Thanks!
It sounds very pure at the top end, as most OTLs I've heard seem to; not a trace of hardness or shrill behavior. This makes it a real easy listen. Strings, brass piano, guitar and keyboards all sound superb and voices have an eerie presence in the room. The bass end is deep, controlled and textured, with acoustic basses in particular, coming over beautifully woody and rattly.
There is only about 1W available into 8 Ohms but my 98dB/W Fane 12-250-TC single driver speakers go plenty loud enough without causing any strain on the amp.
It sounds very pure at the top end, as most OTLs I've heard seem to; not a trace of hardness or shrill behavior. This makes it a real easy listen. Strings, brass piano, guitar and keyboards all sound superb and voices have an eerie presence in the room. The bass end is deep, controlled and textured, with acoustic basses in particular, coming over beautifully woody and rattly.
There is only about 1W available into 8 Ohms but my 98dB/W Fane 12-250-TC single driver speakers go plenty loud enough without causing any strain on the amp.
Very nice amp also nice design Steve, congrats, did you use a solid state power supply? What kind of OTP did you used ? ........all the best
Interesting. Love to hear more. Looks like the system is shoehorned into a small space. well done!
Steve, I'm fascinated by the 13E1 even though I don't know much about it beyond Morgan Jones.
Yes, the power supply is solid state. Each 13E1 draws nearly half an amp at 160V. There are no output transformers, the 13E1s operate in single ended configuration, so use capacitors on the outputs to keep DC out of the speakers.
Of course output transformerless operation of power vacuum tubes to drive speakers is appallingly inefficient and high levels of feedback need to be employed, in order to get the output impedance low enough to drive loudspeakers directly.
Aside from OTL headphone amplifiers, which are sensible enough, a single tube OTL amp driving actual loudspeakers is one of the daftest ideas ever thought of and as far as I know, there is only the Russian 6C33C and 13E1 capable of pulling off that feat as a single tube.
The 6C33C will drive a 16 Ohm load for about a watt of output power, the 13E1 will drive an 8 Ohm load for about the same power. Pitiful, and any speaker under 98dB efficient or below 8 Ohms need not apply. But the sound that comes out, if you have the right speaker is wonderful.
What the world needs for these kinds of amp is a great 32 Ohm speaker.
@Carl
I became interested in the 13E1 after Morgan Jones and his Crystal Palace amp, got myself four of them around 2008 but never did anything with them. It was a guy called Wolfgang, who posts on here (I think) and also Bruce Rozenblit's Transcendent Audio forum who fired my imagination with a 6C33C single tube OTL. His amp was/is a 6C33C OTL configured as a power cathode follower with a TL783 regulator chip running as a constant cathode current sink to provide the bias and stop the darned thing red plating.
I figured that the 13E1 could do the same, as it is similar to the 6C33C but with higher gain and more power handling capability (95W max dissipation in triode mode) so I thought, why not build an OTL with the tube.
There are two of us in the UK building 13E1 OTLs as far as I'm aware. I've finished mine and the other guy is about half way through his build. We cooperated with each other and Wolfgang on the cct design.
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Thanks Steve. I believe it may have been your work with the 6AS7 in another forum that I read a while ago before starting to play with that tube. I've been interested in OTL but a bright engineer friend had big challenges when he built one and I've figured I wouldn't try it. But a single tube version would be an interesting project. Sadly the 13E1 is beyond my budget now (but the 6C33C...). If you write up the project I'd be interested.
I haven't designed a 6C33C OTL, but here you'll find a schematic for one.
Remember These? - Page 2 - audio-talk
Remember These? - Page 2 - audio-talk
Interesting reading on a quick glance.
Testing high-end headphone version of Edelweiss-3 amplifier. The same 8.2W at asymmetric saturation, frequency response from 8.7 Hz to 72 kHz. About 100 KHz ringing, also no longer than 1 period. Results with NP Acoustic transformers are almost the same as with Edcor USA transformers. The only minus of EDCOR Electronics Corporation transformers is, they do not offer multi-tap secondaries with SE transformers.
Left TRS output for high sensitivity headphones, XLR and right TRS outputs for planar magnetic headphones. Auxilary output on the rear panel for 16 Ohm speakers, with servo-control.
Left TRS output for high sensitivity headphones, XLR and right TRS outputs for planar magnetic headphones. Auxilary output on the rear panel for 16 Ohm speakers, with servo-control.
