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Yeah- that is all why I started looking into OTLs.

Everyone I knew that was playing around with building OPTs had a garage full of prototypes. And certainly with any transformer-coupled amp the OPT is the heart of its nature and quality.

The OTLs allowed me to get crazy bandwidth. Before I started bandwidth limiting in the voltage amplifier some of my prototypes (this was in the 1970s) could be used as a Radio Frequency booster amplifier- I used one to make 50 watts as a booster for a walkie talkie at 27MHz. But that sort of bandwidth can cause tweeters to get damaged if any RF gets into your system so we never made any production amps with that sort of bandwidth.

But we do make them that have no phase shift at 20Hz or 20KHz. Since I've also produced LPs from some recordings that I've done I have a pretty good idea of what that actually sounds like. I recommend any audiophile do something similar if they can; having a real reference recording on hand really allows you to know what you're hearing.

I used to think that there were things that could not be measured that we are hearing. I don't think that anymore; instead I've come to realize that usually what's happening is that most of what's important that we can measure never gets reported on the spec sheets. To that end, I feel that the distortion signature (the spectrum of harmonics generated) is more important that what the THD is; if you can get the signature right then its OK to get low THD but not the other way 'round!

Phase shift is important in my book. You don't need bandwidth to get it right if you run enough feedback, but if you're not running enough or if you run none then you need bandwidth. You can't hear phase shift at any one frequency but the ear will perceive it as a coloration if it occurs over a spectrum. So an amp that is rolled off at 50KHz can sound dark as a result.

I like what the head engineer at Scott said about this decades ago:
"If it measures good and sounds bad, -- it is bad. If it sounds good and measures bad, -- you've measured the wrong thing."​

I would simply add that it helps to also understand how the ear perceives sound and how that relates to engineering. Most spec sheets ignore human hearing perceptual rules.

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