I need to figure out how to safely ship these heavier amps to
@amirm for testing and I will wait until his back is better.
I am willing to bet that these amps will beat the average SINAD.
1960s era: American Mid-Century Craftsmanship
JBL SA600. At the time, performance exceeded the capabilities of instrumentation. They knew that it measured 0.2% THD with zero feedback up to about 10 Watts, and they claimed that with negative feedback, the THD should be 1/50th of that.
http://www.aes.org/e-lib/browse.cfm?elib=1091
100 dB SNR at 10W or lower.
Guesstimated SINAD of 84-88 depending if the THD really is as good as thought.
McIntosh MC2105. People love the blue meters, and the reliability of this amp is well established. This is also a vintage amp that continues to hold its value.
Not the same amp, but it does show that measured performance can be very good with auto formers
Mc2255 Measurements
I think we hit the threshold of audibility with these amplifiers in a listening positioning for recreational listening with normal ambient noise. You may gain more detail with newer amps and more power with newer amps.
1980s era: Japanese Economic Miracle “Bubble” Era
Accuphase P-266. Switchable Class A or AB. SNR rated to 120 dB. THD is competitive against modern Class AB amps. Lower power than today’s best.
http://www.accuphase.com/cat/p-266en.pdf
Kenwood L-08M. Final generation of the DC high speed amplifier backed with Kenwood Sigma Drive. 20,000 damping factor. Only 116 dB SNR and hiss can be heard with your ear directly to the tweeter of a high-efficiency JBL 4319. More noise than today’s best but still one of the highest damping factors of any amplifier.
https://1001hifi.blogspot.com/2018/04/kenwood-l-08m-rebirth-of-amplifier1980.html
2000s era: Audiophile Jewelry Era
McIntosh MC2102. The tube amp build to match solid state performance. Equivalent of a high-precision mechanical watch, it pulls out all the stops to produce an amplifier with no transistors in the signal path to achieve a measured performance that matches an average solid state amp. Imagine a mechanicslcwatch with the reliability of accuracy or a Casio solar. Tubes provide the benefit of the soft clipping and harmonics of tubes as you drive the volume up.
Devialet Phantom Silver: Not a traditional amp in the classic sense, but unlike the Devialet Expert that was measured here, a highly DSP’d speaker with superb bass extension at average listening levels of 80-85dB. Plagued by idiosyncratic software. The original firmaware allows it to be run in a pure direct optical, low latency mode which is where the speaker performs the best. The current generation Phantoms have dropped that low latency feature.