I'm trying to fix a hum/buzz problem in my amplifier. This is the setup.
I have a pair of ICEpower 100AS2 amps that take a balanced input. However, I'm connecting an unbalanced RCA source to them.
I'm not quite sure how to properly connect unbalanced to balanced. Originally I tried amp's positive to RCA's positive, and amp's negative and ground to the RCA's negative. Then I tried + to + and - to - and simply did not connect the ground to anything. Both hums.
If I don't plug anything in, there is no hum/buzz. My source is a MacBook Pro with a Asus Xonar U7 sound card. I noticed if my MacBook Pro is connected to the power supply, it will buzz. If I disconnect the power and run on battery, the hum/buzz is gone.
Any idea on how I can fix this problem?
Thanks
I have a pair of ICEpower 100AS2 amps that take a balanced input. However, I'm connecting an unbalanced RCA source to them.
I'm not quite sure how to properly connect unbalanced to balanced. Originally I tried amp's positive to RCA's positive, and amp's negative and ground to the RCA's negative. Then I tried + to + and - to - and simply did not connect the ground to anything. Both hums.
If I don't plug anything in, there is no hum/buzz. My source is a MacBook Pro with a Asus Xonar U7 sound card. I noticed if my MacBook Pro is connected to the power supply, it will buzz. If I disconnect the power and run on battery, the hum/buzz is gone.
Any idea on how I can fix this problem?
Thanks
When you connected RCA+ to Balanced+ and ground to ground, did you also connect Balanced- to ground?
Yes I've tried that in one instance.
I'm quite confused on what to do. A number of people told me that you connect RCA+ to balanced + and RCA ground to balanced ground AND balanced -.
However, Rane says you ignore the balanced ground cable in figure 17.
Sound System Interconnection
Which way is the correct way to hook up unbalanced to balanced?
Did you connect protective earth to the amplifier?
You might want to look at this application note "Amplifier signal input wiring"
Should be applicable for every unbalanced to balanced connection.
You might want to look at this application note "Amplifier signal input wiring"
Should be applicable for every unbalanced to balanced connection.
The noise originates from the apple power supply. This is a class 2 equipment, i.e. no protective Earth is connected. Connect PE with the GND-shielding of your audio-wiring and the noise is gone
No
I need this to be noise free with everything, just like every other amp I've used with my MacBook Pro.
That's good. Protective earth is only for safety and should only be connected as such. It should not be connected as ground or as some people say 'audio ground'. In balanced applications with unbalanced source the bal- should be connected the ground. Balanced is a differential amplification, meaning it amplifies the difference between bal+ en bal-. If bal- is left floating, it might act as an antenna. You may also connect bal- via an RC filter to ground if that feels better. Just read the application note I have linked and in addition the 'Dealing with legacy pin 1 problems'.
Indeed, that is is really good. Where did you find this? Which link do you refer to?
He's tried that and it still hums, I suggested trying leaving the negative input floating because it may well have a resistive reference to ground anyway. My Rane equaliser has an RCA input that is connected internally to the balanced input in the way I have stated
So I got 4 of these.
https://www.amazon.com/BOSS-Audio-B25N-Filter-Systems/dp/B000LP4RMG
When I use one of them in the system, it kills all hum/buzz. However, one only covers 2/4 channels on my speaker. I need to use a second one to cover all 4 channels. But if I add in the second one, the resulting buzz/hum of all 4 channels is quite a bit louder than if none of the transformers were used.
Any thoughts?
https://www.amazon.com/BOSS-Audio-B25N-Filter-Systems/dp/B000LP4RMG
When I use one of them in the system, it kills all hum/buzz. However, one only covers 2/4 channels on my speaker. I need to use a second one to cover all 4 channels. But if I add in the second one, the resulting buzz/hum of all 4 channels is quite a bit louder than if none of the transformers were used.
Any thoughts?
Take a sheet of paper, draw all your system connections.
The problem will appear
I don't have a background in electronics, hence the all in one, plug and play ICEpower amps.
If the isolation transformers is seen as a ground, then I clearly made a ground loop. But then, how in the world would I isolate more than 2 channels?
That's a great idea! But the U7 and the computer is connected by USB.
Or are you saying attach a cable to the 3.5mm input on the U7, where that cable is connected to an isolator?
I may have looked at a different model, not sure. I read the audio input was a 3.5mm jack on the U7.
Does the audio input travel through the USB cable from the computer?
Does the audio input travel through the USB cable from the computer?
Think of the U7 as a DAC. It takes digital audio from the PC through USB and outputs 8 channel analog.
- Status
- Not open for further replies.