Wopl 700 series 2 with a slight buzz at midrange speakers

Rickyboy

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#1
Hi ! i have just received my old phase linear 700/2 with a new WOPL conversion , main board , backplane and new matched transistors ......... i have also added a watts abundant relay/ protection board , so far so good , i have also replaced the 9800 uf capacitors for new , 15000uk ones ( bought them at Joe`s .

the only problem i have is that i hear a little buzz on the midrange speaker , no matter how high or low the volume knobs are or if the preamplifier is hooked to it or not ......

any clue here ?? anybody experienced something similar ?

thank you!
 
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Billboard

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#2
What speakers, and do Both behave the same way? Try and download a tone generator to your phone/iPad and sweep across the freq and see is you can isolate the freq that you hear the buzz.
 

Rickyboy

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#3
Speakers are AR 9’s , both speakers have the same slight buzz at the midrange speakers . Preamp either disconnected or volume down , PL volume knobs at their minimum…..maybe a mass issue?
 

MarkWComer

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#4
Ground loop?
Maybe some other electronic equipment nearby is inducing the buzz.
Polarized plug? Try switching it the other way.
 

pennysdad

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#5
Generally, if it's a buzz, you need to add an earth to the chassis.
If it's a hum, then you have a loop and need to disconnect an earth [somewhere].
 

Rickyboy

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#6
The amp has a 2 leg power cord and gets the ground from the preamp since it has a 3 leg cord , but the noise continues ….it is not a “mmmmmmmmmmmm” it’s like a buzz
 

George S.

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#7
You have the amps power cord plugged into the preamps built in power "power strip"? Try plugging the amps power cord into the wall and see if it makes a difference. Also try flipping the amps power cord plug 180 degrees at the wall. Still doing it? For testing purposes, get a long heavy duty extension cord and try the above from another part of your homes power.
I use power strips bought at the big box store to power my system. Every component is left "on" to minimize wear on those old hard to replace power switches, my on/off is on the power strips, with no component power cords plugged into the preamp. The system is dead quiet, like a black hole.
 
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Rickyboy

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#9
You have the amps power cord plugged into the preamps built in power "power strip"? Try plugging the amps power cord into the wall and see if it makes a difference. Also try flipping the amps power cord plug 180 degrees at the wall. Still doing it? For testing purposes, get a long heavy duty extension cord and try the above from another part of your homes power.
I use power strips bought at the big box store to power my system. Every component is left "on" to minimize wear on those old hard to replace power switches, my on/off is on the power strips, with no component power cords plugged into the preamp. The system is dead quiet, like a black hole.
amp is plugged to a power strip . i have never plugged it to the preamp power outlet
 

pennysdad

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#10
The amp has a 2 leg power cord and gets the ground from the preamp since it has a 3 leg cord , but the noise continues ….it is not a “mmmmmmmmmmmm” it’s like a buzz
You misread my reply.
Just try and add a chassis earth.
Can't hurt.
Connect a piece of wire to a known good earth. Touch the other end to some bare metal on the amp.

Oops, I see you were replying to someone else. Sorry.

Anyway, add an earth.
 
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Gepetto

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#11
Post several good pictures of the internal wiring dress within your amp. It matters...
Have you snubbed the bridge rectifier with caps to kill the snap off?
Have you changed the bridge type from the original?
 

Rickyboy

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#12
Post several good pictures of the internal wiring dress within your amp. It matters...
Have you snubbed the bridge rectifier with caps to kill the snap off?
Have you changed the bridge type from the original?
What you mean with “to kill the snap off “?
Bridge is the original
 

Rickyboy

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#13
You misread my reply.
Just try and add a chassis earth.
Can't hurt.
Connect a piece of wire to a known good earth. Touch the other end to some bare metal on the amp.

Oops, I see you were replying to someone else. Sorry.

Anyway, add an earth.
I have connected a fawcett to the amp via soldering lead , no improvements on that buzz
 

pennysdad

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#14
I have connected a fawcett to the amp via soldering lead , no improvements on that buzz
It was worth a shot. I've had in the past surprisingly good results.
Lots of high quality amps don't have earths connected to the case, [eg like the Bryston that I used to have] and the case then has a hard time 'shielding'.
My RTA when connected to my system creates a buzz until I run a seperate earth to it. Took me ages to figure that one out.
Sorry it didn't work out.
 

MarkWComer

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#15
What you mean with “to kill the snap off “?
Bridge is the original
The AC current phase change in the rectifier creates “switching noise,” which is eliminated by the addition of capacitors on the legs of the rectifier. That’s what he means by “snap off.”

Given that you tried everything else, this may be the issue. Rectifiers are nothing more than four diodes, one or more may be at fault. Easily tested with a continuity tester or ohmmeter.
 

Gepetto

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#16
The AC current phase change in the rectifier creates “switching noise,” which is eliminated by the addition of capacitors on the legs of the rectifier. That’s what he means by “snap off.”

Given that you tried everything else, this may be the issue. Rectifiers are nothing more than four diodes, one or more may be at fault. Easily tested with a continuity tester or ohmmeter.
waveform.jpg
 

WOPL Sniffer

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#20
I have a pair of speakers I used to use for testing, damn thing buzzed on 2 WOPL's I finished, I pulled my hair out trying to finger it out. Changed out to another set and never got any more noise. They are relegated to the "just in case pile". Damn Infinity speakers.....
 
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