Well, I wonder if you would like the "unconventional rectifier" in the power supply of my phono stage. It runs twin 300B tubes as rectifiers.
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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@larryi the 300b can work for lower power equipment like a phono stage. Power tubes can be used as rectifiers, I wouldn't use them for high powered tube amps, but they can make lower power equipment sound really good. |
@atmasphere , your mention of a better diode brought me to attention like a retriever near a duck pond. I went right to Mouser to learn a bit more and I would like to try subbing them into my Decware Zenkit1 and possibly my Dynakit ST-35. The Zenkit uses a pair of Vishay RGP10M-E3/54 diodes and the Dynakit uses a pair of IN4007 diodes. Could appropriate HEXFRED diodes be used to replace the existing diodes in each amp without other modifications? The Zenkit is more of interest because that power supply has been troublesome from the start. Initially it had ~60-120 hz hum problems that I reduced by adding more capacitance to the power supply. But lately there has been an intermittent sound while playing that is more in the 1000-2000 hz range. Your mention of oscillation caused by the solid state diodes around 2 khz earlier in this thread make me think this could be diode related. The St-35 has been nice and quiet right from the start so I may not mess with that unless it seems there is something to be gained. Tell me more and thanks for being generous with your experiance as in the past! |
If the equipment is already designed with solid state rectifiers then yes, there are HEXFREDs rated at 1200V with plenty of Amperage.
@sounds_real_audio This is really debatable (I’m doing it right now...). I’ve found that using properly snubbed semiconductors in the power supply sounds better and measures better than a tube rectifier. They have different design requirements of course (apparently not everyone understands how to snub them for example). If used correctly I find no tradeoffs. FWIW, one of the best tube amps from the vintage era was the HK Citation 2, which employed a solid state supply. It was a Voltage doubler style which was common with many American tube amps (ex.: Fisher). |
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