Not a ground loop hum???

Sean:

Once again, you have proven to be 'da man! That's exactly the thread I had in mind. Looks like I've got some work to do. Thanks very much for your valuable input and advice.

Max

PS... I'm not offended in the least. The US and Canada, despite recent disagreements, have one of the closest relationships between nations on Earth. Some humour in the relationship can help keep it healthy. To paraphrase: "A bit of foolishness now and then is cherished by the wisest of men." Not that I'm wise, far from it, but I think the message is pretty wise itself. All the best.

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.

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

Just thought I'd provide an update. I checked the outlets on the MR1200 power conditioner with the polarity-checker-plug, which indicates the hot and neutral are reversed for all three duplexes. Arrrrgh! So, do I open up this $750US piece of equipment and try to properly wire the damn thing or do I return it to Blue Circle? Seeing as how I'm not technically/electrically qualified, I'm tempted by the latter option.

Max

I had sent an e-mail to Blue Circle and the response was as Brooks1 and Sean have indicated. Balanced power outlets will indeed show reversed hot and neutral or other icorrect wiring, because there is 60V coming from the neutral and 60V coming from the hot in relation to ground.

Blue Circle insists that it is likely really dirty incoming AC causing mechanical noise in the transformers of the MR1200. I'm back to my question of why bother with this relatively expensive power conditioner to prevent noise in the stereo components only to have the conditioner make noise.

I've swtiched over to the $200 Monster HT1000 power bar that was lying around since I received the $750 MR1200. Guess what, no noise from the HT1000. This just ticks me off.

Next week we move into our new house, so I'm really eager to see what kind of results I will get from these two units plugged into the dedicated line I had installed. Will the MR1200 continue to hum? Will the Monster piece mash the Blue Circle again? Enquiring minds want to know! FWIW, I'll post my findings in a few days and continue to ponder Chris VenHaus' solution of wiring two 0.47uF 600V Auricaps in parallel in the dedicated outlet if the MR1200 is still noisy. Has anyone out there tried the latter yet?

Thanks again to all for your comments and ideas.

Max

Sean, the MR1200 does indeed convert the AC from the wall into balanced power provided at its outlets. Are you saying that it should not hum regardless of how dirty the incoming AC may be? That was my assumption when I purchased the piece, given the filtering that it is supposed to perform and the positive reviews that BC has garnered for their balanced power line conditioners.

I've got the product designer/maker telling me that the noise is due to really dirty AC and that there's nothing to be done except have one of their power cords fitted with a quiet device that will resolve the noise issue in the MR1200. On the other hand there is the possibility of a QC issue with my unit.

I'm going to test the MR1200 in the new house next week and see what happens. If it's still noisy, perhaps I'll send it to BC for a check-up. Beyond that, I'm just not sure what to do.

Danny, I'm guessing the main difference is that the HT1000 does not have a transformer, or at least not one that converts the incoming AC of 120v in relation to ground into balanced AC of 60v from the hot and 60v from the neutral, so there is no possibility of transformer hum. The purported advantage of a balanced power line conditioner, such as the Blue Circle Music Rings among others, is that it offers even greater benefits in terms of lowered noise floor, etc. Not in my set-up though.

Thanks once more for the input. Much appreciated.

Max

Completely forgot to provide an update on the situation with my MR1200. Well, after trying it out in our new house and hearing the same level of noise, I sent the power conditioner back to Blue Circle, paid for shipping and about $60 for the filter add-on. They also checked it for mechanical and QC issues. Once I had it back home and inserted into the audio system, no more noise/hum from the unit!

Now I have two other noise isses to resolve. One is hum from the speakers, which increases in intensity as the volume is turned up. Could this be the inherent noise from the tubes in the preamp and or CD player? I've read in a couple of places about the noise from high gain preamps being audible through high-efficiency speakers? My speakers have a rated sensitivity of 101dB.

The other noise I recently discovered when I tapped the chassis of my preamp by accident. I gave the middle of the face plate a a light rap and heard distortion out of the left channel speaker. Any ideas?

Thanks again for any advice and suggestions.

Max

Hi Newbee,

Thanks for your response. That's correct, the hum is not audible when music is playing.

Damn that tube! I don't know a lot about tubes, but I should have thought about the possibility of it being microphonic. Time for a new pair I guess.

Regards.

Max