• 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.

RH84 Rev2 Build w/Premium parts

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I had been looking to build a "real" SE after hearing the results of a Piccolo ECL86 SET I built years ago with old console parts. Last year I built a set of Markaudio 12.2P Pensils and wanted an amp to complement them. I looked at 300B, 2A3, etc. but the BOM cost was just too high. I ran across Alex's RH84 and have always loved the sound of the EL84. I contacted Alex and he was VERY helpful throughout the process and I come to find out he has a Rev.2 of the schematic with a zener to set the G2 voltage on the pentode and a constant current supply to bias the EL84.

I ordered all Obbligato film caps, Transcendar 10W OPT's, Riken carbon grid stoppers and Dale RN60 metal films. For tubes I am running a triple mica E81CC and a set of TAD EL84-STR's.

I decided to modify the power supply from Alex's design to utilize a TJ mesh plate 274b rectifier, so the first cap is a 4.7uf and the second is a 100uf, both Obbligato film.

To house all the loot, I chose the beautiful Hammond walnut chassis. The plan is to later build a line stage, phono stage and headphone amp on the same chassis for a matching quad of tube gear.

The build went without a hitch. All voltages checked out after plugging in junk tubes. I put the good tubes in and it played oh so sweet music!

The detail is incredible! Coupled with the Markaudio 12p's, it gives a level of detail and realism that truly makes the musicians sound like they are sharing the same room as me. ...but not to a fault! I have heard a Van Alstine true balanced system and it was incredibly detailed, but was like a cheese grater to my ears! The highs are crisp and clean, the midrange is as expected from any Class-A tube amp with female vocals to die for! The bass seemed a bit lacking at first, but I soon realized it was still there but a perceived loss as my old console SE had a more muddied bottom end making it seem louder. The other shocking phenomena was the almost complete lack of hum from the AC heaters. I left them floating and can hear only a slight hum at full volume once I get within 12" of the cones. At this point not even worth modification to try and reduce it since it is so benign.

While this amp is not a powerhouse by any stretch of the imagination, it is on of the most detailed and engaging amps I have heard. I found myself listening to tracks on CD's that I usually skip past because the never intrigued my interest. The only other system I found this "engaging" was an Audio Note kits demo using their complete top-of-the-line kits from CD transport, DAC, 300B transformer interstage mono blocks to their signature AN-E's. While my system is not as full an audible spectrum as the Audio Note system, mine also did not cost $100k! It will be a pleasure burning-in my ears to this new amp and rediscovering my music collection yet again! :D

Enough chatter ... now for what you really opened my thread for ... pictures:


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I may rebuild the 6BQ5 with the components on the underside of the PC board.
I would probably put a 12AX7 in place of the 12AT7 also. Notice the OPT's of the 6V6 are smaller than on the 6BQ5 and still it out performs the 6BQ5.


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