Are your service ports doing you a disservice?
By Roy Gregory
While parallel grounding of both chassis and signal have been rapidly gaining currency, there’s one noise-source that is regularly overlooked. Those in the know when it comes to CH Precision components have long recognised that, as well as optimising the separate signal and chassis grounds, there’s additional performance to be gained by connecting the USB firmware upgrade port (a fixture on every CH product) to some form of ground shunt. It started out using a CAD Ground Control GC1 or one of the Entreq pieces. It continued with the arrival of the Nordost Qkore grounding devices. But all of these approaches can count cost and complexity against them, involving not just an expensive grounding box, but yet another cable (aerial) to route from the system’s components back to some central point.
Thankfully, those clever people at CAD have come up with a solution, a small device that works on both redundant USB inputs and service ports. The somewhat confusingly named USB Control – at least it’s confusing unless you are familiar with CAD’s range of Ground Control products – is about the size of (and could easily be mistaken for) a USB dongle. Encased in matt black acrylic, it’s got a USB A nose on it but otherwise it’s about as discrete as an audio tweak can get. But don’t let its diminutive dimensions or understated appearance fool you. This thing is kryptonite for the spurious noise generated by USB circuitry.
Digital devices…
My initial interest fastened on applying the USB Control to the firmware ports on my CH components, starting with the C1.2 DAC. The results were both immediate and musically significant. Running the C1.2 with either the Wadia S7i or D1.5 transport (I prefer to use optical disc for such comparisons, simply because of its stability and it’s consistent superiority to all but the best streamed sources) I started by playing the Jordi Savall/Le Concert des Nations Brandenburg Concertos (AliaVox AVSA 9871 A+B), particularly the opening movements of Concerto Nos. V and VI. Inserting the USB Control into the firmware port (note – NOT the USB Audio input: the modular nature of the C1.2 means that normally there will only be a USB Audio input if/when the owner needs one, which means it won’t be spare) brought an obvious change to the musical presentation, both in terms of tempo/intelligibility and tonality. Notes and phrases were more explicitly placed and shaped, the counterpoint more apparent, Bach’s graceful structuring more elegantly revealed and played. Instruments took on a warmer tonal balance, with richer colours, better harmonic development and a greater sense of presence. It’s not just the notes that were more clearly placed. The instrumental spread was more clearly defined, with each instrument both more solid and more stable. The added sense of pattern and precision was particularly apparent in the solo harpsichord passage that follows the opening bars of Concerto No. V. So often, the instrument can sound like a jumbled cascade of notes (hence Sir Adrian’s infamous comments) but the USB Control brought a sense of, order and purpose to the playing, body and a richer harmonic complexity to the instrument, the very sense of organisation necessary to allow the musical continuity to flow from strings to keyboard in a natural progression. Musicologists often cite this as the first – or at least a nascent – keyboard concerto. With the USB Control in place, the body, structure and presence of the harpsichord part underpin its importance and make you understand why that is.
