Measurements provide insight into what is heard - and why. They're never a substitute for listening, which always must be the first and last evaluation technique.
There's no conflict between the measured/calculated gain data I provided and the empirical experience cited. As I will demonstrate below, they actually agree quite well. But, in the end, ya gotta listen ... read on!
My data is for the Tempest's separate stages - MC, MM, and Line. So the total gain for MM thru Line is (33+13)=46dB and MC thru Line is (20+33+13)=66dB. These gain figures fit the Benz high- and low-output parameters cited in the prior post.
Moreover, 30 to 40 dB is a verrrrry typical mid-band gain figure for MM phono preamps or stages, be they freestanding or integrated into the control preamp, as I've found during 35+ years of tinkering in the guts of audio gear, both as a hobbyist and professionally (broadcasting). I'm contemplating several tube MM designs of my own that have around 35dB at mid-band (add 20dB from a good transformer and the MC gain will be sufficient for most decent cartridges).
And, finally, the Stratos has higher gain than many power amps. So it needs lower input levels to get you the desired sound level out of your speakers, hence lesser preceding gains work just fine, as long as you don't get into noise trouble. I haven't measured my Stratos Extreme, so I won't cite any gain numbers until I do.
I use an Ortofon Kontrapunkt B, with 0.5V output (that's 15-20dB less than the "typical" MM). It performed well with the Tempest, which is much quieter than the Acurus P10 used before (and now, while the Tempest is in Indy).
To consider the overall gain necessary analytically, one must start from desired sound level and work backwards, through speaker efficiency, power amp gain, and preamp stage gains. Because of the substantial variations in the first two parameters from product-to-product, requirements for the latter are highly system-dependent. Let's presume that one desires 100dB SPL at 1m from the speakers, with an efficiency of 87dB and power amp gain of 31dB. The necessary preamp gain, for a 0.5mV MC cartridge, is approximately 45dB. The maximum gain of the Tempest in MC mode is around 66dB, so 21dB of attenuation is required from the volume control, which achieves that near mid-rotation (12:00). Hmm ... this result agrees with my experience and that cited in the prior post!
But, for MC cartridges, the most important performance parameter of the preamp is its noise floor. Minimizing that is the primary challenge in designing phono preamp stages. And the better examples available today are pretty close to the theoretical limit of what's possible. The noise limitations of low-level preamplification is why I tend to prefer high-quality transformers for MC step-up (a bias that is, undoubtedly, a product of my age and experience with more noisy circuits during my formative years). Their gain comes with no added noise penalty, if they're installed correctly.
Below 0.2V output with the Tempest? Depends on your ears and listening environment, say I. My hearing resolution is pretty good (well, it was before the left ear got tubed last week), but the overall sensitivity is not good and hasn't been for years (my ear surgeon has the residents studying under him examine my ears as examples of abnormality). I would probably be reasonably pleased with the performance of lower output MC cartridges, for I would not perceive the effectively-raised noise floor because of my hearing limitations. Someone without any hearing deficiency (e.g., my wife) would hear the noise and would not be happy. And I'd have a hard time resisting the temptation to A/B compare with a transformer.
So, we've come full circle. In the end, the ear is the largest variable, so listening must be the final means of determining how little MC output is tolerable.
Karl
