Tube boost + overdrive running off a 9 volt battery

[dano12]

Matsumin's Valve Caster, a 12AU7-based booster and light overdrive running at 9 volts. A very fun little circuit that has a minimal parts count and actually generates a good amount of boost and some overdrive.

It appears Matsumin's site has gone 404'd on us, but here is my redrawn schematic with a few cap substitutions.

You can even run this one of a 9 volt battery if you don't mind chewing through batteries Otherwise, and 9 volt adaptor will be fine.

I was particularly surprised as to the effectiveness of the simple tone control...

Enjoy!

<edit: also simple enough to build 90% of the circuit right on the back of a tube socket>

[Marcos - Munky]

Cool!!! Any soundclips? I have only one tube, and don't know what to built with it, so I ask for soundclips to know how it sounds.

[kurtlives]

Nice

Anymore pics of the whole circut?

[Zben3129]

Not that familiar with tubes....

but 12au7....can this be a 12ax7 in this case?

[Zben3129]

After a little more research, it seems that au and ax are correct pin for pin, and the ax has about 7x more gain than au. However, i dont know if it is possible to run the ax in this circuit due to 9vdc?

Also how will the sound be? If its more overdriven, that could be a good thing. I'm just looking to get into tubes a little

[MasaRGR]

It appears Matsumin's site has gone 404'd on us, but here is my redrawn schematic with a few cap substitutions.

He moved his site recently to a new address http://www.matsumin.net/

Thanks for the schematic! Looks like fun

[Papa_lazerous]

this is getting built this weekend!  got all the bits sitting around.  Nice bit of tube mojo to add to the pedal board I think 

[jakenold]

Nice work dano!

I was wondering, what needs to be changed say I want to run this at high voltage?

[dano12]

Cool!!! Any soundclips? I have only one tube, and don't know what to built with it, so I ask for soundclips to know how it sounds.

No clips yet, but it sounds pretty nice. On the overdrive side it is a bit raspy, but I think that could be tamed with some filtering caps.

Anymore pics of the whole circut?

Will try and box it up tonight for pix!

but 12au7....can this be a 12ax7 in this case?

If I remember correctly, the relative gain of the 12A*7 tubes goes something like this:
12AU7   20
12AV7   40
12AY7   50
12AT7   60
12AX7   100

I built it wih the 12AU7/12U7 as specified on the schematic. I tried a 12AT7 and it was too much gain and sounded really bad. I also tried a couple of 12AX7s and it sounded even worse--pretty much unusable. I'm not really very knowledgeable about biasing tubes, but I suspect using an AT7 or AX7 will require resistor value changes.

After a little more research, it seems that au and ax are correct pin for pin, and the ax has about 7x more gain than au. However, i dont know if it is possible to run the ax in this circuit due to 9vdc?

From the little I know, you'll probably want to go up to 12vDC to use the AX7. Here's a diagram for using a 12AX7 as a clipper pair based on info from another thread here:


So 12 volt to heater 4 and heater 5 to ground might work.

He moved his site recently to a new address http://www.matsumin.net/

Thanks very much for the link! I'll update my schemo tonight to add the new URL.

Nice work dano! I was wondering, what needs to be changed say I want to run this at high voltage?

I think this design made the usual compromises to run at low voltage. If you are going to create a tube boost/overdrive and are using high voltage, that are lots of better designs out there.

Thanks to Matsumin for this fun circuit.

[kurtlives]

Could you post a vero layout?

Does the tube light up btw?

[Papa_lazerous]

Could you post a vero layout?

Does the tube light up btw?

The tube will have to light up or it wouldn't conduct....

You could do as the picture above and put most components on the tube socket, or even a nice little tag board layout.  Its really such a simple build it might be a good learning excersize to try and make your own layout and then post it here and ask someone to check it over.  Should only take a short time 

[Zben3129]

I may try this out. Does anyone have a spare 12au7 or socket?

[dano12]

Vero is left as the dreaded "exercise for the reader". Mainly because I suck at vero. But you can build it entirely on the tube socket, pots and jacks.

And yes, it does glow!

[kurtlives]

Could you post a vero layout?

Does the tube light up btw?

The tube will have to light up or it wouldn't conduct....

You could do as the picture above and put most components on the tube socket, or even a nice little tag board layout.  Its really such a simple build it might be a good learning excersize to try and make your own layout and then post it here and ask someone to check it over.  Should only take a short time 

Alright thanks, that is probbly what I will do.

I am new to building frm schems.....Is this negative ground?

How do I wire the 3PDT? WHere is the input and output?

[the_random_hero]

Vero is left as the dreaded "exercise for the reader". Mainly because I suck at vero. But you can build it entirely on the tube socket, pots and jacks.

And yes, it does glow!

Looks awesome, but have you tried running it on 12VDC? I'm sure you would get a lot nicer response out of it

[Aren]

I was just wondering the same thing...
Also, it seems like it could be a fantastic input stage in front of a 386 based practice amp or a speaker simulator. I'll try to get my hands on a 12AU7 and build one of those. Does it require an 8 pin socket? (sorry, completely clueless about tubes...)
Can anyone recommend a good supplier that will ship to Canada?

[kurtlives]

^tubesandmore.com

If I remember correctly, the relative gain of the 12A*7 tubes goes something like this:
12AU7   20
12AV7   40
12AY7   50
12AT7   60
12AX7   100

If I wanted to use something besides a 12AU7 would I need to do any mods?

[dano12]

Regarding the 386 amp, that's the route I'm taking with my wired tube socket thing. Trying to fit it in a small plastic case.

For the questions about using a tube other than the 12AU7, as said earlier, they are higher gain and won't work nicely unless you modify the circuit, I don't know how to do that part.

tubesandmore.com has the tube and sockets, it is the standard 9-pin tube socket you would use for guitar amp preamp sections.

Here is a rough *unverified* wiring diagram for anyone who wants to try it.

[GibsonGM]

There are a few other circuits like this...the MarshaValve is one which feeds a JFET, I believe.  They're good ones to get started with tube work )
I think if you tried to modify the circuit for 12AX7 use, you might end up in a no-win situation....they're really supposed to run on 100+volts, and at 9v, that's just asking a lot!  But it's worth a try if you have something sitting on the breadboard.   There are also low-voltage tubes that would work nicely for a higher-gain setting.
Expect to blow thru batteries (use wall wart), the heaters draw a LOT of current!

[letsgocoyote]

after building 32154 different electra and bazz fuss variations, i think this may end up being the first new kind of project to tackle!