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Thread: Solid State Rectifiers?

  1. #1
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    Default Solid State Rectifiers?

    why do companies like epiphone, blackheart, harley benton etc. go through all the trouble of designing the tube signal paths, the tube transformers and the control interfaces and stuff, then put in a solid state rectifier?

    wouldnt having SS technology in a tube amp lose the warm sound?
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  2. #2
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    Quote Originally Posted by ibanezjunkie
    why do companies like epiphone, blackheart, harley benton etc. go through all the trouble of designing the tube signal paths, the tube transformers and the control interfaces and stuff, then put in a solid state rectifier?

    wouldnt having SS technology in a tube amp lose the warm sound?
    No, the rectifiers are not in the signal path.

    Most of the amps you mentioned are single ended, Class A amps. There is near constant current draw from the power supply in a Class A amp. The only benefit to having a tube rectifier in a tube circuit is that it will sag and compress, but only in a push pull Class AB amp which does not have constant current draw on the power supply.

    Two minor advantages of tube rectifiers are: 1) some tube rectifiers (but not all!) are slow start up so they only pass the high voltage after the tubes have warmed up and 2) the internal resistance of a tube rectifier is higher than SS diodes so an am will produce lower voltages with a tube recto than with SS diodes. But these are negated by 1) using a standby switch and 2) using a transformer with lower voltages for use with SS diodes.

    Solid state rectifiers are used because they are less expensive, do not wear out like tubes do, and do not require an extra low voltage winding on the power transformer.

    An advantage of using SS diodes is that lots of capacitance can be used in the power supply. Tube rectifiers tend to have lower limits on the amount of capacitance that can be used. Too much capacitance in the first stage of the power supply will prematurely wear out a tube rectifier.

    There are many Class A vintage amps that do use tube rectifiers, but these were manufactured at a time when vacuum tubes were actually cheaper than SS diodes. The Fender Champ comes to mind. Had SS diodes been cheaper than tubes back when Fender was manufacturing Champs, you can bet Leo Fender would have used them instead of tube rectifiers.

    tung

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