Tube boost + overdrive running off a 9 volt battery

[iccaros]

if you build this pedal right it sounds good at 9 volts but only with a 12au7 tube. I have never run across cothode stripping in a tube at 9 volts by the way. I am sure it can happen but it hasnt yet and I gigged a triple caster really hard for over a year. 12 volts is nice and the higher you go the better they sound. at about 100 volts and up they sound really good but there are many other designs that sound better. I run one at 9 volts and another at 45 as they sound great both ways for different things. its not really a distortion pedal. it just adds a little drive on top of whatever you got going already. I use them to "warm up" solid state amps and they do it well. They also fatten up a single coil guitar nicley. For what its worth. Oh yeah and when i run higher voltage i run 9 volts from the dc jack to pin 5 and ground pin 4. 9 is un connected. i run a seperate wire to my voltage multiplier smps or whatever voodoo i am using. Be careful though. and make sure your parts are rated for the higher voltage.  this stuff can kill you  Cheers, Greg

Zambo makes good points, who's experience is worth more than theory.
I believe he is not seeing cathode striping because of the low voltage on the plates http://www.diyaudio.com/forums/tubes-valves/79405-doubts-cathode-stripping-tubes.html, and well made tubes, some tubes may not fair as well. The 12AU7 and the 12U7 are really the same tube, with the 12U7 having more gain, but meant to run at 12Volts. IF you pull an old 12AU7 datasheet, it and the 12U7 match up. In the 12U7 datasheet they say 10volts min for the heaters.  They mention shorter tube life. But has 12U7 is cheep and they mean 1000's of hours of still uses-full life, which even on tour is more than a year.

here is more information on heaters http://www.freewebs.com/valvewizard/heater.html
also @ zambo have you tried a Toroidal Power transformer? from 12V ac to upto 240Vdc?
http://www.hoffmanamps.com/MyStore/perlshop.cgi?action=template&thispage=Transformers&ORDER_ID=274142820

I am thinking of using one with a compactron 6AF11 amp I am building. I could pull my 12 volts off the 12V ac transformer and then the rest at 240V

[tasos]

thanks guys...can 18v kill me?
i will get back when i get my tube...i have read that the 12ax7 has more gain...do you think this would work nicely using the same schematic[i know the two tubes have different pinout] with 18v and 9v on the heaters?

[iccaros]

I have not had luck even @ 30 volts making a 12AX7 sound good in this design.

as for voltage, AMP's kill not voltage. so under the right situation 1 volt can kill you. But I would not worry to much. You should practice  safe habits, don't touch the electronics while on with two hands. have non conducting shoes. ect...

Why I think the 12AX7 sounds bad in this design
1) the plate and cathode values are created for a very steep load line for a 12AU7 changing the design may help,
2) the 12AU7 was make to run in low voltage designs, with the 12u7 as the tested version, but also high voltage designed with out a isolation transformer, unlike say the 12K5

[tasos]

ok!no 12ax7 for me!
i will do as i said...max1044 voltage doubler...as for the heaters would 12v or 9v would be better?[9v from dc jack or 18v from max1044 and then 12v regulator?]

[merlinb]

as for the heaters would 12v or 9v would be better?[9v from dc jack or 18v from max1044 and then 12v regulator?]

Strictly you can have 12V heaters (18V regulated down to 12V) or 6V heaters (9V regulated down to 6V).

If you run the 12V heaters at only 9V gain may be lower, but it will work. I would suggest running at a 'proper' voltage (6V or 12V), since you can always reduce it later.

No, 18V cannot kill you. You won't even feel anything until above 60V.

[zambo]

yeah sorry about the scare there....18 volts is no big but i have seen a lot of guys get crazy from this project and jump up to over 150 volt projects, which gets a bit more freaky. @ icarros - I have not tried a toroidal yet but would like to. I have been building amps full scale latley to kind of get my theory and building skills up to par ( results are debatable lol) so i havent messed with anything under 250 volts for a while now. I am about to start building small stuff again as its where i really have fun. Doing the 2 x 12au7 push pull parallel amp again with a high gain preamp running a smps. Got to see if i can get it sounding good....results when i get it going again! 

[iccaros]

yeah sorry about the scare there....18 volts is no big but i have seen a lot of guys get crazy from this project and jump up to over 150 volt projects, which gets a bit more freaky. @ icarros - I have not tried a toroidal yet but would like to. I have been building amps full scale latley to kind of get my theory and building skills up to par ( results are debatable lol) so i havent messed with anything under 250 volts for a while now. I am about to start building small stuff again as its where i really have fun. Doing the 2 x 12au7 push pull parallel amp again with a high gain preamp running a smps. Got to see if i can get it sounding good....results when i get it going again! 

Thanks Zambo
I am looking at using one for a compactron amp design. I got some 6AF11 off ebay. The have Twin Triode - Sharp-Cutoff Pentode. I see a higher fain 2 watt champ coming together.
But I have been working with 12volt tubes made for car radios, skip the first min, as the tubes warm up. This is a single 12u7 and 2 12K5 with a valve-caster, Its still in design lend your opinions

[1878]

I know this isn't what most peeps want, but what would be the best way to get the CLEANEST boost from the Valvecaster ?? I'm hoping to use this as a preamp.

[iccaros]

I know this isn't what most peeps want, but what would be the best way to get the CLEANEST boost from the Valvecaster ?? I'm hoping to use this as a preamp.

Since the Gain pot is setting the BIAS of the tube @ 50K it is almost clean.
I would put a 100 or 250 k pot and twist until you like it. Then measure what it is and use the closest resistor value. Same with the second cathode (pin ,  Also some cathode bypass caps may help, a .1uf is a good start, but they can adjust tone

a really good change would be to put a 50K on the cathode with a 6.8uf cap with a 1meg pot connect to the cap. So the cap and pot is in parallel with the 50K. This would be a brightness gain
 

[1878]

Thanks very much

[zambo]

@ Iccaros- Nive man! All that is running off of 12 volts? Sweet! I love little amps! I am starting a new thread for one today. 2 x 12au7 amp running on 9volt adaptor .

@ 1878 -  more voltage ( 18 volts or more) and smaller anode/plate  resistors is a good start as well. I like the cathode biased at typical 1.5 k and 2.8 k values but the adjustable pot is cool too. Voltage = volume and volume = headroom in general. I am not the sharpest tool in the shed but this has been my experience so far. Smart guys feel free to chime in anytime!

[tasos]

@ Iccaros- Nive man! All that is running off of 12 volts? Sweet! I love little amps! I am starting a new thread for one today. 2 x 12au7 amp running on 9volt adaptor .

i want the link!

[zambo]

at your service! http://www.diystompboxes.com/smfforum/index.php?topic=91500.0   

[Ratbones]

I'm having trouble with my build... It's an independent pentode boost and valvecaster in one enclosure.
I've got a separate voltage regulator circuit on vero that I'm trying to use to distribute the different voltage requirements throughout the build.

So, I'm using a 7812 and an LM317 to do this... I know something is wrong, as they get hot very quick and don't produce much voltage at all.
I have it built on my breadboard, and it seems to be working fine. I've cataloged some multimeter readings in hopes of finding the culprit.

The following are the values I've found on my breadboard, with values taken directly from the pedal in bold:
voltages (12v 800ma wall wart)
7812
pin 1: 16.1v 5.11v
pin 2: 0v  .03v
pin 3: 11.55v  2.52v

317
pin 1: .02v  .02v
pin 2: 1.12v  .02v
pin 3: 11.55v  2.5v

Continuity to ground (no voltage in)
7812
pin 1: 1  1
pin 2: ~0  ~0
pin 3: ~1241  ~978

317
pin 1: ~0  ~0
pin 2: ~215  ~0
pin 3: ~1241  ~980

with voltage
7812
pin 1: 1  1
pin 2: ~0  ~0
pin 3: 1  1

317
pin 1: ~0  ~0
pin 2: ~1800  ~0
pin 3: ~1244  1


Obviously, with the input voltage being so low, the 7812 and 317 aren't going to function right, but the v reading straight from the dc jack on the pedal reads about 5.1v... Should this suggest that the problem is before the regulator circuit? Does anyone have any idea where to start troubleshooting this?

[iccaros]

I'm having trouble with my build... It's an independent pentode boost and valvecaster in one enclosure.
I've got a separate voltage regulator circuit on vero that I'm trying to use to distribute the different voltage requirements throughout the build.

So, I'm using a 7812 and an LM317 to do this... I know something is wrong, as they get hot very quick and don't produce much voltage at all.
I have it built on my breadboard, and it seems to be working fine. I've cataloged some multimeter readings in hopes of finding the culprit.

The following are the values I've found on my breadboard, with values taken directly from the pedal in bold:
voltages (12v 800ma wall wart)
7812
pin 1: 16.1v 5.11v
pin 2: 0v  .03v
pin 3: 11.55v  2.52v

317
pin 1: .02v  .02v
pin 2: 1.12v  .02v
pin 3: 11.55v  2.5v

Continuity to ground (no voltage in)
7812
pin 1: 1  1
pin 2: ~0  ~0
pin 3: ~1241  ~978

317
pin 1: ~0  ~0
pin 2: ~215  ~0
pin 3: ~1241  ~980

with voltage
7812
pin 1: 1  1
pin 2: ~0  ~0
pin 3: 1  1

317
pin 1: ~0  ~0
pin 2: ~1800  ~0
pin 3: ~1244  1


Obviously, with the input voltage being so low, the 7812 and 317 aren't going to function right, but the v reading straight from the dc jack on the pedal reads about 5.1v... Should this suggest that the problem is before the regulator circuit? Does anyone have any idea where to start troubleshooting this?

Each need at least 2 volts to operate, you do know they have different pin outs right? These voltages look like mine when I wired a lm317 like a 7812. 
can you draw out how they are connected.

using this pinout 16volts to pin 1, ground on pin 2 and vout on pin 3. should be 16, 0, 12.

for the 317
pin 1 is your adjustment, so you should have a 100 - 250 ohm resister from here to pin 2 and a 5k pot to ground.
Pin 2 is your Vcc or Vout
Pin 3 is voltage in.


I would pull each connection and only connect one regulator at a time, no tubes in.  Remember the heat sink is Vout also so do not have it touch the case or ground.

[Ratbones]

Oh, goodness, the heatsink is vout!?!? That's an awfully silly thing for me to have overlooked... because I have both to-220 cases bolted directly to the enclosure, which is grounded... So if I want to utilize the enclosure for heat wicking, I need to electrically isolate both regulators with something that conducts heat, but not electricity huh?

[tasos]

Oh, goodness, the heatsink is vout!?!? That's an awfully silly thing for me to have overlooked... because I have both to-220 cases bolted directly to the enclosure, which is grounded... So if I want to utilize the enclosure for heat wicking, I need to electrically isolate both regulators with something that conducts heat, but not electricity huh?

there are special rubber isolators...they look like this
http://t1.gstatic.com/images?q=tbn:ANd9GcR4SNS7n72GOSzHbt4VfeHfHPHCnmO30j80SprA-XnZ5al0vxVf&t=1

[Ratbones]

Thanks for the advice!

Just now pulled the screws bolting the regs to the enclosure and slipped a piece of paper between the regulators and aluminum wall...

Hot damn! The thing works!!! And it sings!!! With the pentode boost driving the 12au7 this thing is monstrous!

[iccaros]

Thanks for the advice!

Just now pulled the screws bolting the regs to the enclosure and slipped a piece of paper between the regulators and aluminum wall...

Hot damn! The thing works!!! And it sings!!! With the pentode boost driving the 12au7 this thing is monstrous!

so you have a schamatic for the pentode boost? I am looking at some 5902 submini pentodes. I am most intrested on how you did loading between the pentode and the 12au7 or is its grid resistance good enough.

[Ratbones]

I actually just used Frequency Central's awesome super simple submini pentode boost here: http://www.diystompboxes.com/smfforum/index.php?topic=70524.0

And as far as loading, I'm not sure I follow... This is my first build with tubes, and I'd love to learn more, so let me know if there is a better approach than this!
Here's a diagram:

Guitar input --> true bypass switchable pentaboost --> true bypass switchable valvecaster --> guitar out

So the way I've done it was just what seemed to be a simple way of having either, both or neither engaged at once.

Is there a better way?