Tube boost + overdrive running off a 9 volt battery

[tasos]

I've built a couple of valvecasters, but none of them play well with my active bass... if i put a simple JFET buffer in front do you think that would help?

I doubled c1,c2,c3 and changed c4[tone cap] to 47nf...try different values to get what you like...47nf gives you a deep tone but not too muddy...

[runmikeyrun]

I've built a couple of valvecasters, but none of them play well with my active bass... if i put a simple JFET buffer in front do you think that would help?

Well an active bass has a buffer? right? What is it you do not like about the sound? 

The sound is harsh, non-musical distortion, thin and weak, almost splattery like a misbiased transistor.  It works great with passive basses and guitars.

[iccaros]

I've built a couple of valvecasters, but none of them play well with my active bass... if i put a simple JFET buffer in front do you think that would help?

Well an active bass has a buffer? right? What is it you do not like about the sound? 

The sound is harsh, non-musical distortion, thin and weak, almost splattery like a misbiased transistor.  It works great with passive basses and guitars.

I put a basic opamp buffer in front, but you could also try making the first stage a cathode follower

also raising voltage may help, I found that mine sounded that way until I got over 24Vdc.. getting ready to rebuild mine at around 80 volts..

[nexekho]

A bit of a n00b question, but my DC jack has only two pins, which correspond to + and - on the power brick.  Is attaching the ground loop to the - ok or is it wrong?

Thanks.

(about 65% through a build here)

[nexekho]

Completed the circuit!  Built it, checked it, jacked it up, WORKED FIRST TIME.   

Next step: box it up.

Clips a bit harsher than I expected but it's pretty easy to dial it back.

Thanks for all your help and the schematics!

[Renegadrian]

uhm sorry...what is that?! What are those green LEDs for!?

[nexekho]

I moved caps 1, 2 and 4 to a board because my poly boxes have really short legs and added three LEDs which sit at the top of the tube and light it up.

It's a mess at the moment.

[runmikeyrun]

uhm sorry...what is that?! What are those green LEDs for!?

are you thinking what i'm thinking?  Clipping diodes?   

[runmikeyrun]

I've built a couple of valvecasters, but none of them play well with my active bass... if i put a simple JFET buffer in front do you think that would help?

Well an active bass has a buffer? right? What is it you do not like about the sound? 

The sound is harsh, non-musical distortion, thin and weak, almost splattery like a misbiased transistor.  It works great with passive basses and guitars.

I put a basic opamp buffer in front, but you could also try making the first stage a cathode follower

also raising voltage may help, I found that mine sounded that way until I got over 24Vdc.. getting ready to rebuild mine at around 80 volts..

Thanks Steve for the input.  I just built Jack Orman's JFET buffer/splitter.  I will try that in front of my one valvy to see if there's a difference.  It definitely made a difference in front of my big muff clone.  If that doesn't do it, i will head to goodwill and try to find a 24v laptop PS.  I only have an 18v one here.

I'm curious on that note... I used a 7812 VR on my last build.  I couldn't put more than 18v into it because I'm pretty sure it would fry.  How can i get 12v to run the heaters from 24v?  Can i just wire two tube's heaters in series or do I have to worry about hum?

[nexekho]

uhm sorry...what is that?! What are those green LEDs for!?

are you thinking what i'm thinking?  Clipping diodes?   

No!  They're just in series with a current limiting resistor on the same board with a second switch to turn them off, the whole subcircuit running in parallel with the tube drive across the jack.  Works perfectly.  In my arrangement, the jacks and switches are at the bottom, then the tube, then the board with the caps and the LEDs points down the tube lighting it up green and then the dials are up the top.

[runmikeyrun]

uhm sorry...what is that?! What are those green LEDs for!?

are you thinking what i'm thinking?  Clipping diodes?   

No!  They're just in series with a current limiting resistor on the same board with a second switch to turn them off, the whole subcircuit running in parallel with the tube drive across the jack.  Works perfectly.  In my arrangement, the jacks and switches are at the bottom, then the tube, then the board with the caps and the LEDs points down the tube lighting it up green and then the dials are up the top.

Right on!  The valvecasters I built I super glued a very bright LED into the middle of the base of the tube socket.  When the effect was on the tube lit up. 

[iccaros]

I'm curious on that note... I used a 7812 VR on my last build.  I couldn't put more than 18v into it because I'm pretty sure it would fry.  How can i get 12v to run the heaters from 24v?  Can i just wire two tube's heaters in series or do I have to worry about hum?

A 7812 would work but need   heat sink, I think it can drop up to 35V... but I don't have the datasheet in front of me. if you use the to-3 package the pedal housing can be the heat sink, with the normal package you need a separation or use negative voltage regulator. 

using V= I*R
you want to drop 12 volts, the heaters pull .15 amps so
12/.15 = 80 ohms,
take current and resistance (.15 * 80 = 1.8 watts)

so a 2 watt would work, 3 - 4 better.

In either case you have to give off 1.8 watts of power so heat sin

[runmikeyrun]

cool... thanks for the info.  I don't like using voltage regulators in tube circuits though, i always have problems with hum.  Can i just run the heaters in series @ 24v?  That would be much easier for me.

[iccaros]

cool... thanks for the info.  I don't like using voltage regulators in tube circuits though, i always have problems with hum.  Can i just run the heaters in series @ 24v?  That would be much easier for me.

if you have two tubes.. one tube in series is 12V  and 6.3 in parallel

[runmikeyrun]

cool, thanks... that's what i thought.  I do plan on using two 12au7s.  If i can find a higher supply, i'll use more tubes.  You can never have enough gain!  lol

EDIT- I just thought of something.  Provided i have enough current, can i tap voltage for the plates and heaters from one transformer?  Or should I have two separate ones?  I don't want to induce any noise or hum.

EDIT (again!)- Ok Radio Shack has a 12v transfomer at 450ma and a 25v transformer at 450ma.  How many tubes can I power safely with each of those?  I would use the 12v for heaters and 25v for the plates.  I know the twincaster I built wasn't happy with anything less than a 1A supply @ 12v, otherwise i had sag, but that was with the heaters and plates running off the same wall wart.

[iccaros]

cool, thanks... that's what i thought.  I do plan on using two 12au7s.  If i can find a higher supply, i'll use more tubes.  You can never have enough gain!  lol

EDIT- I just thought of something.  Provided i have enough current, can i tap voltage for the plates and heaters from one transformer?  Or should I have two separate ones?  I don't want to induce any noise or hum.

EDIT (again!)- Ok Radio Shack has a 12v transfomer at 450ma and a 25v transformer at 450ma.  How many tubes can I power safely with each of those?  I would use the 12v for heaters and 25v for the plates.  I know the twincaster I built wasn't happy with anything less than a 1A supply @ 12v, otherwise i had sag, but that was with the heaters and plates running off the same wall wart.

see here --> http://www.diystompboxes.com/smfforum/index.php?topic=74088.0

A simple voltage multiplier would be better, I pick up 1amp 12V wall warts at Good Will for less than $3
Feed the plates off the multiplier and the heaters off the 12V input.

[runmikeyrun]

Those are interesting.  I'm going to do some experimentation when I get the cash to pick up a few tube sockets and a couple of those trannies.  Maybe try out a nixie supply too.  I figure with 4 tubes the enclosure will be a little larger than normal anyways, so I should have room for two small trannies.  I also have a small single ended stereo amp in the basement, might look at that PT to see what kind of taps it has.

[iccaros]

also I did this project with 12V
Worked well for me, would like others to test and give me feedback to improve it.. its a 12ax7 and 6au6 pentode on 12v

I added an opamp buffer in front of the 12ax7, unity gain so it just effected the input loading.

http://www.diystompboxes.com/smfforum/index.php?topic=91745.0

[runmikeyrun]

that's an interesting circuit... i'm going to investigate.  It's possible i have a 6au6 in my basement... I have a couple of oddball tubes floating around and that sounds familiar.  Thanks for the link!

[dam28]

Point me in the right direction if this has been said before BUT....

Just been reading through this thread. I have just finished building the tube boost! It sounds cool but the amount of "boost" I get is quite small. Is this common? I get a nice bit of crunch but not much boosting action. Running it of my bench power supply, set to 9V.

Cheers!