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Vintage Audio (record players, hi-fi etc) Amplifiers, speakers, gramophones and other audio equipment. |
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1st Dec 2011, 2:18 pm | #1 |
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'Underwater' sound from valved amp.
Very quick question. Am I correct in thinking that an 'underwater' ripple sound on a valve amp is likely to be caused bad electrolytic smoothing caps?
Thanks, Nick. |
1st Dec 2011, 4:00 pm | #2 |
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Re: 'underwater' sound
I wouldn't think so. Bad smoothing capacitors give rise to a loud low pitched hum, which is unmistakable.
You problem is more likely down to leaky paper dielectric capacitors, dirty switch contacts, dirty valve pins or dirty potentiometer tracks.
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1st Dec 2011, 9:34 pm | #3 |
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Re: 'Underwater' sound from valved amp.
Sounds like motorboating or instability.
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1st Dec 2011, 9:43 pm | #4 |
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Re: 'Underwater' sound from valved amp.
He could be trying to describe hum....induced before the volume control and modulating the signal. Maybe the poster can be a little more specific of the symptons.
Lawrence |
1st Dec 2011, 10:31 pm | #5 |
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Re: 'Underwater' sound from valved amp.
"Under water ripple sound" could be many things, but I don't think hum is one of them.
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1st Dec 2011, 10:37 pm | #6 |
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Re: 'Underwater' sound from valved amp.
Not quite sure what underwater sound means, but it may be that one of the pre-amp valves has gone microphonic causing hollow sound. More information would help.
Bill |
1st Dec 2011, 10:50 pm | #7 | |
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Re: 'Underwater' sound from valved amp.
Quote:
Lawrence. Last edited by ms660; 1st Dec 2011 at 11:00 pm. |
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2nd Dec 2011, 12:27 am | #8 |
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Re: 'Underwater' sound from valved amp.
hi, the signal modulates. there is no hum
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2nd Dec 2011, 1:30 am | #9 |
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Re: 'Underwater' sound from valved amp.
What is being modulated by what?
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2nd Dec 2011, 2:51 am | #10 | |
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Re: 'Underwater' sound from valved amp.
Hello Nick,
Quote:
Regards, Dave. |
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2nd Dec 2011, 5:36 am | #11 |
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Re: 'Underwater' sound from valved amp.
Hi, it's probably too subtle to do a recording but it's 'there'. It's the actual audio signal fluctuating.
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2nd Dec 2011, 5:43 am | #12 |
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Re: 'Underwater' sound from valved amp.
Push pull amp? Give me technical aspects, and i'll attempt to give you the things causing the problem/
-Chris |
2nd Dec 2011, 7:55 am | #13 |
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Re: 'Underwater' sound from valved amp.
It would be useful to know the make and model, it's not an Ashdown by any chance?
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2nd Dec 2011, 9:47 am | #14 |
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Re: 'Underwater' sound from valved amp.
Motorboating?
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2nd Dec 2011, 11:47 am | #15 |
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Re: 'Underwater' sound from valved amp.
Is this valve amp a guitar amp or audio amp?
If it is a guitar amp it might have a tremelo (effect) SEAN
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2nd Dec 2011, 3:25 pm | #16 |
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Re: 'Underwater' sound from valved amp.
Maybe it's because you are up at 4:36AM?
I would stop using it as it could be signs of a fault that could cause damage. Let's have a model number and pics. |
2nd Dec 2011, 10:53 pm | #18 |
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Re: 'Underwater' sound from valved amp.
Cheers Mick jokes aside, it does sound a bit like that but not as exagerated.
Amp details here P.30 http://thearcadeboneyard.com/Jukebox...0Combined).pdf Moderator's note. Warning - if you have a slow internet connection you might want to be aware that this file is 28M and will take forever to load. Last edited by Brian R Pateman; 3rd Dec 2011 at 10:01 am. Reason: Moderator's note added. |
3rd Dec 2011, 12:22 am | #19 |
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Re: 'Underwater' sound from valved amp.
Has the amp been restored recently? If not I would want to give it a full health check:
- Test output valve grids are 0V (leaky audio coupling capacitors) - Check individual anode currents as it uses shared cathode bias arrangement - Check voltages against schematic As it's stereo, the obvious question is does it do the same on both channels? are the noises present when there is no input or is it just distortion of the sound? does the amount of distortion change with increased volume? |
3rd Dec 2011, 7:44 pm | #20 |
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Re: 'Underwater' sound from valved amp.
hi, yes the sound is on both channels and it is only apparent with audio input. i have ordered a cap kit and will do the necessaries.
thanks, nick |