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Request for help with squealing noise in 2.2 biamp system
Request for help with squealing noise in 2.2 biamp system
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Old 23rd June 2019, 08:01 PM   #1
sandston is offline sandston  United States
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Join Date: Sep 2012
Location: Los Angeles
Default Request for help with squealing noise in 2.2 biamp system

I am desperartely seeking help on some system noise I started encountering with the addition of two new SVS SB4000 subwoofers into my system. I replaced two older subwoofers( Elac debut 12 and a Cadence CSX-12). The new SVS subwoofers seem to be injecting a high pitch squealing noise that is coming out of my mains. My system consists of a Decware CSP2+ preamp with two output per channel. My amps are monoblock Melody 845-1 tube units. I have gone through all the possibilities with SVS and they agreed to send me new amps to replace the ones that came with the units. The new amps create the same squealing noise. To give some additional background when I turn the preamp off the noise still is present in the mains. The high pitch squeal is not effected by changes in volume. The sound appears to be emanating from the SVS subwoofers amplifiers. My typical mains are 94db efficient but its still audible in some 86db speakers I own. The Decware CSP2+ preamp has output level controls. One for the left and one for the right channel. It effects both R and Left line level outputs equally. Even with the preamp turned off when I turn the output level all the way up in one channel or all the way down the squealing stops. In the other channel it stops when turned all the way up but not when turned all the way down. This points to some possible grounding issue within the preamp...possibly? This did not happen with my other subwoofers. The other thought is that is some type of impedance mismatch happening between the tube amps and the solid state amps being on essentially a Y-Splitter at the preamp. I currently put a DSpeaker unit between the subs and the preamp and this essentially blocks the noise however I would prefer not to have this additional A-D-A stage in my system. The entire system is powered through a PSAudio P10 regenerator so I would suspect that this is not a global ground loop issue.

Any thought wisdom or advice from the community would be appreciated. I would really like to keep these subs in my system but before I move on I would like to have an idea of what is happening so I can avoid this moving forward. I am happy to provide input and output impedance numbers for the units if somebody feels this might help. Thanks for any help or advice in advanced.
Regards,
Steve C
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Old 23rd June 2019, 08:11 PM   #2
sandston is offline sandston  United States
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Join Date: Sep 2012
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One more thing I forgot to mention is when I hook my amps up to the high pass outputs on the sub I still get the squealing sound which leads me to believe the preamp is grounding the noise out of the system when the output is maxed out and serving to mitigate not create this noise but this is just a theory.
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Old 23rd June 2019, 08:23 PM   #3
rayma is offline rayma  United States
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Join Date: Apr 2011
Quote:
Originally Posted by sandston View Post
when I hook my amps up to the high pass outputs on the sub I still get the squealing sound which leads me to believe the preamp is grounding the noise out of the system when the output is maxed out
Can you substitute a different preamp, any kind, for testing?
Seems like a ground loop due to the preamp.

Last edited by rayma; 23rd June 2019 at 08:28 PM.
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Old 23rd June 2019, 08:48 PM   #4
sandston is offline sandston  United States
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Join Date: Sep 2012
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I dont have a seperate preamp to substitute however when i run the amps out of the line level high pass output on the subs. Taking the preamp out of the system completely I get the dreaded squeal. So in this scenario all we have in the equation is subs and monoblocks . The issue is also channel dependent in all configurations. Turn off left sub no squealing in left speaker.

This occurs with both subs and monos plugged into the P10 regenerator and plugged into wall same circuit and plugged into wall separate circuits. Cant seem to find my cheater plugs so have not tried try that yet.

Thank you for your response. Please keep the suggestions coming.
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Old 23rd June 2019, 09:00 PM   #5
rayma is offline rayma  United States
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Quote:
Originally Posted by sandston View Post
This occurs with both subs and monos plugged into the P10 regenerator and plugged into wall same circuit and plugged into wall separate circuits. Cant seem to find my cheater plugs so have not tried try that yet.
Yes, do try cheater plugs on all the components' plugs simultaneously.
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Old 24th June 2019, 12:05 AM   #6
sandston is offline sandston  United States
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Tried the cheater plugs. Didn't change a thing. Completely perplexed by this one.
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Old 24th June 2019, 05:40 AM   #7
ubergeeknz is online now ubergeeknz  New Zealand
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IMHO return them, get different ones... This sounds like too much trouble honestly!
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Old 24th June 2019, 09:59 AM   #8
Mark Tillotson is online now Mark Tillotson
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Location: Cambridge UK
My instinct is you have some ultrasonic spurs from the digital stuff that are getting detected or intermodulated down to the audio band? Or perhaps there's a lot of class-D switching frequency leakage back into the mains that's causing havoc?
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