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The Silver Rock “Meteor” AVC

The story of a new Autoformer, or how to create an AVC for the absolute purist. Some time ago, one of our customers and Silver Rock enthusiast made an inquiry for a cost-no-object TVC. After he tried the latest MC Step Up called “Meteor”, which was built into a stealth type of wooden cabinet, he was so impressed that he wanted the same cabinet and magnetic core to be used for a silver wire reference volume control. The cabinet was not so much the problem when considering such a project. We had developed it already for the Mc Step Up transformer, so it was available. It was the winding of several thousand turns onto a toroidal magnetic core and the 22 logarithmically set output loops, which were the real challenge. Indeed, the special magnetic core we use in the “Meteor” Mc Step Up does not allow for machine winding (using the traditional toroidal transformer winding machines), but calls for 100% hand labour. Moreover, the customer wanted to have the HF resonance set as high as possible, and thus a very wide bandwidth as well as less than 100 ohms DCR. After several trials, we decided to go for an autotransformer volume control device. Mind you, even AVC do have HF resonance and it took us a few more prototypes to get there. In the end, we came up with a device that is resonance free up to 2 MHz, where it slowly starts to attenuate the signal with a 6 dB slope.

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It takes two and a half days of hand labour (no machine in the process whatsoever) to produce such a coil. Each AVC is then carefully mounted into a cylindrically shaped wooden enclosure, and a pair of the latter is then mounted into the “Meteor” cabinet. The meteor cabinet that was first used for the MC Step up transformer is a very special design. It is CNC milled out of a single block of wood. Not only its outer shape is of stealth technology, but also the inside shows not right angles. This allows for very low impact of sound waves to the outside of the cabinet, while waves travelling in the inside of the wood also find only a minimum number of flat surfaces. The combination of the “Meteor” cabinet and the new AVC is sonically very much superior to any magnetic volume setting device we have ever heard. The customer is happy with this very special item and we decided to add it to our list of products that are regularly available. This ACV was meant for the purist, and thus has only one stereo input and stereo output.

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Silver Rock “Meteor” AVC features:

• Cryo treated Silver wire • 22 algorithmically set outputs • 75 ohms DCR • 80 Hy primary inductance • Toroidal magnetic core of very special properties • Hand coiled using no machine whatsoever • Bandwidth up to 2 MHz • “Meteor” type of wooden stealth cabinet