Oleg's EML 20B Based One Tube
Single Ended Triode Stereo Amp
- Single ended Pure Class A, 5-7 wpc
- 2x EML 20B tubes used as output tubes
- 5U4 rectification
- Input-driver driven output stage
- Custom would Electra Print-output transformers
- Lundahl 7903 high level mic input transformers
- DC-heated output tubes
- Based on a proprietary fixed-bias circuit (adjustable biasing on the output tubes)
- 240 VAC operated.
Built for Oleg Artemev of Moscow, Russia
Completed on 1/25/11
Two words sums up this amp's characteristics: smooth and transparent.
The circuit is designed so as to not get in the way of how the 20B truly sounds. I am also very impressed with the bass
response - when I first turned it on to listen, it made me check to see if my sub was on and it wasn't!
I get lots of inquires about this amp, particularly the circuit design. Since I
worked very hard to get the schematic drawn up and due to my fear of someone using it for commercial purposes, I choose to
keep the circuit proprietary. But here are Some hints which I would like to share. If you're clever, you might just be able
to figure it out by looking at the picture of the wiring, along with those hints:
1:4 ratio on LL7903s
- EML 20B: 390 - 450 VDC on the plate and biased at 40-60 mA
- 10K:8 ohms OPTs
I also get lots of questions
about how this amp compares to the Tron Voyager One amp. I honestly don't know since I don't feel like blowing $14K on a piece of audio equipment just to find out. From
what I understood, the Voyager needs to be coupled to a preamp that is specifically designed to drive the amp. Obviously,
there is no need for doing this on my design, thanks to those Lundahl input irons. So, my version is standalone
that can be mated directly to a source or to an active preamp. I find the latter is beneficial since the amp is
not high gain.
All in all, this is a great amp for those who delve into
the world of SET amps. The only downside is that it's relatively expensive to built. A pair of EML 20B is around $400,
depending on the vendor, $250 - $300 for a pair of LL 7903, and $300 - $900 for a pair of quality 10K OPTs. Having
said, the price is well worth is for the outcome.