2. amps-preamps
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Why tube rectification?

This question is directed at the distinguished members of the forum who design and build tube amps or those who have knowledge of tube amp design. All the tube amps I own/have built us two diodes for rectification. Diodes are cheap, compact and last the life of the amplifier in most cases. Examples include the Dynaco ST-35, the Decware Zenkit1 (which is basically a Decware SE84) and the Elekit TU-8900. All reasonably well respected amps. Yet many of the more expensive amps go with tube rectification, which obviously involves the downside of another tube, more power, more space.

These two competing solutions both supply the basic power to the audio tubes and output transformers, so only indirectly interact with the sound signal. I have not read anything that explains what tube rectification brings to the party. But it must have some upside to offset it's obvious downsides. If I changed over one of the above amps to tube from diode rectification what would I be likely to  hear?

bruce19

Showing 1 response by joshua43214

joshua43214
60 posts
 

I will add something that has not yet been mentioned explicitly.
 

What you are listening to from an amp/pre-amp is the power supply - not the signal being sent to it.

 

It is a bit of a misnomer that we call these things amplifiers. It implies that the signal itself is being amplified, and the other stuff is just there to help.

What is in fact happening is that the voltage from the power supply is being modulated by the input signal, and the input signal itself is swallowed by the tube/transistor. So what happens is the voltage from the power supply is either directed to ground or to the speaker, and the input signal simply regulates how much of that goes where.

 

This is why power supplies, especially in preamps and DACs, are so critical. You are literally listening to the sound of the rectifier after is has been smoothed out by some capacitors.

 

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