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Old 15th March 2008, 01:55 AM   #1
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Default my amp is acting like a transducer!?

So I recently fixed the buzz on my EL34 amp but now something even stranger is happening. With no speakers connected I can hear the music playing back from the amp itself. The sound seems to emanate from the OPT's. Its mostly the higher frequencies from about 2kHz onwards.

When I hook up loudspeakers the amplifier plays alright but doesn't sound as good as it should. The highs are harsh and the overall sound has a veil to it. Any ideas whats going on? Are the OPT's busted?
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Old 15th March 2008, 02:02 AM   #2
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Don't play the amp without the speaker. You will blow yours OPT!
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Old 15th March 2008, 02:17 AM   #3
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Quote:
Don't play the amp without the speaker. You will blow yours OPT!
Thanks diegot, I am aware of that but owing to the unusual circumstances I just had to try it out for a few seconds. This still doesn't help me though : (
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Old 15th March 2008, 02:41 AM   #4
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It's pretty normal for transformers (even tubes) to "sing" a bit..

Quote:
I just had to try it out for a few seconds.
Thats all it takes to fry an OPT.
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Old 15th March 2008, 02:42 AM   #5
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Most OPT's will "speak to you", even when loaded. The sound from the speakers covers it up. Some are louder than others, and potted ones are usually silent. You have a lot of magnetic field being modulated by the audio. Any metal that can vibrate, will. Usually it is the end bells.

Operating a tube amplifier without a load can indeed take out the OPT, and other parts.
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Old 15th March 2008, 03:18 AM   #6
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So what are the symptoms of a fried OPT? My amp still plays allright through speakers. Thanks for the input fellas.
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Old 15th March 2008, 04:28 AM   #7
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Quote:
Originally posted by audio_moksha
So what are the symptoms of a fried OPT? My amp still plays allright through speakers. Thanks for the input fellas.
If that happens, there won't be any doubt about it: fireworks inside the finals, smoking cathode resistors, and popped fuses and/or mains fuses or circuit breakers.
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Old 15th March 2008, 09:15 AM   #8
jnb is offline jnb  Australia
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You could try tightening the bolts on the transformer.
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Old 15th March 2008, 05:41 PM   #9
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tightening the bolts helped quite a bit. Thanks guys...
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Old 15th March 2008, 06:04 PM   #10
bigwill is offline bigwill  United Kingdom
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I've heard KT77s "sing" before! With the amp connected to a dummy load I could hear the music, I listened closely expecting it to be coming from the OPTs but it was in fact the tubes!
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