Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: kagliostro on October 31, 2010, 03:13:41 am
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I've this little amp (see attached photo)
it is an old modulator for a Radio Frequency Transmitter (STE AA12)
uses 1 x ef86 - 1 x ecc81 - 2 x el84
it is claimed to have
10w at 250v B+
15W at 300v B+
bandwidth 300Hz-8500Hz within 3db at 10W (with the modulator transformer)
there are also some caps connected to grids to avoid radio frequency noise
Well my first idea was a matchless DC30 (only ef86 channel)
as it is a PCB unit to obtain it I must modify the existing printed circuit because of the use of the concertina splitter instead of a long tail, but I would like don't do it if not strictly necessary
I developed some ideas but need councils
If I maintain the concertina and the use of the other half tube as a gain stage (like in the original schematic) I think I can insert a tone Stack
Vox AC30 ?
or what about a rotary switch like in the Matchless DC30 and Weber Kit 6d30
have also an idea for a progressive bass cut
see schematics in next post
(I put also .sch version if you want to put on it your mod to be show here)
what do you think about ? which will be your choice ?
Other question I'm not sure if is better or not to maintain the 16uf bypass cap in parallel with the 2.2Kohm resistor mounted to the cathode of the phase splitter
Also I think it will be better to use an ecc82 instead of an ecc81, don't know about the use of an ecc83 because I think the gain will rise much, your council ?
please comment, say your opinion, give councils
I've many ideas but I'm confused about what can be better
Many Thanks
Kagliostro
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Other documentation
Kagliostro
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My schematics
Kagliostro
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> concertina splitter instead of a long tail, but I would like don't do it if not strictly necessary
It's fine. Don't change that.
I'd use it exactly the way it is. Maybe you don't need tone controls.