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Help with loud pop when AC kicks on - phono amp problem

Hi everyone,

Back with yet another power line issue.  I have a Croft RIAA phono amp power that is causing a very loud pop whenever the AC unit kicks on and again when the fan starts a few seconds later.  In some cases the pop is so loud that it can be heard three rooms away.  It can be heard over even the loudest music peaks.  I'm afraid that it might damage the unit or the speakers, so I'm hesitant to use it.  I'm not sure if new tubes might make a difference.  I hooked a CD player up to the integrated amp (right now I'm using a Jolida hybrid while I'm shopping for a new integrated), and there is no noise when the A/C starts up if only the CD player is hooked up. 

I have tried two different power cords.  Plugged the Croft into the wall, into a PLC Thingee power conditioner, and into a Furman power conditioner.  In all cases it still pops to one degree or another.  

Any thoughts on whether it's worth hunting for the problem.  I had some similar issues with a Heed Quasar phono stage.  But haven't noticed it on a couple of other phono stages.  Seems very hit and miss.

Would welcome any advice.  Thanks!
Scott
smrex13
almarg's avatar
almarg
8,673 posts
 
Hi Scott,

As I recall some of the phono stages you've tried in the past have had issues involving pickup of radio signals.  So in part for that reason I wouldn't totally rule out the possibility that the means by which the air conditioner is causing the issue is by coupling of RFI through the air, rather than by its effects on the power line.  Especially if the air conditioner is located in the same room as the phono stage.

And also given that a Furman power conditioner didn't resolve the problem, as some of their models provide very good filtering down to the low kHz range.  What model Furman was it?  And did it seem to make a perceivable difference in the severity of the problem?

Best regards,
-- Al
    
minkwelder
191 posts
 
If I may interject, I too have had a popping sound that had begun recently, only it happens when activating certain light switches. I had recently replaced my line stage as well as my phono stage, so I didn't know where the fault may lie. The AC does not cause any problems.

The line stage is a W4S STP/SE and the phono stage: HEED QUASAR! Hmmmmmmm.
smrex13 OP
423 posts
 
@minkwelder - interesting that you are having some issues with the Quasar, too.  I thought it sounded fantastic, but it had a surprising sensitivity to noise, especially for a unit with an outboard power supply. 

@almarg - the A/C unit is outiside the apartment (its central A/C).  I think the integrated may have as much to do with the interference as the phono stage.  It seems much louder since I started using the Jolida.  The Belles Soloist had a similar (or even more severe) issue as it reacted to every light switch in the apartment.  The only other problems I've had have been with the A/C switching on.  The Furman was an entry level model - 15i, so certainly not the most powerful unit they make.  

Thanks, Scott

almarg's avatar
almarg
8,673 posts
 
Scott, ok, so it probably isn't airborne RFI that is responsible.

It appears that the two outlets on the rear of the Furman Elite 15i that are indicated as being just for video equipment incorporate some ultrasonic filtering that is not provided on the other outlets, in addition to providing the filtering the other outlets provide.  So for experimental purposes, at least, it may be worthwhile trying those outlets for the Croft and the Jolida.

Minkwelder, are the light switches you referred to controlling fluorescent or compact fluorescent lighting?  Those can generate significant noise and RFI, especially (I believe) as they get older, and especially while they are in the process of turning on.  And are the switches dimmer types, which can also be significant noise generators?

Best regards,
-- Al
 
minkwelder
191 posts
 
Yes, Al, the lights are fluorescent - and are older ones at that. I have been thinking of replacing them with LED, which I’m hoping will not cause the same sort of problem. The switches are newer silent type and not dimmers.

BTW, I didn’t mean to hijack the thread, but thought my experience may also shed some light on what Scott is experiencing.
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