Author Topic: so I want to build a vacuum tube pedal  (Read 2176 times)

GhostofJohnToad

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so I want to build a vacuum tube pedal
« on: September 14, 2012, 09:02:24 AM »
Just acquired about 100 or so old NOS tubes of varying flavors including 12ax7 and other commons.  I really would like to get my feet wet in the world of tubes.  Well figuratively at least.  I'd love to build a OD type of pedal.  I would run strictly off mains no batteries, size is not concern.  Are there any build able projects out there for something like this?  Something relatively low component count to get an idea of how this all works.

JakeFuzz

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Re: so I want to build a vacuum tube pedal
« Reply #1 on: September 14, 2012, 09:19:07 AM »
I am building my second full voltage tube overdrive right now. Let me say that it is not easy and will take more time and money to build than a regular pedal. I don't think there is a canned project for a full plate voltage tube overdrive but I have a few places to get started.

Look into Weber's step up transformer. It goes from a 12VAC 1A wall wart to about 260VAC 40mA. Which when rectified and running 2 12AX7's gives me about 380VDC. This IMO is the best way to get to your plate voltage if you are running 1-3 tubes.

Weber's parts are super cheap. This includes filter caps  ;)

Using a cap can will save you space but they are more expensive.

I would find an amp you really like and re-make the pre-amp. This is the easiest starting point. Nothing really needs to be changed. I add an extra 12AX7 gain stage at the end to "approximate" the phase inverter.

You will need access to large drill bits for the tube sockets and the cap can (if you are using one).

Tag board is much cleaner and easier to wire directly to the tube sockets than PTP. PTP is a huge mess but saves a ton of space.

Get shielded wire for the input and low voltage lines. This had me stumped for a month.

Get a large enclosure. My layouts tend to be much larger than the typical SS pedals to include things like rectifiers and bolting on the transformer.

Hope that helps if you decide to take up the challenge. Check out my build report on a Marshall 1959 pre here:

http://www.madbeanpedals.com/forum/index.php?topic=4670.0


I am currently building switchable channel Vox AC30 with an EF86/12AX& input with tagboard and it is huge. So far I am about a month in and getting ready to wire although I have been taking my own sweet time  ;D good luck!

 

dbharris

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Re: so I want to build a vacuum tube pedal
« Reply #2 on: September 14, 2012, 10:23:59 AM »
I think these projects are always really cool.  But I have to wonder why not just build them into rack mounts or a separate chassis, so you could have several different pre-amps available to plug into a stand alone power amp?  It seems more cost effective to me.  Anyways, good luck I would love to see the results of what you decide to build.

-Dan

nzCdog

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Re: so I want to build a vacuum tube pedal
« Reply #3 on: September 14, 2012, 05:14:27 PM »
I'm slowly working on a pcb for a tube OD after some boobtube tweakerising and reading... I'll post it once I get done :)