• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

Are rectifier tubes still relevant? Why would you use one, or avoid using one?

Rectifier tubes still relevant in NEW designs?

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There is another thread where I posted my experience with super fast diodes ala MUR680. I have never liked them. Nor RC snubber.

This requires sensitive ears, and if you do have ones, you will NOT ignore the effect of diodes...

In my prediction, the bad sound I perceive is an indirect effect of the reverse current spike (very high Q) of the super fast diode. Diodes that are known to have low Q are Schottky...

Bad diodes have: (a) high Q (b) excessive ringing (c) soft recovery. But (b) and (c) is a compromise. You often need soft recovery to avoid ringing.

If you have non-sensitive ears, you can test diodes difference by using FM radio and check the level of interference. Some diodes will allow serious interference. But it doesn't mean that diodes with the less interference is the best. I think this is the effect of ringing/oscillation (b), which is not as critical/important/intrusive as (a).


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People that tell you you can't hear the difference between tube rectifiers and SS rectifiers can't hear the difference between tube rectifiers and SS rectifiers. And that is also true between different tube rectifiers.

The fact is they sound different. It's just a matter of which sound you prefer. There are advantages and disadvantages to each. Some of which can be overcome by using them both in unison.
As additional points perhaps we could go over

1. Why (outside of purists and "authenticity") would tube rectifiers be favored by guitarists?

2. Is all diode rectification created equal (aside from poor circuit design) and what does GOOD look like, what does BAD look like?

1. The tube rectifier along with a limited energy reserve adds some very nice compression. It's a feel thing too, guitar players don't just hear their amps, they feel them.

2. Aside from good/bad design (snubbers etc..) picking the better components that are available will yield the best results of course. e.g. UF4007 vs 1N4007
I used tube rectifiers in a current build because i had more B+ voltage than i needed. Rather then trying to dump 30-40 volts with resistors i used the tubes instead, mainly because i had never used them before.

Once i had the supply reconfigured to present the same voltage to the plate chokes i couldn't tell the difference in sound.
I still like television damper diodes. They combine nicely with silicon diodes in certain circuits. I have a huge stash of them - got them at less than a buck apiece a few years ago.. and I usually have an extra 6v AC winding for them, space is not an issue, and they bring the B+ up slowly.

That said, my phono amp's power supply is solid state and regulated all the way.

A disadvantage of tube rectifiers (except for guitarists) is they
severely limit the value of the first power supply capacitor.

So for hifi it makes the power supply more complicated,
but for guitarists the rail droop is all part and parcel of
the "soul" of the valve amplifier.

I'm only a bass player, but have an ancient Traynor
15W valve bass combo, I completely understand.

FWIW the best bass rig I've ever played through
was a Fender Bassman 130W and a Traynor 4x12.

This thing near maximum volume did amazing
things depending on how hard you played. I
could try and explain why technically, but
that is not the point, playing it was great.

As a one off, I just enjoyed how good it was.
The sound accentuated (compared to what
I was used to) what I was doing in a good
way, and the feedback just spurred you on.

I guess that is my example of the "feel" of
an instrument amplifier, the way it responds.

rgds, sreten.
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Slow turn on is not something to sneeze at. Many sino amps use SS rectification with the effect being poor reliability as the big surge hit lowers the first caps lifespan significantly. I personally, love using tube rectifiers since i am building my own amps, because they allow much more flexibility in the B+ voltage. The voltage drop from different rectifiers can be used to great advantage to dial in the exact voltage you need.
Since tube rectifiers have a specified current capability, the first capacitor is usually of smaller value less than 50uf and some rectifiers specify around 8uf for a cap input. This can be an advantage as a very high quality first cap can be used. Of course ripple reduction is a concern which is usually done with inductors and much larger caps following the inductor, or a series of caps and chokes.
Regarding sound quality of one vs the other that is an issue that is highly contentious and best left for another post.
So no one can give any real explanation why all these different diodes sound different just that there ears are better? Pointless thread.
The fact that there is a discussion shows a point of difference in sound. You should try it yourself and try to define the differences. To me the difference is not huge and i prefer to use valve rectifiers for several reasons and the sound quality is not at the top of the list but it certainly isnt a detriment to sound quality neither. As with most thing audiophile, there is no cut and dried results, rather a subtle difference. The fact that both are acceptable is the most significant aspect. regards, Dak
They don't "sound" like some SS diodes do. Most TV damper diodes are inherently "soft switching" - which is something that is not all that easy to 'scope...

Is soft synonymous with slow?
I recently read that IN14001 is inferior in audio use due to it's slow (can't find the post now, have been all over the site)
What is the difference if any?

What is a good damper diode # to replace a 5u4? I mean, what IS a GOOD damper diode?

+Jay your explanation is appreciated.

+DAK808 What are the reasons you prefer to use valve rectifiers if not sound? I see you listed slow turn on. Anything else?
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