Dedicated phono-pre for MM only?

Hi, Axel, it makes sense that newcomers to vinyl would benefit from using MM cartridges initially. And having a high quality, affordable (but dedicated) MM phono stage would be something they could continue to use as they upgraded the turntable and other components. The Graham Slee Reflex and Elevator appears to be one option that fits the upgrade path. I don't have the experience to offer an opinion as to whether it's high end or not.

But I think that for many people starting out, committing to MM cartridges due to a specialized phono preamp is not a comfortable decision. I know when I purchased my first "real" phono preamp, I chose one that had a wide range of gain and loading options because I wanted to be able to experiment with different cartridges without having to purchase additional components; i.e., a SUT or headamp.

But it seems (based on the discussions of this thread) that a dedicated MM phono preamp may not be the best design for adding LOMC capabilities, thus requiring a completely different LOMC preamp to get optimal sound. There's no simple (or affordable?) solution. '-)

Hi, Lewm, I didn't offer the Jadis as a reference, Axel mentioned it in his initial post. I checked some prices and one their premium designs (JP80MC) was approaching $20,000 USD. That's when I retracted my suggestion of the Reflex as an example of a high quality dedicated MM stage. Not really fair to compare a $1300 USD phono preamp with one costing more than ten times that. Or maybe it is... '-)

Tom

Has anyone compared the MM stage in the solid state EAR 324 to the one in the tubed EAR 88PB? The 324 allows adjustable impedance (including 100K) and capacitance whereas the 88PB is 47K only with no adjustments.

Hi Saudio
EAR 324, a good one in the context of MM - alas it showed some issues with too little head-room in the 20Hz region. Not a lot going on down there mostly, but still.

The 88PB would be more ===> MC targeted I'd guess.

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 . . .