My amp is acting like a transducer!?

audio_moksha · 15th March 2008, 01:55 AM

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?

diegot · 15th March 2008, 02:02 AM

Don't play the amp without the speaker. You will blow yours OPT!

audio_moksha · 15th March 2008, 02:17 AM

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 : (

DigitalJunkie · 15th March 2008, 02:41 AM

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.

tubelab.com · 15th March 2008, 02:42 AM

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.

audio_moksha · 15th March 2008, 03:18 AM

So what are the symptoms of a fried OPT? My amp still plays allright through speakers. Thanks for the input fellas.

Miles Prower · 15th March 2008, 04:28 AM

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.

jnb · 15th March 2008, 09:15 AM

You could try tightening the bolts on the transformer.

audio_moksha · 15th March 2008, 05:41 PM

tightening the bolts helped quite a bit. Thanks guys...

bigwill · 15th March 2008, 06:04 PM

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!

15th March 2008, 01:55 AM	#1
audio_moksha diyAudio Member Join Date: Oct 2006 Location: Los Angeles	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?

15th March 2008, 02:42 AM	#5
tubelab.com diyAudio Member Join Date: Jul 2005 Location: South Florida	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. __________________ Too much power is almost enough! Turn it up till it explodes - then back up just a little.

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15th March 2008, 02:02 AM	#2
diegot diyAudio Member Join Date: Sep 2004 Location: Brazil	Don't play the amp without the speaker. You will blow yours OPT!

15th March 2008, 03:18 AM	#6
audio_moksha diyAudio Member Join Date: Oct 2006 Location: Los Angeles	So what are the symptoms of a fried OPT? My amp still plays allright through speakers. Thanks for the input fellas.

15th March 2008, 09:15 AM	#8
jnb diyAudio Member Join Date: Dec 2006	You could try tightening the bolts on the transformer.

15th March 2008, 05:41 PM	#9
audio_moksha diyAudio Member Join Date: Oct 2006 Location: Los Angeles	tightening the bolts helped quite a bit. Thanks guys...

15th March 2008, 06:04 PM	#10
bigwill diyAudio Member Join Date: Dec 2004 Location: UK	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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