DIY amplifier quesitons...

  • Thread starter Thread starter pikingrin
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pikingrin

pikingrin

what is this?
First off, I didn't know where to post this, so if it belongs elsewhere let me know...

I am at that point where I would like to build my own tube amp, something along the lines of a Mesa Roadking, with different tube options in one unit and all. Now, I have never built one before, never done anything except re-solder some stuff on a solid state. So here come the questions...

A) Is it cheaper to "roll your own" when it comes to tube amps?

B) Where is a good source of parts that are high quality?

C) Schematics... Any good resources on how to properly interpret them? Any sites out there that would have some along the lines of what I am interested in doing?

Any help is appreciated...
 
pikingrin said:
I am at that point where I would like to build my own tube amp, something along the lines of a Mesa Roadking, with different tube options in one unit and all. Now, I have never built one before, never done anything except re-solder some stuff on a solid state. So here come the questions...
Click to expand...


Most people start with a Fender Champ or something small.
 
Yeah, build a Champ, and I might even be tempted to skip the tube rectifier and use a solid state power supply. Parts Express has most if not all the parts you'd need, including tubes, sockets, the output transformer, caps, speaker, vinyl or carpet for the cabinet & grille cloth, connectors . . .

Beware the voltages inside! They are MUCH higher than a solid state amp!
 
Here's my annotated Champ schematic. In addition to my comments on the schematic, be careful to note ratings of resistors--nominal is 1/4W on most schematics, but 1/2W here (see note), but some are specified as 1W. I usually use 1W resistors wherever the voltage is real high, even if the power drop isn't that much, just 'cause :o Most other resistors don't need to be 1/2W. Actually I never use 1/2W, that's just annoying to have to have 3 ratings of resistors. If it needs 1/2W, I use 1W. But anyway . . .

For the capacitors, note the voltage rating--some of them are labeled, the rest are supposed to be 400V. The tone circuit, for example, those caps should all be at least 250V (easier to source for polys). On the other hand, the caps in the cathode bias are labeled 25-25, meaning 25uF, 25V rating.

Also with caps, you have to know the type and the polarity, if applicable. All the electrolytic caps on the schemo have a + and - to indicate polarity. The caps without that label are nonpolarized types, I used poly film caps for those although I imagine Fender probably used ceramics. The 600V cap right off the fuse should be a UL listed ceramic type for power supplies, although I don't know if the original used one of that type.

In addition to the three controls (volume, treble, bass), I'd consider adding a post control by substituting a 250K pot for the 220K resistor going into the 6V6 grid.
 
Also I should have labeled the input jacks. You probably don't need the two inputs, so leave out jack #2 and the 68K resistors, and wire the 1M resistor from the jack #1 sleeve to ground.
 
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