Tube boost + overdrive running off a 9 volt battery

[BlueJay]

Hi all,

I just started looking at this thread a couple days ago, and I found this diagram.  Is this an proper/accurate diagram for the standard valvemaster with a stomp switch, etc?  (You know, without any mods?)  Thanks so much!

Yea, that layout was the one I used and it works beautifully.  Almost have my first build completed, except I need to replace the stomp-switch since I borrowed this one from another pedal and it's got issues...but otherwise the pedal works great.  Had some hum from a dirty power supply initally, but made a separate in-line voltage regulator/filter following earlier instructions (on page 18 of this thread).  After I replace the switch with a more heavy-duty one, I can then trade it to my coworker who wanted this...and start on the next build.  I am thinking of going with a two-stage pedal next, feeding one Valvy into another in one chassis like others on this site have done (also including the regulator/filter internally). 

As for what I named it? I just picked a name that was just too appropriate for a 12AU7 running cold
Here are some pics:

[zambo]

Ok, Probably been said on here but....I lowered the input cap to .002 uf on my first valvecaster and ran it into a second one stock. Holy cool tube crunch. If you are looking for more gain...quit...just buy another tube and socket and build a second one. Put in the dpdt mini toggle and put stock input cap on one side and .002 uf on the other. You will not be disapointed. I left them in different boxes because I use one all the time for my "clean" tone and the other one is an insert on my vox tone lab. It turns on and off as I switch patches giving me distortion or not etc. Just though I would share. Both are running at 9v from a onespot wallwart.

[stallik]

Hi, I've been watching for quite some time, got round to building my first Valvecater over the festive season and though I'd share my findings..

My build is the standard single valve circuit running a Phillips (mil) 12 AU7. The only mod I made was to incorporate a simple audio relay in order to switch the on/off LED as I didn't have the correct footswitch. This made no difference to the sound. I run it at 10.6 volts

I tested it on 2 amps:

Mesa Boogie DC5 - On the clean channel there is a lot of extra gain and some overdrive but nothing to write home about. my Vox Valvetone pedal does a better job. On the dirty channel, there is a little extra drive but really this amp does not like this pedal too much.

70's Roost Sessionmaster. (50w) OMG!!! Running the amp at 8 pre & whatever the family will stand on the master, with the Valvetone flat out on all controls, there is a HUGE boost in volume. More importantly, the overdrive is wonderful, wonderful, wonderful. The amazing thing is the sensitivity to pick attack. Played gently - round smooth clean tones. dig in and the overdrive is simple amazing. no need to adjust the guitar volume (though it works as you would expect) just do everything with your hands. I'm obviously overdriving the preamp which is in turn overdriving the power amp so ? cascading gain? whatever -I love it. Compared to the Vox pedal which i've always liked, there is less overdrive but the sound is just so much more open

It also responds very well to the vox pedal being placed before it - boosting the gain further but not really changing the sounds so now I'll put a 2 valve version together. I'm keeping the current pedal intact as I don't want to change it and building from scratch will allow me to redesign the box as the current one suffers from bad placement of the in/out sockets when on a pedalboard. The cables look messy

Final point is re the AU7 / AX7 thing. I tried it with a newish AX7 and as expected, the sound was not great however, an old Brimar AX7 sounds very similar to the AU7 when used with the Roost. It didn't work well with the boogie.

Here's a pic of the finished article - no innards - started off neat then got worse and worse - think spaghetti and goliath welding and you'll be about there.
Sorry about the logo - my workmate's idea of a bit of fun but I've left it on

A HUGE thankyou to everone who has had a hand in this - I've really enjoyed building this thing
Regards
Kevin

[Renegadrian]

I LIKE THE WAY IT LOOKS!!! 

[Ripthorn]

Cool looking box, just don't try to sell it.

[ca cat]

One question - is it possible to run valvecaster or similar 12au7 tube based overdrive on 18V? are there any necesary modifications? I am asking because I don't want to stick a regulator in the enclousure and I already have an 18V power supply.

[earthtonesaudio]

The plate voltage can go way beyond +18V safely, but NEVER exceed the heater voltage rating.  For a 12au7 it's 12.6V in series, or 6.3V in parallel.

[dukie]

Hi guys ive been trying to build a tube stompbox for a week and none of them seems to work.  i've tried to build GGG Tube Driver and failed, switch to Marsha Valve Tube also failed, and then yesterday i build Valvecaster..also failed. im using NOS Hitachi 12ax7 from the 80's. i know this tube isn't sound good in valvecaster setup, but i build it just to test the tube and valvecaster had the simplest schematic. i'm sure every cables and connection goes where it should but still the circuit produce no sound at all. im using 12VDC 1200ma power adapter by the way.

So whats happened with my setup?is it the tube malfunctioning?ive read few articles about how to powering the tube heater and a little confused because some mentioned that the 12ax7 work at best when the heaters are wired parallel at 6.3v instead of 12.6v series, while other articles and talk in this forum mentioned  no problems wired it either way?im wiring my tube in series with  pin 4 goes to 12vdc and pin 5 to ground.

If i want to wired the heater in parallel 6.3v do i need to create a  R/C voltage divider?and if i do need the divider whats the value for the divider resistor and capacitor?thanks!

cheers..

[ca cat]

So I yust have to use a proppriete resistor values to ensure those voltages to heaters and everything is going ok? How about the power? 1/4 W resistors are propably not acceptable? i shoulg go for higher ratings?

[Renegadrian]

ok jokin...as for the tube, I tried an AX7 and it sounded really bad, but the sound came out...It's strange you got no sound at all...Does the tube light up!? Maybe you count the pins in the wrong direction?! (I know it's a stupid point, but it happens, sometimes the easiest things give trouble...) - Check your tube pins and see if the heathers give some light...

And yeah the tube should work fine with the adapter you have and the wiring you wrote...

[earthtonesaudio]

The first time I wired up a tube (a few weeks ago!) I got the pinout upside-down... and I have been doing this long enough that I should know better!  Double check everything, and make sure the connections really are what you think they are.

[dukie]

Hi i double check it and i think im wiring it the way it should, because i can see clearly through the glass that the 4th & 5th pin are the heater and the 9th pin is the heater center tap?and no the heaters are not light up, but the tube glass get warmer.

And to test the circuit (the marsha valve) i replaced the tube with two 2sk30 JFET,change the first stage plate resistor for a 100k trim, tweak the trimmer a little and there is a sound!now im really, really, reallly confused  what the tube is going on here?
I must have done something wrong with the tube but i,..i, i just.. dang my head hurts!

Now i summon the Tube God to come down and shed some light on this!


...meanwhile i think i'll tweak the 2sk30 "Marsha FET" instead 


cheers!

[anchovie]

I've found that preamp tubes glow way less when the heaters are powered by DC. I've got a box of random tubes that I've been messing around with on the breadboard and with some of them I can only see a pair of tiny orange dots at the top if I turn the lights out! I know they all work from testing them in an amp head (AC heaters). The glass getting warm is the sign that you need, I guess tubes aren't designed to always give an impressive display!

I've also found that not all 12AX7s guarantee an output with the 12V plate voltage. I've got a Fender tube that gives no output, JJs and EH that give a very weak output and the strongest comes from a couple of Chinese no-name tubes (one pulled from an old Marshall Valvestate). They still sound really thin compared to my Philips 12AU7, which gives the highest output of all.

[frequencycentral]

If i want to wired the heater in parallel 6.3v do i need to create a  R/C voltage divider?and if i do need the divider whats the value for the divider resistor and capacitor?thanks!

A voltage divider won't work. Trust me on this. Running the heater at 6.3v is a little wasteful as it will consume twice as much power as running it at 12v (300m vs 150ma). Bit if you really want to run it at 6.3v, connect pins 4 and 5 to ground and feed 6.3v into pin 9. You can derive 6.3v (or 6v, which is close enough) in a number of ways:

- use a 7806 voltage regulator
- use a 7805 voltage regulator with two 1n4148 between the 7805's pin 2 and ground
- use a LM317 and associated components, as in the Subcaster
- use a voltage drop resistor in series with the heater. This effectively forms a voltage divider, as the heater is a resistor itself. The ohmage/wattage of the voltage drop resistor will depend in what power supply you plan to use with it. An 18 ohm 2 watt resistor for a 12 volt supply, or a 10 ohm 1 watt resistor for a 9 volt supply.

[Renegadrian]

I've found that preamp tubes glow way less when the heaters are powered by DC. I've got a box of random tubes that I've been messing around with on the breadboard and with some of them I can only see a pair of tiny orange dots at the top if I turn the lights out! I know they all work from testing them in an amp head (AC heaters). The glass getting warm is the sign that you need, I guess tubes aren't designed to always give an impressive display!

I've also found that not all 12AX7s guarantee an output with the 12V plate voltage. I've got a Fender tube that gives no output, JJs and EH that give a very weak output and the strongest comes from a couple of Chinese no-name tubes (one pulled from an old Marshall Valvestate). They still sound really thin compared to my Philips 12AU7, which gives the highest output of all.

Yeah tubes aren't light bulbs! but yeah they should display some kind of heating, as they are heaters THAT'S THEIR JOB!!! 

[dukie]

I've found that preamp tubes glow way less when the heaters are powered by DC. I've got a box of random tubes that I've been messing around with on the breadboard and with some of them I can only see a pair of tiny orange dots at the top if I turn the lights out! I know they all work from testing them in an amp head (AC heaters). The glass getting warm is the sign that you need, I guess tubes aren't designed to always give an impressive display!

Hi Anchovie i think you had unfinished sentence here..so what do i need, more voltage?if it is then what voltage that is adequate to heat this tube?18v,24v?because if 18v or 24v is enough then i'll build a voltage doubler circuit to heat it. Anyway when i switch the effect on with the tube running on 12v the other effect that use the same daisy chains power dimmed for a about 30 second or so before back to normal but their leds are not as bright as before the valvecaster is on.

If i want to wired the heater in parallel 6.3v do i need to create a  R/C voltage divider?and if i do need the divider whats the value for the divider resistor and capacitor?thanks!

A voltage divider won't work. Trust me on this. Running the heater at 6.3v is a little wasteful as it will consume twice as much power as running it at 12v (300m vs 150ma). Bit if you really want to run it at 6.3v, connect pins 4 and 5 to ground and feed 6.3v into pin 9. You can derive 6.3v (or 6v, which is close enough) in a number of ways:

- use a 7806 voltage regulator
- use a 7805 voltage regulator with two 1n4148 between the 7805's pin 2 and ground
- use a LM317 and associated components, as in the Subcaster
- use a voltage drop resistor in series with the heater. This effectively forms a voltage divider, as the heater is a resistor itself. The ohmage/wattage of the voltage drop resistor will depend in what power supply you plan to use with it. An 18 ohm 2 watt resistor for a 12 volt supply, or a 10 ohm 1 watt resistor for a 9 volt supply.

Yeah the 6v voltage divider is not working, i just tried it and the tube is not even warm.tried the 9 volt supply with 10 Ohm 1 watt trick too but the tube is dead cold.


cheers!

[anchovie]

Hi dukie, I meant that warm glass is the sign that you need to confirm that the heaters are working! Don't go over 12.6V for 12A*7 heaters in series, that's what they're designed to use and too much will kill them.

The LEDs dimming on your other effects in the daisy chain suggests that the current draw is more than your PSU can put out. What are its specs?

[dukie]

Hi dukie, I meant that warm glass is the sign that you need to confirm that the heaters are working! Don't go over 12.6V for 12A*7 heaters in series, that's what they're designed to use and too much will kill them.

The LEDs dimming on your other effects in the daisy chain suggests that the current draw is more than your PSU can put out. What are its specs?

Hi Anchovie, my PSU is an unregulated 12vdc 1200ma (14.5Va Max) with variable voltage (1.5v-12v) and polarity selector that i modified with Dano's Hum Filter circuit.
What PSU spec that is needed to properly heat 12ax7 tubes?I mean the valvecaster can run on 9v DC and aside form 12ax7 bad sound, some people here reported no problem using it?

You said earlier that not all 12ax7 can output sound, so is it possible that i got this kind of tubes?
Maybe i should buy 12Au7 and throw this "no output 12ax7 tubes" out..
But im still curious..


Cheers!

[earthtonesaudio]

Running the heater at 6.3v is a little wasteful as it will consume twice as much power as running it at 12v (300m vs 150ma).

Power dissipation of the heaters is determined by P=IV, so
P=(6.3V)(0.300A)=1.89W
or
P=(12.6V)(0.150A)=1.89W


But this is assuming you already have either a 12.6V supply, or a 6.3V supply.  Dropping a 12V supply down to 6V, with a regulator, resistor, diodes, or anything, will consume additional power.

[ca cat]

If i want to wired the heater in parallel 6.3v do i need to create a  R/C voltage divider?and if i do need the divider whats the value for the divider resistor and capacitor?thanks!

A voltage divider won't work. Trust me on this. Running the heater at 6.3v is a little wasteful as it will consume twice as much power as running it at 12v (300m vs 150ma). Bit if you really want to run it at 6.3v, connect pins 4 and 5 to ground and feed 6.3v into pin 9. You can derive 6.3v (or 6v, which is close enough) in a number of ways:

- use a 7806 voltage regulator
- use a 7805 voltage regulator with two 1n4148 between the 7805's pin 2 and ground
- use a LM317 and associated components, as in the Subcaster
- use a voltage drop resistor in series with the heater. This effectively forms a voltage divider, as the heater is a resistor itself. The ohmage/wattage of the voltage drop resistor will depend in what power supply you plan to use with it. An 18 ohm 2 watt resistor for a 12 volt supply, or a 10 ohm 1 watt resistor for a 9 volt supply.

Hey, frequencycentral, will voltage divider work for valvecaster / twincaster type OD pedal, that will run on 18V? The divider is for heaters in series... I want to do this because I don't have any 7806 regulators...