And as a postscript, let’s not forget that the SRX mods have implications for existing Tom Evans owners too, in that they offer both an upgrade path for Groove owners and the option for cartridge matching across the range, enhancing the performance available to MicroGroove users as well.
The Herron Audio VTPH-2 Vacuum Tube Phono Preamplifier
While tubes have a long and honourable history when it comes to amplifying the signal from moving-magnet cartridges, moving-coil stages relying on thermionic devices are altogether more rarified and tend to be temperamental. So, given Herron Audio’s reputation for sound engineering, solid technical performance and exceptional consistency, it’s no surprise to find that, whilst Keith Herron’s VTPH-1 standalone phono-stage coupled passive RIAA equalization with tubes for its movingmagnet section, the moving-coil version added a solid-state stage to provide the necessary extra gain. Otherwise, the unit was business as usual for a Herron design: thoughtful and conservative engineering (for which read “solid” as opposed to the all to frequent “flaky”), matched parts, exemplary technical performance, almost obsessive attention to detail. And like the other Herron products, the result was a performance that belied the surprisingly modest price-tag. Which was a bit of a problem. You see, the VTPH-1 was a no-holdsbarred, minimalist design intended for a few analogue die-hards of Keith’s acquaintance. Unfortunately, the word got round and demand rapidly outstripped supply, causing a rapid reappraisal of the situation – and a far less rapid evolution of the design into a more manufacturable and user friendly device. Along the way component choice and tolerances were further refined, along with some of the thinking behind the product.
Enter then the VTPH-2, visually essentially identical to the VTPH-1 – at least from the front: the same compact and solidly constructed chassis, the same three LEDs to indicate the start-up sequence and operating status (blue now rather than green, to match the latest line-stages). But round the back things get a whole lot more adventurous, with double the socket count for starters. So, whilst the VTPH-1 was a dedicated design, either movingmagnet or moving-coil, the -2 is a switchable device, with inputs for both high and low output pick-ups. Also, where the high-gain version of the -1 required a technician to solder resistors across the inputs to fix loading, parallel sockets and loading plugs make user adjustment a doddle. And yes, hardwired loading resistors do sound better so that option remains, once of course you’ve decided on the optimum value. Incidentally, Herron encourage you to at least try the moving-coil inputs as supplied, wide open or in effect, with an infinite loading value – of which more later.
Much of the circuit topology itself remains essentially the same, the MM section and power supply arrangements being almost identical to the earlier version. There’s also the sophisticated three-stage slow-start arrangement, designed to protect the performance of the valves so critical to noise performance. But the solid-state gainstage is all-new, employing different FETs and a new circuit. Couple this with various refinements and improved component quality and matching elsewhere and you’ve got sound reasons for the uplift in performance over the -1. And yes, the -2 does sound better… Supplied as standard with a quartet of 12AX7s and a single 12AT7, offering 69dB of gain in moving-coil mode and 48dB with moving-magnets, replacing two of the 12AX7s with 12AT7s will trim the gain in both instances by 5dB, a useful option when it comes to matching cartridge output and overall system gain for optimum results. Finally, there’s a mains polarity switch on the rear panel, something that should really be obligatory on all electronics – and yet another example of Keith Herron’s no-nonsense approach to engineering that matters. And you get all that for $3650. Yes, US dollars; inexplicably the Herron products have no UK distribution at present, although they can be purchased in 230V versions from Herron direct – just remember to add shipping, duty and VAT.
Even leaving aside the increased versatility of the VTPH-2 it is still a clearly superior unit to the original version. Side by side comparison with both phono-stages loaded at 47K, the -2 immediately displays superior transparency, separation, a broader tonal palette and more harmonic texture. Voices and instruments are more easily differentiated, the way they fit together much more obvious. Remove the input loading plugs and run the unit wide open and there’s a further gain in tonal purity and immediacy, an easy, breathy quality and delicacy that makes this mode a really worthwhile alternative to those who prefer not to load their coils down. However, personally speaking I’ve never followed that path. Load the input down (interestingly the Titan i preferred a 200 Ohm load on the Herron as opposed to 100 Ohms elsewhere*) and the sense of focus, spatial separation and control all increase significantly.