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

[Renegadrian]

Yeah, it's great to have 50V from a wall wart...
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...

[frequencycentral]

Yeah, it's great to have 50V from a wall wart...
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...

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!

[Renegadrian]

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.

[svstee]

What about using that turbo mod with a dpdt stomp and LED on the pentadriver?

[frequencycentral]

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.

[Renegadrian]

____    ____
|_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?!

[frequencycentral]

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

[svstee]

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.

[frequencycentral]

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.

[tranceracer]

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!   

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

[frequencycentral]

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!   

Aw shucks! 

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.

[svstee]

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:


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?

[frequencycentral]

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.

[decc]

- 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.

[frequencycentral]

- 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

[decc]

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.

[frequencycentral]

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.

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!

[decc]

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...

[decc]

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.

[frequencycentral]

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?

Here's to my new favorite pedal.

Until your next build?