OT- Amp Build Pics

[Doug H]

For those of you who are building amps. I just finished an amp build and I uploaded some pics of the build here:

http://f2.pg.photos.yahoo.com/ph/dougbhammond/my_photos

Go to the "Octal Fatness" folder and click on "Start Here". It will take you through the sequence of steps I took to build it.

I'll upload the schem to my site tonight, in case anyone is interested.

Doug

[AL]

Very nice!!!  I'm not real familiar with amp building so here's a few (possibly) stupid questions.

1) What kind of amp is it?
2) Where did you get the parts - the chasis especially?
3) Where did the drilling template come from? Or did you do it yourself and if so what things did you take into consideration?

Thanks

AL

[Aharon]

Very nice Doug.Looking forward to seeing the schematic.
TAke care
Aharon

[Doug H]

Very nice!!!  I'm not real familiar with amp building so here's a few (possibly) stupid questions.

1) What kind of amp is it?
2) Where did you get the parts - the chasis especially?
3) Where did the drilling template come from? Or did you do it yourself and if so what things did you take into consideration?

Thanks

AL

Thanks for the interest, AL.

The amp is call an "Octal Fatness". It was designed by David Jones, who hangs out at ax84. It uses a 6SJ7 octal pentode in the preamp (the black metal tube).  There is a 1/2 12ax7 gain stage and a buffered tone stack. The output stage can use a 6V6, 6AR6, or 6L6 power tube, depending on the loudness and tone desired. I used a variable power resistor for the output stage cathode circuit so it could be biased for the different tubes.

The parts are a mixture of leftovers, surplus buys, and some new stuff I got from Antique Electronics. The power transformer is from my Electar 10, which I gutted. The output transformer is from AES, the filter caps, terminal strips, and other parts are mostly surplus, some leftovers. The chassis is a surplus modem chassis like I used on the Firefly.

I made the drilling templates myself in Powerpoint. I did a "lo-fi" model of the parts and chassis in Powerpoint, just modeling the outlines of them as blocks. This allowed me to figure out part placement and fit-checking on the computer before I drilled the first hole. I derived the templates from that.

This is David's design. I added the variable resistor and did a couple minor tweaks to balance out the freq response between clean and overdriven tones. It has a lot of headroom and goes from a pretty clean with a sweet high freq response through a bluesy overdrive to kind of a "classic rock" sound when the gain is dimed. It has a lot of sustain whether dirty or clean. When clean, the chords "ring" when you let them sustain.

I used it in my weekly gig on Sunday and am very happy with it. I needed something more flexible and louder than the Firefly and it delivered. I used the guitar volume to control gain, from clean to overdrive with a little volume boost for leads. No pedals, just the guitar plugged straight into the amp the way God intended. (Just kidding... :lol:) Noisewise it is very quiet and has a real quality sound to it. The keyboardist kept remarking about how good it sounded. David did a great job on this design.

Doug

[Paul Marossy]

Nice work, Doug. Looks like a cool little amp. I'm going to AX84.com right now to check it out...

EDIT: I've looked at that schematic. If I have the right one, it looks incredibly simple! Just a 6SJ7 and a 12AX7? I thought that I saw more tubes in your pics, but I can't get to that page right now...

EDIT AGAIN: Oh, I read the post above and saw that you have to add an output tube to it... a 6L6 or 6V6 would probably sound good. I wonder what an EL34 would sound like.

[petemoore]

Very Nice Work. I dream about undertaking such an endeavor someday soon.