• 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.

my third RH84

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mctavish

Member
Joined 2008
Hey everyone! Im just starting my third RH84 on an ''existing chassis'' and i've got three 9 pin sockets and one octal on a very small chassis. My power transformer has two 6.3v secondaries and no 5v, so ive been trying to think of a tube solution.

Does anyone know of a 6.3v octal FW rectifier capable of 150 or so m.a.d.c.? I have a few 6X5's but there not capable of that kinda current...

Thanks!
 
M

mctavish

Member
Joined 2008
Hmmm... yes Akai. What a hidden gem. I've picked up many over the years just to butcher them. There dipped in wax (so no corrosion:)) and each have their own power tranny and cute little choke. Its a recipe for nice S.E. amps, and if your lucky they come with some good Matsushita EL84 's!:cool:
 
Shoog

Shoog

Member
Joined 2002
Since your've built two successful RH84 amps, why not try a bit of variety. The partial feedback approach works best with a high output impedance driver - so a pentode is just the job. I have had great success using a 6AU6 in similar circuits. I would be more than interested to find out if there was a noticable difference in sound quality doing it the right way.

Shoog
 
M

mctavish

Member
Joined 2008
I've tried A triode-strapped EF86 in some experiments which sounded very nice, Plenty of gain. I've also built an amp with trioded EF804 driving 6v6's with some p2p feedback for my father-in-law with a pod dock and he seems quite pleased.

Were you using the 6au6 as a pentode? I vaguely remember a push-pull thread with some plate to plate feedback going on, was that you Shoog?
 
Shoog

Shoog

Member
Joined 2002
Yes I did use the 6AU6 as a pentode in two partial feedback PP amps now. As Bigwill says doing anything else defeats the object of the exercise.
The EF86 doesn't make the best candidate - you need something which will carry a standing current of at least 5mA at about 150V on the plate - this makes the 6AU6 an excellent candidate - and its dirt cheap.

Shoog
 
pjanda1

pjanda1

Member
Joined 2005
wildburroaudio.com
I'm interested in a 6au6 version. I'm sitting on a couple of Sony TC500 R2R's (SE 6aq5) that I was thinking of making into an RH84. But they've already got the 6au6's! They also have 6CA4 rectifiers, I was thinking of using two in parallel (I know one would do it, but two would keep the resistance a little closer to the 5U4 that is specified, and I know AK carefully optimized the circuit).

pj
www.wildburroaudio.com
 
Shoog

Shoog

Member
Joined 2002
If you have an amp which uses 6AU6's it should already have a screen supply so all you would need to do is work out a suitable operating point. Can you lay your hands on a schematic.
I wouldn't bother paralleling the recifiers, this circuit is very forgiving of slight variations and the lower impedance won't make a lot of difference if the power supply has a choke.

Shoog
 
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