|HOME| |DIY FAQ| |GEO FAQ| |Debugging Page| |Links| |Schematics| |Wiki| |Layouts Gallery| |STORE|
|AMPAGE| |GEOFEX| |AMZ|

Welcome, Guest. Please login or register.
Did you miss your activation email?
October 31, 2014, 03:05:45 AM
972630 Posts in 103666 Topics by 33091 Members
Latest Member: IanEric.com
Home Help Login Register
DIYstompboxes.com  |  DIY Stompboxes  |  Building your own stompbox  |  BLACK FOREST High Gain Preamp - Based on the Bogner Uberschall 0 Members and 1 Guest are viewing this topic. « previous next »
Pages: 1 ... 22 23 24 25 26 [27] 28 29 30 31 32 ... 50 Go Down Print
Author Topic: BLACK FOREST High Gain Preamp - Based on the Bogner Uberschall  (Read 100007 times)
jymaze
Posts: 122


Re: BLACK FOREST High Gain Preamp - Based on the Bogner Uberschall
« Reply #520 on: March 05, 2013, 07:29:57 AM »

Deadastronaut,

Muamp have a lot of gain (about 300) so it may be way too much gain then for the circuit unless other stages are suppressed.

To minimize noise, the best way is to maximize the gain of the first stage that has gain (if you have a quiet buffer as first stage it is ok), so it makes sense to have a first stage with a lot of gain like a mu-amp I agree.

I personally believe the best is to use an opamp where you can have huge gain and very good PSRR all at once (PSRR is horrible with cascaded jfet circuits), then after that the contribution of the rest of the circuit to the overall noise should be limited.
Logged
fretzburner
Posts: 216



Re: BLACK FOREST High Gain Preamp - Based on the Bogner Uberschall
« Reply #521 on: March 05, 2013, 07:46:39 AM »

jymaze,
So what i did is not optimal because i lessen the gain of first stage(V1).I noticed now that seems i need some more gain with this 2SK152 at V1.Maybe will try to play a bit to really used to this then evaluate again if i need to place back the K117.
Logged
jymaze
Posts: 122


Re: BLACK FOREST High Gain Preamp - Based on the Bogner Uberschall
« Reply #522 on: March 05, 2013, 08:43:30 AM »

You are right. Optimally, you should lessen total gain by removing gain from the last stage at first.

The noise of cascaded gain stages is governed by the Friis formula if you want to google it. Basically the first gain stage is the most important: it should have low intrinsic noise ratio (low input noise and high PSRR) and high gain. From the second gain stage and then on, the noise contribution decreases fast, for each stage being inversely proportional to the gain of the stage immediately preceding it.

The first stage can be a buffer though, as long as it is very very quiet it does not impact the chain and the second stage is virtually a first stage in the chain then.
Logged
J0K3RX
Posts: 1383


Jim - Earth 2014


WWW
Re: BLACK FOREST High Gain Preamp - Based on the Bogner Uberschall
« Reply #523 on: March 05, 2013, 09:23:39 PM »



jim....have you tried a 2 fet 1st stage config like the bsiab...may be quieter noise wise....just thinking aloud as the spitty is very quiet...

Rob,


I had thought about that along with a thousand other ideas that have been spinning around in my head like a sh!t tornado...

I don't necessarily know that the cause of this "HUM" is due solely to or even partially to having too much gain? Was just a guess...? Now I am leaning more towards the J201 being unsuitable for the 1st stage due to it being too noisy along with the 2N5457/58, 2SK117... Again, just a guess but from looking at the dats sheets it looks to be true? Does anybody know how these jfets compare with the Russian KP303A? I can't find a data sheet (that I can translate)...? Most people are looking at the IDSS - drain-to-source leakage current, i.e. the current that flows when the switch is off... While one jfet can have almost the same IDSS, the "noise figure versus source resistance is vastly different. J201's from what I can tell appear to be well suited until you get to looking at the noise figures! There may be other factors as well..? From what I can tell these are the best suited for these high gain jobs (2SK30ATM-R, 2SK30ATM-Y, 2SK30ATM-O / The 2SK208-R, 2SK208-Y, 2SK208-O / The 2SK879-R, 2SK879-Y, 2SK879-O) And all of the "R" class are as rare as a liberal at a NRA convention!!! These are all basically the same, not sure about the GR classification, may work also in certain areas? jymaze, correct me if I am wrong,if fretzburner was able to use the 2SK117GR then the 2SK30ATM-GR will most likely work (from what I can tell) and the noise will be very low! These are easily purchased online, I think Thai Shine/Tayda carries the Y and GR class? The BF245's look to be next in line...

jymaze, what about these?
http://www.calogic.net/pdf/SST404_Datasheet_Rev_A.pdf
« Last Edit: March 05, 2013, 09:32:32 PM by J0K3RX » Logged

If it sounds good, then it is good...
J0K3RX
Posts: 1383


Jim - Earth 2014


WWW
Re: BLACK FOREST High Gain Preamp - Based on the Bogner Uberschall
« Reply #524 on: March 05, 2013, 10:40:35 PM »

Just found a couple 2SK30A-Y in my transistor pile that I raped from some junk radios, vcrs, TV's and everything I can find... Anyway, I tested it (had to make and adapter since different pinout but I like it! Very tube like but the HUM is still there yet ever so faint... Doesn't seem to be missing any gain either...
Logged

If it sounds good, then it is good...
fretzburner
Posts: 216



Re: BLACK FOREST High Gain Preamp - Based on the Bogner Uberschall
« Reply #525 on: March 05, 2013, 10:46:28 PM »

Tried again today for V1 2SK30A-Y no more noise issue but just same gain or little more than 2SK152.As what i have tried,2SK117-GR seems ok as for gain but a little more noisy than these 2SK152 and 2SK30A-Y.
Logged
J0K3RX
Posts: 1383


Jim - Earth 2014


WWW
Re: BLACK FOREST High Gain Preamp - Based on the Bogner Uberschall
« Reply #526 on: March 06, 2013, 02:17:14 AM »

Tried again today for V1 2SK30A-Y no more noise issue but just same gain or little more than 2SK152.As what i have tried,2SK117-GR seems ok as for gain but a little more noisy than these 2SK152 and 2SK30A-Y.

I played around with different value resistors from input to ground... tried many and 18k was the magical number for me.. didn't dampen the tone or sustain but just enough to completely kill the hum and no noise when I turn my volume pot back on my guitar. Cleans up real good too. I went back to the J201 for this just because it gives more gain than the 2sk30... not alot but I was still getting a small bit of noise on the volume roll back on the guitar... The 18k and the J201 is perfect. Also sounds killer with the simple cab sim and the hotline2 cab sim!!! Also, if I use a tube screamer in front it really kicks it in the nuts! I am going to make another one and see if I can reproduce it consistantly...

I had an idea, maybe for another preamp hybrid we could completely remove the 1st stage and replace it with a tube screamer or a SOS or SOCJ... So it would be a TS with 3 gain stages after, then a buffer, tone stack and then another buffer! I think it would sound insane since the tube screamer has a great tube like tone with great edge and no noise like the jfet stage! It sounds good with the tube screamer in front of the preamp anyway so why even mess with that noisy 1st stage anyway!? A TS sounds good on it's own so just figured it would make a good 1st stage? Maybe crazy but I am gonna try!

Logged

If it sounds good, then it is good...
euronymous0001
Posts: 139


Re: BLACK FOREST High Gain Preamp - Based on the Bogner Uberschall
« Reply #527 on: March 06, 2013, 03:29:15 AM »

jok3r,

i've read from somewhere else  Wink that the BJT buffer in the TS9/TS808 input helps in keeping the noise down. maybe a bjt buffer in front of the circuit could kill some of the noise

don't take my word as if I:
1) i've tried this; and
2) i know what im saying

just suggesting from what i read.  Grin
Logged
jymaze
Posts: 122


Re: BLACK FOREST High Gain Preamp - Based on the Bogner Uberschall
« Reply #528 on: March 06, 2013, 07:58:01 AM »

Yep Jok3rx, that was my project: Build it with one less stage at the end and replace the first stage with a TS like thing (way more gain that a jfet stage). The problem is that the voicing has to be kept and it is not that easy to do for the whole gain range.

Changing the fet on the first stage should have only a minor effect on the whole gain. Not expecting more than a +/-6dB difference in gain on a total gain of 80-90 dB... Hardly anything to write home about.

I think the most important is to  choose a low noise fet, so basically NOT a J201. But as of 2N5457 versus a 2SK30, while there is certainly a difference in term of intrinsic noise, it should not produce a radical change because I still believe most of the noise is picked up by the high impedance input and from the power supply and amplified.

Why is a TS in front of it helping that much noise-wise... Still not totally sure. And that bjt buffer in the TS is not the best buffer I have ever seen... Usually I find Boss pedals noisy.
Logged
J0K3RX
Posts: 1383


Jim - Earth 2014


WWW
Re: BLACK FOREST High Gain Preamp - Based on the Bogner Uberschall
« Reply #529 on: March 06, 2013, 11:24:03 AM »

Yep Jok3rx, that was my project: Build it with one less stage at the end and replace the first stage with a TS like thing (way more gain that a jfet stage). The problem is that the voicing has to be kept and it is not that easy to do for the whole gain range.

Changing the fet on the first stage should have only a minor effect on the whole gain. Not expecting more than a +/-6dB difference in gain on a total gain of 80-90 dB... Hardly anything to write home about.

I think the most important is to  choose a low noise fet, so basically NOT a J201. But as of 2N5457 versus a 2SK30, while there is certainly a difference in term of intrinsic noise, it should not produce a radical change because I still believe most of the noise is picked up by the high impedance input and from the power supply and amplified.

Why is a TS in front of it helping that much noise-wise... Still not totally sure. And that bjt buffer in the TS is not the best buffer I have ever seen... Usually I find Boss pedals noisy.

Like I said, the way I have mine now it's noise free but I am not really comfortable with the resistor across the input to ground! I think it will change from guitar to guitar.. My 3 guitars are pretty evenly matched as far as output/pickups etc.. I hate to alter the circuit too much because I love the tone and the gain it produces! I think the best way to go is a hardwired/permanent buffer (not sure which would be the most effective and transparent?) in front of preamp! Put it on a small vero or perf board for now... I will make a layout as soon as I decide on what is the best one (any ideas besides the TS buffer?) If we start changing the circuit it seems like it creates a chain reaction of other issues that are never ending... So far nothing has squashed the HUM to my satisfaction! Yes, mine works perfectly with my guitars but who knows what it will do with other guitars?  

Solutions:
1. Add permanant buffer in front of the input. I can easily redraw the layout to accommodate this, may be a slight bit deeper but can be done! What about an opamp buffer?
2. Build pedal with on-board tube screamer or variant - When tube screamer is on will act as "lead channel" extra tight, edge etc. / When off will just utilize the TS buffer. If you want "true bypass" either use an A/B switch to completely bypass the pedal or put a second stomp switch in the pedal that bypasses both the TS and the preamp. Not hard to do! Plus the way that the preamp is laid out gives plenty of room inside the enclosure for other stuff unless you are one of those people who likes to jam everything into an enclosure the size of a lipstick case for whatever reason unknown to me? Small is Not a good idea for high gain circuits in my opinion anyway ...

jymaze - I bypassed the 4th gain stage/mosfet and didn't sound good at all! Sounded like it got neutered (lost it's balls)  icon_cry

By the way - I built the other Russian preamps/pedals that don't use mosfets like the Uber, Bogner XTC and Soldano, all jfet/J201 and none of them have any noise what so ever but non of them have the beastly gain that the mosfet designs have either so go figure icon_rolleyes Actually, they don't even come close and absolutely require the aid of a tube screamer to get anywhere near the mosfet killers! They are more along the lines of the Dr.Boogie, maybe a little less gain...  
« Last Edit: March 06, 2013, 11:37:20 AM by J0K3RX » Logged

If it sounds good, then it is good...
jymaze
Posts: 122


Re: BLACK FOREST High Gain Preamp - Based on the Bogner Uberschall
« Reply #530 on: March 06, 2013, 12:40:24 PM »

I agree, it is always a dilemma: The balls of over-the-top gain versus the uncontrollable noise.

Anecdote:
 I have a Line 6 amp and it sounds okay for what it is, I use it once in a while. So last week I plug it in and put it on high gain and it just sounds much more exciting and ballsy than usual, but with weird background noise. Then I check my pedal board and I was running my Riot clone with gain at 3 o' clock into it. So yes, over the top gain gives balls, but it gets noisy...

So suppressing V4 sounds neutered... but at least did it lower the noise to positively? Also, neutered compared to the original would still be ok for other folks, if a Dr Boogie sounds neutered to you, then dropping V4 on this one may not be that bad in all respect...

You can book end the whole thing between a double opamp buffer I guess (you can even suppress V6 then). Opamps are the best transparent buffers from an electronic point of view, much better than a lone bjt.

What settings do you use on your TS by curiosity? Do you use it more for the gain or the eq?
Logged
J0K3RX
Posts: 1383


Jim - Earth 2014


WWW
Re: BLACK FOREST High Gain Preamp - Based on the Bogner Uberschall
« Reply #531 on: March 06, 2013, 01:21:57 PM »

What settings do you use on your TS by curiosity? Do you use it more for the gain or the eq?

Well I use it a couple of ways just depends on my ears...

1. I use it for very slight edge, not really gain so much - Gain on 0 or 1 / Tone on 5 or half way / Level on 2 or 3, just cracked enough to let the full guitar signal come through. This gives it a tight edge on the lows and a slight bit more sustain.

2. I turn the gain down on the preamp to about 5 - Then on the TS I set the Gain on about 3 / The Tone the same as before / The Level on about 5 or 6. This does about the same thing but give you a slightly different bite and attack.

Note: When I say for example Gain on 5 or Level on 3 I am referring to the actual rotation level of the pots, NOT the o'clock position...

I could do without a tone knob all together as I very rarely even move mine, always stays in the middle or a bit less.

I don't use the tube screamer like a lot of others do like say run it into a clean or slightly dirty amp and use the higher settings on the tube screamer to get my overdrive sound... I just use it for slight edge, that's it! The Engl hardly even needs it but others like the Dr.Boogie etc. kinda need the help... Not knocking the Boogie at all, it's a great pedal! Most (a lot) of people use it as a distortion box and run it into the front input of their amp, that gives it a lot more balls but if you run it straight into a PC or power amp it's a different story all together... I don't like using it as a distortion box. If I am gonna do that I will use a Riot or Crunch Box or something like that into the front of an amp! I'm not really a person that likes to run a "preamp" into another preamp... But hey, if it sounds good, then it is good! icon_wink

« Last Edit: March 06, 2013, 01:27:15 PM by J0K3RX » Logged

If it sounds good, then it is good...
fretzburner
Posts: 216



Re: BLACK FOREST High Gain Preamp - Based on the Bogner Uberschall
« Reply #532 on: March 06, 2013, 04:40:12 PM »

First time used this preamp direct to subway rocket return input and sounds huge.compared it to amp alone way more gain than the crunch channel,while with the contour channel same gain but the boogie sounds more bass.Both of them have natural(acceptable) noise with guitar volume full and same noise level between this preamp and the boogie amp alone.So I think my quest to lower the noise level is over now.And i did not use a buffer at preamp input.Changes made to the circuit is just the 33k to 100k resistor R19,some supply filter caps and the first stage 2SK30A-Y.
Like Jok3rx said i don't want to heavily alter the circuit because stock from schematic this preamp sounds very very good except that noise.
Note:when i say preamp i'm referring it to this engl build.
Logged
euronymous0001
Posts: 139


Re: BLACK FOREST High Gain Preamp - Based on the Bogner Uberschall
« Reply #533 on: March 08, 2013, 07:16:29 AM »

hey jok3r, have you tried using BS170 instead of 2N7000?  icon_mrgreen
Logged
bluebunny
Posts: 1641


Marc B.


WWW
Re: BLACK FOREST High Gain Preamp - Based on the Bogner Uberschall
« Reply #534 on: March 08, 2013, 09:30:32 AM »

hey jok3r, have you tried using BS170 instead of 2N7000?  icon_mrgreen

As I understand, they are pretty much interchangeable.  Careful with orientation: they "face" in opposite directions.  Anything to add from your experience, Jim?
Logged

[M][a][r][c]
Ohm's Law - much like Coles Law, but with less cabbage...
euronymous0001
Posts: 139


Re: BLACK FOREST High Gain Preamp - Based on the Bogner Uberschall
« Reply #535 on: March 08, 2013, 09:53:55 AM »

hey jok3r, have you tried using BS170 instead of 2N7000?  icon_mrgreen

As I understand, they are pretty much interchangeable.  Careful with orientation: they "face" in opposite directions.  Anything to add from your experience, Jim?


soulsonic, AFAIK, stated that the BS170 where "smoother" than the 2N7000 which where "grittier". I'm NOT sure if this will solve the problem because it was not said that it WAS MORE QUIET.   icon_wink
Logged
J0K3RX
Posts: 1383


Jim - Earth 2014


WWW
Re: BLACK FOREST High Gain Preamp - Based on the Bogner Uberschall
« Reply #536 on: March 08, 2013, 06:48:53 PM »

hey jok3r, have you tried using BS170 instead of 2N7000?  icon_mrgreen

As I understand, they are pretty much interchangeable.  Careful with orientation: they "face" in opposite directions.  Anything to add from your experience, Jim?

Tried the BS170's.. 1 - They make no difference in the noise factor here, still noisy. 2 - They are a slight bit rounder/warmer sounding, maybe a good thing, maybe not... depends on what you like. I like the 2n7000 more because they sound plenty warm and seem to give it an extra bit of edge. Also, I like them because they are CHEEEP! I can get like 50 2n7000's for the price of 5 BS170's. Don't get me wrong, if the BS170's made an improvement in the tone, attack, gain, "NOISE" and over all better sound I would not hesitate for a moment to buy/use them over the 2n7000's but, I actually think the 7000's sound better!  

Ok, Here is "MY" fix for the HUM/NOISE... This works!!! As I said a couple pages back if I stick a retail tube screamer (mine is the TS7 with the TS808 mod) with buffered bypass (not true bypass) in front of the Engl preamp pedal it kills the noise and the guitar volume knob roll back noise increase problem 100%!!! That is just with the TS in bypass mode. There is no gain loss, no tone loss, no sustain loss just kills the noise 100%! The only noise left is pure high gain and normal noise associated with high gain, a little bit of noise is to be expected but it's very minimal considering the gain this thing puts out!! There is a distinct difference between "normal noise" and this constant over riding low level hum that consumes the sound! It's like there is another guitar cord unplugged laying on the ground buzzzing in the background. Anyway, the buffer in this TS7 completely cures this 100%.

Now, I have built a TS input buffer and it didn't work,meaning it didn't fix the hum sound like my TS7...
I used this buffer, pretty common... 2nd diagram.. I tried a 2n5088 and a 2n3904
http://www.muzique.com/lab/tsbuff.htm  

Must not be the same as the TS7 buffer? Anyway, if you look up the schematics for the TS7 you get different buffers with different schematics etc.. Looks like the "real" schematic is using two 2SC1815's for the input/bypass buffer? Or, am I reading this thing wrong? Sorry, can't find the link for it but I have the pdf... Whatever the TS7 is using is the ticket to a 100% bug free working preamp!!!

Edit: still can't find the original pdf to the TS7 but found this and has some cut outs from the schematic, one has the input buffer...
http://www.marksmart.net/gearhack/ts7/carboncomp/carboncomp.html
« Last Edit: March 08, 2013, 07:09:26 PM by J0K3RX » Logged

If it sounds good, then it is good...
bluesdevil
Posts: 972

Just a Bill in Florida


Re: BLACK FOREST High Gain Preamp - Based on the Bogner Uberschall
« Reply #537 on: March 08, 2013, 08:53:55 PM »

About the TS buffer circuit:
I wonder if you would use that 510k resistor that's connected to +4.5v or omit ?
EDIT:
Nevermind.... what a stupid f&%^$# question!!


« Last Edit: March 08, 2013, 09:40:37 PM by bluesdevil » Logged

"I like the box caps because when I'm done populating the board it looks like a little city....and I'm the Mayor!" - armdnrdy
jymaze
Posts: 122


Re: BLACK FOREST High Gain Preamp - Based on the Bogner Uberschall
« Reply #538 on: March 09, 2013, 12:01:52 AM »

This buffer thing is really weird for sure Jok3rx. It is like anything in the same enclosure as the preamp is doomed with noise.

When you put your TS7 before the Engl MOSfet on your board, they both share the same power supply?
Logged
J0K3RX
Posts: 1383


Jim - Earth 2014


WWW
Re: BLACK FOREST High Gain Preamp - Based on the Bogner Uberschall
« Reply #539 on: March 09, 2013, 12:51:24 AM »

When you put your TS7 before the Engl MOSfet on your board, they both share the same power supply?

Sure do.. yup!
Logged

If it sounds good, then it is good...
Pages: 1 ... 22 23 24 25 26 [27] 28 29 30 31 32 ... 50 Go Up Print 
« previous next »
Jump to: