LAK - very interesting possibility. There's been lots of work in our panel over the years. i will try to check it out! |
Will have updates later this week. Am meeting with a fellow Audiogon'r on Thursday, and the dealer on Friday. |
Thanks for all your thoughts, suggestions and quips :-)
So, first, yes, the amp makes this hum with ONLY it plugged in with the speakers connected. All other equipment was disconnected for this experiment. This same hum occurs in two different outlets (which, to be fair, are likely on the same "line" in my house). Each outlet has a different high quality audiophile outlet.
Second, didn't mention this, but prior to purchasing this amp, I auditioned a tube amp, and it too created a hum through the speakers....it, however, got louder when volume was increased. For the Coda amp, the hum "volume" stays the same regardless of output volume on the amp.
Third, I have tried different power cords, and have plugged different power cords into: the power outlet (wall), a high quality power strip, and/or a line conditioner. Nothing has impacted the hum.
Fourth, I am aware of possibility that speaker cables over power cords might create hum and have moved all cables/cords around to no effect (doesn't seem to change anything).
I have not tried shorting the inputs.....thought about it, but not done it yet. Maybe that'll be tomorrow's experiment if i can get to RS before it closes.
Any other ideas would be appreciated.
Maybe I just have exceptionally "dirty" power? If so, would that explain this symptom? And then, what the heck would I do about it?
Thanks again!
matt |
Sounds like many of you are concerned about the "health" of my outlets. The house was brand new in 1990....meaning all new (to code) electrical at that time. I did install both audiophile outlets myself....and know they were done correctly. I do have a halogen cable lighting system installed in the living room, and the transformers live in coves at the top of the walls where the suspect outlets are located. I do, however, have the lighting system completely off when I play music, as I am aware of the noise that the lights add to the system. Is there any chance that the presence of the transformers 8 feet above the outlets might be a cause of this issue....even if the lighting system is turned off? I will start with the extension cord suggestion, and go from there. Thanks to all of you for your suggestions. I'll report back. |
Well, I wasn't able to get to RS today (did a nearly 4 hour bike ride in 85 degree heat.....kinda beat), but, I was able to do the extension cord test. Used a (probably) 14 gauge 25 foot Home Depot type extension cord. Tried it in two separate outlets: one across the living room from the outlets I've mentioned, one down the hall. NO CHANGE!
I then tried changing the inputs on the amp (not that I have anything plugged in aside from my XLR and speaker cables), and ran through them all, with each remote outlet (with extension cord attached), and then again with amp plugged into the power strip I've been using. NO CHANGE on any input.
You know.....despite what they said at the factory, I am beginning to wonder about this amp. But, the argument against that was the experience with the previous (tube) amp, with different speakers and cabling. Same hum, except variable based on volume of amp.
I tried one other experiment.....with the amp plugged into it's usual power strip, I tried some other speakers I have in the house....a set of Monitor Audio Silver 7's. Believe it or not.....still heard the same hum!!
I live in a semi-rural neighborhood in the SF Bay Area. There's low density housing and no industry locally. You'd think that would create for some pretty high quality electrical sources? Sounds like I need to buy that outlet checker.
I have contacted the salesperson from the shop at which I purchased the DAC....he said he'd be able to come by this week and try to sort out the situation.
Any other ideas aside from bringing my amp to another location (I could probably do that with the shop at which I bought the DAC)??
This situation is really perplexing and annoying....
Matt |
Been doing a bit more reading elsewhere......would an "isolation transformer" help in this situation? Is it possible to install one immediately after the wall outlet (i.e., can I plug my power strip into the transformer)? Am I shooting from the hip? |
Thanks for the additional suggestions upon which to follow up. Given that it's a holiday weekend, nothing will happen with the dealer until next week.
The outlet in the hallway is definitely a different circuit than the ones in the living room. I am aware of that from previous adventures in turning off circuits :-)
I'll follow up here in the next few days. I guess I'm coming to the hypothesis that there's something amiss with the electricity in my living room.
Thanks again for all the great input.
Matt |
Al - there is no hum coming from the amp itself.
Mental - I have already tried the experiment of disconnecting everything from the amp aside from speakers cables and the power cord. I get the hum just with that minimal set of "items" plugged in.
Matt |
Went over to fellow Audiogoner drubin earlier today (thanks Dan!!) to try my amp in his system. Had the same exact problem occur in his system that I do in mine; hum coming through speakers when as little as (any) power cord and speaker cables are plugged in. He heard it too!!
Looks like my amp has a problem. I just contacted Coda and am waiting for a response. Odd that they claimed to have not heard it when it was at the factory less than a month ago. This time, I'll bring it in myself, and make sure that I have someone there listen to it with me. Fortunately, they're only about an hour away.
(As a complete aside.....I almost bought a highly regarded integrated from a european manufacturer before I purchased the Coda. They were offering a screaming deal (I know it was legit). I kept on musing about "if there are any problems with this, how am I going to get this fixed?" Glad I listened to that little inner voice and bought domestically (and, locally, as it turned out).
I'll keep you apprised as this saga continues. Kudos to those that thought it was an amp problem all along. You get extra points for that call :-)
Matt |
I got a response from Coda within 2 hours. They want the amp back at the factory, and will pay for shipping both directions. They verified that they had listened to the amp through their speakers, and could not hear the hum.
The hum is stable at about 37 db, and is audible in my listening position 9 feet away from the speakers when there are quiet passages in the music (or when no music is playing). Is this level of hum normal in quality sound systems? |
Jim (Jea-48) - just curious if you could say more about what/how to do the AM radio experiment. Should I actually tune into a station......or just set it to the very beginning or end of the band? What am I listening for if I set it to the station....I have very poor reception around here as I'm in a very hilly location?
Just curious about this suggestion.
Matt |
I had an opportunity today to go to a local audio store. Brought in the integrated, thinking, if I can still hear the hum, and the staff can hear it, then we've isolated the problem. And, fortunately, the problem remained, obvious to all ears. It was interesting to me that after listening to my integrated hum away, the salesperson plugged in a $1000 integrated into the exact same cords, cables and connects......and all I heard was a blissful silence. For those of you who thought my amp was problematic, you are correct. Alas, I'm still waiting for the word from CODA for when they'll be ready to receive my amp for repair; the owner/founder has been out due to a severe injury, so I'm biding my time waiting for his return. |
After much delay, I finally got my problem resolved.....and quite nicely!
Doug Dale, the owner of Coda, had been severely injured many months ago and has been off work until last week. Much of the delay that I experienced was due to Doug's absence. He was apologetic for the delay.
As soon as he got back to work, he decided to simply swap out my unit for a new one that he had tested and was sure worked to spec....with no noise. I brought my amp in today. We listened to it in his listening room and (thankfully) heard the noise....although it was MUCH quieter in his room with his Legacy speakers that it was in my room with my speakers. We then listened to the new amp that he had selected to replace mine.....it wasn't dead quiet, but the noise was of a much less obtrusive nature that he said was normal and (I believe) related to the volume control used.
I brought the amp back to my house, plugged it in and......it's lovely...no noise. Again, not dead quiet, but WAY more quiet than my previous unit. Since the replacement unit is new I'll have to break it in again, but, frankly, that's not that bad a prospect :-)
Doug did say that very infrequently, generally due to shipping issues (dropping, rough treatment) some wires get slightly loose and may cause the issue I have been having. Oh well, just bad luck on my part.
It was cool seeing the Coda facility.....there's only 4 employees (that I saw) including Doug, so it's a small operation. But they're producing some neat products.
OK, I'll check back in in a few weeks....but I'm VERY heartened with today's news. Thanks again to all of you for your support and help. |
