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platplaas 2nd January 2011 02:10 AM

RH84 (EL84) Choke etc...
I have started research for parts selection / sourcing for the RH 84 amplifier.

For the power and output transformers I am going with Edcor models.

However, I can't seem to find a 20H 50ma choke as called for in the schematic. Ideally I would like to use Edcor so that everything matches and so that I can buy / ship in one batch...but Edcor only makes the following models:
5H at 200ma
10H at 200ma
10H at 300ma

Would any of these work for this design?

Here is a link to the schematic: RH 84 - Tube Audio ...... RH DESIGN

platplaas 2nd January 2011 02:17 AM

On another note: Capacitors

It seems that the critical capacitor is the .22uF in the middle of the schematic. I am going to use a Mundorf Silver Oil for this one.

For the other capacitors I am using a mixed bag of Solen MKP and Mundorf MKP (metallized polypropylene), except for the big 220uf cap for which I am using a Jensen Electrolytic. (To keep cost and sizes down.)

Any suggestions or recommendations on selection of Capacitors for best bang for the buck?

Ty_Bower 2nd January 2011 03:14 AM


Originally Posted by platplaas (
10H at 200ma

Any of the three chokes you noted would work fine. The more Henries, the better. Make sure you've got enough current rating for both channels. I'd think 50 mA would be sufficient for only one channel. 100 mA should do fine for both channels, but it won't hurt anything if you've got extra.

6L6 2nd January 2011 03:46 AM

What speakers are you going to use with this amp? It's output will be about 3 watts.

I would strongly suggest a Push-Pull EL84 amp for a first project.

However, if you are set on this design, and want to copy it directly, Electra-Print can make a 20H 50ma choke.

platplaas 2nd January 2011 04:13 AM

The amp will be powering Fostex FE206en speakers - which are fairly efficient.

mach1 2nd January 2011 05:27 AM

edcors or hammond will be fine. I would start with Russian K40y caps, then see if you want to burn money later.

platplaas 2nd January 2011 03:06 PM

Out of curiosity - what kind of audible effect would result from using a choke with lower inductance? (10H vs 20H) Is the DC current somehow less 'smoothed' and does this affect the quality of the audio?

Thanks for the feedback so far.

Svein_B 2nd January 2011 03:19 PM

There may be more PS ripple (hum / buzz), depending also on PS capacitor sizes.

If you use reasonably large value for the second PS cap, say 470uF, a 2.5H choke such as Hammond 159T will usually also work fine if space or cost is an issue.


platplaas 2nd January 2011 03:52 PM

Re: Capacitors and Rusion PIO - I find it challenging to find the right value capacitors - and the few that I can find are often in lots of 10 or more. (Though very reasonably priced...)

Any alternatives to Ebay?

platplaas 2nd January 2011 03:53 PM

If I use a 10H (vs 20H) choke - would I need to adjust the value of the 220uf Capacitor?

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