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Audible Buzz from Lexicon: dimmers & microwave?

Greetings all, I've scoured through the forums here and other sites to try and find an answer to a perplexing buzz that's been coming from the chassis of my Lexicon LX-7. The buzzing does not come through my speakers--ever. The buzzing comes from the Lexicon.

I have done the following:
1) I have brought my Lexicon in to be serviced. It passed with flying colors and *no buzzing*
2) I have switched power cords three times (Shunyata, Transparent, stock)
3) I have disconnected all balanced cables and speaker interconnects from the Lexicon. It sill buzzes regardless of whether or not something is connected.
4) I have plugged my Lexicon into my Panamax power conditioner
internetmin
davehrab's avatar
davehrab
380 posts
 
The massive toroidal transformer in your Lexicon amp is most likely being effected/rattled by DC Offset ... the DC offset is being created by all the switching power supplies in your household appliance's and anything that has a remote control including your cable box/DVR and your flat screen

The DC Offset is created by the switching power supplies which use half wave bridge rectifiers that draw current in uneven pulses ... these uneven pulses will cause big toroidal transformers to rattle, buzz, or hum ... causing the transformer to lose some of it's efficacy and reducing it's headroom and dynamics ... not good in home theater

The DC Offset enters your amp through the power cord so disconnecting ICs and speaker cables will have no effect as the pulsing Offset is entering on the power line ... switching power cords will not help either as they merely act as a conduit to the Tranny

I've also never seen a power conditioner that deals with DC Offset ... although Bryston does incorporates a DC Offset blocking circuit in some of their amps

Channel Island and PS Audio offer units that may be worth looking into
jea48
4,416 posts
 
http://www.diyaudio.com/forums/solid-state/2080-dc-filter.html
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internetmin OP
258 posts
 
Thanks for this Dave. Really great info. I'm wondering if anyone else has a way to deal with this at the panel and isolate my A/V gear?? Jea, this is a good link but I'm not an electrician and not sure what this means in practical terms. I've had electricians come in with no real luck here. Polarity and phase are fine, voltage registers fine, the outlet is a Shunyata and is fine, the circuit is a dedicated 20 amp and it's fine. The neutral is fine. They also moved the circuit from the sub panel to the main panel. No luck. One thing that gets the buzzing on the lexicon amp's transformer is the microwave oven's stove lights (it's over the stove and has a hood light). If it's on "low" the buzzing from the Lexicon is VERY loud (again only from the chassis). The kitchen dimmers also appear to (sometimes) impact the loudness of the transformer buzz. I ordered the PS Audio Hum Buster III from Music Direct in Chicago (Mark there was FANTASTIC). WE'll see how that goes. Now, is there ANY WAY AT ALL to check for DC offset? The electricians plugged in their meter and DC registered as "0" but they were perplexed at the notion that DC could be on the AC lines. I printed out forum threads, etc. but they really didn't know how to do anything different. Thanks all.
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