Electrical "fun" with my apartment

[EndersShadow]

So I am in need of some advice/thoughts.

My Carver M1.0t has been connected up to my system for a couple days now and I have been having some slight issues. It appears that its got something to do with my electrical in the aparment I live in.

Now this is my first M1.0t which is a unique design and a much higher power amp than my other Carver (which is plugged into my APC H15) so some of this may be normal so let me know if what I am hearing is to be expected.

When I first turn on my M1.0t their is some humming from the transformer that is pretty low level but it stays constant when the amp is on. It kinda sounds like a toned down bug zapper.

When my M1.0t is on and I have the music paused on my computer and the Audio GD has the volume turned all the way down there is a VERY low hiss from the tweeters you can only hear when your literally on top of them. If I crank the volume the hiss gets worse, but how loud it is or isnt is dependent upon the volume level. Once the source is playing the hiss goes away and does not come over the top of the music.

When I turn it off there is about a 5 second pause and then a thump that comes through the speakers. Sometimes its a small one, sometimes its friggin loud.

Now according to the shop (who I trust) these issues were not present when they got the amp, or at any point before, during or after their testing/upgrading of the amp. I believe them as the seller also told me that (minus the thump which was there) the hissing issues present when I first got the amp were not there for him.

So this all points to something in my system/wiring generating the noise. On top of this we had some trouble a while back with our Uverse reciever freezing up downstairs watching On Demand movies. When the tech came out he told me his tests indicated there was some electrical interference that he thought could be the source of the issue. He thought it was related to my APC H15 as when he unplugged it his tests indicated the noise levels dropped. We then as a result went from a wired reciever downstairs to a wireless one and have not had any issues since then.

I should mention that at no point have we heard/noticed any noise or signal degredation with any of our other source gear including my Carver 705x (which has been plugged direct into the wall and also into the APC H15 with no difference in sound).

When these issues first arose I simply assumed that the tech was right and for giggles disconnected the APC H15 downstairs. The issues were still there.

Right now I have the amp connected upstairs to my Audio GD NFB-5 dac/pre via RCA which is connected to my computer. The amp is plugged directly into the wall on the top outlet. The bottom outlet has a Belkin cheap little surge protector strip on it that has my computer, the Audio GD and my Mini-ITX compter connected to it.

In the same room I have 2 long 2 plug extension cords used to connect the jack the wall switch controlls to 2 different lights. One of these cords runs right underneath where all this gear is tucked behind the baseboard where it is next to the Network cable for the desktop computer in the room. I also have on another outlet under my computer desk, my computer monitor, a printer and the charger for my wireless keyboard attached to another belking surge protector.


Here is what I have tried so far to get rid of the hiss that has not worked.

1. Switched from a cheap powercord to a PS Audio Premier cord
2. Tried a different set of RCA's (Audioquest G-Snakes to cheap Rat Shack)
3. Disconnected the RCA's and just had the amp on with no source music (hiss was only there if your on top the tweeter)

Here is what I have tried to solve the turn off thump:

1. Ensure pre has volume all the way down then turn off the amp first, then the pre
2. Ensure pre has volume all the way down then turn off pre first, then amp

Here are my thoughts on what I plan on trying next.

1. Take amp to my parents and test it out there to see if hiss still exists. If not it could be either my USB DAC/Pre or the wiring causing the noise
2. Use a "cheater" plug which as I understand it is a 2 prong to 3 prong adaptor (see pic below) to see if that eliminate the noise.

3. Use my Integra 5.9 downstairs to ensure its not the Audio GD adding the noise to the system.

Other than that, do any of you have any suggestions for what I might try to narrow down what might be causing the issue, or any possible solutions to fix it I havent listed?

[George Grand]

The Carver Corp. came out with a "fix" for that thump problem. Good luck.

[EndersShadow]

The Carver Corp. came out with a "fix" for that thump problem. Good luck.

I am aware of the "thump" fix, however I might be wrong here, but I think the shop did that upgrade to the unit.

I was informed that the transformer hum is common with these type of Carver amps as I suspected but wanted to verify anyway

[treitz3]

Hello, EndersShadow. Did you acquire this amp from Rich or Tom? If it still thumps, then the revision [fix] has not been properly completed. IIRC, the amps I had did have a slight hum in the xnsfrmr. Somewhat of a surge-type noise at start up which dwindled down to a steady, low level hum after that. If it makes the lights slightly dim upon start up, that was fairly normal as well.

Tom

[EndersShadow]

Hello, EndersShadow. Did you acquire this amp from Rich or Tom? If it still thumps, then the revision [fix] has not been properly completed. IIRC, the amps I had did have a slight hum in the xnsfrmr. Somewhat of a surge-type noise at start up which dwindled down to a steady, low level hum after that. If it makes the lights slightly dim upon start up, that was fairly normal as well.

Tom

Aquired it from Ed on CarverAudio early last year. Had some issues initially (or so I thought) so sent it to Tom a couple weeks before Carverfest. Just got it back this week. After then benched it and went through it, they tested it all weekend long and couldnt get the thump to show.

Your description of the hum is accurate. Sounds like a bug zapper when it first turns on then drops to low level. I wouldnt even notice it in my main system, but in my 2 channel I am about 1 foot away from it and since I have been listening hard for hissing noticed it.

[treitz3]

Hmmm, see if you can talk with Tom or Anders about possible suggestions or remedies. If the revisions/modifications have been done, there is no reason I can think of that the amp should produce a thump. James, Rich or Tom should have the schematics for the revision to eliminate the turn off thump. It's something relatively simple IIRC, like an added resistor and a connection or two to ground if I'm not mistaken but I wouldn't hold me to that. It's been years since I even looked at them.

Tom

[Speedskater]

Right now, I'll only touch on one point.
Switched lighting can be a noise & interference problem. The in-wall wires can take strange paths creating large loop antennas. Some dimmers and some new High Efficiency lighting systems (LED & CFL) are good noise & interference generators. The extension cords near your equipment only make it worse.

[EndersShadow]

So did some additional testing...... and found out the following:

The noise when the volume knob is turned up in my test system is from the dac/pre itself, or the wiring upstairs (dont care which TBH)

When connected downstairs to my Integra DTR 5.9 that issue doesnt happen. There is still a VERY VERY SLIGHT hiss with your ear on the tweeter with nothing playing, but nothing worth messing with.

The turn off thump is still there regardless. It wasnt as bad the couple times I turned it on and off downstairs but that may be due to it not being used for a long period so I am letting it hang out tonight downstairs and will turn it off when I go to bed and see how loud the thump is.

[Drenis]

There should be no thump upon powering down. A slight thump on start up is fine. The faint slight hiss, is common on all Carver amps it seems. It should not change at all with any gain/volume adjustment. My TFM-42 did it too and I made a big deal outta nothing...

I know a VERY good tech if you need.

[specd_out]

Mine has a hiss but its very slight, and does not increase with volume. When I turn mine on I hear a faint buzz that kinda revs up then the lights flicker and all is well. It all happens within about 3 seconds. I dunno what causes that but it does it every time

[DSkip]

Dan, I never had that issue with my Jolida until I swapped a Pangea AC-14 for the AC-9. Now, I've got constant transformer hum, but its only noticeable when the music stops. It doesn't change w/ volume and ONLY happened after the PC swap.