First impression: Herron VTPH-2A phono preamp

georgehifi,
Before I start rewiring my system, I'll probably set the gain as low as it will go on my preamp (Parasound JC 2 BP) and kick the gain up on my 4B Cubed. A fun adventure for tomorrow. As far as the Goldpoint is concerned, I haven't used it in about six years and really don't remember the impedance. I'm sure I have literature on it somewhere or it's tagged on the unit.
Just finished listening to some old Starship, Knee Deep In The Hoopla. I'll bet I listened to the song Sara six times. The VTPH-2A is something really special. I've gotta know what rob67 thinks of the unit in his system. I wouldn't be surprised if it puts a grin on his face from ear to ear.

Yeah I saw that with the 4B cube it has two switchable gain settings.

Here’s something you may like to know, "if" this gain changing is done where most are done, the same way I used to do my tube or solid state amps I built, via changing the nfb (negative feedback ratio).
Then you may like to know that a higher gain setting is a lower feedback ratio, which "can" give the 4b a slightly more tube sound with a little less damping factor and maybe more 2hd.

Cheers George

Prof, you mentioned the Parasound and Sim Audio phono stages.  What were the other three you tried previously?

Prof--glad you like! One of those rare products in high end that exceeds the hype and yet somehow flies below most people's radar. What you get: SQ approaching the limits of what is possible yet a relative bargain compared with most ultra-high-end stages AND what is arguably finest customer support extent. Have fun!

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