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Valve amp power failures

R

rescuest3ve

pfm Member
Is this a common thing?

Reason I ask is because EVERY valve integrated i've had now - a Copland CSA29, Audio Note OTO, and now, yesterday, a New Audio Frontiers Performance, have had a power supply failure which has resulted in being sent off to be fixed. It's worth noting that these are all second hand - each perhaps 10 years old at least - so I know that the likelihood of failure is higher than new, but all three for the same problem? One thing that crossed my mind is that I've been in London flats, so maybe I have a power supply issue that could be helped with a conditioner?

I terms of usage, I usually have the amps on for circa 1-2hrs per day, and they're never left on full time, only turned on a few mins before being used so they warm up.

Anyone have any thoughts on this? Am I just unlucky, or being optimistic to think these amps can last many years without issue?
 
I tried out a couple of integrated valve amps and both suffered power supply failures, great when working but gave up and returned to SS. Again might have just been unlucky.
 
I've been thinking of going class A solid state, but fear I'll lose out on that low power, high sensitivity magic that I get with valves and my AN speakers. At the moment it seems like I'm running a fleet of expensive, vintage race cars: wonderful for the three months they're running, but require so much bloody downtime.
 
When you say 'power supply failure' do you mean that the reservoir and smoothing capacitors failed? Going back to my youth when everything had valves the things that failed apart from the valves themselves were the electrolytic capacitors. High voltage and heat from the valves wears the caps out. You'll have a similar problem with SS but can expect a longer life before failure.

As to valves and SS. Neither is truly better than the other and if competently designed and built should sound the same.

Cheers,

DV
 
Yes, had a valve integrated go pyro on me, a resistor IIRC. Wussed out with valve pre and SS power in the end for more peace of mind.
 
It may be that your electricity supply is at the upper end of the tolerance band, i.e 253V, and your amps don't like it.
 
There is a mystery as to what precisely the OP means by "power supply failures" but with well designed valve power amps the power supply will be just as reliable as that of a SS power amp. If they use a valve rectifier then that will be the most unreliable part. More sensible manufacturers will use SS rectifiers.

The output valves are by far the most unreliable aspect of valve power amps. Probably 90% of faults are due to these.
They can cause collateral damage when they go and sometimes this can include to the power supply but most commonly it will be burnt out resistors around the valve.

Unfortunately modern production of output valves is way behind what it was back in the day and specifically in terms of reliability. As power levels go up reliability drops. eg a pair of KT88 can theoretically give 100W but try this with anything but stupidly expensive genuine NOS GEC and they would probably last say a month...
 
Darth Vader said:
When you say 'power supply failure' do you mean that the reservoir and smoothing capacitors failed?
Click to expand...

The Copland had issues blowing the small internal fuse every time I turned it on. It was explained as a power supply problem (that was a good few years ago, so I can't remember exact details). The caps on the Audio Note OTO only had about 20 hours on them before the mains transformer decided to crap out, and most recently the NAF integrated now is also burning through internal fuses, so I'm guessing it's the same issue as the Copland, though I won't know that til I can get it looked at... What a palaver!
 
Several weeks ago I did what you are thinking of doing. At a considerable loss I sold my excellent 300b amp and bought a Sugden Masterclass, class A solid state. Apart from a blown Psvane just out of warranty bloody expensive valve, I had no trouble from the 300b amp. But getting it checked out following the blown valve involved humping the 70lbs plus amp in and out of the car and a very unappealing drive. I am 79 years old. The only other reason for selling was, after a few years I got sick of seeing the grey grey Pasvane valves and the heavyweight amp.

Overall, I am pleased I made the decision. I got rid of the almost inaudible hum from the speakers with the 300b and inherited a very low buzz from the Sugden amp, no sound from speakers. I didn't get chance to compare the two amps side by side, but I wouldn't reverse my decision and am very happy with what the Sugden puts through my AN speakers.
 
Brian S said:
Several weeks ago I did what you are thinking of doing. At a considerable loss I sold my excellent 300b amp and bought a Sugden Masterclass, class A solid state.
Click to expand...

Funnily enough, I have been looking at a sugden. A stereophile review of the a21a through some AN-Es wasnt particularly favourable, but I bet a masterclass is quite special. Glad you're happy!
 
I’m in this situation myself. Have largely decided that valves and me don’t get along, and the next (final) amp will probably be class A s/s. By the way, sonically you have nothing to fear; good class A runs good valve amps very close where it matters, and appear to offer other benefits as well.
 
While my Audio Note Oto is a lovely sounding thing it hasn't been as reliable as the solid state amps I've had - so much so that it ended up being mothballed for quite a few years until I finally sent it back to Audio Note for a proper service. I keep a back-up amp to replace it whenever it does pack in though!
 
I had a few valve amps in years gone by, all with reliability issues, bar a Papworth TVA10. It may be that I just didn’t own that one long enough. Never had an issue with a solid state amp. I would like to try valves again but, now I’m in Madeira, I’m reluctant to risk it.
 
A properly engineered valve amp should be as reliable as a SS amp other than issues to do with output valves.
If you can get NOS output valves that will make them vastly more reliable.... at a cost! Vastly more?
lets say you have an amp of 80WPC that uses KT88's. Don't be surprised if it fails about every 6 months and takes out a resistor or two and a fuse each time. That's not unusual. All modern KT88's are total crap, Chinese ones by far the worst and this includes the premium priced ones (Black Treasure, Psvane etc). Russian much better. If bothered about valve matching then it's a set of 4 new output valves every time and usually a re-biasing. Get genuine GEC NOS valves and you will likely get five years or more from them and they will probably last long enough to actually wear out rather than fail.

A pair of Quad II, rebuilt and using real GEC KT66's can give 20 years use without even changing a valve and a rebuilt Leak Stereo 20 with good NOS output valves or the equally good Russian military surplus ones and using a Mullard GZ34 rectifier (MUST be Mullard GZ34 for uber reliability) will routinely give 5 - 8 years or so and then you're only changing the output valves cos they're getting a bit worn and it's getting a bit bloaty. Similar with a Radford STA25 and that has SS rectifiers so no rectifier to wear out. I'm assuming around 1-2 hour a day use here.

For those going SS class A I can't recommend highly enough the early Krell KSA50. It sounds as good as all the hyperbole spouting reviews said. Weirdly sensitive to what pre or passive comes before it though! Can change, chameleon like, from sounding like a powerful Quad II valve amp with a 50K passive pot to sounding like it turns on a sixpence and the bass could crack walnuts with a 10K passive pot IME.... Odd. Never in a million years would you think it was the same power amp in use in these two cases!
 
The valve amp I designed 30 years ago is still going strong. It has its original valves and PSU caps.
I chose a very conservative power output, and this is the secret. My 6CA7 valve PP produce about 25 W when manufacturers like CJ draw a hefty 50 W from them.
I used to work in a cinema that used an old valve projector which had had nothing done on it for 30 years.
 
SteveG said:
While my Audio Note Oto is a lovely sounding thing it hasn't been as reliable as the solid state amps I've had - so much so that it ended up being mothballed for quite a few years until I finally sent it back to Audio Note for a proper service. I keep a back-up amp to replace it whenever it does pack in though!
Click to expand...

Now, if I can find a class A SS with the same signature as an OTO, I think I'd be sorted!
 
For a SS amp that really "sounds like a valve amp", for better or worse, the original late 60's Sugden A21 of 10WPC fits the bill but the required total rebuild (they are now 50 years old and run hot) is very expensive.
In fact I'd say my rebuilt and modded valved Stereo 20 sounds a wee bit more "modern" and "SS" than a Sugden!
 
Don't forget anything electronic can fail. However, there is no reason why a valve amplifier should be any more unreliable than a solid state amplifier assuming it has been designed and constructed properly with good parts and components. I've had thousands of amps through our workshop since the mid 1980s and a good number of those were poorly designed, where the valves were pushed beyond their design limits to meet certain power outputs. Then you have the use of Chinese made valves. Enough said.
 
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