Favorite 300B: Sophia vs KR

Just to clarify a few things regarding the Electra-Fidelity amp referenced by Auntjenof2. The amp is a proprietary (patent pending) Class A3 design by Jack Elliano of Electra-Print. In developing this Class A3 design we enlisted the assistance of Ralph Karsten in reviewing Jack's research, however, he was not involved in the circuit design process. Ralph was very supportive of Jack's effort and the result is that we now have two amplifiers in production that will operate in Class A3. The A3-500 is a 300B SET amp with a circuit designed by Jack Elliano that puts out roughly 10 watts. We are sending an amp to Ralph on loan for use in a new project he has started. The yet unnamed EL-34 amp puts out roughly 12 watts. The circuit for this amp dates back 20 years or so and was originally developed by Cy Brennamen with assistance from Jack Elliano and voiced by Bruce Edgar for use with his horn speakers. Jack recently updated the circuit for Class A3 operation and has achieved substantial improvement as a result.

The 300B version was at THE SHOW Las Vegas this past January shown with Fritz Speakers Carbon 7's. The amp easily drove the 87 dB speakers which astounded quite a few people since on paper this appeared to be a huge mismatch. We will show the 300b and EL-34 in Newport this June. Our room will feature Fritz Speakers, WyWires, and Resolution Audio products as well. If you are attending the show feel free to stop by for a listen.

Charles, bear in mind that I'm not the technical brains of the operation nor will we be able to disclose everything about this design since some of it will be kept proprietary until patents are issued. I would not say that the design is necessarily unique from traditional Class A, but it is different in that while the product of the plate power on the output tubes might be the same in both classes (ex. 300B tube), the voltage in an A3 circuit is higher and the current is lower. Since the power is developed by more voltage the result is more lifelike dynamics. This holds true only if the tube can take the increased voltage in A3. Not all can. We could not do this with a 45 or 2A3, but the 300B and EL-34 were rugged enough to take on the increased voltage. Today in an effort to determine if more power could be generated, my partner Jack burned through a number of EL-84's and 7189's that failed the test. We will most likely just stick with the 300B and EL-34 and be satisfied with the 10 -12 watts of power.

What has also been accomplished using this Class A3 circuit is a drop in THD and more importantly IMD. Measurements indicate a lower noise floor as well. This was one of the first things we noticed when swapping out the Coincident amps for our amp in Auntjenof2's.

Charles, the output tubes are biased on the high end, so yes, tube life is likely to suffer somewhat. On the other hand the sonics are improved. Such is the trade off.

Perhaps we can work out a demo for you. If you go to the Electra Fidelity website, complete the contact us form, and send it off I will respond with my phone number so we can chat. We would like as many people as possible to hear this unit. Shows are obviously a good method, but in ones own system is always better. Auntjenof2 just happens to be in the same town which made things easier for him.

Jcote, got it and will be in touch.

No problem Jason. It was great speaking with you and look forward to meeting you in a few weeks.