Tube MM Phono Buffer

[watchnerd]

I'm enjoying playing the tube rolling game with my Fi Yph (passive RIAA, 2 x 6922/6DJ8 for gain).

But I realized I don't really need a passive RIAA, as my Devialet already has RIAA via DSP built in, which should be theoretically superior to even a passive network.

So I started thinking 'why not just have a tube buffer between my SUT and MM amp inputs'?

But when I look at various tube buffer or tube line stage options, they seem to all have 10k input impedance, which isn't going to work well with my 1:15 SUT in terms of reflected resistance for cartridge loading (>100 ohm for my current carts).

Is there such a thing as a tube gain stage, no RIAA, with 47k input?

Are there DIY options?

 

[SIY]

Putting a buffer in that spot will add a boatload of noise with no good return. If you insist on going that route, just change the input resistors to 47k.

 

[watchnerd]

Putting a buffer in that spot will add a boatload of noise with no good return. If you insist on going that route, just change the input resistors to 47k.

I'm probably not using the right vocabulary.

I'm curious about tube stage / tube effects box that would fit something like this

LOMC -> SUT 1:15 (output ~5mV) -> 47k input tube stage with little to no gain -> MM input on Devialet

I guess that's not a tube buffer? "Tube buffer" seems to be the term used for unity gain tube devices that I see sold.

This has no purpose other than just dicking around with the box of tubes I have.

 

[somebodyelse]

It's the right term, but an unusual application. I'd encourage dicking around. Does the Devialet have a tape loop or pre-out/power-in where you could use the buffer at line level? That would give you the effect with less noise penalty, and would work for all inputs not just the turntable.

 

[SIY]

I'm probably not using the right vocabulary.

You were, but what you're thinking about adds a noise source with no gain at a low level point in the circuitry. Not only that, but the small voltage swings at that spot means that the non-linearity of the "buffer" (scare quotes deliberate) will not be exercised and you won't get much of your desired fuzz and dirt.

 

[watchnerd]

It's the right term, but an unusual application. I'd encourage dicking around. Does the Devialet have a tape loop or pre-out/power-in where you could use the buffer at line level? That would give you the effect with less noise penalty, and would work for all inputs not just the turntable.

Yes, it does, but the only other input I use is Ethernet.

 

[watchnerd]

You were, but what you're thinking about adds a noise source with no gain at a low level point in the circuitry. Not only that, but the small voltage swings at that spot means that the non-linearity of the "buffer" (scare quotes deliberate) will not be exercised and you won't get much of your desired fuzz and dirt.

The Yph has about 30 dB of gain, with a passive RIAA, and and at normal listening levels, doesn't have any noise I can hear with my ears to the speakers (when combined with the SUT and the Devialet set for 0.4V input at line level).

Would noise be less of an issue of the hypothetical gain was higher than unity, i.e. same as the phono stage, but minus the RIAA?