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Registered Member #1225
Joined: Sat Jan 12 2008, 01:24AM
Location: Beaumont, Texas, USA
Posts: 2253
I had some tubes laying around, along with a metal enclosure with sockets, a power transformer, smoothing cap, and 2 audio transformers attached (there was an amp inside). I ripped everything out of the enclosure, and started working on a new circuit. It is just a basic amp circuit, taken from a few different places and the original circuit.
I desoldered all of the original wires (other than the filament connections) and used them again. I used different capacitors and components than where used originally in the enclosure, but they where all from other vacuum tube stuff (like TV audio stuff). One of the resistors starts smoking after about 10-15 minutes. It is 1kohm and 2-3 watts, and the full power goes through that (the tube supply). I am going to add another 1.2k resistor in parallel with that one, as i needed lower resistance anyway.
I use a 6EU7 1.2 watt twin triode for preamp, and 6BQ5 12w pentode as final output. I have two of those pentodes and the sockets, so this will be two channel soon. The rectifier tube is a dual diode 6CA4.
It sounds pretty good, for a first amp imo. I have hooked it up to an electric guitar, a radio, and my Zen and they all worked well.
Video:
Pics: #1 The whole amp #2 The output jacks (original) and the input 3mm jack that i got from a stereo, and i drilled a hole. #3 The guts. #4 A resistor made from 4 220k resistors in series for 880k (called for 800k)
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First vacuum tube amplifier.
