Guitar tube overdrive schematic

[pboser]

Hi all,
I've gotten the idea to make a tube overdrive for my guitar playing 11-year-old son.  (I figure it will please him for it to sound nasty without disturbing the whole house!)  Any suggestions on schematics?  I don't know that it needs to be in pedal format - I could make it in a box to go on/next to his amp instead, so it can be my usual construction style - too big, messy, ugly.  I guess I'll have to make it safe, though!
Thanks,
Pete

 

[Paul Joppa]

What is the signal level? Can you tap into the amp, or are you looking for something between guitar and amp?

I'm thinking Quickie or a variant - safe battery power, you know...

 

[pboser]

Guess I wasn't too clear - I envisioned something between the guitar and amp.  Hmmm, quickie may be an idea - maybe putting the channels in series to get more overload.

 

[Doc B]

Matchless Hotbox. Badcat copied it. It's a good one. I built a clone without the tone controls. Compared to a Badcat it was bass light, but distorts like a mother.

http://www.freeinfosociety.com/electronics/schemview.php?id=904

Or...if you just want a dirty blues sound and not a metal-ly hard clipped sound and your amp is low powered but has plenty of gain just use a 25W speaker L-pad on your speaker as a brake. That's what I do with my SE 6V6 amp that has two stages of 12AX7. Turn the L-pad down and then crank the amp volume to get the desired level of distortion. Sounds really bluesey.

 

[JC]

Now, you're thinking!  Of the tubed distortion effects I've seen, many have used the 12AX7 to just add a high gain stage in front of the input to the amp.  Sometimes with some passive EQ to boost high freqs more.

You won't need much in the way of current for the B+ with this approach.  Two small 120V:12V tranny's would do it.  120VAC to the 120VAC primary of tranny one; 12VAC from secondary of tranny one to 12VAC secondary of tranny two; at this junction, take 12VAC to run the filament, from the primary of tranny 2, you will get 120VAC which you can rectify and filter for B+.  Use a voltage doubler if you want a bunch.

You get the transformer isolation this way, without hunting up a "special" transformer.

Alternatively, the little transformer from a Foreplay 2 would also do nicely for a little one tube circuit of this variety.

If I run across a schematic, I will try to post it in this thread; the input stage of most 60s Fenders could also give you some ideas.

 

[pboser]

You guys are reading my mind!

Doc - thanks.  That's the one I found in my internet search that seemed most appropriate for a diy interpretation, so I'm glad to have the confirmation that it would be worthwhile.  And the Lpad idea sounds good too - I didn't think of that idea!  It's a little SE tube amp I got cheap a couple of years ago (Elektar Tube 10) - I think I have a 6L6 in there now.  You've got me thinking - maybe I'll try one of those transformer volume controls they sell for wall mounting (for in wall speakers, etc.)

JC - you're thinking just what I was!  I was thinking 12a*7, considering the two 120:12V tranny trick, and also remembered I have a little transformer just like the one used in the original foreplay.  I'll take a look at the Fender schematics, too.

Thanks for the help - this is a great community!  My next question will probably be about suggestions for a DIY lefty guitar project (my son is a lefty and is outgrowing his 3/4 size Johnson Strat copy).

 

[Doc B]

My next question will probably be about suggestions for a DIY lefty guitar project

Unfortunately I don't think that outfits like Saga make leftys. I built a Tele style Saga from Dan Torres a few years ago, and for the money it's a very neat starter guitar. But if the budget allows, build a Partscaster from parts you pick yourself. There are all sorts of cool parts around these days for making your own Tele or Strat copy, and all sorts of instruction on the web for assembling them. Top of the heap for bodies and necks is probably Warmoth. They are homeys, out of Puyallup, WA (and they are running a 20% off sale right now).

I have a maple and ebony Warmoth neck with gold toned frets on my Tele style Partscaster and it was not super cheap but it is friggin' beautiful. I bought a no-name spalted maple over two piece mahogany body off of ebay rather than buy a Warmoth one to save $100 and I regret it, because I had to deal with the steeper part of learning curve of the guy who made it - the bridge has to sit about 1/8" closer to the neck than it should and intonation is a bit of a challenge with the saddles I used. And the guy used some crappy stuff to fill the gouges he made with his router on the back and I had to finish it with dark walnut tinted French polish. And on top of that the seam between the two pieces of mahogany has a hairline in it. I will probably replace the body with one from Warmoth at some point. But it sounds pretty good and the educational experience was one of my better ones.

 

[JC]

Evidently, Doc and I were on the same page, too, as I think he was posting that schematic while I was writing my reply!

For solid-state kits, this guy has some pretty cool stuff:

http://www.bigtonemusic.com/CloneMainPage.html

I've assembled a few for friends, otherwise I have no affiliation with them.

I'm curious what Doc used for a power transformer when he built that Matchless clone...

 

[Tim G.]

I will throw another angle at this one.  I put together a little circuit based on the Powerman and Firefly amps out there that use subminiture 6021 tubes.  It has some nice overdrive sound to it, a cascoded gain stage a la Firefly, and can drive a 2x10 cabinet to some fairly acceptible volume levels.  Lots of gain without blowing out the windows, very neighbor friendly!

Just another thought...