Ultra Class A Superdrive Power Amp: Build report

[dano12]

I happened across Tim Escobedo's "Ultra Class A Superdrive Power Amp/Signature Series" (that's a fun name) and thought it would be fun to build it. Very few parts so I worked to fit it into the smallest enclosure I could muster:



So far, so good. Even the battery fits in there.

I also wanted to mount the transformer and transistor on the top of the case to make it look like a little amp. After a bit of playing, I recalled Behringer's fantastic valve enhancement techonology wherein they place a small amber led behind the 12AX7 starved-plate tubes to give the illusion of a glowing valve.

Aha! What if I mount the transistor in a hollowed out 12A*7 tube and stick a LED behind it? Pointless gimmickry or ground-breaking sonic advancement--you be the judge.

Ok enough with the singular wit and banter. The completed amp:



And just to prove that the tube actually does glow:



It is really not very loud. In fact, I've had stomach rumblings that have higher output than this thing. But, put a booster or fuzz in front of it and you'll have loads of fun.

Key lesson learned in this build: Cutting the bottoms off tubes and cleaning them out....well, expect a lot of do-overs. I went through a gross of burned out tubes before getting one cut without it shattering.

[KerryF]

awsome looking.  do you have a link to the layout or schematic.  it may be cool to mount of of these things under a plexiglass cover.  I havent actually worked with tubes or transformers yet.  This looks easy, but would you recommend it as a first tube and transformer build?

[dano12]

awsome looking.  do you have a link to the layout or schematic.  it may be cool to mount of of these things under a plexiglass cover.  I havent actually worked with tubes or transformers yet.  This looks easy, but would you recommend it as a first tube and transformer build?

The schematic is available at http://www.geocities.com/tpe123/folkurban/fuzz/snippets.html.

Note that this isn't actually a tube circuit. It uses a basic silicon transistor and a small output transformer. I stuck the transistor in a tube case to be silly.

I would guess it puts out just a bit over .0000001 watts So not terribly useful, but fun nonetheless.

By "first tube and transformer build" I'm guessing you mean a small tube amp?  If that's the case, here are some possible choices:

- Build a real tube amp from a kit. I've built the Guytronix Ardmore and am working on the Gilmore Jr. Some folks get a bit nervous about the high voltages, but if you take your time and treat the live circuit with respect and caution, its pretty safe and easy. I would *highly* recommend this to anyone who has done a few pedals--building an all tube amp is just a cool thing to try.

- Build a hybrid. There are very few starved-plate (i.e. you can get by with a 12vDC adaptor for your tubes, no high voltages) amp designs. A more practical approach may be to consider a tube-preamp into a LM386 power amp (like the Ruby).

- Forget the power amp and just start mucking around with tubes. There are a couple of very interesting tube pedal builds right here on the forum.

[Seljer]

I stared at that thing for 2 minutes before I realised what was going on 

[KerryF]

haha yea after i posted im like, wait a second... thats not a tube, theres a transistor and led in there so theres no way thats a tube circuit.  haha.  looks cool though.

[MartyMart]

SUPERB !!!   

MM

[Satch12879]

You know what would have been really hot? If you could have figured out a way to use a LED + light pipe to make the pseudo-tube where you mounted the transistor glow.

[dano12]

You know what would have been really hot? If you could have figured out a way to use a LED + light pipe to make the pseudo-tube where you mounted the transistor glow.

Interesting idea. I actually have some light-pipes from and old project....

[Mark Hammer]

Remember that old ad from A/DA about how "real amps glow in the dark"?