Dedicated phono-pre for MM only?

I just paid too much for a B&O MMC20CL off eBay. I hope I will be happy.

I think that I was looking at that one too . . . glad you got it. If it's in good shape, then you didn't overpay. Stellar cartridge.

On the AD797 - this opamp is capable of extremely high performance, but it's definately NOT one to swap into an existing circuit without careful consideration, especially if it originally uses TL072s! The AD797 really shines with low source impedances (not MM cartridges), but on the other hand, it can be limited in its useable output current . . . so it doesn't necessarily do the best job of driving the low-impedance feedback network that suits its low eN characteristics. That's why I used the discrete JFETs as a buffer, and why I used it in the second stage, where it can be driven from the low source impedance of the first. The AD745 is FET-input, so it works great with an MM cartridge . . . but it's not stable at lower gains, so stability and phase margin have to be carefully considered in application. Then there's the fact that the TL072 is a dual, and AD797 and AD745 are singles.

For general TL072 replacement, try OP249.

Dear Lewm: That's right, if I need a different load impedance then I soldered a new resistor value, no switch. Normaly almost all the LOMC cartridges comes with a very low internal resistance where 100 Ohms can cope all them. The other subject is that due to the Ponolinepreamplifier characteristics you don't need to change the load impedance, only in extreme very extreme cases.

Lewm, one way or the other normaly a switch makes a degradation to the cartridge signal so you have to make a decision on trade-offs between quality or convenience, we choose for quality performance.

Regards and enjoy the music,
Raul.

Raul, Just another one of life's compromises.

Kirkus, Would you care to comment in more detail on your earlier statement that a balanced input is per se not ideal for an MM cartridge? At least I think that is what you meant to say.

By the way, thanks largely to Kirkus' input I am beginning to learn some things about MM phono stages and phono stages in general that I did not know.

This thread has been informative and I'm better understanding some of the nuances of phono stage design, both MM and MC architecture.

And I'm beginning to see the value in having a dedicated MC phono preamplifier if LOMC cartridges are preferred. Why bother with 40 dB gain and 47K loading for MM cartridges. The design would, at most, have binding posts to change loading resistors. Being able to change the amplification (gain) would be handy but not necessary if the output voltages of the preferred cartridges were within a fairly close range.

Is such a phono preamplifier available?

Tom

Oops. Meant to include a thank you to Axel and Lewm for answering with understandable information. And Axel, I didn't intend to sidetrack the thread with my question about dedicated MC phono preamps. Just seemed like a similar question in that having phono stages designed specifically for the type of cartridge engine makes sense.

What I'm not sure about is whether you'd be able to hear the difference (as Lewm suggests) between a dedicated minimalist design vs a preamp with variable gain/loading options. I often read that it does make a difference, that having switches or plugs or jumpers degrades the signal, but as Lewm also suggests, if the problem is that noticeable, why do even high end manufacturers provide gain/loading flexibility in their phono preamps?

Tom