I know about it no more than I know about amplification tubes.
My only point is that I'm trying to protect my investment in extremely high priced tubes that probably I'll not be able to replace with the same. Since some people say that there is a possibility that applying HT while tubes are cold may shorten their life, I'd rather be safe than sorry.
Hi !
I dont think you need to buy another quad,because as far as i know the EL156 can last 50 000 hours,if not overdriven. So,if you use them 2 or 3 hours a day ,they will last many and many years! but is like you say- better be safe than sorry- Use the HT delay!
Silvino
No, all the tube amps I have and had so far don't use tube rectifiers.
In a SET amp I have, a Chinese EL156 met its' maker after about a month. A couple of Russian 6550 lasted only few months.
Silvinio,
My power amp is used for both music and home theater. It works about 12 hours a day, some times more.
My power amp is used for both music and home theater. It works about 12 hours a day, some times more.
Russian 6550 look like 6П27С. They are rugged enough tubes, and work years in guitar amps that abuse them. If EL156 died in your amp, they may work there in regimes way above specs. No filament magic can help.
GU-50 tubes in my amps work several years, no sign of sound degradation. However, their technology and materials are superior to used in production of civil tubes like EL34, 6550, EL156, etc...
Those Russian 6550 worked for few months in a Conrad Johnson amp that doesn't drive them beyond specs.
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Sorry a bit late catching all this, working away again, 80 hour weeks🙁
That artical is indeed the work of Morgan Jones. It was published in Electronics World around 2002/3. I have the magazine at home somewhere.
Sorry to go OT a bit but great topic and something I have often thought about. Even KV rated indirectly heated rectifiers in old kit dont have a delay so the whole poisoning/ion bombardment thing is a myth (unless they are gassy).
Cheers Matt.
That artical is indeed the work of Morgan Jones. It was published in Electronics World around 2002/3. I have the magazine at home somewhere.
Sorry to go OT a bit but great topic and something I have often thought about. Even KV rated indirectly heated rectifiers in old kit dont have a delay so the whole poisoning/ion bombardment thing is a myth (unless they are gassy).
Cheers Matt.
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Just thought a bit about it (again, probably already thought this and forgot🙂)
Rectifiers, especially >1KV jobs have a rather hard time whilst warming up. The warming cathode will be hotter in some areas causing more localised heating through extra current density in that area. In the norm this would be no probs as the cathode area is vast. In extreme cases it could damage the cathode (unlikely). All this is also made worse by the high current peaks charging the caps up.
Signal valves and output valves do not suffer in this way. The only thing that can really do them in (in this way) as Wavebourn correctly states is slamming the HT on to them with a standby switch/relay.
Even with SS rectification a standby arangement is not needed.
It is only needed to protect caps from over voltage and in large transmitter type apps such as induction heating etc to protect the sometimes extremely expensive power supply components.
Perhaps a not ideal compromise is slowly ramping up the supply with SS parts that become obsolete over night?
Cheers Matt.
Rectifiers, especially >1KV jobs have a rather hard time whilst warming up. The warming cathode will be hotter in some areas causing more localised heating through extra current density in that area. In the norm this would be no probs as the cathode area is vast. In extreme cases it could damage the cathode (unlikely). All this is also made worse by the high current peaks charging the caps up.
Signal valves and output valves do not suffer in this way. The only thing that can really do them in (in this way) as Wavebourn correctly states is slamming the HT on to them with a standby switch/relay.
Even with SS rectification a standby arangement is not needed.
It is only needed to protect caps from over voltage and in large transmitter type apps such as induction heating etc to protect the sometimes extremely expensive power supply components.
Perhaps a not ideal compromise is slowly ramping up the supply with SS parts that become obsolete over night?
Cheers Matt.
You all may be correct, for I don't know it for a fact.
However, why does Morgan Jones use HT delay in some of his designs? Is he also given to blind superstition?
Let me put it differently.
Would there be any harm to the signal and output tubes should the HT rectifier's filament be delayed?
However, why does Morgan Jones use HT delay in some of his designs? Is he also given to blind superstition?
Let me put it differently.
Would there be any harm to the signal and output tubes should the HT rectifier's filament be delayed?
In the case of the Scrapbox, it's because of the specific requirements of the 6528. In the Crystal Palace, I think it's probably unnecessary.
It does not matter, good or bad potentiometers to use to bias tubes such a way so they will die young and blooming.
Please don't think I advocate Russian tubes, they usually have spread of parameters wider than barn gates. It is a well known fact. But they have in datasheets warning that more than one parameter can't be at maximum, otherwise it will die younger.
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To all who think warming up indirectly-heated cathodes is a waste of time - can you prove that J.H. van de Weijer's note, that appeared in 1996 (rec.audio.tubes) is wrong?
The NV-Philips man suggests that heating the cathode causes stray charge on loose cathode particles to leak away - which stops them being drawn to grid-1 where they may make the grid emissive.
He's not saying this always happens; it depends on the cathode design, materials, the heater cycling history, and probably more. So the kind of argument like 'my table radio has the same valves as installed in 1932 and it still works good' is not enough to deny that warm-up is important for critical applications - and I certainly regard my voltage amplifiers as critical.
Emission from grid-1 makes noise and distortion as well as leakage (which may also be gas), not something we want in any good amplifier.
Maybe we need 500 valves that have been used for 40 years each in SS rectified amps. Hand them over to someone with a serious microscopy facility, and look for old chunks of cathode on them. Until someone offers evidence of that quality, I'll keep warming my valves before the HT goes on!
The NV-Philips man suggests that heating the cathode causes stray charge on loose cathode particles to leak away - which stops them being drawn to grid-1 where they may make the grid emissive.
He's not saying this always happens; it depends on the cathode design, materials, the heater cycling history, and probably more. So the kind of argument like 'my table radio has the same valves as installed in 1932 and it still works good' is not enough to deny that warm-up is important for critical applications - and I certainly regard my voltage amplifiers as critical.
Emission from grid-1 makes noise and distortion as well as leakage (which may also be gas), not something we want in any good amplifier.
Maybe we need 500 valves that have been used for 40 years each in SS rectified amps. Hand them over to someone with a serious microscopy facility, and look for old chunks of cathode on them. Until someone offers evidence of that quality, I'll keep warming my valves before the HT goes on!
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