Dedicated phono-pre for MM only?

I think he was referring to the generally much higher and more reactive impedance of MMs and the fact that these parameters may not be identical for each phase of the output in a SINGLE channel, using a balanced circuit. This creates a noise that cannot be cancelled by the balanced topology and is instead amplified. Channel balance has nothing to do with it. If I am full of baloney, perhaps Kirkus will correct me.

Actually Lewm, you got it exactly.

Now why do you think, do I have NO hum what so ever with a FULLY opened pre, going balanced into a balanced phono-line-pre?

Well I'd say that you happen to have good synergy between the cartridge, tonearm wiring, and preamp input stage, at least in the sense that its noise-rejection happens to be sufficient to completely eliminate interference from the particular amount of mains-frequency magnetic flux to which it is being subjected.

Now whether or not the ML engineers anticipated/designed for a similar level of performance in other situations or environments, I have no idea . . . but for yours, they got it right.

Thanks Kirkus,
gotta get lucky once in a while in this here Audio game.

But as you mention as well, noise is only one facet of it all.
As I noted - tonality is yet another thing. In fact, funny enough it also seem very high on Raul's list of evaluation criteria too :-)

Axel

Axel, perhaps one reason you don't have "hum" is that the noise that might result from Kirkus' theorem would not necessarily be in the spectrum that we recognize as hum (60Hz or 120Hz, in the US; 50Hz or 100Hz in Germany). The noise he is talking about could be random in frequency (I think) and might not be audible as noise until one took steps to eliminate it and listened for the difference.

Lewm,
yes, I think this could be right.
It again would explain that even some well noted/quoted phono-stage designer(s) like SE.
There was Lamm's Vladimir Shushurin? that stated his clear and decided preference for SE -- but I think he then uses a trannie to change the output to balanced.
His main argument also was 'noise' and could well be what you just mentioned.

The new PassLabs-X15 seem very well regarded (best ever, etc.) would be most interesting to know what circuit it uses.

Axel

Hi Kirkus,
during an earlier part of the MM, balanced vs unbalanced and common-mode rejection posting the SUT subject came up shortly.

It may not fully relate to this thread, but let me try.

You mentioned in your example a 50 ohm SUT input impedance with a 5 ohm DCR MC cart. Explaining some advantages with regard to hum rejection, and how this of course can not be realised in an MM specific phono-pre (as a trannie cannot be used etc.)

Would you share your explanation, why with the use of an SUT (in my listening) some other parameters then hum are notably changed/improved i.e.

- more dynamic depth (better hi/low SPL differentiation)
- more powerful bass
- more hall/room information, stage depth

I could add some more, but it should do for this example.

Cart parameters:
3 ohm DCR
0.3mV output @ 5cm/sec

SUT parameters:
1:31.6 ratio (30dB, i.e. natural impedance 47ohm with 47k)
- primary DCR 1.5 ohm
- secondary DCR ~ 65 ohm (as I recall)
- primary loading 13 ohm (paral. with 47 ohm nat. imp.) i.e. 10 ohm that the cart sees.

If nothing else, it could high-light how very different a MC stage might just be as compared to an MM stage. So we'd be back at the subject, of sorts.

Many thanks,
Axel