[audion]

I have a modded SB3 (output op amps have been removed by Vinny). I connect it directly to an amplifier (AKSA 55). I am getting really loud humming from the speakers. I've tried taking the ground from the unused headphone output and connect it to the amplifier ground. That reduced the hum dramatically, but there is still some hum left. Hooking up the SB3 to a commercial receiver (without ground plug) did not produce any hum.
I had a CD player connected to AKSA. The CD player did not have a ground plug on the power cord. Connecting the ground of the CD player to the amplifier ground eliminated the initial hum (which wasn't too bad) completely. Any ideas on what I can try?

[Vinnie R.]

I have a modded SB3 (output op amps have been removed by Vinny). I connect it directly to an amplifier (AKSA 55). I am getting really loud humming from the speakers. I've tried taking the ground from the unused headphone output and connect it to the amplifier ground. That reduced the hum dramatically, but there is still some hum left. Hooking up the SB3 to a commercial receiver (without ground plug) did not produce any hum.
I had a CD player connected to AKSA. The CD player did not have a ground plug on the power cord. Connecting the ground of the CD player to the amplifier ground eliminated the initial hum (which wasn't too bad) completely. Any ideas on what I can try?

Hi George,

I used to own an AKSA 55 years ago.  I recall having the same problem.  When I disconnected the GND from the power cord to the amp, this solved the problem.  They make "cheater plugs" that do this as well.

NOTE: The GND is for safety (in case the chassis were to ever become 'live' by a live 120Vac wire), so you need to be aware of this   

Best regards,

Vinnie

[Steve Eddy]

I used to own an AKSA 55 years ago.

55 years ago? I didn't know AKSA was around back in 1951. You and Hugh must be much older than I thought. 

I recall having the same problem.  When I disconnected the GND from the power cord to the amp, this solved the problem.  They make "cheater plugs" that do this as well.

NOTE: The GND is for safety (in case the chassis were to ever become 'live' by a live 120Vac wire), so you need to be aware of this 

Yes, it is for safety and defeating it isn't the best thing to do in my opinion.

One solution would be to insulate any RCA jacks and such from the chassis and tie the amplifier's signal ground to the chassis through a 50 ohm resistor in series with a 0.01uF capacitor. This provides a high impedance between the signal ground and safety ground at audio frequencies, but allows for a low impedance connection with the chassis so it can better provide RF shielding.

A better solution in my opinion would be to add a pair of input transformers to the amplifier and/or a pair of output transformers to the SqueezeBox.

se