Tube boost + overdrive running off a 9 volt battery

[PaulBass]

I put a 12AU7 in my Behringer MIC100 and noticed it sounded less harsh than than the 12AX7. The specs of the AC adapter says the output is 9V 300ma AC (It's actually 12V AC measured with a MM). So can the Valvecaster run on AC voltage instead of DC? Or does it require an entire dofferent circuit?

[MaxPower]

If you look at the insides of the MIC100 I think you'll find diodes/bridge rectifier near the power supply jack.

This is a bit obsolete but I'll post it anyway for anyone who might be interested:
In the July 2002 issue of Poptronics there was a project called "The Tubester" which was a plate-starved tube preamp. It used a 741 op-amp at the input to boost the guitar signal which was then fed to a 6F5 tube which could be driven to distortion/overdrive (whatever), and then went to another 741 set to unity gain (for impedance matching purposes). It used two 9 Volt batteries for the circuit and 4 C batteries for the heater. The circuit is similar to the one at Valve Wizard's (?)  website.

I searched for the article online; the only place I found it required a subscription to see it (assuming they actually had it). If anyone is interested maybe your local library has it archived (university libraries might be a better choice).

[rutabaga bob]

Okay, folks...I'm back, after first experiment with the 6J6a.  Set it up like a 'Valvemaster'...used .022 input cap, .04 coupling cap, 100k log gain pot, and a 51 ohm cathode rsistor (taken from the datasheet), bypassed with a 10uF cap.  Ran 47k plate resistors, but with 79 volts from Adriano's 40106 voltage multiplier.  Plugged it into a Kalamazoo Model 1 and tried various gain settings.  It definitely works, but will need tweaking - raunchy at max gain, and somewhat bass-y...not bad for a first run, though.  As always, any suggestions are appreciated.  Larry

[rutabaga bob]

After several tweaks, here's what I came up with, if anyone wants to give it a go:
47k plates
.01 input cap
470k to ground
.01 coupling cap
47k grid-stopper
.04 output cap
grounded cathode
500k gain pot
100k volume

[jorgeibanez]

construi o meu e funcionou legal. gostaria de saber se alguem tem um esquema de um pre com 12au7 pra 12 volts com som limpo ? obrigado

[psychedelicfish]

Desculpe se isso não faz sentido, eu não falo português, mas eu usei o Google Translate  . De qualquer forma, há um tempo atrás eu estava brincando com um circuito que dá um som limpo com um tubo 12AT7 em 24V, mas deve funcionar da mesma com uma 12AU7 em 12V. Aqui está o esquema:

Você pode deixar o resistor 66r e ligar os aquecedores em frente a fonte de alimentação de 12V. Se você só quer um som limpo, em seguida, deixar de fora a chave eo capacitor.

[JRM]

Well as of right now this is were my Valve-Master Project Stands...

Below is not verified...



Ok things to note...
1. C4/C5 can be left off as it sounds fine without them

2. R4/R5 sound good anywhere from 1k to 0 (they effect gain and volume greatly)

3. R2/R3 sound good anywhere from 1k to 100k (they effect and volume greatly)

4. D1/C6/C7/R6 Form very basic power filtering plus reverse polarity protection. http://www.beavisaudio.com/projects/Huminator/index.htm

5. I leave an extra space after the hook up cables in purpose sp you can drill through the boad there and run the wire through so that the solder joint is never stressed.

6. The Tone Shaper is this http://www.muzique.com/lab/swtc.htm

7. This may come in handy for getting R2/R3/R4/R5/C4/C5 tuned to the correct values... http://www.ampbooks.com/home/amplifier-calculators/cathode-capacitor/
(C4/C5 are each one CK) (R2/R3 are each one RL) (R4/R5 are each one RK)

8. C1/C2 Higher value like 22nF also works but the bass can get out of hand fast...

I hope this helps... the real battle with this pedal will be tuning the amount of volume increase while still preserving the quality of the sound... will have more for you guys later.

I know you've stated that the layout wasn't verified but I've found one issue: there's a cut under R3 that makes the circuit wrong. Otherwise it's ok. I've readyour post as I'm fine tuning my Valvemaster (I've finaly made an enclosure for it) and I'm looking to some succesfull set points. I might change the tone section as I've found it pretty useless.
I've used the standard Valvemaster layout, fed by a stabilized 12,6V power supply (home and custom made). I've changed R2 and R3 by 100k trims and R4 and R5 by 10k trims. Sounded better on breadboard than now (I'll have to double check). Current values are 47k and 510R respectivley for R2/R3 and R4/R5 but I'm not happy with the action of the gain pot: first I get hum/noise, then a cool boost (with no hum/noise) and when I try to get in overdrive region it hums again and doesn't look to have enough gain. On the other hand it can get loud (with volume pot quite high) enough to overdrive my amp if I push it's gain a little bit.

[Kesh]

Desculpe se isso não faz sentido, eu não falo português, mas eu usei o Google Translate  . De qualquer forma, há um tempo atrás eu estava brincando com um circuito que dá um som limpo com um tubo 12AT7 em 24V, mas deve funcionar da mesma com uma 12AU7 em 12V. Aqui está o esquema:

Você pode deixar o resistor 66r e ligar os aquecedores em frente a fonte de alimentação de 12V. Se você só quer um som limpo, em seguida, deixar de fora a chave eo capacitor.

No idea what you are saying, but any reason for using an SRPP?

[psychedelicfish]

I was playing around on my breadboard and decided to try it out. It sounded good so I posted a schematic

[presaa]

I built a twincaster and it sounds great for about 5 minutes then it gets splatty. I checked voltages and the only one that's not right is pin 3 of the second tube. I'm getting 3volts on it for some reason.

[kurtlives]

I built a twincaster and it sounds great for about 5 minutes then it gets splatty. I checked voltages and the only one that's not right is pin 3 of the second tube. I'm getting 3volts on it for some reason.

Make sure you got the resistors going from the tubes grid's to ground (pins 2 and 7).

[JRM]

I still have problems with my Valvemaster.
I've changed the tone section to a super simple solution, though very effective, wiring the cap between the pot wiper and the ground, meaning that I have a variable frequency low pass filter (the simplest variation of Mark Hammer's Stupidly Wonderful Tone Control, with R1=0). It's quite ok rolling off the highs.
No matter the changes I do in the trimpots, I can't get rid of hum. Tweaking the tripots (V+ to anode and cathode to ground resistances) definately changes the gain of the pedal but it doesn't heal the hum problem. Not happy also with the gain pot response but have no ideas about hou to solve it.
Could it be a problem with the tube? I'll change it and test it.

[presaa]

Thanks Kurt I'll check that

[timd]

If I omit the tone pot, do I also omit C4 on the original schematic? That is just the cap that is part of the r/c tonestack right?

[psychedelicfish]

If I omit the tone pot, do I also omit C4 on the original schematic? That is just the cap that is part of the r/c tonestack right?

yes

[timd]

Thanks!

[toplak666]

Said I'd post a pic of the finished thing a while ago but then I forgot... ^^' And now I remembered! Friend still hasn't gotten arround to polishing it but other than that I think it looks pretty good. Working on a modified triple valvemaster circuit at the moment. Will keep you posted if I find anything worth mentioning.

[vigilante397]

I know there's a million posts on here, so I don't know how actively people still, look, but I need some help. I'm following the original Matsumin schematic for the valve caster with no switch or LED (I tried it with those modifications and it didn't work  ).

When I plug it in and power it on the tube lights up but I don't get any signal. When I turn up the amp volume I get a rather pleasant feedback sound, but the guitar doesn't affect the sound at all. Any thoughts/troubleshooting tips? I'll try to get some pictures posted later so you can get a better look at what I may have done wrong.

[tc53]

I could tell more with pictures, but check that you have no solder shorts and check voltages on pins 1 & 6. They should be between 6 and 9 volts, with 6 a bit higher than 1.

happy tubes to you!

[Burdin]

Hi,
I build this effect and it seem that it works, but I have one problem and I would be realy grateful if somone can explain to me, what's goin on.
I'm using this effect for a bass, but I wouldn't say that's the issue. Chain is following: pasive bass -> valvecaster -> lexicon alpha (external PC sound card) -> directly to amplifier (it's not going over the pc), this chain is ok, no problem, everything works fine, but when I use normal amp, in my case it's Trace Elliot GP12 smx here comes problem. Chain is similar, bass-> valvecaster - > trace -> cab, there's almost no change in sound when I turn with any of pots, doesn't react to volume, gain, tone ... nothing, and the result sound it's not plesant, there's feedback from a cab, but when I connect effect to effect loop, it works as it should, why?
I would like to overdrive sound before preamp, it's better for me. So, now I use effect loop, but it's not good.  Thank for all answers.