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Not a ground loop hum???

I thought I had a ground loop hum, given that with my pre, cdp and amp all on, without any music playing, there is a hum emanating from my speakers. Following the advice seen here and elsewhere, I went out and got some cheater plugs to try and hunt down this annoying and, at times, distracting hum.

My system comprises: Anthem CD-1 (with DH-Labs power cord), Blue Circle BC21.1 tube pre (with BC62 pc), BC22 amp (Zu Cable BoK pc), Rune loudspeakers by Zu Cable (hooked up with Zu Cable Libtec speaker cable), Blue Circle MR1200 balanced power line conditioner/distributor (Zu Cable BoK pc), and van den Hul D102 MKIII interconnents.

Well, with the three components' power cord fitted with a cheater plug and all plugged into the power conditioner, the hum was still present, same intensity, volume, etc. Removing the cheater plugs one by one starting with the cdp, then pre, then amp, there was no reduction in the hum. In fact, I think I may have heard it get worse at one point.

Any ideas out there as to the cause of the hum? Maybe the tubes in the system are the culprit. There is a pair of Siemens CCa (6922 type) with Pearl tube coolers installed in the pre, and the tube in the cdp is a Telefunken CCa with a tube cooler.
mghcanuck
newbee
4,767 posts
 
Have you looked at your IC's - I've had a hum from time to time from the IC's passing too near a transformer (in my case, the amps). One way to check this out is starting at the amps disconnect and reconnect IC's going back to the source, one at a time (be sure to turn the amp off each time). You will be able to at least figure out which component is causing the hum and then you can check the IC's. Good luck.......
jmcgrogan2's avatar
jmcgrogan2
6,346 posts
 
If you have a video cable line or satelite cable, disconnect it, see if the hum goes away. I went through a similar situation a year or so ago. I tried cheater plugs, floating grounds, etc, etc. It wound up the ground loop hum was coming from my cable line. Radio Shack sells ground loop isolators if this is the case. I'm using a MIT Iso-LinQ, no more hum.

Regards,
John
sean
6,231 posts
 
Have you ever verified that your equipment and AC outlets are properly oriented in terms of polarity? Some components are HIGHLY sensitive to AC polarity. Having one component that is not oriented properly connected to others that are oriented properly can introduce a hum into the system.

Out of curiosity, how loud is the hum and at what distance from the speakers is it audible? Is the hum a constant level or does it vary with the gain of the preamp? Have you ever tried connecting the amp to the speakers by itself to see if it hums? If not, try that and see what happens. If no hum, hook up the preamp to the amp and then give that a shot. If nothing, then hook up the CD to the pre and see what happens. If you get a hum with all three hooked up, then try the CD directly into the amp ( NO discs in the unit unless you can vary the output of the CD player ). As usual, it is all just a matter of step by step diagnostics and trouble-shooting. Sean
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sugarbrie
3,854 posts
 
All good suggestions above...

I had an interconnect hum once because the solder on a RCA plug was cracked, probably from being moved around too much over the years...

Resoldering did the trick...
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