First impression: Herron VTPH-2A phono preamp

Professorsvsu, congratulations and continue to enjoy! I know you will, being one of several other members here using the VTPH2 or 2A/ART-9 combo.

Regarding passive preamps, the Herron phono stage is not suitable for driving a low impedance passive preamp. One reason being that its nominally 400 ohm output impedance undoubtedly rises to much higher values at deep bass frequencies, due to the use of a coupling capacitor at its output. (Also, btw, the configuration providing a 400 ohm output impedance provides 64 db of gain, not 69 db as was stated above. And I assume you have the 64 db version, which is what I and most VTPH owners have purchased).

From the manuals for the VTPH-2 and 2A:

We recommend that the VTPH-2A be used with a line stage having an input impedance of 50,000 ohms or higher for optimum performance.

And a direct quote of a response Keith Herron provided just yesterday to a member who asked him if the VTPH-2A could be used with a 20K load impedance (see this thread):

"We have VTPH-2A customers that are using preamplifiers with 20k Ohms RCA single ended input impedances that are pleased with the sound.
I don’t recommend going any lower than that. The 2 X 12AX7, 3 X 12AT7 version of the VTPH-2A has an output impedance of 400 Ohms so it will drive the Ayre preamplifier much better."

Also, I suspect that the degree to which those driving 20K with the VTPH-2A are "pleased with the sound" depends on how much deep bass extension their speakers provide, since one of the major consequences of this kind of impedance issue is deep bass rolloff.

Best regards,
-- Al

salectric,
I owned a Vincent and two Graham Slee phono preamps as well. They were disappointments, especially for the money. Until I purchased the VTPH-2A, the best bang for the buck phono preamp that I've owned was the Neo 310LP.

@dweller -- a while back there was a thread on the Chinook, and I distinctly remember more than one responder saying the Allnic H1201 and Herron VTPH (sorry, can't remember version) were significantly preferred in comparison.  Not surprisingly, there was praise for the Steelhead although obviously at a higher price point.  Just dusting off some synapses here and sorry for the sidetrack, but hope it helps. 

almarg

I can see where your coming from Al, the 400ohm is fine, as you say if the output coupling cap is too small there would be some rolling off the bass too early with a 10kohm passive.
 
I just did some calculations and if that coupling cap is 1uf or more all is fine. Do you know how big it is maybe you have one? I have sent an email and asked Keith I will post it up when he reply's. 

And if it is less than 1uf there's no trouble or much cost making it bigger, and at the same time a better quality one.

And the gain can be either: From Herron
Gain MC Mode
(2 X 12AX7, 3 X 12AT7) 64 dB
(4 X 12AX7, 1 X 12AT7) 69 dB

Cheers George