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Phono Pre Impedance Matching- Herron VTPH -2A or Manley Chinook

The upgrade bug has bitten again, and I’m contemplating trading in my beloved MAGI Phonomenal for a new phono preamp.

At the top of the list (and the top of my budget) is the Herron VTPH-2A.  Of course, there’s nowhere in my area to audition, so I’m going on the universally glowing reviews here and elsewhere about this phono stage. My one reservation… The dreaded impedance matching issues between the Herron and my LFD NCSE MkII.

LFD doesn’t publish input impedance specs for this integrated, but an email to its designer yielded the following response: “Since the NCSE … uses a passive preamplifier section, the input impedance is around 16k ohms”

The Herron’s output impedance is 400ohms.  In speaking with Keith Herron, he agreed that though this wasn’t the worst match, there might be some compromise in overall dynamics with this combination. In all I’ve read, it seems that this would result in an attenuation of the deepest lows.  Frequencies that my Harbeth SHL5+ at 40Hz may not attain in the first place.

Second up would be the Manley Chinook, also glowingly reviewed and which lists its output impedance at 91 ohms.  Clearly a much better ratio and as a bonus, the Chinook is more readily available used and would be a slightly smaller bite in the wallet. But I hate to think that I'm missing out on a very good thing.

The persistent question: Which would be the greater compromise? 


krabbypantz

Showing 1 response by mulveling

mulveling's avatar
mulveling
1,774 posts
 
16k is a tough load for a lot of tube gear. Don’t go by just the single listed impedance number (eg 91 ohms for the Manley). This can vary by frequency, usually drastically rising for low frequencies due to output caps. As Keith mentioned, often you’re most worried about performance in the bass frequencies, where a lowering ratio of input to output impedances can result in very audible roll-off. Even what looks look like a minor roll-off on paper can have audible effects. I’d at least ask Manley what they think before assuming the Chinook will be performing optimally into 16k. 

I love tube phono stages, but I’m afraid that your tough 16k load will be at best a mild compromise for many of the best units. It could possibly help on some units to replace the output caps with larger ones.

I currently own Rogue Ares Magnum, Herron VTPH-2A, and a VAC Renaissance phono stages. All great performers at their various price points (the VAC is very spendy but sings like magic). All of those companies are run by great guys that back their products and are happy to help out!
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