I agree with you Brett. The Collins rigs were strictly communication rigs, not HIFI. I had a 75A4 for a long time and compared it to other 75A4 RCVRs at the time and all of them had poor audio reproduction. A good bit of the distortion was with the detection and audio output stages. I built a MOSFET source follower where I picked up the 455KC IF and fed it to another AM/FM stereo HIFI radio with its on 10-15 watt audio output stage. I disable the mixer and OSC in the outboard HF and fed the 455KC from the 75A4 into the IFs of the outboard HF radio. This helped a lot but found some of the distortion was from the mixer of the 75A4. I understand there is a modification for that now, requiring a tube swap to a dual triode and rewiring. The 75A4 and its type are famous for accuracy and stability. As for as stock receivers go on fidelity, the HQ129, HQ145, S-85, NC303 (not NC300) has outperformed all for me.
John, WA5BXO
