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Dedicated phono-pre for MM only?

Hi All,
the subject of phono-pres, specifically 'adapted' to MM came up in some related postings.

IF, and only if, MMs are much to ones liking --- why spend your buck on some 'halve backed' 60dB plus, MC gain requirement, stage? Why not consider put the $$$ into a TOP 40dB gain stage of either SS or tube?

Raul had more thoughs on the subject as he mentioned before, and might share, why he knows that a TOP MM compared to MC stage circuit requirement might NOT be -one suit fits all-.

There could even be a nice argument to fit a tube gain stage only into an otherwise SS only system!?

Again, the $buck saved on the 20dB plus circuitry could be translated into the BEST circuit for an MM.
I realise, that most such stages were simply fitted inside some older TOP pre-amps, (e.g. Jadis...).
I have not come across a **dedicated** , current 40dB stage neither in nor outside a pre-amp.

Thank you,
Axel
axelwahl
tketcham
291 posts
 
So it seems that a quality SUT, or, a high quality dedicated MC phono stage, is the key for MC cartridges. Since MC cartridge designs include a fairly wide range of output voltages and internal impedances, and thus gain and loading requirements, it may necessitate a range of dedicated MC phono stages if someone wants to listen to a variety of LOMC cartridges.

Too bad, because that sounds expensive. Is the added expense (of having multiple dedicated MC phono stages) worth the perceived improvements in sound?

Tom
lewm
12,878 posts
 
Tom, I did not get that message (that the range of output voltages and inernal impedances of MC cartridges presents a problem per se) from Kirkus' long post. I will have to re-read it, but I think he is saying that the much higher output impedance and reactance of an MM cartridge poses a problem for MM phono pre design.
Kirkus, Given your depth of knowledge of this subject, are there any commercially available phono preamps that seem up to snuff for use with MM cartridges exclusively?
tketcham
291 posts
 
Lewm, my mistake for not including the intended recipient in my post. (I don't post here at Audiogon very often so am not used to the continuous thread format.) I was trying to get a sense from Axel (and others) if it was worth the added expense of having dedicated phono stages for several LOMC cartridges, each with a unique amplification and loading requirement. That's making the assumption (and the analogy to a dedicated MM stage) that to get the best sound from a phono stage, the design must be specific to the cartridge.

If so, then the question might also be asked: Dedicated phono-pre for (specific) LOMC only?

Tom
axelwahl OP
788 posts
 
Hi Tom
you say:
>>> it may necessitate a range of dedicated MC phono stages if someone wants to listen to a variety of LOMC cartridges <<<
I can not support that logic as e.g.: all women are people, there for all people are women? :-)

Loading with MC stages and to some smaller degree loading of SUTs (secondary and primary side) takes care of the variations in MC's DCR and output voltage. Of course a mismatched SUT/cart can not be made to work by loading e.g. if it would overload the phono-stage.

Greetings,
Axel
quiddity
119 posts
 

Kirkus

Thanks for that, I will have a more careful look at the design calculations for my MM only phono amp. The input stage is currently using 2SK389BL as diff amps with simple resistive loads (balanced inputs, there's no need for a feedback connection to the diffamp 'cos there isn't any feedback).

It will be easy enough to change these to cascode.

Mark Kelly
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