advertisement


valve amp reliability

It is official feature, I once opened it. There was plate for different voltages, but no markings which is which. But if it worth doing, will find out how it is needed to be done. Thanks.
 
gints said:
It is official feature, I once opened it. There was plate for different voltages, but no markings which is which. But if it worth doing, will find out how it is needed to be done. Thanks.
Click to expand...

Not that critical in your case as you are only 10V over but, as TonyL said, if you want to maximise longevity of valves and caps it's just about worth doing..
 
Found a picture which I took when opened amp. Looks that Photobucket wants money for sharing photo on forums.
There was markings on that voltage plate. Is it enought just to move that single wire from 220v place to 230v place or something else must be done? I cannot see other side of plate without removing it, it feels for me too simple.
 
Surely there is a manual somewhere? On most vintage amps changing the voltage is as simple as pulling a selector plug out and relocating it in the corresponding voltage position. You are just changing taps on a transformer.
 
abbydog said:
Curious why you say tube rectifiers are silly? Seems solid state ones are a less than ideal alternative. I run various, including 6860WA and 6550s, and have not had an issue with them.
Click to expand...

I used to have a pair of 2nd audio innovations triode amps ,some years ago ,they had solid state rectification, I then fitted a pair of Border Patrol valve rectified psu's, the improvement was dramatic!

Much more composed and dynamic, before when the music became more challenging and complex ,the amplifier seemed to lose control and become congested .

Apparently the critical difference was the use of a choke input filter which is unique to Border Patrol as most manufacturers use choke smoothing with capacitor input filter .
 
The only all valve amp I've had was a Prologue 2, bought used. Really liked it. But one day one of the output valve bases went aflame. The valve itself was fine (went back to Watford to be tested) and it turned out to be a resistor (repaired by the dealer).

PrimaLuna's have a good reliability rep as far as I can gather so it may just have been very unlucky. Glad I was present though as it was all getting rather pyrotechnic!

It's not put me off valve amps altogether (current a Croft, albeit with just input valves; considering a Oto), but from that experience I'd just say a) have a good repair option or tech to hand, b) personally wouldn't leave it unattended for any time - at least anything with output valves.
 
One good thing about valve amps is when they fail they only tend to harm themseves. When solid state amps fail the badly designed ones without proper speaker protection can send DC through your valuable speaker destroys the voice coils and crossover, in some cases of some really bad ones even setting the speakers alight! No valve amp can do that as the output transformer blocks DC. The amp may blow itself up, but it is harmless to the surrounding components as long as it doesn’t actually catch fire!
 
Hadn't appreciated that re SS amps potentially alighting speakers - crikey!

Yeah, really don't want to sound dramatic but the suddenness of the flames and the heat they were generating when up close really was quite alarming, and I wouldn't be surprised if the amp itself might have gone up. God speed to those who've had valve amps for years on end with no issues, but from that experience I'd heed some caution or at least awareness of what can happen.
 
A failure that dramatic from either class of amp is thankfully very rare indeed. As an aside I spend a day a week running/deminstrating a very early valve computer (the SSEM replica at MOSI), a machine that has around 560 valves in it, contains very high voltages and has shed-loads of old capacitors, carbon resistors etc. I’ve been doing it for around five years now and with the exception of one resistor starting to smoke a few months ago (that was later found to be under-spec) we have had no catastrophic fails at all.

It is worth remembering just how widespread valve technology was prior to the advent of the transistor. Everyone had valve radios, radiograms, TVs etc and whilst failures were not that uncommon failures resulting in fire were. Much of this kit was enclosed in flammable wooden cabinets too. I’d argue something like a properly rebuilt Leak or Quad out on display and well ventilated has to be safer than it was back in its era. Even so I don’t leave mine on unattended longer than a quick bathroom break or whatever, but I don’t leave solid state amps powered up either (I consider leaving kit on 24/7 madness). I am also aware that whilst the Leak Stereo 20 is a very reliable amp if it does go wrong it tends to go wrong pretty damn fast as the fusing is not as good as it could be. As such I want to be there to notice a valve plate glowing or whatever and pull the plug!

My guess is the vast majority of today’s valve amp failures are due to poorly specified power supplies on Chinese amps, poor quality new production tubes and badly restored/“tweaked” vintage kit. High quality kit properly maintained and running at the correct voltage should be very stable. My argument above as ti just how many 50-60 year old Quads, Leaks etc one sees with at least some of their original valves backs this up.
 
gints said:
Found a picture which I took when opened amp. Looks that Photobucket wants money for sharing photo on forums.
There was markings on that voltage plate. Is it enought just to move that single wire from 220v place to 230v place or something else must be done? I cannot see other side of plate without removing it, it feels for me too simple.
Click to expand...
It doesn't have to be complicated. As Tony says you are just connecting it to a different part of the transformer and engaging fewer coils.
 
chris@panteg said:
I used to have a pair of 2nd audio innovations triode amps ,some years ago ,they had solid state rectification, I then fitted a pair of Border Patrol valve rectified psu's, the improvement was dramatic!

Much more composed and dynamic, before when the music became more challenging and complex ,the amplifier seemed to lose control and become congested .

Apparently the critical difference was the use of a choke input filter which is unique to Border Patrol as most manufacturers use choke smoothing with capacitor input filter .
Click to expand...

Nope nothing to do with SS or valve rectification. There is no difference in the sound. Any changes or improvements would be due to bigger and better smoothing caps and better grounding layout etc.
 
Jez, no the critical difference is the choke input filter configuration, this is what makes the improvement, as I said .
 
Tony L said:
One good thing about valve amps is when they fail they only tend to harm themseves. When solid state amps fail the badly designed ones without proper speaker protection can send DC through your valuable speaker destroys the voice coils and crossover, in some cases of some really bad ones even setting the speakers alight! No valve amp can do that as the output transformer blocks DC. The amp may blow itself up, but it is harmless to the surrounding components as long as it doesn’t actually catch fire!
Click to expand...

In all my years on hi-fi forums, I have never heard of such a thing happening to someone’s loudspeakers. What are these badly designed amplifiers you speak of?
 
Ahem, here we go, and at the risk of rustling some feathers which is not my intention.
I'm an electronics engineer and design amplifiers, and can confirm that a choke input power supply provides better regulation than a capacitor input supply, regardless as to whether it is followed by a choke. The benefit is most useful on class AB amps where the current drawn varies to some extent. In a purely class A, then it won't make much difference.
 
Actually I should also add that the rectifier valve has a much easier time with the current as it is not subjected to anything like the same peak current as with cap input.
 
John said:
In all my years on hi-fi forums, I have never heard of such a thing happening to someone’s loudspeakers. What are these badly designed amplifiers you speak of?
Click to expand...
Can be any amp that lacks a transformer output, or capacitor output, so most SS designs. If a tranny goes short then you can get supply rail voltage DC delivered direct to the output. If it has a DC blocker, no problem, if not then you can blow speakers. Some speakers have a cap blocker, FWIW, but there is a sonic impact.
 
You must log in or register to reply here.


advertisement


Back
Top