Output from computer produces noise on Akai AM-2350

[greenflash]

Well I've been fighting with an issue with my computer to amp sound output.

In a previous thread I started (link at the bottom, thanks @Oldsansui441 ) I indicated that there was a noise/humming in my Akai amp, discovering that it would sort of go away after pressing the bass knob.

I did the cleaning up etc, took the amp elsewhere and it worked well.. I eventually put another amp which.. Ended up with the same noise.

I changed cables, speakers, disconnected stuff (deck etc) and finally went back to the Akai. Again, same thing.
So I realize that unplugging the miniplug->RCA from the computer and connecting a FIIO player instead would take away ALL hum/hiss etc (Didn't I try that before??). Crystal sound (so far at least).

I am using a fiio DAC with the computer. I also tried direct line out connection. Definitely the computer is the problem..

Do I need some kind of protection/isolation? Anybody had the same experience? Thanks!!

Previous post:
http://audiokarma.org/forums/index....0-noise-in-the-bass-knob.704328/#post-9454582

 

[BilboBaggins]

I've had that problem in the past. Do you have a long cable run between the computer and the amp?

My solution was to put in a high quality cable between the two. But yours could also be a noisy component or power supply in the computer. If you have a spare computer try that? It would be a quick way of isolating if the problem is in the computer. Of course you will have to move the sound card too, but that could be your next step if the second computer output is clean.

I use a Mac Pro with iTunes and an airport express now, and I use the optical output on the airport express to optical in on one amp, and analog out on two others to different stereos in the house.

Good luck, and let us know what the fix ends up being.

 

[petehall347]

likely power supply noise .if its a laptop try running it on its battery .

 

[greenflash]

I've had that problem in the past. Do you have a long cable run between the computer and the amp?

My solution was to put in a high quality cable between the two. But yours could also be a noisy component or power supply in the computer. If you have a spare computer try that? It would be a quick way of isolating if the problem is in the computer. Of course you will have to move the sound card too, but that could be your next step if the second computer output is clean.

I use a Mac Pro with iTunes and an airport express now, and I use the optical output on the airport express to optical in on one amp, and analog out on two others to different stereos in the house.

Good luck, and let us know what the fix ends up being.

Oh that's good experience as I am using an Intel NUC with Mac OS (until I figure out what's wrong with my sound driver on Windows 10, a different matter). Truth is it failed on Windows too. But it's something that comes and goes. It seemed to improve as I found a miniplug to RCA with the protection (not sure how it's called). In both cases, the Windows laptop and the Intel NUC I have two options: the crappy analog output or the fiio DAC that I connect thru USB.

The NUC has a external adapter (12v) same as the laptop, of course, and then minimal power supply inside. I guess I'll look at the cable; also will try to connect the NUC's power supply to the APC UPS (it's a stabilizer too).

 

[greenflash]

likely power supply noise .if its a laptop try running it on its battery .

Yep Pete it all indicates that has to be related with the power.. Will try things in that area and report back. Also serves as a log, I did lot of things in the past and I'm confused already in fact as said above the problem went away for awhile.

 

[petehall347]

i have had plenty of noisy supplies to deal with it .
one fix was to use an isolation for the mains electricity supply .
another was to use a power inverter to run laptop off .
another was simply run laptop off batteries .
and another was an isolation transformer in the signal chain from laptop to amp .

 

[greenflash]

Below is the RCA cable I'm using to connect from the Q1 DAC (also in sight).
I turned all off to connect the NUC's power adapter (same as a laptop adapter) to the UPS.. And it was already connected.
I re-powered everything up and.. As in other occasions the hiss/humming is gone. Not sure until when.

@petehall347, can you tell me more about:

- The power inverter? We run here on 220v (with adapters that are 110-220v), but I *think* I read somebody in my country saying that connecting the adapter to 110v though unnecessary may take away interference. An overkill but if that helps I'll try it. A power inverter is something similar?

- The main electricity supply isolation, you mean like grounding the whole line right? Because well I don't have that, I mean no grounding rod in the house unfortunately.

- The isolation transformer.. that is very interesting. How does that work? Can you link me to some product like this? If not too expensive and available locally I might go for it.

Thanks!

 

[petehall347]

power inverter is same thing as your ups when you unplug from the mains supply ..it converts battery power to mains power.
mains isolation through a large isolation transformer ..220v to 220v .

 

[greenflash]

power inverter is same thing as your ups when you unplug from the mains supply ..it converts battery power to mains power.
mains isolation through a large isolation transformer ..220v to 220v .

I see now. Then I guess I'll wait until the noise comes up again (for now silent as could be.. Discharged because of powering off? Odd!) And then if it happens I'll try the 110v adapter (ugly), the better cable probably, and mostly, I'll look into the power inverter. OR: Taking everything away from this nook and build it up elsewhere and try all different options.