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Electrical issue

I have an electrical issue/s that I could use some help with. It's a hum issue, but after exhaustive research here and on AA I still cannot figure it out. I have 4 dedicated lines for my stereo run approximately 75 feet with 10/2 romex all connected to Porter Ports. I own Von Schweikert DB-99's, which have a powered sub built in. I have tried lifting the grounds on all the equipment except one(and every conceivable variation,I think), I've tried plugging everything into a power strip and then that into just one outlet, I've even tried using other outlets(not dedicated). In the end, if I disconnect everything and just plug the speaker into the wall with no other connections I will get a hum thru the woofer only. I have even put a PS Audio P500 between the speaker and the outlet to see if it made any difference to the hum, but no luck. If I leave the speaker wires connected and turn on the main amp then I will hear hum thru all the speakers(tweeter/mid/woofer).

I called VS and spoke with Kevin and he said that the signal is split in the speaker before the sub amp which would suggest that the hum is coming from my electrical system rather than my equipment. IOW, if I heard hum only thru the woofer and not the other drivers when the main amp is connected then there could be a problem with the sub amp, but this is not the case.

My house is new and the electrical and grounding system seem to be in good shape. I have checked every outlet I could find with a polarity/ground checker and did not find any problems. My panel is grounded both to the water line and a spiral rod buried next to the house. According to the builder these are acceptable to code here in Austin, Tx.

The only thing that seems odd is that when my A/C turns on, and sometimes my TV, the lights will dim for a second. I had the builder double check all the connections and made sure the proper gauge of wire etc. was used to hook up the A/C, but nothing seems to be wrong. Is it perhaps the Transformer on the pole outside? It's definitely old as it looks a bit rusty up there(new house - old neighborhood).

The hum is not particularily loud, but i can here from my listening position 10 feet away when no music is playing. I appreciate any help you may have to offer, and I'll answer as many questions as you have because I'd really like to solve this.

Thanks,
Matt
mab33
mab33 OP
101 posts
 
Hi Sherod,

Well, yes, but not in the way I thought I would. I can't count the number of times I had my friend Terry, who is an electrician, over to the house to try whatever I had read about in an effort to kill the noise. In the end, it never made any difference, well, that I could tell at least.

Then, I replaced my preamp and phono stage with Raul's Essential 3150 Phono/Line preamp, and all the noise went away. Actually, not all of it, if I put my ear within a few inches of the driver I can still hear a tiny bit of noise, but I think that's fairly normal and it definitely doesn't bother me or become audible from the listening position.

I have to tell you that this makes no sense to me. In the posts above I described unplugging everything in the system and disconnenting the speaker cables so that I could effectively isolate one speaker. I then plugged in the sub amp of just the one speaker with nothing else attached. This still resulted in the same amount of noise, but only thru the woofer, because the mid and tweeter were not recieving any signal/power. Since this, I presumed, meant it wasn't any of the other equipment, or a typical ground loop problem, I focused my attention on the electrical power coming to/thru the house. Nothing I tried, however, worked.

So, I have no idea why changing to the Essential fixed the problem, but it did and I can only tell you that I popped one of my best bottles of wine that night and sat there alone listening to the silence between songs in total amazement/relief/bewilderment until I was not thinking clearly anymore and called it a night:-).

The Essential does run fully balanced and now everything in the system, except the CD player, runs balanced connections as well, including my tonearm, so perhaps that has something to do with it. The power supply on the Essential is a fairly sophisticated beast and very well could be responsible, but ultimately I have given up trying to figure out why and have happily accepted the result.

There are a couple of threads in the Analog forum that discuss the Essential 3150 if you're interested. Mine is not the only system that got quieter after installing it according to at least one post. Needless to say I'm very happy with it!

Matt
gregm
3,411 posts
 
I have given up trying to figure out why and have happily accepted the result.
Noise is probably coming from the mains and the pre has a serious grounding scheme on it (finally!). Balanced helps with common mode rejection.

I had a similar problem and solved it with a symmetrical double filter (for AC).
mab33 OP
101 posts
 
Can you tell us more about the filter you are using?
gregm
3,411 posts
 
Mab33 -- I haven't seen the schematics, I'm afraid, so there is little I can actually say about the circuit.

It was made by an acquiaintance and its intended use is for medical diagnostic equip -- not hi-fi.
The net result is to lower the noise floor considerably in my system; it also eliminated the usual buzz & hum. Strangely, the sonic improvement was remarkably clear even on my cdp which, purportedly, already has an AC "filter" of sorts...
twc
42 posts
 
I am still not at the bottom of my hum problem but I think I finally have a line on it. With the speakers connected to the amp and the pre disconnected I have hum on the right channnel only. With pre connected hum is in both speakers. I put my older amp in and the speakers are silent, thus I have concluded that it has to be in the amp. I am going to take the amp to another house and connect it to the speakers and if I still hear the hum it is definately the amp. I have many hours of trouble shooting this problem. I have tried cheater plugs, different interconnects and power cords you name it and I have tried it. Should know for sure this weekend.
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