RH84 Builders, Post Comments Here

[soundmotor]

I am continuing to weed out & trim down extraneous gear I've accumulated over the years and I came across a set of transformers from a console amp I'd forgotten about. Nothing special, they are likely from an RCA stereo SE EL84 using a single 6EU7, 2X EL84, & 1X 5Y3. I have not come across a choke yet although I am pretty sure I have something close enough to use. Some questions on the RH84 design -

(1) Since it will be class-A, what is the reasoning behind the choke value being so large @ 20H?

(2) Could a smaller value choke be used with more filter capacitance?

(3) Has anyone built one without the choke at all instead using a dropping resistor?

(4) Where did this design originate?

 

[PabloL]

I've read most of the posts on this amp. The designer stated that the PSU was drawn deliberately simple. He wanted the design to be tested with a variety of psu's. So whats important is that the voltage is well filtered, in the ballpark voltage wise and the psu can supply the current. So the value of the choke is not "critical." In my plan I have my current favorite setup a C-LC-LC-RC.

http://www.diyaudio.com/forums/showthread.php?s=&threadid=47048

Check the above link for more info

 

[Kegger]

He used a single GIANT choke to make it filter decent with basicaly 1 filtering stage.

I would use a "normal" choke, then an additional RC stage after that to filter it nicely.

 

[soundmotor]

He used a single GIANT choke to make it filter decent with basicaly 1 filtering stage.

I would use a "normal" choke, then an additional RC stage after that to filter it nicely.

Thanks Kegger, kind of what I thought but verification never hurts.

I'd love to see some pictures too of everyone's completed RH84's.

:thmbsp:

 

[eedork]

There's also no regulation on the EL84 screens, which is another reason the power supply is so 'stiff'.

I built an RH84 using junk parts from an old Silvertone console. I made a few minor changes to accommodate the parts I had on hand. Specifically, I used solid state rectification, a little more capacitance in the power supply, and an old choke that was a little smaller than the original design called for (maybe 10 or 11H). I really liked this amp and bought better transformers (Edcor) to rebuild it at some point.

One modification I thought about trying was regulating the screens. I also thought about re-configuring for ultra-linear operation since the Edcor outputs have a UL tap. I never got around to either, but when I rebuild (if it ever happens . . . . ) I may try both.

I think I read somewhere that some builders tried regulated screens and didn't notice much of a difference. The stock power supply is stiff enough to not sag significantly under load..

-Matt

-Matt

 

[tim614]

i built one as my first build great design very simpleand sound absolutely awsome ,but i would suggest to use all new parts it'll turn out better
parts count are very minimum .
just follow the schematic you won't be disappointed.
btw: i use 15h-75ma choke and edcor optx and for the ptx i had a old chicago from another amp .