I am enjoying the thoughtful responses so far. Thanks gentle people.
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?
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I'll be the devil's advocate here. I just bought an all-tube higher end preamp that uses all tube except for the rectification. It even has a tube voltage regulator. My concern about tube rectification was the heat generated and the high failure rates of these tubes. It seems like every time I read a post about some tube equipment's failure it's the rectifier tube. This is just my personal opinion and I'm sure the tube makes a difference in the sound but by how much. I chose lower heat and reliability over the small amount of possible sound improvement for my purchasing decision. Just my .02. |
Nothing wrong with that choice, IMO. Generally tube rectifier failures occur in power amplifiers with high current draws. The Dynaco ST70 is notorious for eating Chinese 5AR4s. In a preamp there usually isn't enough current being drawn to worry about a tube rectifier failing. But there are exceptions. The 6X5, used in a number of tube preamps, is not very robust and I've had at least one fail. |
@willywonka I don't know why tube equipment manufacturers don't use rectifier tubes such as the 3b22 or 3b28, I have had no problems with these rectifier tubes even if I leave them on 24/7 for months at a time, plus they can be used for high wattage power amps. These types of tubes also have very good regulation as they drop a constant 15 volts up to there operating limits, which are very high. I think the reason they are not used more often is the cost of the filament current that the transformer has to have. |
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