Tube boost + overdrive running off a 9 volt battery

[dynotouch]

First of all, welcome This was my very first DIY build, and i think it's a very good introduction to building.

Second, I never run tube pedals on anything less than 12V. I've also found that the lower the current rating of a power supply the noisier it is. I first tried it with 9v 300mA and it was dreadful, so I used 12v 300mA and it was better, but I ended up settling on a 12v 1000mA power supply, and it runs amazingly. I have heard a lot of people say they prefer it with an 18v supply for the headroom just as you mentioned.

Welcome again and good luck
[/quote]

awesome... thanks for those tips. i need to go back and just read thru the entire thread still, i think it'll be quite useful to take in the entire discussions and all that it has to offer. I just read the first few pages and then kinda went hog wild thru my e-junk seeing what i had laying around. think i have most of what's needed to mock up a test & tweak board like resistors and old amp chassis with 9 pin sockets, but I'll need to go out and get the needed caps and a 12au7 (all i have is 12ax's) or get them from someone here(??) I'll keep posting here as i progress ..thanks!

[dynotouch]

^Just a reminder to keep the heaters at 12V in series or 6V in parallel.

Thanks! ...how about 9vdc in series/parallel

[Jdansti]

I've never tried 9V on the heaters.  The tube really is designed to be run on 12V in series (6V parallel), although some people have used 9V in series. Maybe someone who's done that will chime in on the performance.

You could use 9V and drop the voltage to 6V using a regulator and wire the heaters in parallel. Alternately, I'm not sure if a resistive voltage divider is a good idea on this circuit to get 6V from 9V. Maybe someone who knows more than I could answer that.

If you decide to go above 12V on the plates, stay within the voltage limits for the heaters by dropping the voltage going to them.

[dynotouch]

I've never tried 9V on the heaters.  The tube really is designed to be run on 12V in series (6V parallel), although some people have used 9V in series. Maybe someone who's done that will chime in on the performance.

You could use 9V and drop the voltage to 6V using a regulator and wire the heaters in parallel. Alternately, I'm not sure if a resistive voltage divider is a good idea on this circuit to get 6V from 9V. Maybe someone who knows more than I could answer that.

If you decide to go above 12V on the plates, stay within the voltage limits for the heaters by dropping the voltage going to them.

Cool, yeah i wouldn't attempt to exceed 12v either on the heaters(or 6.3 in parallel). going by the diagram and scheme provided here by a member and it must be parallel and the heaters are getting 6vdc...no??

[Jdansti]

There are a lot of schematics on this thread.    The original one on page 1 uses 9V on the heaters in series (through pins 4 and 5). If you want the full effect that the heaters can provide and still use a 9V PSU, then use 9V as shown in the schematic, except you would add an LM7806 regulator to get 6V just for the heaters. Positive 6V to pins 4 and 5 and ground pin 9.

I can draw it out when I have more time this evening if you need it. Maybe someone who knows of an existing schematic or layout will chime in before then.

I think it would be better to find a 12V PSU, add a little filtering to the power if necessary, and run the whole thing on 12V using the original schematic.

Let me know if you need a drawing for using 9V.

[dynotouch]

There are a lot of schematics on this thread.    The original one on page 1 uses 9V on the heaters in series (through pins 4 and 5). If you want the full effect that the heaters can provide and still use a 9V PSU, then use 9V as shown in the schematic, except you would add an LM7806 regulator to get 6V just for the heaters. Positive 6V to pins 4 and 5 and ground pin 9.

I can draw it out when I have more time this evening if you need it. Maybe someone who knows of an existing schematic or layout will chime in before then.

I think it would be better to find a 12V PSU, add a little filtering to the power if necessary, and run the whole thing on 12V using the original schematic.

Let me know if you need a drawing for using 9V.

think ill just stick to the original design that dano12 provided in the beginning of the thread and go from there. actually, I'm almost done just need to inspect and wait for the tube with i ordered and should be here any day. i'll report! thnxQ

[Jdansti]

Sounds good. Let us know how it turns out!

[dynotouch]

It's purdy much built but not working yet(??). didn't have a 12au7 to test with so i tried a 12ax and got nothing at all and vdc from a battery dropped to about 5.3v when measured from the plates and the heaters were only getting something like 3v or visa-versa so i'm not doing something right (besides the obvious of trying the 12ax7). also i have the physical circuit spread out over a 8"x 6" board so i wonder of thats too big for such low current and voltage?? waiting on a 12au7 in the mail and need to find filtered and regulated 9vdc psu(has anyone here aver built a pedal apt supply... is there another thread dealing with that kind of build??)   ....I'll go back over my work and report. thanks!

Btw: (i'll be simultaneously starting an component upgrade & mod project to my vintage ibanez cs9 st chorus pedal and searching for input and suggestions about that on another thread somewhere more subject orientated as such)

[Jdansti]

Try a fresh 9V battery. Most people use a wall wart because the heaters will run a battery down pretty quick.

[zambo]

It's purdy much built but not working yet(??). didn't have a 12au7 to test with so i tried a 12ax and got nothing at all and vdc from a battery dropped to about 5.3v when measured from the plates and the heaters were only getting something like 3v or visa-versa so i'm not doing something right (besides the obvious of trying the 12ax7). also i have the physical circuit spread out over a 8"x 6" board so i wonder of thats too big for such low current and voltage?? waiting on a 12au7 in the mail and need to find filtered and regulated 9vdc psu(has anyone here aver built a pedal apt supply... is there another thread dealing with that kind of build??)   ....I'll go back over my work and report. thanks!

Btw: (i'll be simultaneously starting an component upgrade & mod project to my vintage ibanez cs9 st chorus pedal and searching for input and suggestions about that on another thread somewhere more subject orientated as such)

12ax7 doesnt always work in this design. Cant remember why. to much plate resistance or something. at7 same thing. Some do work, but its hit and miss. 12au7 works consistently. you probably built it right.

[Vanwilliams]

There ya' have it. Ain't she a beaut? With this design you should be able to get nice crunch tones from the first stage and great drive sounds from the second stage.

This should work with all 12A_7 tubes, but keep in mind that while other tubes should work with plate voltages above 9v, 12AX7s need at least 18v for the plates. They just don't sound right otherwise... I can't say for sure but I suspect 12AT7s would require 18v too.
The first volume pot is completely optional but I recommend leaving it in. You can get more sounds by fiddling with it while using both stages.
This is ment to be used with two true bypass circuits. One for the first stage and one for the second. Didn't bother putting those in the schematic because I figured if you can wire up this circuit you should be able to wire in a bypass...

You diystompboxes veterans are welcome to fix any mistakes in the schematic. I'm still pretty new to tube circuits...

[Vanwilliams]

Does the doublemaster schematic work? I am thinking about building it. If it does work, are the 12v and 18v working at the same time? Where would I put two 3dbt switches. I understand most of the schematic, I just don't know where to insert things.

[duck_arse]

hello and welcome to the forum, van.

the heater current at 12V for a 12a_7 valve is 150mA. you have two valves, so you need a minimum heater current of 300mA. if you get yourself a good, clean 18V supply, at least 400mA rated, you can then use a 12V three terminal regulator on a nice big heatsink for the heaters, and power the whole mess, no fuss.

as for if it works, it might be too much gain to be stable, I don't know. you can only try it. as for switches, you'd have to decide what setup you wanted and which sections you want switched.

[toplak666]

Does the doublemaster schematic work? I am thinking about building it. If it does work, are the 12v and 18v working at the same time? Where would I put two 3dbt switches. I understand most of the schematic, I just don't know where to insert things.

As long as you keep the plate voltage 18V or higher it should work nicely. You might notice that it has a bit (or a lot) too much bass. In that case you should make these modifications:

Anytime you make a circuit like this and it starts to become Hi gain you you will get parasitic oscillations etc. Sheilded wire helps a ton.Good layout and a grounded enclosure also helps a ton. Also, tubes run at low voltage will start to get dc on the grids when pushed into clipping. put a capacitor on the input pins ( 2, 7 ) Thats what c1 does on the original schematic otherwise your guitar volume would be scratchy. make sure you put the grid leak resistor after the cap like the example of c1 on the original. Also putting small value caps from plate to ground to bleed of some of the extreme high end will help. I wouldnt do it on stage 1 but on stage two and three it helps a lot. Using small grid caps helps tame some of the farty sounds as well. When you run tubes in space charge they develop a lot of bass and a lot oh high end which is nice on a single tube. makes that warm tubey break up. cascade it through 6 stages and you get to many highs and to much bass amplified and reamplified. starts making weird feed back. that will cause signal to die out like that as well. by using smaller coupling caps ( .001 or .002 ) in the 3,4,5,6 stages you cut out some of the farty bass. bleeding off the extreme highs from the plates on the same stages leaves behind a signal thats been boosted in the mids a lot. I built one of the first ( maybe the first? ) triple valve caster and built several more versions of it experimenting as I went. This is what I learned along the way. Hope it helps and good luck!!

Oh, and omit the two tone controll pots... They are pretty useless.

[duck_arse]

toplak - regarding the useless tone controls, have you tried the swtc config, like so?



amz has a bunch a stuff on this style control here:
http://www.muzique.com/lab/swtc.htm

[Vanwilliams]

Hey duck_arse, what if I used 12au7 tubes instead of12ax7's? Could I then power it using 9v and have a problem with gain? Or if I did 50/50 on the two tubes and had two modes: 1 would be 12au7 and 12ax7, and the second would also have a 12au7 and 12ax7, so then I have less gain, but still some bite?

[toplak666]

toplak - regarding the useless tone controls, have you tried the swtc config, like so?



amz has a bunch a stuff on this style control here:
http://www.muzique.com/lab/swtc.htm

Havent tried that yet... I'm probably gona use some kind of simple 3 or 2 band EQ next time but these tone controlls look pretty cool.

[duck_arse]

van, the amount of controllable gain and the "9V question" are 2 different problems. the heaters on 12a_7 valves can be run at 6V wired in parallel or 12V wired in series, as they are shown in the doublemaster diagram. at 6V they draw twice the current, but the doublemaster still wants 18V on its plates. there are circuits in this thread (I would hope so, given its title) describing 9V plates and 6V heaters. also ways to get more than 9V from a 9V supply.

as for the gain, 2 x ax might work and pose no probs for you, or it might just scream all the time. once you have your sockets wired right, you can just plug and play, you could even try 12at7 (I think that's the right number). I've never used this series valves in this type circuit, only some low-gain vhf (6V heaters only) types I have. toplak might be better able to tell about the overall gain here.

[dynotouch]

It's purdy much built but not working yet(??). didn't have a 12au7 to test with so i tried a 12ax and got nothing at all and vdc from a battery dropped to about 5.3v when measured from the plates and the heaters were only getting something like 3v or visa-versa so i'm not doing something right (besides the obvious of trying the 12ax7). also i have the physical circuit spread out over a 8"x 6" board so i wonder of thats too big for such low current and voltage?? waiting on a 12au7 in the mail and need to find filtered and regulated 9vdc psu(has anyone here aver built a pedal apt supply... is there another thread dealing with that kind of build??)   ....I'll go back over my work and report. thanks!

Btw: (i'll be simultaneously starting an component upgrade & mod project to my vintage ibanez cs9 st chorus pedal and searching for input and suggestions about that on another thread somewhere more subject orientated as such)

12ax7 doesnt always work in this design. Cant remember why. to much plate resistance or something. at7 same thing. Some do work, but its hit and miss. 12au7 works consistently. you probably built it right.

Sounds good. Let us know how it turns out!

Been away working N stuff but now I'm back with a 12au7 in hand and the report is IT WORKS! ..well sorta :/ it powers up and the preamp is active and seems to be working from somewhere close to the tone control-on as it gets amplitude boost and frequency control but haven't yet figured why my guitar signal isn't making it thru and input gain control doesn't seem to do anything, but the output pot does seem to be working. using vintage A&B 100K type J pots for both (...no right??) probably something simple. I'll spend a little time with it today and see if i can get'er going. thanks!

[zambo]

there is a resistor frim grid to ground ( 1M ) if you have that in the wrong place it doesnt work. try that first. should be from pin 2 to ground.  should be one from pin 7 to ground as well. I dont recall the stock schematic.