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Electrical "fun" with my apartment
BeanOffline
#1 Posted: Friday, March 1, 2013 1:27:32 PM(UTC)
 
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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.
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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?
 
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B-ManOffline
#2 Posted: Friday, March 1, 2013 1:39:10 PM(UTC)
 
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The "transformer noise" is normal and present with most Carver amps that use the mag field technology.
 
There is a service bulletin that details the fix for the "turn off thump". $5 in parts and a few minutes with a soldering iron...
 
As far as the hiss, unplug any source from the amp, turn the amp on and see if there is hiss at the speakers. If so, the amp is the source. If not, your source is the culprit. The fact that it gets louder with the volume control leads me to believe it is your source.
 
As far as "power conditioners" go, I've always felt that the power supply in the amp is the power conditioner. Look at the ratings - the low noise and power envelope were achieved without any fancy power conditioning equipment. As far as surge protection goes that is always a gamble we take. I will share this - I've had a lot of my Carver gear for a long time (20+ years) and it was never plugged into anything but the wall. I lived in central Florida (the lightning capital of the world - literally) and I never had a power damage issue.
 
Of course, your mileage may vary.... 
BeanOffline
#3 Posted: Friday, March 1, 2013 2:21:39 PM(UTC)
 
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B-Man;120540 wrote:
The "transformer noise" is normal and present with most Carver amps that use the mag field technology.
 
Good, I was thinking that was the case, but figured I would get verification.  Once its working like it should I may look at putting some dynamat on the top cover if the noise is bothersome (which I doubt it will be given the distance from it to where we sit)
 
B-Man;120540 wrote:
There is a service bulletin that details the fix for the "turn off thump". $5 in parts and a few minutes with a soldering iron...
 
I am aware however I am under the impression the repair shop had done that "fix".  I will call and verify again, but I believe they serviced the amp and did all the service upgrades in addition to adding the binding posts and IEC plug.  I am not very tech savvy and I didnt ask what specific parts/resistors they replaced, however I know they did replace a bunch of stuff inside the amp (can post pics if needed)
 
B-Man;120540 wrote:
As far as the hiss, unplug any source from the amp, turn the amp on and see if there is hiss at the speakers. If so, the amp is the source.
 
I have done that.  The hiss is there (but only if your literally ear on tweeter).  I read that a low level hiss like that was common in high wattage amps, but was concerned when once the source is connected with nothing playing and the volume increased the hiss gets worse.
 
B-Man;120540 wrote:
As far as "power conditioners" go, I've always felt that the power supply in the amp is the power conditioner. Look at the ratings - the low noise and power envelope were achieved without any fancy power conditioning equipment. As far as surge protection goes that is always a gamble we take. I will share this - I've had a lot of my Carver gear for a long time (20+ years) and it was never plugged into anything but the wall. I lived in central Florida (the lightning capital of the world - literally) and I never had a power damage issue.
Of course, your mileage may vary....
 
Understand.  I listed all the electrical items in the room on the chance maybe one of them (extension cords) was acting as an antenna for EMI of some sort and putting noise in the system somehow (grasping at straws here).
 
My AV705x is on a APC H15 on its high current plug.  I would prefer to put my M1.0t on its other high current plug (for the sub in this case) just so its got voltage regulation as thats why I got the H15 over the H10 and also its got a surge protector on it. 
 
With as much as I have invested in this puppy I would hate for it to go out.  If I need to go direct to the wall thats not a problem provided I dont get any noise.
BeanOffline
#4 Posted: Friday, March 1, 2013 2:36:07 PM(UTC)
 
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Here are some pics (iphone quality).  If you want ones of a specific area let me know and I will take them tonight.
 
 
 
 
 
 

B-ManOffline
#5 Posted: Friday, March 1, 2013 2:42:00 PM(UTC)
 
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It looks like the thump fix was not installed on the input board, unless they somehow installed the parts on the component side of the board (VERY unlikely).
 
This is a picture of the thump mod from Rich's tutorial:
 
 
 
The pictures you posted of the input board clearly don't have those additional components. 
SteveFordOffline
#6 Posted: Friday, March 1, 2013 3:14:16 PM(UTC)
 
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If you have to put your ear up against a tweeter to hear the hiss it's not worth worrying about.
Lots of old junk all over the place.
BeanOffline
#7 Posted: Friday, March 1, 2013 3:26:09 PM(UTC)
 
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SteveFord;120546 wrote:
If you have to put your ear up against a tweeter to hear the hiss it's not worth worrying about.

 
Agreed, however since it increases when the volume is turned up and the source is paused I am concerned.
 
Here is the real world scenario for this amp.  Its end location is connected to my main system downstairs I use daily for TV/Xbox 360, etc.  It will stay on 24/7 (unless the power goes out).  With the hiss doing what it is if I have this connected to my AVR (as my source) and the volume at say my normal listening level of 50 for the TV and I hit the mute or pause button on my DVR, I dont want to hear a hiss out of my left and right speaker which is what it appears will happen.
SteveFordOffline
#8 Posted: Friday, March 1, 2013 3:36:50 PM(UTC)
 
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Did you do what B-man suggested and unplug things one at a time and see if the hiss disappears?
It might be something as stupid as an interconnect.
 
Lots of old junk all over the place.
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#10 Posted: Friday, March 1, 2013 3:44:27 PM(UTC)
 
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If you have it cranked all the way up with say the CD/DVD on pause, and the hiss is loud... thats normal for me on my kappas with the ribbons. But i want you to understand thats not an electrical hum like feedback loop noise like you would hear in a PA system. Saw you use the term bug zapper, that makes me wonder if your hearing a soft hiss or a soft buzz. As in electrical buzz.
Living room..."11.4 setup" Sunfire TGP-III/4 Silver 7t's/Infinity Kappa 9A (main)/Sunfire CRS3 (main)/4 TFM-45's/Sunfire CRS3C (center)/Apple TV/Wadia 171i/SD/A-490T /Pro-Ject RPM 5.1 v2/JD9-II/WA6/Infinity PS-312 sub & Sunfire Signature Sub (rear)/2 Martin Logan Dynamo 1000 subs (front)/AV-806X/4 Infinity C255ES bi pole speakers for sur, sur back and side axis/70" Sharp Aquos LC-70LE733U/Oppo BDP-95 Blu-ray/Power+RCA Interconnects & 9ga speaker cable by Douglas Connection.

Garage... CT-17/AudioSource EQ Eight Series II /TFM-15cb/AV-64/M-0.5t/4 Infinity micro sl speakers/2 Martin Logan Motion 4/Infinity Entra 12" Sub.

Road Show... TDR-1500/TFM-55/M-200t Gold"Hashey"Mod.

Spares...(BSR EQ-3000)(Infinity Kappa 6)(SD/A-490t)(2 TFM-42's)(TFM-45)(AV-705X)(M-1.0t MKII OPT2)(DTL-200)(AudioSource Model EQ Nine)

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BeanOffline
#9 Posted: Friday, March 1, 2013 4:25:35 PM(UTC)
 
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SteveFord;120548 wrote:
Did you do what B-man suggested and unplug things one at a time and see if the hiss disappears?
It might be something as stupid as an interconnect.
 

 
Are you talking about unplugging things in the system itself?  If so I can give that a shot, however the only real cord I can pull is the USB cable from my computer to the USB DAC/Pre.
 
I have already pulled the pre to amp connections and the hiss was there just at a low level.  Part of me wonders if the volume knob/potentmeter on the Audio GD unit might not be the problem.
 
The RCA pre-outs can be either fixed or variable.  You pull a jumper from the board to make it variable (which I have done).  I did this because when using the WASAPI driver for USB the volume is locked at 100%.
 
If however I use coaxial out of my computer instead and put the Audio GD unit in fixed output I believe I could then control the volume up or down with the computer....  Am I correct or would that just put the unit at 100% volume and blow my speakers lol.
 
I think just to be safe first thing I will do when I get home is connect it to my Integra and LSi's and just see what happens if I mute the TV and turn up the volume.
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