TORPEDO III is coming!!
This is a prototype that I finished this weekend. I'll let Dsavitsk explain the details. In my layman's understanding, he's using a differential (balanced) circuit within the amp to cancel all of the common mode distortion and noise, then combining the result using the OPT's (OutPut Transformers). The result is very similar to his ECP Audio DSHA-1, except that a tube is providing the gain stage. Yes, this means the Torpedo III is a tube hybrid, but unlike any tube hybrid heretofore available. Sound is remarkably detailed from deep bass to extended highs and at the same time, no harshness, no tizziness, even with the most complicated of passages.
The tube basis is the ubiquitous and high-quality 12AU7. However, unlike most amps based on the 12AU7, the Torpedo III can take a wide range of gains. This means you can use the 12AY7, the 12AU7 and all its numerous variants, and even the 12AX7. Versatility extraordinaire!
Beyond that, the Torpedo III uses the same planform as the Torpedo I. That means the same case, the same hardware, and the same Edcor transformers (but with a future upgrade to Cinemag output transformers). You could even build a PCB-only and then replace it within an existing Torpedo I case. I guess I'll have to start selling transformers to make that possible, but that's OK. Edcor and I will have a little discussion, soon.
So far, I've used the Grado HF-2, AKG K712, KSC-75's, and the Sennheiser HD580 (just for the heck of it). The Torpedo III handled all of them with ease and with a sound quality like I've never heard before, long-term. Yes, I've heard some very expensive stuff before, but that was only a headphone meet's quick impression - not something I could live with and call my own. The source I've used is the PupDAC with the DoodleBug, perfectly adequate for great detail and low-noise. I haven't made measurements yet, but compared to the Torpedo I (already quite good and free of audible hum), the background is very black, with absolutely no noise whatsoever.
Construction is a bit tight in spots, but nothing anyone who's built a Torpedo I can't handle. You will note the large number of box film caps. Dsavitsk recommended them - Epcos - from Mouser, so I tried them. I see no reason to use anything else, but the pads are quite flexible for some very expensive alternatives, for those that are interested. You may also notice four heat sinks instead of the three on the Torpedo I. There are several other differences, but all in all, very similar to the Torpedo I - same transformers, same Alps volume pot, headphone jack, Z-switch, IEC inlet, etc. Just a couple of 9-pin tube sockets and some very special stuff in-between.