First impression: Herron VTPH-2A phono preamp


I got my VTPH-2A this morning and it's up and running. After about five hours of spinning vinyl, I'm pretty sure I've wet myself, MULTIPLE TIMES! I've primarily played vinyl that I've had for decades, music that I thought I was intimately familiar with. I was wrong. There's nuance I never knew existed. Everything about the VTPH-2A is "right". The bass is tight, vocals superb, instruments have places, etc.  All that I've listened to sounds new and fresh and the most masterfully recorded vinyl sounds live. What I've read about on this forum concerning the VTPH-2A (pretty much all stellar) is true. I've had five different phono preamps and nothing can compete with this, NOTHING. It's a bad ass and definitely a keeper.
professorsvsu
@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. 

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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 
Hi George,

No, I don't know what the value of the coupling cap is, as I've never had occasion to open my unit.  One reason being that I've never felt tempted to do any tube-rolling with it, and in the process perhaps messing up the voicing Keith has achieved.

But in addition to what I mentioned earlier, that the manual recommends 50K or more as being optimal as well as Keith's statement that he would not recommend less than 20K, a few months ago he explicitly recommended to another member that the VTPH-2A not be used in conjunction with a 10K load, stating as follows (quoted by member Uberwaltz in a post dated 4-2-2018 in this thread):

Hi Kevin,

Thanks for the note. I like to see, as a general rule in high end audio, an impedance ratio of at least 1 to 100 (output impedance to input impedance) when using tubes or solid state as loading the circuits down generally reduces the quality of the sound. I have seen similar impedance ratio recommendations from Audio Research and other high end audio companies.

Solid state circuits generally have much lower output impedances than tube circuits. 10k Ohm input impedances are a standard typically used in professional audio, but this does not work as well for tube based high end audio equipment.

The two 12AX7, three 12AT7 version of our VTPH-2A has an output impedance of 400 Ohms which performs best into a 40k Ohm or higher line stage input. Some people are using them with line stage inputs that are a little less than that with reasonable results, especially if their cartridge has a lower output voltage. Your integrated with a 10k or 5k single ended input would likely restrict dynamics substantially, even with a very low output phono cartridge. I can't recommend that combination. Audio is supposed to be fun.

Another thing to watch for is that some line stages (particularly digital ones) have a very low input voltage limitation which can cause overload (clipping) with some analog sources. That can sound nasty.

For the reasons above I design our line stages with a 100k Ohm input impedance and a wide input voltage margin in order to get the best sound quality from tube based sources such as phono stages, tape machines, tuners, and DACs with tube output stages. I wish everyone would do that.

I hope this short explanation helps.

Best Regards,

Keith

Best regards,
-- Al 
that the manual recommends 50K or more as being optimal

Yes as I said before that could very well be because of the output cap size, as you know 400ohm is fine to drive a 10kohm load. 1:20 ratio is no problem even 1:10 also
We’ll find out that cap size if Keith emails me the info.

Cheers George