1) affordable phono-stage with MM (Reflex?)
2) good stage with MM
3) good stage with SUT and MC (Note: not mentioned headamps i.e. Elevator)
4) top stage with MC
2) and 3) maybe on par, and MC = LO MC > 0.4mV "
Hi Axel - I think its really difficult to make these kinds of general heirarchical statements about performance, price and topology . . . for a few reasons:
- You can't assume that providing the additional required voltage gain is always going to be the biggest challenge when designing a phono preamp for use with an MC cartridge . . . it may be for some designs, but definately not all.
- The usual axiom of "price and performance don't always go together" . . . even though they do frequently, we must always be skeptical here.
- I think that the implementation of an external SUT will always be a compromise - mainly because the transformer will have to be designed in a specific way to provide a "standard" step-up ratio that works well (in terms of voltage gain and output impedance) with a "standard" MM phono input. In a phono stage such as my own, the transformer (a Jensen JT-346) has a turns ratio that is much lower than a typical SUT (thus much higher performance) and provides a perfect En/In match to the electronics that follow it, which in turn have had their gain adjusted to suit the paramters of the SUT. That is, the transformer and electronics have been designed specifically to work together, not as a "universal" add-on solution.
On the subject of accurate RIAA . . . I was actually inspired by Raul's postings to take this matter very seriously in my own design. This isn't an easy thing . . . there are specific challanges to even measuring it to better than +/- 0.01dB across a 40-dB-ish range of signal level, as most test equipment must either generate or measure it through several output/input measurement ranges. For this, I was lucky to have an APx 525 on loan as an extra test set to verify the results against the AP2700's measurements . . . suffice it to say there needs to be some very careful hand-selection of parts to even begin to come close to this level of accuracy.
And there's the question of . . . why should the preamp be so precise, when no cartridge is anywhere close to this? Well, error is error . . . and it's always statistically additive in this case. After all, our CD players and amplifiers should have extremely precise response, even though a loudspeaker can't come anywhere close . . .
