The back-story behind CH Precision’s eagerly awaited P10 Phono-stage
By Roy Gregory
The launch of the CH Precision P10 phono-stage in Munich this year has to be the worst kept secret in audio. Given that the P1 has become something of a universal benchmark amongst the serious audiophile and reviewer community, the new product has existing P1 owners champing at the bit – including yours truly! But while everybody knows that it’s going to happen, nobody seems quite sure what to expect. With detail so thin on the ground that even rumours are rare, I took the opportunity on a recent visit to the new CH offices in Préverenges to extract the pertinent information from CH CEO Florian Cossy. I’d love to say that I snuck a listen too, but the performance of the P10 remains well and truly under wraps. In the meantime, here are the details that the company is prepared to discuss…
Like every 10 Series product before it, the P10 consists of an audio chassis and a separate, dedicated power supply. It sports the same arrow straight feature line and box dimensions as the L10 and is available in the same three colours (grey, anthracite and champagne). The basic operation and the five front-panel buttons are identical to the P1. That’s where the similarities with the 1 Series product end. The changes are so numerous and so far-reaching that it’s necessary to break the functionality down into different blocks, just to avoid confusion.
Inputs…
The P10 is equipped with four phono-inputs (as opposed to the three on the P1) all with both balanced and RCA socketry. Two are current sensing and two the more conventional voltage sensing. The current sensing inputs now offer more gain with more finely discriminated gain steps (3dB rather than 5dB). But the major work has gone into narrowing the gap in performance between the voltage sensing inputs and the gain sensing alternatives. This reflects both the versatility of the voltage sensing topology (it accommodates anything up to and including MM cartridges and external step up transformers) and the fact that the two different approaches favour different cartridge types. While the current sensing inputs work best with cartridges with low internal impedance (<20Ω, ideally <10Ω), cartridges with higher internal impedance favour a voltage sensing input. The gain has been increased and the gain structure has been revised. But the most obvious difference is that the loading steps have been narrowed dramatically. The lowest available impedance is now 5Ω, with 0.25Ω increments to 10Ω, 0.5Ω steps to 20Ω and 1Ω steps from there to 100Ω. Although the size of the steps does increase thereafter, by the time you get to 47kΩ they’re still only 1kΩ each and they stretch all the way to 100kΩ!
One other change is the addition of the ground lift switch also found on the L10. The signal and chassis grounds each have their own 4mm socket (along with a 4mm chassis ground socket on the PSU) but they can be linked using the small rocker switch above them, rather than the large jumper used on the 1 Series products.
Circuit topology…
Where the L10 employed essentially the same circuit as the L1, with a shorter signal path, better components and the routing of the tracks refined to minimise induced noise, the P10 adopts a new circuit topology when compared to the P1, built around five stages rather than three. The P1 depends on a passive EQ section sandwiched between gain stages. The P10 adopts a more complex solution with three gain stages sandwiching a pair of passive EQ stages. By adopting a differential gain strategy, CH has been able to increase the overall gain (now 97dB of gain on the voltage inputs) while reducing noise levels. Given that the P1 is already one of the quietest phono-stages around, this is an enticing prospect. The input buffer has been heavily revised (presumably reaping the benefits of similar changes introduced with the M10) while the circuitry for the voltage inputs is now fully discrete. The revised current inputs are now more linear, irrespective of the gain setting used.
