Stuart Polansky wrote:
Okay, clarification here. Roscoe and I were both assuming that this was an OTL design. Not the case; there is an output transformer. The advantage in this circuit may lie in that the output tubes are functioning in cathode follower mode. Cathode followers have very low distortion compared to grounded grid or grounded cathode designs (think degenerative feedback across the cathode resistor). That's the good news. The bad news is that the gain of a transformer coupled output stage in cathode follower mode is going to be way less than unity.
So the demand for gain falls on the input stages. That gain needs to be very large and controlling the distortion there is another problem. Broskie has written on it extensively, I'd read up. Dave Berning has an opinion on the CF output stage as well. Maybe he'll chip in here.....
Personally, at $2k, I'd pass on them. Not even close. If it was an OTL design, I'd have to hear them, because I'm thinking wholesale rebuild with modern parts.
I think collector value and non-DIY users would be interested in this. As for a DIY guy, I COMPLETELY agree with Roscoe....Do It YOURSELF for lots less and a better finished product!!
Stuart
Stuart, you have this sussed out correctly, Berning's name did crop up on a discussion in diyaudio as there was a person building a clone of the EV A50 and was asking questions about it. The gist seems to be that you cannot build one for cheap because of the iron, so $2k is probably not a bad deal, but is out of reach for me at this time. I would think that an OTL would be a cheaper build, no output tranny! Oh well, maybe another time, besides, got too many projects I need to get done before taking on another!