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AUDIO FORUMS >> D.I.Y. >> Bridge Rectifier ?
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Message started by Brian on 05/01/19 at 02:51:41

Title: Bridge Rectifier ?
Post by Brian on 05/01/19 at 02:51:41

I do not see tube amps with 2 or more rectifier tubes. There used to be such a circuit. Perhaps it was only used for machinery of some kind and not music amps. Has someone here used a music amplifier with a Bridge Rectifier? Does someone know why we do not see them today?

Brian

Title: Re: Bridge Rectifier ?
Post by 4krow on 05/01/19 at 03:41:03

My limited knowledge would say that the circuit of the amp may only require one voltage, and that may be a positive voltage. Another design may require a negative voltage as well (some equipment uses both pos and neg), and this is where the second rectifier tube would be used. Certainly not fact, but just my guess.

Title: Re: Bridge Rectifier ?
Post by Colin B on 05/01/19 at 20:23:47

Rectification is the conversion of AC to DC so you really only need one device per circuit. Having a second would make no sense. Similarly, negative voltage and positive voltage are the same except for differences in reference points since at the end of the day overall voltage is nothing other than relative difference between some reference that gets declared "ground" and the output of the power supply, with overall voltage being simply output-reference. There isn't any difference in the actual power supplies, instead the difference is entirely in what your circuit topology is and while my circuit design skills are pretty rusty I'm fairly certain that you can use the same power supply (computers use the same power converter to energize both the positive and negative rails for example). As for usage, opamps need negative voltage (aka negative feedback) for stabilization, so any circuit topology that replicates an opamp will need it. But still, it's about reference points as opposed to actually being anything special.

EDIT: there are amps with two rectifiers. On here the mini torii, full-size torii, and the ZMA all have dual rectifiers. Similarly in other places. These are all true dual-mono amps with each input transformer and rectifier servicing their half of the chassis.

Title: Re: Bridge Rectifier ?
Post by Archie on 05/02/19 at 00:51:03

Quote:

... and the ZMA all have dual rectifiers.

Unless I'm missing something, the ZMA does not use a rectifier tube(s).

Title: Re: Bridge Rectifier ?
Post by Colin B on 05/02/19 at 02:21:09

It might not have rectifier tubes but it has to be doing rectification somewhere, presumably via a bridge diode on each side inside of the chassis, with smoothing done by the mega-caps.

Title: Re: Bridge Rectifier ?
Post by Jeff of Arabica on 05/02/19 at 07:18:23

The ZMA does not have rectification tubes, but rather uses bridge diodes using Vishay Ultra Fast UF5408 rectifiers.