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Akai Guitar Amp Project - Round 2

Thanks JonL. I will try dropping that resistor to 1k. Right now the 250pF cap is made up of 2 100pF in parallel, all I could find. I think I will also try changing that. I am using the Akai/Fender schematic I made, but without feedback right now.
 
Eh, changed to the 1k and it did little. It's like it needs 2 to 3 times more output. Playing it at full and not even bothering the wife. Need to try that cap and possibly reduce that resistor in the second stage as well. No overdrive/distortion at all.
 
If all your circuit values and voltages match the schematic, it *ought* to work just fine. If you are that far off in the output, the mods I suggested won't fix the problem. They're more for flavoring the amp rather than changing it radically (though that tone control cap is like Tabasco, not subtle and not for everyone). Is your volume control a 1 Meg as called out? Is the speaker OK? I've seen some amps that played really quiet, didn't sound like a speaker problem, but the voice coil had separated from the cone some. Cathode resistor on the 6AQ5 correct? What have you got for the resistors on the input jack? The Fender schematic is tricky to read about how that whole network works.
 
DOH. It works! I had a 47k resistor where it should have been a 47Ω. Also missing a ground from tx out. Singing great now!
 
sloober said:
Nice grab. The M8 has the coolest knobs on it. I need to find one I can raid. Here is the original thread for the amp project.
John

http://www.audiokarma.org/forums/showthread.php?t=295427&highlight=akai

and this...

http://www.audiokarma.org/forums/showthread.php?t=301665&highlight=akai
Click to expand...

Thanks John. Knobs are good. I'll have to put this project on hold for a bit (damned work) but when I get ready to start I may hit you up for some direction on the electronic mods. Pretty new at this but very enthusiastic.
 
sloober said:
DOH. It works! I had a 47k resistor where it should have been a 47Ω. Also missing a ground from tx out. Singing great now!
Click to expand...

Oh, that will do it! Kills all the gain from the second half of the 12AX7, and drastically increased the NFB (until you disconnected that.)

So, how's it sound???
 
Good to me, need to have some real guitar players test it out. For now I'm gonna pretty her up with some paint. Put a working vu meter back on and that is cool. John
 
Yeah!

Got it all painted last night. Used silver hammer tone on the face, and more metallic blue on the face trim. I found a set of rub-on letters I have had for about 25 years. Got them at radio-shack and they have all sorts of electrical words and markings. A little clear over them should protect them.
The rectangular knobs for bass and treble are from a polygraph machine (thanks Alan!) Large knob is from Cary Audio.

Heading to a guitar shop today to have them test it out. John
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That looks great! I'd love to have something like that in my now small collection. I wish I had saved the cases for all the Akai/Roberts amps I have.

Looking forward to hearing what the local guitar community thinks of it.
 
It took some work but was pretty easy. I put tape on the back of the left hole, then filled it with JBweld (bondo would do fine). After a little sanding, I drilled 2 new holes on my drill press. Make sure you leave room for the pots body!
All the lettering had to go, and it is etched in, so it needs sanding and a couple coats of primer when done. Then I used Hammertone paint. Stuff works great and has that vintage look.
 
That'll put it to the test. I love guitars and have several but after years of noodling I still suck. My own gear always sounds better when someone else is playing it.
 
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Ain't that the truth. I can only make bad sounds out of it, unless I hooked it up to my CD player. Within 3 seconds of a guy playing it at the guitar shop, I was all smiles. There is a guy in my neighborhood who I have heard in his garage from time to time. I need to go hang with him.
 
Sloober: I found this old thread about a 6aq5/Fender AA764 amp that you built. Would you happen to have the final revised schematic that you used? I tried to PM you but it said that your box was full. Thanks.

patrick620@yahoo.com
 
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Patrick, Sloober hasn't been on AK in over a year and hasn't posted in longer than that. You might try clicking on his name and sending him an email.
 
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