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Need some ideas for a new build

BadassBob

BadassBob

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I have a hankerin' to build a new SE amp and Im stumped on where to go with it. I have the transformers in my possession, the PT is a Dynaclone PA774 with 2x 6.3V @ 2.5a, and the secondary is 330-0-330 @ 180ma. The OPTs are James 6112HS. The transformers are currently in my get*set*go, but Im looking for something different. SET or SEP will both be fine, the simpler the circuit, the better. Any good schematics floating about? Most the schematics Ive looked at have a 5V winding for the rectifier, which my PT does not have, so that will limit my rectifier choices. Any suggestions?
 
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Or if you want to go the octal route with your rectifier you could try a 6X5 or 6AX5 (the GE's I have look like a 5AR4 inside).
 
My current amp uses 6AX5s, no shortage of those. I have quite a few of the GEs, and find them more durable than other 6AX5s. What choices would I have as far as output and driver tubes? I can read a schematic, but Im not good enough to design my own circuits yet. Im shooting for ~5W of output power...maybe use a triode strapped EL34?
 
BadassBob said:
My current amp uses 6AX5s, no shortage of those. I have quite a few of the GEs, and find them more durable than other 6AX5s. What choices would I have as far as output and driver tubes? I can read a schematic, but Im not good enough to design my own circuits yet. Im shooting for ~5W of output power...maybe use a triode strapped EL34?
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That would be closer to 9 watts with a 5K Z or 6 with a 10k. Check your current draw on that 6v tap, sounds like you will have a pretty good load.
 
I think at 9W, these James OPTs will be running out of steam, as theyre the smaller OTs of their lineup, supposedly good for ~10W. They have 2.5k, 3.5k, and 5k primaries on them.
 
That's cool, you could use the 5k, and run the EL34 nice and easy. I have a EL34 strapped single ended job. It sounds really nice, tons of detail, but easy to listen to. I'm driving the EL34s with 6SL7s (paralleled sections), and using 5AR4s for rectification duty.
 
HMMMMMMMMMMMM :D. The plot thickens. I have a ton of 6SL7s lying around...any way I could incorporate a 6AX5 rectifier with the EL34s? Do you have a schematic by any chance?
 
Not at the moment, but a couple folks want me to draw one, so I probably should. It's a very simple circuit.
 
OK, if you have two 6.3v windings at 2.5 amps each, you could actually use one winding per channel and have a rectifier for each channel. EL34 is 1.5a, 6SL7 is .3a, and 6X5 is .6a. That would give you 2.4 filament amps per channel. Got any chokes?
 
I have a Dynaclone C354 choke...I believe its 1.5H. I have no problem buying parts, just wondered what I could do with the transformers I have. How many chokes will I need, and at what inductance?
 
Depends on what you want to do, and what you need to do to get the voltage clean and where you want it. Maybe someone that knows Duncan Power supply builder could chime in and run some sims. I think you would want at least one 10hy choke with an air gap.
 
Maybe a pair 6AU4GTA damper diodes set-up for fullwave. But with a 1.8 amp current draw for a 6AU4GTA, it doesn't leave much current left for other tubes unless you use a extra filament transformer. 6AU4 is a tough half wave rectifier.
 
6ca4 and 6AX5 are pretty much a wash. Each will do 150 ma at around 350v. If you do the 6AX5, you would have an all octal amp.:thmbsp:
 
hey-Hey!!!,
Go for a big pair of damper diodes like 6AU4. That will leave the OE power TX enough juice to run the amplifier tubes if you hang the rectifier tubes from a separate 6.3V transformer. That route will set you back about $15, and give you a conservatively run set of rectifier tubes.
cheers,
Douglas
 
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