Dedicated phono-pre for MM only?

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 . . .

Hi:

I was following the thread the last few days for a different reason than most of the previous participants. I have a Supratek Chenin that has only a MC input and I want to experiment with one of the Moving Irons made by Soundsmith that require a MM input. Currently mi analogue rig is Teres 255/Triplanar VII/Zyx Airy 3 and I am puting together a second analogue rig that would be finished in a couple of weeks. I bought a Townshend Rock III with a Moerch DP-6 and a totally refurbished Lenco L 75 (with a 70 pound plinth) with a Micro Seiki MA 505. I want to install the Soundsmith The Voice in both of those tables and see how it sounds. I can even install the Moerch in the Lenco and see what happens. That is the reason I am looking for a dedicated MM pre-pre. Thank you very much for this very informative thread and the options that you are considering. I will look for the K&K, Whest, Aqvox, Haberman and Allnic here on Audiogon and buy one of them. Regards, Pablo.

Hi Kirkus,
as always, a thoughtful and well laid out response.

As far as SUTs go, yes they need to be matched, well matched! But if done, they have some 'magic' of their own and can make an MC something more full of 'live' and vibrant.

As to this RIAA 'ping-pong' you say: "Well, error is error . . . and it's always statistically additive in this case"
Not necessarily since there are errors to the (-) and (+) side of the curve, yes?
And we are actually talking about observed 'tolerances' just not quite the same as ERROR, in my vocab anyway.
Now, tolerances can be additive or subtractive.

This would also mean that some of this 'synergy' so often mentioned, is just one of the things that make one cart sound better in a given set-up then in another.

As far as SUTs go, yes they need to be matched, well matched! But if done, they have some 'magic' of their own and can make an MC something more full of 'live' and vibrant.

Oh yes, absolutely agreed! Even in a purely technical sense, there are many inherent advantages to transformer-coupling a LOMC cartridge . . . and I obviously chose this approach myself. I simply wanted to give counterpoint for those that feel that SUTs are inherently inaccurate and colored - because I understand how one could come to this conclusion . . . as most implementations on the market IMO don't really realize the full performance possible in the transformer approach.

Not necessarily since there are errors to the (-) and (+) side of the curve, yes?
And we are actually talking about observed 'tolerances' just not quite the same as ERROR, in my vocab anyway.
Now, tolerances can be additive or subtractive.

From a statistical/tolerance standpoint, yes, this is purely additive error. In electronics design, there is a specific procedure called "monte-carlo" analysis . . . which takes the maximum allowable tolerances of each component and combines them all in the absolutely worst-case situations - and this gives you the performance tolerance of the entire circuit.

In the audio chain, to define frequency-response as a deviation from perfection . . . keep in mind that in this definition we may have no idea exactly what the particular error is for each part, only that they are within certain limits. So while we can hope for that perfect synergy where every error just happens to cancel each other out . . . if we are to truly take responsibility for the performance, we have to assume the "perfect storm" where all the errors just happen to add up in the worst way.

Hi Kirkus,
>>> ... assume the "perfect storm" where all the errors just happen to add up in the worst way.<<<

"Monte Carlo" analysis, OK... the inventor must have lost it ALL then - worst case.
BUT he did not consider any form of 'synergy'. The importance of synergy has been pointed out over and over, in fact lots and lots of times by Raul himself :-)
Must be some concession to this 0.075% perfection.

I worked in pcb, and later semiconductor assembly, that gives me that practical bias what can be done if it gets 'commercially' viable.
No way to have much better then 1% components on a tape-fed bonder doing SMDs, as I mentioned earlier.
Also no way to start improving tolerances after the stuff (not only SMDs) are on the pcb. (Note: >3x rework = reject)

I have a pretty good idea, that this is where some realism in terms of tolerances has to prevail, meaning ALL hand build, bespoke, and nothing done 'commercially' will qualify --- seriously, that doesn't float my boat yet.

Why? Because a lot of 'bespoke' products have plenty more hidden QA issues then something more 'commercial', where errors have been weeded out to a much higher degree.