As an EE, my opinion is that transformers are the most logical choice. They convert impedance and voltage inherently which makes them perfectly suited for step up of small voltages. Transistors can do it too but aren't nearly as elegant a solution, either in terms of physics or design.
But I am not a vinyl guy so I haven't made any direct comparisons. It probably depends on everything anyway so I doubt you can get a clear answer to your question.
There is an article in the September Sterophile by Art Dudley talking about transformer step-up devices for MC cartridges and how to select the optimal gain and loading for your particular cartridge. He discuss a relatively inexpensive unit from K&K Audio in NC (www.kandkaudio.com) that has selectable gain and can be bought either assembled or in kit form. I thought about trying one myself as I use an Aesthetix Rhea unit to provide all the gain for my MC cartridge. The only thing that has kept me from trying this is the requirement of buying another pair of expensive interconnect cables. This might be a good solution for your application.
Are their any differences in sound quality? Certainly.
Which is the better choice? It depends on your budget and sonic priorities.
I own a PV-11A and a pair of Bent Audio (S&B TX-103, copper) transformers. For the money they do remarkably well, though with SUT's it is critical to get impedance loading exactly right. This requires in-system experimentation with combinations of resistors. Don't expect optimum results from plug 'n' play.
I also own a world class active MC/MM/line preamp (Nick Doshi Alaap) which easily outclasses the c-j/Bent pair. The MC stage uses FET's and it has enough gain for the lowest of LOMC's. The MM and line stages are all tube, so that both raises and answers Viridian's question.
Why did Nick choose FET's for MC gain? Because in his circuit they provide cleaner, quieter low level gain than tubes without the ultrasonic ringing and bloat common to transformers. In the end, it's as much about implementation as it is about theory. Every gain device has strengths and weaknesses. It's the skill of the designer that makes it work, or not.
If you're on a practical budget a PV-10A with a good tranny is a real winner. The S&B's are one good choice, especially with the silver wire, and there are others. If budget's not a concern it's possible to beat trannies with (some) active gain stages, but it takes a major expenditure and the rest of the system needs to be able to take advantage.
I'd have to respectfully disagree with Aball. I'm also an E.E. I would agree that transformers are usually a better choice sonically than op-amps. Tubes seem to be about the least desirable way to do a high gain stage. As Doug said, it's really all in the implementation. Below a certain signal level the transformers will act as a filter because some of the minute changes in the original MC signal will be insufficient to induce them in the secondary windings. The result is a loss of low level detail. Now, whether that is a good or bad thing can be argued as a matter of personal taste. Much like the choice between detail and what some would call musical. IMO, if you're missing the details you're missing the music.
The key is to match the particular transformer load to a given cartridge. Don't expect to get just one pair of step-up transformers and expect to play around with tons of different carts. They might work well with a bunch of carts, but chances are slim. Rarely is synergy more important.
"Below a certain signal level the transformers will act as a filter because some of the minute changes in the original MC signal will be insufficient to induce them in the secondary windings. "
Amazing, over 25 years in this hobby and of all the reasons I've heard not to use transformers I have never heard that, nor does it make any sense to me. I see how transformers can be frequency dependent but not amplitude. Please explain.
You've got it right, Herman. Those very tiny variations in frequency aren't always going to be able to be reproduced on the other windings. Now, put those tiny fluctuations on an even smaller signal and they really get lost. It's a smoothing effect.
You're putting words in my mouth, Herman. I said nothing about a lower amplitude limit. The entire signal does not get through a transformer intact and what does get through is changed. It is even more evident with low output MC cartridges. If you've ever heard a well implemented SS gain stage you'll understand what I'm talking about.
That's not to say the signal is not being changed in a FET stage. But to date, it is the best sounding solution I've heard. Not to say I've heard 'em all by any means.
Dan, I guess I misinterpreted your post but in my world signal level = amplitude. I don't see what else it could mean.
Below a certain signal level the transformers will act as a filter because some of the minute changes in the original MC signal will be insufficient to induce them in the secondary windings. The result is a loss of low level detail.
I've owned and heard some of the most highly regarded SS and tube phono stages that did not use transformers (including Aesthetix and Pass Xono) and my present one that does, among others. To my ear the transformer stages were better.
Back to the original question. Your choices are very limited for a stand alone active stage to boost the signal so your MM stage can use an MC. CJ used to make one a long time ago but I don't know of any others. I think you will be very happy with a quality transformer.
Touche, Arthur! :) The iron in my Lectron is excellent, but the intricacies of the signal from the catridge have already been flushed out by then.
And apologies to all for my over-simplistic, barely intelligible attempts at explaining why I don't think transformers are the best way to go for MC gain stage. That's a side effect of watching a baseball game, football game, catching up on audio threads all at the same time. And, with it being a holiday weekend, all spiced up with a bit of Ol' Number 7.
I also used to own Aesthetix and I would completely agree with Herman that compared to that implementation I would take the step-ups in a heart beat. But transformers over my Alaap MC gain stage or Raul and Jose's Essential? No way.
Since we don't know what cartridge he's planning on using, I'm not sure that the transformers would be the easiest solution for Havel. There is still quite a bit of load tweaking he'll have to do to optimize things.
Dan, at the level of equipment you are talking about the difference in transformer vs. active starts, or probably has long been, a matter of taste. We're talking here about boosting a MC up so a CJ PV10A can use it, not replace the pre with a mega-buck phono stage. I've owned one and the CJ is a great pre for the money, but it isn't practical to mate your suggestions to a $700 preamp. Transformers are the only practical solution.
AND, loaded on whiskey or not, quality step up transformers do not lose any detail vs. an active stage. On the contrary, at some point the lowest level signals from the cartridge fall below the noise floor of the active input stage and are therefore lost. This doesn't happen with a transformer.
Dear Halev: I don't want to argue ( this time ) what others already posted about step up transformer but IMHO the best step up transformer is no step up transformer.
Now, IMHO too I think that you could have a very good quality sound performance through MM cartridges ( that beats many high price MC ones ) that does not needs another stage/filter ( step up transformer/gain ) , you can find several very good MM cartridges out there.