The difference isn't night and day or anything.
Note to others trying this pedal: Use the LM317, not the LM317L, for the heaters. I thought the smaller TO-92 version would be fine since it's rated at 100mA. However its max PD is 625mW and deriving the 1.25V from a 9V battery (let alone a 12V adapter) is 775mW. I suppose I could stage two of them (9V->5V, 5V-1.25V) until I get the correct larger model.
Quote from: decc on March 19, 2009, 10:03:35 PM
If you like the way it sounds I wouldn't bother. The difference isn't night and day or anything.
Note to others trying this pedal: Use the LM317, not the LM317L, for the heaters. I thought the smaller TO-92 version would be fine since it's rated at 100mA. However its max PD is 625mW and deriving the 1.25V from a 9V battery (let alone a 12V adapter) is 775mW. I suppose I could stage two of them (9V->5V, 5V-1.25V) until I get the correct larger model.
I'd love to see some photots and hear some soundclips of you build
decc!
QuoteI'd love to see some photots and hear some soundclips of you build decc!
Well, first I have to put it in an enclosure, paint it, learn to play, etc. :)
So, um, did anyone else notice that the screen grids are all out of whack/mis-biased? They're supposed to be slightly negative compared to the anode in order to reflect back any electrons that get free (or something like that. I'm a bit rusty at this.) According to The Wizard:
QuoteFor normal operation the quiescent screen voltage will be less than the anode voltage. If the screen grid were to be connected to a higher voltage than the anode, then the screen current will act as the primary anode, effectively 'stealing' current from the anode. This excessive screen current can lead to overdissipation of the screen and subsequent destruction, especially if the stage is overdriven. It is possible to design stages this way, but is neither recommended nor much use for guitar.
But in my build, and in the voltages I see people posting, pin 2 is
higher than pin 1. Which makes sense since they both have a 100k resistor. Since the anode resistor sets the gain, and I didn't want to mess with the turbo mod, I experimented with the screen grid resistor. A value of 390K results in V
G2 of about 6.4V and a V
A of 8.8V. (I'm running off 18V.) The screen grid is now negative to the anode and having the idle state right at mid-rail seems correct. With the turbo on V
G2 doesn't change and the anode is at about 16V when dialed in by ear.
Doesn't sound any different though!
Quote from: decc on March 20, 2009, 07:47:27 PM
So, um, did anyone else notice that the screen grids are all out of whack/mis-biased? They're supposed to be slightly negative compared to the anode in order to reflect back any electrons that get free (or something like that. I'm a bit rusty at this.) According to The Wizard:
QuoteFor normal operation the quiescent screen voltage will be less than the anode voltage. If the screen grid were to be connected to a higher voltage than the anode, then the screen current will act as the primary anode, effectively 'stealing' current from the anode. This excessive screen current can lead to overdissipation of the screen and subsequent destruction, especially if the stage is overdriven. It is possible to design stages this way, but is neither recommended nor much use for guitar.
But in my build, and in the voltages I see people posting, pin 2 is higher than pin 1. Which makes sense since they both have a 100k resistor. Since the anode resistor sets the gain, and I didn't want to mess with the turbo mod, I experimented with the screen grid resistor. A value of 390K results in VG2 of about 6.4V and a VA of 8.8V. (I'm running off 18V.) The screen grid is now negative to the anode and having the idle state right at mid-rail seems correct. With the turbo on VG2 doesn't change and the anode is at about 16V when dialed in by ear.
Doesn't sound any different though!
That's very interesting and well worth knowing. I seem to remember that while breadboarding I found that using a higher screen grid resistor also required using a higher screen grid cap to get the most gain from this circuit. One configuration I tried which worked well was 1M/10uf. Do you think the current configuration is bad for the tube in the long term? The turbo mod does set the anode voltage significantly higher than the screen voltage on the first stage (but not the second).
Quote from: decc on March 20, 2009, 07:47:27 PM
QuoteI'd love to see some photots and hear some soundclips of you build decc!
Well, first I have to put it in an enclosure, paint it, learn to play, etc. :)
:icon_eek:
Quote from: frequencycentral on March 21, 2009, 06:44:51 AM
That's very interesting and well worth knowing. I seem to remember that while breadboarding I found that using a higher screen grid resistor also required using a higher screen grid cap to get the most gain from this circuit. One configuration I tried which worked well was 1M/10uf. Do you think the current configuration is bad for the tube in the long term? The turbo mod does set the anode voltage significantly higher than the screen voltage on the first stage (but not the second).
Yeah, as I understand it having the screen grid higher than the anode is going to damage the tubes. The datasheet has the typical operating point equal to that of the anode though so I guess that it doesn't have to be much lower to do its job. Too low probably has detrimental effects too.
I'm also wondering about the safety of the turbo mod. When I measured my circuit (again, running off 18V) I got 115mV across the 1k resistor. So according to the math from the AX84 quote:
V
Effective = V
A + (I
A * R
Load) = 16V + (115uA * 1.0082M) = 131V!
Now obviously that voltage isn't present, but I interpret the "effective" part to mean how much current there is. With r
a = 20k this would be 6.5mA, above the max spec of 5mA (typical 3mA). I tweaked it back down to 8.73V + (65uA * 1.0082M) = 54V -> 2.7mA. Didn't sound any different so it may be possible to accidentally tune-by-ear and end up out of spec.
I found that, at least with a single-turn pot, it's pretty difficult to hit the right spot. I would think I had it tuned and then later find either quiet notes being gated or loud ones being hard clipped as if the transistor was in the audio path. I think I'm going to see if we can get the same super-gain effect with larger anode resistors or maybe just another charge-pump stage for the first tube.
decc, any update to this thread? I am getting ready to build this circuit and am very curious about your outcome.
Sure. Let's see what I ended up with.
Screen Voltages: I think I'm correct. My build has 100k anode resistors and 390k screen resistors, although putting in a trimpot there would let you dial in something closer to ideal (maybe 330k-370k). The idea being to have the screen voltage as close to, but not over the anode voltage. I didn't try putting in new caps since the 1uF seems to work, although as I understand it smaller values will provide less gain to lower frequencies if you want to try tuning that.
2nd Stage Coupling: I was wrong about this one. What I was seeing in classic tube schematics was a cathode follower driving a Marshall/Fender tonestack. The important detail I was missing here was that M/F stack does not have a DC path to ground, while the Big Muff one does. This throws off the biasing for the tube driving it. So the cap between the anode and tone section should be there. (This only affects the DC state of the tube though. We still have an AC path for both treble and bass to ground which lowers tube #2's gain.)
Turbo Mod: I went without this just because I wanted an all-tube pedal. I know it's not part of the audio path but part of the fun was figuring out how the pentodes are supposed to work without adding in clever hacks. I think the calculations are still correct though.
Gain pot: One thing that bothered me about this pedal was that the gain knob affected volume more than actual distortion. I think in my non-turbo, 24V build the first stage has a gain of about 11x and the second of about 7x. So you get most of the distortion from the first stage (even moreso in a turbo version) and using a gain pot to control the level to the second stage doesn't really have any effect on that at the bottom half of the pot's travel. So I replaced the 8.2k stopper with a 100k one. The idea being that the voltage divider at minimum gain * second stage gain = unity, and turning up from there would start clipping. 160k would match the 7x gain better but I didn't have one on hand.
Grid Resistors & Coupling Caps: I was putting a boost pedal in front of the tubes to see what kind of sounds I could get with a hotter signal and found that with only a light amount of pre-gain I could get the tubes to essentially go silent for a second if I hit a chord particularly hard. After some searching I came across the problem of "blocking distortion" which described the sound I was hearing. I reduced the 47n inter-stage cap to 22n and put a 100k resistor in series between the wiper of the gain pot and the grid of the second tube and the problem went away. I don't have calculations to back up these values but it didn't appear to negatively affect the tone so I'm happy.
Whew. Think that's it.
Thanks for the overview. Looks like you you did some work! I have Rick's original schematic about 90% breadboarded (schedule has been rough lately). I will build the original and then work your mods into it. Again, thanks again for your input.
Obviously a huge thanks to Rick for a really cool schematic.
Rob
I did some more experimenting with this circuit and thought I would let you guys know how higher voltages affect things. I replaced the voltage pump with a switching supply based on the MC34063A controller with an adjustable output from about 18V to 60V.
Findings:
1) This was an unusable circuit due to the noise generated by the switching supply. I used a cheap "bobbin" inductor and even though the controller was running at 90kHz it would put out a nasty hum at about 200Hz due to running in discontinuous mode. Tuning things to run in continuous mode would have helped, though I expect a toroid inductor and giant capacitor (had a 200uF 100V and it was already huge) would help more. Either way switching boost converters can be nasty beasts to tame.
2) There are diminishing returns with respect to plate voltage vs gain. I was going under the rough gain calculation of gain = gm*(RA || RL), and backtracking from the known resistance and measured gain I thought that the low voltage was resulting in low transconductance. However with the supply at 60V I still measured about 20x gain at maximum, not the 60x or so that would results from the 750umhos from the datasheet at full voltage. I found another equation of gain = (gm * sqrt((RA || RL) * ra)) / 2. This matched what I was seeing much better and implies that transconductance doesn't fall off that much at low voltages. Since we are aiming for an overdrive pedal, not a clean one with lots of headroom, the ideal is a point where the gain is highest relative to the supply voltage. Ends up this is roughly around 24V -- so the original 12V + voltage pump was already the way to go.
((Thread Revival Alert))
My PentaDriver Turbo Plus enclosure so far...
(http://img.photobucket.com/albums/v321/mattthegamer463/Guitar%20Pedals/DSC01278Medium.jpg)
(http://img.photobucket.com/albums/v321/mattthegamer463/Guitar%20Pedals/DSC01276Medium.jpg)
I made that metal bar out of 1/4" square steel, it will go in the small holes at the top of the pedal to protect the exposed tubes.
double thread revival action! :D
I've ordered some subminitubes that are due to arrive any day now. They've really similar charactersitics as this, as far as i can tell. They're russian ones. I was just wondering, if you run this at 12V to the anode, what kind of gain do you get? Are we talking low levels, or serious crunch? Is it similar to, for example, the valvecaster with the 6111 tubes?
Quote from: trad3mark on March 12, 2010, 11:49:20 AM
double thread revival action! :D
I've ordered some subminitubes that are due to arrive any day now. They've really similar charactersitics as this, as far as i can tell. They're russian ones. I was just wondering, if you run this at 12V to the anode, what kind of gain do you get? Are we talking low levels, or serious crunch? Is it similar to, for example, the valvecaster with the 6111 tubes?
Probably worth listening to the soundclips:
Quote from: frequencycentral on February 21, 2009, 10:13:00 AM
I have no doubt that you guys are now sick to the teeth of me and my submini tube obsession! Anyway, I recorded a couple of new soundclips of my modded PentaDriver, which is now at the spec of the schematic on page 5 - with the turbo mod and Big Muff style tonestack.
Here's a couple of soundclips, nothing special playing wise, just trying to show what the pedal can do in terms of it's tonal variations.
Signal path:
Squier Telecaster Custom (HB) > PentaDriver > Roland Bolt 60 watt tube combo > Shure SM58 > Event Echo Gina 24 soundcard > Wavelab
This clip is with gain at half, just running through some different tone control settings: http://www.aronnelson.com/DIYFiles/up/PentaDriver_Half_Gain.mp3
This clip is with gain at full, again running through some different tone control settings: http://www.aronnelson.com/DIYFiles/up/PentaDriver_Full_Gain.mp3
beautiful! Thanks for that rick! ;)
The tubes i'm getting, 1J29B-V have REALLY similar characteristics, so looking at these kinds of schematics is a good starting point. That and valvewizard's pages. ;)
That is a really nice gain level though. Really really nice.... :icon_twisted:
I put together a DIY Layout for the Pentadriver Turbo Plus, would someone like to verify it for me? I've double checked it, but fresh eyes are always a good thing.
I left out the bypass footswitch and power switching, because the design was getting too complex looking and not being able to route the wires manually makes it look sloppy.
(http://img.photobucket.com/albums/v321/mattthegamer463/Guitar%20Pedals/pentadriverturboplus.gif)
(http://img.photobucket.com/albums/v321/mattthegamer463/Guitar%20Pedals/PentaDriverTurboPlus-1.jpg)
All done, sounds cool.
(http://img.photobucket.com/albums/v321/mattthegamer463/Guitar%20Pedals/DSC01291Medium.jpg)
(http://img.photobucket.com/albums/v321/mattthegamer463/Guitar%20Pedals/DSC01292Medium.jpg)
Thanks for the design, Rick.
^^^
Nice! Very cool that you fabricated the rollbar. Any gutshots for us?
If it sound as cool as it looks, that's KILLER! :icon_twisted:
Sorry guys, I forgot I took this pic with my phone earlier. Here you go:
(http://img.photobucket.com/albums/v321/mattthegamer463/Guitar%20Pedals/IMAG0093.jpg)
The submini's are mounted to a segment of perf which is epoxied in place on top of the DC jack. Its a tight squeeze in there.
Also, Rick gave me the great idea of using ribbon cables in place of lots o' wires, so simple and yet so effective. I've got two 5672's left, what should I do?
Hello, haven´t been here a while, but as I´m having trouble with the layout here, I wonder if the IC3 is a row too high up? I have a short I can´t figure out anywhoooos...
Sorry to dig up so old topic (golden shovel award to me), yes, the vero board layout seems to be incorrect - the pinout is pin 1 adjust, 2 vout and 3 vin, so the power should go to pin3 (not pin 2 as on vero), pin5 of the tube should be connected to either 1 or 2 (as they're both grounded) and there should be a jumper from pin 1 or 2 to ground (as on the layout shown they are not connected to ground and they should be, according to schematic.