Info provided by Stan Warren:

Facts about the 300S; both real and imagined.

This proto is one of several being considered for production. Reports from people who have heard it are, therefore, important to us. I’ll admit to a bias toward transparency. I go to hear live music whenever I can and I want the stereo at home to get me as close to that as possible. I know that there is a class of listeners who prefer to improve on live just a bit with a softer and warmer sound. If there are enough people who think that way, we will bend the sound of the 300S a little to satisfy those who write checks! The customer is always Write! Still, we hope listeners will give clarity and neutrality a chance to grow on them. It does, you know. If you live with low coloration and blur long enough it becomes difficult to justify using your system as a filter. True, your crappy sources will be obviously crappy. But the good ones…Wow! Enough philosophy! On with the show.

The prototype sent has a 500VA transformer. The production will use around 700VA, more or less. The proto had primitive source-shunt regulation of the input stages. Production will elaborate on this considerably. Proto; power supply capacitors are Jensen four-pole. Production; the same but bigger. Proto; stock output filter. Production; we’ll see, probably a better output filter cap. Proto; simple implementation of linear phase gain block. Production; more refinement with better drive buffers. Proto; cheap, basic black box for a chassis. Production; stronger black box with a nice faceplate and quality connectors on the back. The switching module is from Hypex. We stripped the input circuitry completely and used our own. The target price is $2500, for a 150-200 Watt version of the amp.

Specifications: Bandwidth, same as stock Hypex, or about 50 KHz. Noise, A little…not too much. Distortion, Ditto…about the same as Hypex residual. Input impedance, 22KOhm Gain, 27dB (industry standard).

We hope this information is useful, and would like to thank Danny and the participants for their time and trouble. If you heard our amp and have any comments, please let us know. Chuck Jones, 541/579-1374 Or, SUPERPHON


GR Research Inc.
910 North Jackson
Iowa Park, TX 76367