Feedback?
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Joined: Jun 2005
Posts: 64
old hand
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OP
old hand
Joined: Jun 2005
Posts: 64 |
Looking for some advice. Something curious has crept up in my system. When one of my kids was loudly making an "Ooooohh," sound my left front speaker would mimic it in a sort of feedback response. If I hit pieces of metal together the speaker responds as well. Has anyone experienced this and if so what is the culprit?
I am using a Marantz SR 5005 as a pre/pro that was modded by removing the amp pathway by Outlaw Audio. I then have the L/R off the Marantz going to HT inputs to a Modwright SWL 9.0 being used as a stereo preamp and bypass for home theater. Oppo -83 HDMI to Marantz for home theater, coax to Eastern Electric MiniMax DAC for stereo on to Modwright via RCA. M22's, VP100, and QS 8's.
Thanks, hope I provided enough info.
Sips
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Re: Feedback?
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Joined: Jan 2002
Posts: 3,270
connoisseur
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connoisseur
Joined: Jan 2002
Posts: 3,270 |
Hi power window,
What source are you using when you hear the feedback? I'll guess that somewhere in your system you may have vacuum tubes, which can be quite microphonic with higher sound pressure levels. To check for a microphonic tube, just remove the chassis and tap on the tubes in the amp (or preamp). You'll hear a "ping" sound if the tube is microphonic.
If you were playing vinyl on a turntable, the disc itself can become microphonic, vibrate, and pass on loud acoustical sounds to the phono cartridge and to your system. I have a collection of various weights and clamps for vinyl on a turntable (back when I played vinyl) to prevent feedback.
Regards, Alan Lofft
Alan Lofft, Axiom Resident Expert (Retired)
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Re: Feedback?
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Joined: Jun 2005
Posts: 64
old hand
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OP
old hand
Joined: Jun 2005
Posts: 64 |
You are right about tubes. My stereo preamp with bypass (which is used with all sources) has power and pre tubes. If I perform your diagnostic, does that mean the tube is bad and needs replacing as I do not recall this occurring when this piece of gear entered my system? Thanks for the quick reply and nice to hear from you Alan.
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Re: Feedback?
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Joined: Jun 2005
Posts: 64
old hand
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OP
old hand
Joined: Jun 2005
Posts: 64 |
Alan, side note. I haven't done your diagnostic yet, but the fact that the feedback is only present in the left speaker leads me to believe the left channel tube in my preamp is the culprit. The only question then, is it a bad tube or will a tube damper solve it? Thanks, Sips
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Re: Feedback?
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Joined: Jan 2004
Posts: 13,840 Likes: 13
shareholder in the making
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shareholder in the making
Joined: Jan 2004
Posts: 13,840 Likes: 13 |
or get a solid state amp.
M80s VP180 4xM22ow 4xM3ic EP600 2xEP350 AnthemAVM60 Outlaw7700 EmoA500 Epson5040UB FluanceRT85
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Re: Feedback?
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Joined: Nov 2005
Posts: 1,236
connoisseur
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connoisseur
Joined: Nov 2005
Posts: 1,236 |
M3 and M80
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Re: Feedback?
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Joined: May 2002
Posts: 10,654
shareholder in the making
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shareholder in the making
Joined: May 2002
Posts: 10,654 |
Sips, yes, you've provided enough info and Alan's suggestion about a tube is likely the problem. Even in a pre-amp, using obsolescent tube audio technology can lead to unnecessary problems.
If you haven't yet checked all the tubes, you might first connect the 5005 directly to the amplifier to verify that the problem you describe doesn't then occur.
-----------------------------------
Enjoy the music, not the equipment.
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Re: Feedback?
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Joined: Jan 2002
Posts: 3,270
connoisseur
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connoisseur
Joined: Jan 2002
Posts: 3,270 |
Hi sips,
I think that's a reasonable conclusion about a tube in the left-channel part of the preamp, since that's the channel you're hearing the microphonic feedback.
I forgot to say that you should replace the microphonic tube. I never tried tube dampers back in the tube era, but perhaps one would be effective.
Alan
Alan Lofft, Axiom Resident Expert (Retired)
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Re: Feedback?
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Joined: Jun 2005
Posts: 64
old hand
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OP
old hand
Joined: Jun 2005
Posts: 64 |
Thanks all for the reply/feedback :), as well as the jabs on tube technology. Old technology is not necessarily worse, and conversely new is not better. Variety is what makes this hobby so interesting. Now I'm off to see if someone can wipe the dust off one of those old tube boxes and see if it's the right one.
Cheers
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Re: Feedback?
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Joined: Nov 2005
Posts: 1,236
connoisseur
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connoisseur
Joined: Nov 2005
Posts: 1,236 |
My tube amp brings me great joy.
M3 and M80
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