Not a ground loop hum???

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...

You really need to start by unplugging everything in that circuit, not just in that outlet. Then, plug in only 1 piece at a time to find the hum.
Keep in mind that electricians can do weird things (1 outlet in my basement is tied into a kitchen outlet).

Thanks very much for the responses!!!

The IC's in the system: the pair from cdp to pre and the pair from the pre to amp are both essentially outside the equipment rack and neither of them comes very close to a component's chassis. The IC from tuner to pre rests mostly on the top shelf of my rack. I've tried to ensure that IC's are spaced apart from one another and from the PC's.

The system in question is strictly audio, but I'll look into the ground loop isolator idea if all else fails.

Sean, I was hoping you might comment/advise. I checked the outlet into which the power conditioner is plugged with a 3-prong outlet-checker (I've forgottent the proper name) to ensure its wired properly and it indicates the outlet is OK. As for the outlets on the power conditioner, I did not check those but will do so this evening. Although the cheater plugs I found/purchased don't have the ground blade, they are not reversible as one of the two blades is wider.

I don't have a metre to measure the volume of the hum (I would guess that it's about as loud as a really big bumble bee; can't think of another comparison right now), but it is at a constant level regardless of the position of the attenuator. I can hear it from up to 12 feet away, and when I listen at low volume at night (so as not to disturb my better-half or the littl'uns) I can hear the hum between tracks and during soft passages. My pre has the Shallco stepped attenuator and by low volume I mean it's at the third to fifth step.

I had tried several weeks ago hunting down the source of the hum in the sequence that you suggest, but will have to check again as I can't remember the results.

Sugarbrie, if memory serves, the van den Hul's are not soldered, probably because of the carbon fibre layer, and they are barely a year old. But I'll check this as well. I'd hate to think that one of the BC components could be to blame, but the hum is drivin' me nuts.

On a separate noise issue, my MR1200 makes quite a bit of noise that comes and goes. I wrote to Blue Circle and they suggested the AC to my house may be particularly dirty, so the noise is indicative of the transformer/filtering working hard. I don't know, I mean why pay for conditioning/filtering to keep noise out of the audio components only to have it show up in the conditioner/filter. BC also indicated that it may be due to the on/off cycling of the furnace at this time of year, but the two don't seem to coincide. They'll retrofit the MR1200 or the BC62 PC with a quiet device, but I'm waiting until we move to our new place in a couple of weeks before spending anymore on power conditioning/filtering.

Mghcanuck: I just realized that, going by your moniker, you are probably Canadian. If that is the case, i can no longer help you. Sorry 'bout dat.

Bwahahaha. I had to do that just for the sake of Pbb always spouting off about Canada and the superiority of things Canadian. I hope that he and other Canadians can laugh after they get over the initial shock value. What good is "hanging out" if you can't have some fun at one of someone else's expense : )

Getting back to the point, just because a device uses a three prong or polarized two prong power cord doesn't mean it can't be wired with reverse polarity internally. On top of that, one can have correct polarity, but if there is a difference in ground potential from one component to another ( due to leaky cap's, resistive connections, etc...), you can also run into a hum. You'll need to disconnect ALL of your interconnects to check thi AND have access to an inexpensive multimeter too.

When checking components individually, you have to disconnect interconnects between them, not just turn them off. This is both for checking component polarity AND finding out what specific component or combination of components is causing the hum.

As far as the power line conditioner making noise, it may be something as simple as loose nuts & bolts holding down a transformer or a lack of internal damping. I agree that buying a product to solve a problem and then creating another demonstrates a lack of product engineering. Then again, it might be a great product and simply slipped through the cracks of "Quality Assurance".

Having said that, you might want to check into a device that Kevin Deal of Upscale Audio sells. It is supposed to suppress DC offset problems in the AC line, which can cause some of the problems that you are experiencing. From what i've gathered, i think that he sells it with some type of return policy, so find out the specifics before shelling out the cash.

As a side note, a quantity of DC on the AC mains will cause your transformers to run much hotter than normal. Then again, some high bias amps will "warm" the transformer quite noticeably, so this can be a hit or miss trick when dealing with amps. Sean
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Sean:

Your realisation is correct, eh?! But I appreciate the humour, so no harm done. Pbb may indeed be quite ardent at times, but it probably has more to do with a feeling of inferiority due to living next to such a big and powerful and awe-inspiring and free and great and did I say powerful nation like the US, well I guess there is no "like the US" since it really is the only super-power, and that's just super IMHO, but now I'm rambling and so I'll stop. :-)

Aha, I have a multimeter! What am I measuring for? Sorry, but my electrical knowledge is, shall we say, pretty limited. I gather that the first step is to disconnect all IC's and only have one component plugged in at a time. I seem to remember you may have covered this in another thread where you had a kit that would be shipped from one A'goner to the next so they could check for polarity and difference in ground potential. Could you provide the link to that thread or instructions/advice? Thanks very much.

I am going straight to the Upscale Audio web site to look for the device you mentioned.

Max