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tube vs solid state rectifier?

R

rajuncajun

Member
I am seeking opinions:

I've looked through the forum and not seen much in the way of a direct conversation comparing pros and cons of using a solid state rectifier in your tube amp vs the original tube type (e.g. 5AR4/GZ34 which my old pioneer has).

Some seem to say the tube types are more prone to failure which could damage the amp, also that a solid state rectifier provides faster response to current demands.

Any opinions or experiences with this subject?

How about effects on sound quality that folks have noticed due to rectifier type?

Or does it really mattter?
 
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I sort of like solid state, if you use good diodes (I like Cree). To me a good solid state supply will make the amp more dynamic, quieter, and a little faster. When used for filaments supplies and such, solid state is very easy to regulate too (LM 317s and the like). Even high tension supplies can be easily regulated if someone wants to go that far. Besides that, 5AR4s bring huge money. :D
 
jaymanaa said:
I sort of like solid state, if you use good diodes (I like Cree). To me a good solid state supply will make the amp more dynamic, quieter, and a little faster. When used for filaments supplies and such, solid state is very easy to regulate too (LM 317s and the like). Even high tension supplies can be easily regulated if someone wants to go that far. Besides that, 5AR4s bring huge money. :D
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I am a big fan of HEXFRED rectification. It gives you characteristics similar to tube rectifiers, while providing increased reliability.
 
Tube rectification will intruduce more "sag" at higher (peak) demands, but that may also be a desirable characteristic too. As with solid state/diodes you don't experience that. Now that may sound fine and dandy but here's the problems you would have that would need addressed...
1). Higher voltages that your electrolytic caps may not like or other components.
2). Without some sort standby switch for the B+ or a delay, you now have a rush of voltage on the tubes before they have any chance of warming up, and you will go through output tubes!!
As for more damage with tube rectification...not really as long as the power supply components are healthy..no problem.
 
marty59 said:
Tube rectification will intruduce more "sag" at higher (peak) demands, but that may also be a desirable characteristic too. As with solid state/diodes you don't experience that. Now that may sound fine and dandy but here's the problems you would have that would need addressed...
1). Higher voltages that your electrolytic caps may not like or other components.
2). Without some sort standby switch for the B+ or a delay, you now have a rush of voltage on the tubes before they have any chance of warming up, and you will go through output tubes!!
As for more damage with tube rectification...not really as long as the power supply components are healthy..no problem.
Click to expand...

My HQ145 was modded (by a previous owner) to use SS rectifiers which replaced the original tube. My research says that mod took about 22 watts of load off the power supply circuitry. I guess you could call that a small benefit:scratch2:
 
Sometimes a higher B+ voltage is very desirable when modding. Going to solid state also frees up about 3amps worth of 5v filament winding too, which could be used for "unpopular" tubes. Good NOS quads of 5AQ5s, 5v6s, 5BQ7As, etc.. are cheap, and someday may be all we have left of the good old NOS stuff.:tears:
 
Solid state allows some different power supply topologies as well, like voltage doublers, which are sweet! :D
 
I like tube rectifiers - nostalgia, slow-ramp up times, less 'switching noise' (though the latest ss diodes have mostly 'rectified' that situation') and tube rolling abilities. The best bet is the TV damper diode:

http://www.nutshellhifi.com/triode1.html
Matt Kamna also demonstrated a technique for zooming in on the waveform on the power-transformer secondary (about 10V/div on the scope screen). The rough appearance around the zero-crossing was very obvious with solid-state diodes. HEXFRED's gave a small improvement, but conventional tube rectifiers looked much smoother, and the TV damper diodes were by far the smoothest of all. So even in low-current preamp applications, TV damper diodes give the least noise. I know from experience in the Tektronix Spectrum Analyzer division that it's much easier to eliminate noise at the source than filter it afterward. If there was an even quieter device, I'd use that, but as far as I know, TV damper diodes are the quietest from the viewpoint of switching noise. Considering that the main B+ supply is switching five hundred volts, this is not a small consideration, since switch-noise is radiated in all directions, into the B+ supply, the interior of the chassis, and back into the power cord.
Click to expand...
 
rajuncajun said:
Ah, so it might be unwise to just slap in a solid state rectifier and see how it sounds?
Click to expand...

Rectifiers don't make the sound. The audio tubes make the sound. Now, I am sure that there will be much discussion about switching noise etc. But remember, HH Scott went to silicon diodes when the 340B came out. Prior to that, the 5AR4/GZ34 was the rectifier. Probably one of the best rectifiers because of the current it could handle, very little voltage drop across it. As mentioned, silicon diodes drop about .7 volts. For that matter, some people use several in series to drop voltage.

So, you may ask me, "Have you replaced your GZ34 tubes with silicon diodes in your Scott amplifiers?" My answer is "Certainly Not!". My goal is to have the amp look as much like original as possible to the extent of stuffing the electrolytic capacitors with new components.
 
All hollow-state amps will survive an EMP...solid-state rectifiers will fry. :D

(of course, you'll have other things to worry about at that point)

-D
 
BigVoyevoda said:
Thanks for the discussion, helped explain a lot!

I found this in an article that kinda glosses over;
"A solid state rectifier has no internal resistance whatsoever. It has a very consistent
fixed voltage drop that occurs both at zero or full current (approximately .7 volts). When an amplifier needs power at low frequencies, there will be no limit to the current that travels through the rectifier. This results in an amp with more headroom that is punchier, more articulate and able to deliver the goods in the bottom end."


BigV
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And if you want to slow down the B+, you can use a CL80 between the PT secondary CT to ground. That gives you plenty of time because the cl80 won't warm up and start passing full current until it has a load (like the output tubes).
 
With full apologies to all concerned, I will, once again, speak of "that which must never be spoken".

The power supply, whether tube or SS rectified, does two things:

1. It converts the AC supply to the necessary voltages.
2. Rectifies the AC to pulsating DC.

After these two things are done, the next stop is the filter circuit, which does one thing:

1. Converts the pulsating DC to pure DC, thus removing all traces of what happened before.

Let me repeat that. Once the pulsating DC has been converted to pure DC, there is no trace of what happened before that point. What does that mean? It means that it can't possibly matter what the rectifier was made from.

This has nothing to do with good power supply design, including adequate power transformer sizing, and adequate filter network design. Poor power supply design can, and sometimes does, result in a power supply that cannot meet the amplifier and load requirements without sag. This has nothing to do with what the rectifier is made from. The designer obviously knows what rectifier he has chosen, and will determine the necessary circuit values to give the proper output voltages, given the rectifier chosen. This has nothing to do with what the rectifier is made from.

The output of the filter network is pure DC, thus removing all traces of what happened before.
 
Fisherdude said:
With full apologies to all concerned, I will, once again, speak of "that which must never be spoken".

The power supply, whether tube or SS rectified, does two things:

1. It converts the AC supply to the necessary voltages.
2. Rectifies the AC to pulsating DC.

After these two things are done, the next stop is the filter circuit, which does one thing:

1. Converts the pulsating DC to pure DC, thus removing all traces of what happened before.

Let me repeat that. Once the pulsating DC has been converted to pure DC, there is no trace of what happened before that point. What does that mean? It means that it can't possibly matter what the rectifier was made from.

This has nothing to do with good power supply design, including adequate power transformer sizing, and adequate filter network design. Poor power supply design can, and sometimes does, result in a power supply that cannot meet the amplifier and load requirements without sag. This has nothing to do with what the rectifier is made from. The designer obviously knows what rectifier he has chosen, and will determine the necessary circuit values to give the proper output voltages, given the rectifier chosen. This has nothing to do with what the rectifier is made from.

The output of the filter network is pure DC, thus removing all traces of what happened before.
Click to expand...


Hear hear!
 
kvflyer said:
Hear hear!
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I owe you one, partner.

This is by no means the first time I've posted this, and you're the first person who actually responded. Usually I'm greeted by the sounds of crickets chirping.

Here's another mind boggling thought to consider: I once had this same conversation with a fellow audio guy, who responded with this: "I've listened to two amplifiers, one tube rectified, and one solid state rectified, and they sounded completely different!!".

I responded with: "And you attribute the difference in sound to the rectifier." "Absolutely!!"

"If you attribute the audible difference to the rectifier, that means you think all amplifier circuits sound exactly the same". He said "Bullshit!!"

Well, sorry, that is the only logical, inescapable conclusion.
 
I'm not really on one side of the fence or the other with this. I've got amps that run both, and they both sound fine. I've converted things from vacuum to silicon where I needed the extra voltage or to unload the transformer. can't really say I've noticed anything that I didn't expect from either more voltage or less current load.
 
Fisherdude said:
I owe you one, partner.

This is by no means the first time I've posted this, and you're the first person who actually responded. Usually I'm greeted by the sounds of crickets chirping.

Here's another mind boggling thought to consider: I once had this same conversation with a fellow audio guy, who responded with this: "I've listened to two amplifiers, one tube rectified, and one solid state rectified, and they sounded completely different!!".

I responded with: "And you attribute the difference in sound to the rectifier." "Absolutely!!"

"If you attribute the audible difference to the rectifier, that means you think all amplifier circuits sound exactly the same". He said "Bullshit!!"

Well, sorry, that is the only logical, inescapable conclusion.
Click to expand...

so I guess you really enjoyed that highly objective rectifier tube "review" that was posted here last week then. :smoke:
 
Sorry for a bit of a sidetrack (not totally unrelated)
Jay could you explain a little more or post a link to an explanation or article about using the CL 80 as you mentioned in the earlier post? (I was going to PM but o thought I might not be the only curious one).
 
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