If it's purely an engineering challenge why bother designing yet another DAC?

Mark, yah anything like that I’d get from Mauser ....thx (sorry for being a wise guy!)
They were not cheap new ($500 or so) I think I paid $300 new when they discontinued the line. They can be had nowadays for way under $100 on fleabay......if one could figure out some easy upgrades it’s really well built.

Abraxalito, is that something that can easily be addressed?
I really dont mind using this amp as an educational tool, I have a new crown 2002 for my subs anyhow, and in its current state it’s unusable for any main system. In other words it’s expendable and easily replaceable if need be.
 
These things were touted as bullet proof with lots of protections.
Sonance was/is commercial sound based where longevity was preferred over sq.....that’s my take on it anyway.
I’m all about bypassing any useless stuff that just degrades the signal in the name of reliability! As long as it’s still safe of course.
 
Abraxalito, is that something that can easily be addressed?
I really dont mind using this amp as an educational tool, I have a new crown 2002 for my subs anyhow, and in its current state it’s unusable for any main system.

The ideal wiring for the 0V/screen of the inputs is to connect the RCA shield/0V pin directly to chassis. That might not be possible though, depending on the particulars of your amp ( safety class 1/2). The power transformer centre tap should also go to chassis - that way the CM currents on the input RCAs don't go via any active circuitry. Instead they travel through the chassis, out of harm's way.
 
How would you know if it was on the recording?

The reason behind specifying 'never'. Many recordings are explicit about the primary equipment and environment. Some labels specify placement and reject processing. With a little research a library of usable content should be doable. While flawed in many ways Youtube, Twitch and multiple other sources often provide convenient access to raw live mic feeds, with the added bonus of seeing if the user is speaking into the correct end of the mic. The sound of familiar mics often comes through clearly.
The deeply invested could even record familiar unprocessed voices at the cost of a Umik-1. Perfection won't be required to tell if a system aims at a pleasant valley Sunday experience.
 
Let me humbly draw your attention to a more serious, dominant and seemingly incurable disorder called the Manic Pursuit of Speed and Accuracy (MPSA).
I have that!... come to think of it... I have MAOID (Manic Attention to Other things more Interesting Disorder)... that I must confess (lest be taken seriously) AOID is "not well documented in the literature" for reasons that it is "not documented at all in the literature" by the psychiatric community or otherwise. Though I suspect many would hold up their hands in having a more serious case of it, as I do.
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The analog-to-digital and digital-to-analog conversions are pronouncedly high distortion electrical interfaces. The noisy modern CMOS technique produces plenty of random errors and constitutes a generally hostile environment for the audio signal. The necessary correction mechanisms, high sample rates and accurate clocks are harmful medications killing the patient.

In expanding upon that point, as specific to sample rates alone, we can consider a condition whereupon step function current waveforms are applied to an I/V converter input. If we consider that the rate of rise of input step current exceeds the ability of the I/V to respond, there exists a fixed delay time to the re-acquisition of the flat top of current. If we then consider that the period of overload, whereupon the I/V is not in loop control as "a priori" bad and the period in loop control as "a priori" good, there exists a fixed proportionality of bad to good. That proportionality of good to bad increases as the sampling rate goes down, for reasons that the re-acquisition is a fixed quantity.

This is to suggest that as sampling rates rise there comes a point that good no longer exists, as directly dependant upon the devices performing the I/V.
 
One can only assume the level of incompetence required to operate at that point is strictly an audio thing.

The reason for the inclusion was to identify an end point, as a point to consider backing away from in deciding upon the most advantageous sampling rate in consideration of both the capability of the digital to analog converter and an I/V. It seems the current consensus is necessarily the higher the better.