Dedicated phono-pre for MM only?

Hi Fap, Tketcham
>>> ..this quite simple to build design is amazing! <<<

OP-Amps, not part of the spec I'm thinking of.

I realize it's maybe time to go into more detail.
Also, the 'Jadis' would be single-ended also not part of the idea, good as it my be.

Rough spec. would be:

- 40dB
- tube gain stage (max. to gain stages)
- 1 JFET gain-stage? Maybe, to get minimum tube-rush/noise
- or e.g. Lundal trannies to get the first 20dB?
- shunt regulated power supply
- differential circuit (XLR out-puts, differential wired RCA inputs)
- no volume control
- floating RIAA (between + and - of the differential circuit)
- one box design (if at all possible, by use of good screening)
- No PCBs, screened silver wire for internal wiring.
- Good,e.g. WBT connectors

That should cover the basics. What tubes to use, trannie, resistors (Tantalum, or?) is dependent on the circuit design and implementation.

Greetings,
Axel

Ah, now we have a reference. What you suggest seems reasonable for a manufacturer to offer for sale. (You would certainly know better than I.) But I think you answered your own question as to why they don't: The lack of offerings is most likely a financial decision, not a design decision. If they don't see the market need for a high end dedicated MM stage they aren't going to bother. I guess they don't read the posts from you and Raul. '-)

A question for you, Axel: Do you think that a high quality SUT or headamp could provide the gain and loading needed to turn a high end MM stage into a high end MC stage? Or does the use of external transformers or headamps degrade the signal too much to be considered acceptable for a high end phono stage?

Tom

Axel, you and I are thinking along the same lines, save for the fact that I would not use a transformer anywhere. The desire for a balanced circuit is a real sticking point as almost none of the commercial products offer that. There is the Aqvox, but as far as I can understand from their very confusing ad copy (where they say in one para that it is balanced and in another that it is SE), the balanced circuit, if present, is used only for MC cartridges. If you use the MM inputs, the circuit is SE. The ad also contains some mumbo jumbo about MMs being voltage generators that prefer a SE circuit topology (as compared to MCs). I don't "buy" that logic. The new K&K phono is I think balanced, and I intend to look into that one.

The IC design is interesting, but the ICs used have been surpassed for audio in recent years; I am wondering whether one can just plug in one of the later better sounding ICs, without a re-design.

Herron Audio makes a tube MM Phono Pre-amp. I have not heard it, but I have been using their MC Phono-pre for a number of years (on my second set of tubes), and I have never (yes, never) heard one that was better. As with all things audio, YMMV.

Dave

Correction:

I just checked Herron's site and they have discontinued the dedicated MM phono-pre and now have a combination MM/MC with variable loading provided by changeable plugs.

Interesting looking answer to a common concern.