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Components and Circuits For discussions about component types, alternatives and availability, circuit configurations and modifications etc. Discussions here should be of a general nature and not about specific sets. |
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23rd Apr 2004, 12:08 pm | #1 |
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Mechanical noise inside valves.
Hello everyone!
Built my first tube amp this winter. It's a kind of williamson design. I'm a little puzzled by some kind of mechanical (?) noise from within the power tubes (new EL34B-STR from ruby tubes). The noise is sort of a faint rattling sound. The filament set in motion by the ac current?? Anyones else who have experienced this, or knows if it's normal. The tubes is not overloaded or anything, idle current is ca 20mA. Thankful for ideas, suggestions! /Oskar |
23rd Apr 2004, 2:02 pm | #2 |
Hexode
Join Date: Jan 2003
Location: Darlington (DL3) North East U.K.
Posts: 394
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Re: Mechanical noise.
Hi Oskar
Is the rattling sound heard when the power is first turned on or is it there all of the time? It is quite normal, in my expirience, that valves (tubes) make rattling / clicking noises as they heat up or cool down. Is it possible that you are running the amp without a load ie. loud speakers or dummy load as this is a practice not to be recommended at all, but if it happens, mechanical noise can be heard from the o/p valves in certain conditions. Could you be a little more specific about what conditions you are operating the amp under?
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Chris C G8TJR |
23rd Apr 2004, 4:27 pm | #3 |
Octode
Join Date: May 2003
Location: Belper Derbyshire
Posts: 1,936
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Re: Mechanical noise.
Hello there,
I had a quiet buzzing sound coming from an EZ81 when I built an amplifier. the noise was the filament in the cathode rattling I belive. it started when power was switched on and the frequency was around 50Hz. Replacing the EZ80 solved the problem. Christopher Capener
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23rd Apr 2004, 7:27 pm | #4 |
Retired Dormant Member
Join Date: Mar 2003
Location: Birmingham, West Midlands, UK.
Posts: 785
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Re: Mechanical noise.
Without hearing the exact sound it is obviously difficult to tell, but the nearest thing I've experienced to this was faint leakage in the valve holder itself, very faint sparking causing a buzzing sound. This would have probably been inaudible on its own, but the valve itself (the physical aspect of the valve, not its work in the circuit) acted like a resonant chamber and 'boosted' the audio like a horn on an old gramophone - to begin with of course it sounded like the noise came from the valve!
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24th Apr 2004, 12:31 am | #5 |
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Re: Mechanical noise.
I'm running the amp under " normal " conditions, that is, with speaker, also I'm only playing music, no test tones or anything. The noise is not there when the amp is first powered up, but starts when the tubes get warm. It's not the kind of heat-up or cool-down " clicks " that can be heard from most tubes as you turn the equipment on and off. It's a constant noise, faint rattling, and if I turn the power off, it doesn't fade away, but immidiately stops. I've heard how tubes can actually " play " (mechanically) if you run an amp without load. If arcing was the cause, wouldn't I hear some kind of noise in the spaker as well?
/Oskar |
24th Apr 2004, 7:41 am | #6 |
Dekatron
Join Date: Oct 2003
Location: Croydon, Surrey, UK.
Posts: 7,580
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Re: Mechanical noise.
Hi Oskar.
This is very likely a slight 'heater rattle' similar to the comment made by Chris. I had the same thing with a couple of KT66's in a Quad amplifier many years ago. They were quite old but still OK and they had seen many years of service. I can only assume that the heaters resonated at 50Hz within the cathode causing the rattle. I proved the point when I later fitted brand new replacement valves. It's nothing to worry about unless the noise is excessive and can be heard during gaps in the music. The KT66's I mentioned carried on working and were still going strong after I sold the amp. I've also heard this with line output valves in TV sets, (the larger Octal types like PL36). Power valves may be more prone to this type of thing due to larger heater. Rich.
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24th Apr 2004, 9:45 am | #7 |
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Re: Mechanical noise.
I think you're right RIchard. I find it a bit strange though, the tubes are after all brand new. It's not wery annoying or very loud. You can only hear it if you sit right next to the amp. I think I'll solve this one by cranking up the volume a bit!
Again, thank you all! /Oskar |
24th Apr 2004, 10:31 pm | #8 |
Dekatron
Join Date: Oct 2003
Location: Croydon, Surrey, UK.
Posts: 7,580
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Re: Mechanical noise.
Hi Oskar.
It could be due to the particular brand of valve (tube). Maybe some heaters fit more snugly into the cathode. Rich.
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There are lots of brilliant keyboard players and then there is Rick Wakeman..... |