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Re: Emotive Audio pre-amps

Posted by Al Sekela (A) on May 3, 2002 at 20:49:35

In Reply to: Emotive Audio pre-amps posted by Lew on May 3, 2002 at 08:53:34:

Thanks for the product references, Lew. I was not aware of them, but will look out for them and the chance to listen to them.

Voltage reference tubes were developed before transistor technology led to development of techniques to manufacture silicon diodes with predictable avalanche properties. All the information I have suggests there would be no benefit beyond the retro style factor to use them in a high performance audio circuit, but I learned long ago that effects not predicted by basic theory can have large influences on sound.

Tube rectifiers appear to be enormously inefficient compared to simple and cheap silicon diodes, but we know that the charge stored during forward conduction in conventional silicon rectifier diodes causes significant reverse current spikes with capacitor-input filters. Hexfred diodes minimize this charge. Tube rectifiers do also, so here is a possible explanation for why some audio designers would use them. If we did not have the benefit of Hexfred experience, this second-order effect would not be apparent. I will not rule out some comparable second-order benefit to voltage regulator tubes, but I think it is unlikely that there is one.

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