• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

That's What She Said RH84 Build Log

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Sodacose

Sodacose

Member
Joined 2006
Fixed! I will admit that I did start to sweat when one channel just made terrible humming noises on the first start up.

Walnut menage a trois:



Sweet, sweet music. Sounds fantastic and the CL90 seems to give it a nice slow warm-up. Bass is really impressive, especially considering the little Fostex jobbers it's hooked up to.

I still do not have a volume knob, but I ordered a stepped attenuator for my SSE and if that works out I'll steal the Alps Blue Velvet for this amp. I've got a little trick planned to mount it. I also found a 45V R-Core in my parts stash and now I'm thinking a little voltage doubler cathode follower preamp mate for the RH84 would be fun.
 
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petrnyc

Member
Joined 2016
Sodacose said:
"That is WAY too small!"

"Where do you think you're sticking that??"

"Wow, nice wood."

With an extra 120V secondary power transformer from Antek (w/ 2 x 6.3V heaters @ 2A) , some 6BQ5's and 12AT7s from my stash of tubes, and a few feet of nice walnut left over from another project, I've embarked on an extremely small footprint RH84 build. The top plate on the chassis measures 6" x 10". Because of the small size of the chassis (and the 120V secondary), this will use a voltage doubler to achieve 300V B+ (see this thread where I talked about the PSU).

Here's a layout picture now that I've received all my parts:



The walnut is 1/2" thick mitered at the corners and the top plate is 1/8" aluminum. I used small blocks at the corners to support the top plate and to reinforce the miters. The bolt near the front left is for the toroid under the deck, the choke (back left) is a Hammond, and the OPTs are 5W Transcendars (I'm very excited to use these).

All holes are drilled and the switch/IEC/fuse is mounted (upper right of this pic):



As you can see, this is a tight fit (that's what she said!). I'll mount the voltage doubler 'module' (built on a terminal strip) just behind the power transformer. I'm still working on the best place to fit the filter caps (2 x 220uf, rather large). Anyone have practical advice on placement of these with regards to the OPTs or tube sockets? I'm thinking 'between' the OPTs on the underside to give me as short as possible B+ runs after the filtering.

Finally, here we are with everything test fit:



I'm thinking inputs on the front right of the top plate and volume control on the right side of the front walnut 'apron'.

So far, so good. I'm a bit worried about how tight the power supply is, but you know what they say about good things in small packages (that's what she said!).
Click to expand...
Sodacose, I am looking for a schematic for this amp, would you be able to post it? also, what OPT have you used?
thank you
 
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