The front-end, frequency stability, dial accuracy and re-setability and selectivity are excellent, but the receiver is pure crap from the detector onwards. At first I modified the first stages of the audio section and noise limiter in mine and got fairly decent response using an outboard audio amp, but the product detector still produced highly distorted audio. I hadn't realised how good some SSB signals could sound until I added the SE-3. The tiny audio output transformer in the A-4 is about the same thing you would see in a cheap 5-tube AC/DC broadcast receiver. In later models they made some changes at the factory that made the audio even worse. Art Collins must have been a fan of that narrow, pinched, scratchy, tinny distorted audio you hear with most "vintage" SSB transmitters and transceivers made more than just a few years ago. I suspect it was the influence of the "return" of AM to the ham bands and the subsequent advent of ESSB, that finally got the manufactures of ham equipment to pay attention to audio quality. All my 75A-4s are in too good shape to use, but if I ever run across a real basket-case A-4 beyond redemption, I plan to use the basic front-end, and work that into a switchable i.f. amplifier with the choice of either mechanical filters or the extra i.f. strip from a R-392 that I have, and feed the output of that into the SE-3. I'm supposed to pick up an RCA AR-88 at Dayton. I hope it's repairable if not in working condition, and I'm eager to see how well I like that in comparison to my other receivers.