...and now, the "PentaDriver" 12 volt Pentode Overdrive using Submini 5672 tubes

[frequencycentral]

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:

[Tony Forestiere]

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!

[sweetwilly]

Well, there go the plans for the Pepper Shredder then! 

How are the experiments into other uses for the 5672s coming along?

[frequencycentral]

Well, there go the plans for the Pepper Shredder then! 

You could breadboard this in no time at all.......

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?

[sweetwilly]

You could breadboard this in no time at all.......

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!

[forsakenrider]

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?

[frequencycentral]

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?

[forsakenrider]

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?

[frequencycentral]

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. 

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"!

[Renegadrian]

..... 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!

[forsakenrider]

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.....

[frequencycentral]

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!

[sweetwilly]

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.

[svstee]

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...

[frequencycentral]

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://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.

[svstee]

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.

[svstee]

Here it is:

I'd actually never done a vero layout before today. Hope it doesn't show too much, this is only my third.

Thanks!

[petemoore]

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...

[svstee]

Stupid photobucket!


Any errors?

[frequencycentral]

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!