Class D amps that are superior to all or most?

Ralph,
Are you using tubes on the input....or is it discrete solid state or integrated circuits? Have you tried all kinds (types like toroid or enclosed, wire wound or foil...better wire quality, directionality of the wire, cryoing the coils, whether you run the signal into inner or outer winding on an air core, etc.) of different iron core and air core coils on the output? Everything makes a difference.

You don't need money to get power in class D.  Even the new GaN Premium-Audio stereo amp for $699 is rated for 200 watts a channel and they show a graph showing it not even clipping (usually 1% distortion ) doing 600 watts?  I am going to email them about this because seems to good to be true....maybe a peak power, or one channel driven only?

Are you using tubes on the input....or is it discrete solid state or integrated circuits? Have you tried all kinds (types like toroid or enclosed, wire wound or foil...better wire quality, etc.) of different iron core and air core coils on the output? Everything makes a difference.

The earlier prototypes used no input circuit at all since our preamps have no problems driving a 2K load with plenty of voltage. But obviously we needed more gain so we set it up with opamp inputs. Initially we had used an input transformer but the opamps did a better job with wider bandwidth and lower distortion- and were more musical.


We found off the shelf SMPS to really be hard to work with. They usually have current limiting built in which was problematic. So we went with conventional power transformers and that problem was solved- and for less money by quite a long shot than a proper custom-built SMPS would have cost.


The filter chokes do pose their own issues but almost entirely about how well RFI and EMI is suppressed. If that isn't sorted out properly the amp simply won't sound right and no small part because it can affect other equipment if its leaking noise! If I were you I'd be very careful about replacing the filter choke if you don't have access to a good spectrum analyzer with a calibrated antenna as well as equipment to measure the noise the amp might inject on the AC line.

@atmasphere

when are you releasing your class d amps, ralph...?

surely many devotees here want to hear what the longstanding otl tube amp legend here with almost 10,000 forum posts believes sound right with class d modules in tow !!!

I picked up a Wyred4Sound Class D amp several years ago to fill in while my M60s were back at Ralph's for refurbishment.  I was quite impressed with the sound, and this was a $1k amp, so I'm listening when Ralph says he can build a great amp with the technology in the $5k price point.  Heck even those AGD GaN "tube" amps at $32k look interesting.  I'd like to give them a listen.  (Plus they look cool!)