Pure tube phono preamp

OP,

Not to be against your original idea which I have no recommendation for, just to clarify:

You seem to be both tempted by and concerned about separate SUT. I was too. I avoided MC for many years, because of noise of early pre-pre transformers. That problem's gone.

SUT's have no power, they simply have internal transformers, some with optional resistances. Well built ones have no hum. I put mine next to this and that, just to see, I cannot get any hum out of it.

OP, that's not what you really want; what you want is a SUT feeding into a tube phono amp, that will give you the silence you want plus the musical tube amplification you desire.

I had Zesto Andros PS1 for a couple of years connected Brinkman Bardo with miyajima kansui cartridge, the sound was love on first sound, dynamic, quiet on the background and you can hear all detailes.

a couple of months ago I change the Zesto with Brinkman Edison MKII and the Bardo with Balance, I got improved in all aspects but I can tell you that my previous combinations although not the same level wasn't a slouch either and gave me wonderful results that most of the people would be more than satisfied to have on their systems.

If you are talking about a phono preamp for genuinely low LOMCs, it is not really possible to get the high gain/low noise needed with just tubes.  Hence the need to use opamps, FETs, SUTs, etc., to do so.  Even the ARC Reference Phono 10 uses FETs in addition to tubes.

Of all the options available to get the high gain/low noise needed for LOMCs, many prefer using an SUT because it is a passive device (no active circuitry or power needed).  If the SUT is properly designed and mates well with your cart, they can not only be no/low noise, but also provide more dynamics, liveliness, and texture.  YMMV. 

If you are talking about a phono preamp for genuinely low LOMCs, it is not really possible to get the high gain/low noise needed with just tubes.

This statement is false. The trick is to set of the phono preamp design to be fully differential (which is what of ICs do) *and* to use an effective constant current source to really get the tubes to operate differentially.

A differential gain stage has theoretically 6dB less noise than the same thing operating single-ended. Now if you need more than one stage of gain (which you will) then if both are differential, now you have two stages of gain, each with a theoretical 6dB lower noise floor. Even if you are only getting 5dB per stage, this sort of thing adds up- to less noise.


My rule of thumb is the phono section should be quieter than a silent groove on a good LP. That's easily doable. BTW, finding quiet tubes for this is not hard; three tips: First, avoid Russian-made signal tubes. 2nd, avoid NOS tubes, as people have been scouring the countryside looking for low noise NOS signal tubes for decades- most of the really quiet ones were sold off a long time ago. Sure, you *might* be able to find some that are quiet still but seriously finding them will be a real pain or a whole lotta dollars buying 100 tubes to find 5 that are really silent. You're better off just buying new tubes. We buy 12AT7s 100 at a time and we reject about 10% of them. But if we buy Russian tubes of the same type we reject 90% of them. So the third tip is probably buy the tubes from someone that is grading them for LOMC use.