Joe Davisson's new Guitar amp

[joecool85]

Thought I would try it this way, since the transformers are from RS, and only $10 a piece. Also, I think it will bump the output some.

Let me know how it works out.  I've thought about using the same setup with those transformers for a LM3886 project.

[Joe]

Put another pic up of the board/heatsink. Just a layout, will solder the parts this weekend. You can see the protection circuit on the right-hand side.

http://www.diystompboxes.com/analogalchemy/sch/dc_wip.html

[joecool85]

Put another pic up of the board/heatsink. Just a layout, will solder the parts this weekend. You can see the protection circuit on the right-hand side.

http://www.diystompboxes.com/analogalchemy/sch/dc_wip.html

That looks great!  Good job, Joe!

[Joe]

I tested the amp today, although it's sorta tacked together at the moment and not at all pretty. I designed it to be compatible with a pedal circuit, so that's what I used for a preamp. Sounded pretty good distorted, but I still need to run a clean tone and see how that works out.

My NPN and PNP transistors were mismatched, so there was about 2V offset. I adjusted one of the emitter resistors on the first stage to compensate, but I really think all complementary pairs need to be matched. (Not all the transistors, just each NPN/PNP pair.)

The power supply uses the two radio shack transformers, two bridge rectifiers wired in series, and two 4700uF filter caps & some bleeder resistors.

Edit: Tested the short circuit protection with a screwdriver across the speaker leads, and it works good. Did a little more play testing and am happy with the sound. So it's a matter of wiring some things nicer and tweaking the bias a little.

[joecool85]

I tested the amp today, although it's sorta tacked together at the moment and not at all pretty. I designed it to be compatible with a pedal circuit, so that's what I used for a preamp. Sounded pretty good distorted, but I still need to run a clean tone and see how that works out.

My NPN and PNP transistors were mismatched, so there was about 2V offset. I adjusted one of the emitter resistors on the first stage to compensate, but I really think all complementary pairs need to be matched. (Not all the transistors, just each NPN/PNP pair.)

The power supply uses the two radio shack transformers, two bridge rectifiers wired in series, and two 4700uF filter caps & some bleeder resistors.

Edit: Tested the short circuit protection with a screwdriver across the speaker leads, and it works good. Did a little more play testing and am happy with the sound. So it's a matter of wiring some things nicer and tweaking the bias a little.

You should enter this one in the contest!  Also, once you get it a little more finished I would love to hear a clip or two.

[Brymus]

Radio Shack is gonna wonder why they are selling so many of those trannys soon  :tu:
Again excellent Joe- I imagine alot people will try this one.

[Joe]

Updated the schematic to match my build, and added a few notes.
http://www.diystompboxes.com/analogalchemy/sch/diodepwr.html

[Joe]

Another update:
http://www.diystompboxes.com/analogalchemy/sch/diodepwr.html
(might have to reload the image)

Did some better parts selection, otherwise not too much different.

[Brymus]

Hi Joe really cool.
Are those all Radio Shack components?
That would make this really easy for anyone to build.

[Joe]

I tried to design a "radio-shack" amp before. It's almost possible, but would be more expensive than jusr ordering better stuff.

[joecool85]

I tried to design a "radio-shack" amp before. It's almost possible, but would be more expensive than jusr ordering better stuff.

How well are those transformers working out for you?

[Joe]

The transformers are working great for this, I'll be posting the complete "radio shack" power supply soon!

[Brymus]

I was eyeing them at RS this afternoon.
Thats really sweet idea you had using two of them at 10$ each hard to beat that price.

I am dying to hear what this amp sounds like.

[Joe]

Look what the cat dragged in

[Brymus]

Oh thats quite a coincidence.
I just picked up those RS trannies today.I was gonna try em with my lm3886 but...
Any chance I could get one?