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Re: Need some help reverse engineering a 6BQ5 PP amp

Posted by bean_counter on June 2, 2000 at 09:40:12

In Reply to: Need some help reverse engineering a 6BQ5 PP amp posted by Jon T on June 1, 2000 at 21:55:45:

My experience with console mid-fi amps: snag the power transformer and any good tubes, junk the rest. Look at the draw on the power trannie in the original amp (including fils), measure voltages, and try to figure out what the approximate rating is. Be conservative.

If you want a cheapo project, save the output trannies too and build a new PP 6BQ5 circuit with all new parts. Lots of good designs out there. You might be surprised at the sound, and you WILL learn a lot.

I built a SE 45 amp out of a cheap SE 6BQ5 amp. I was STUNNED at how good $125 could sound.

As far as the odd 150pF capacitor is concerned, I think (not sure) it might be a high-frequency roll-off trick from antique radio days. Gotta figure most folks with these consoles had some pretty nasty LP's. Rolled off probably sounded better!

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