Hi,
I have 3 separate Home made Stereo Power Amplifiers. One is STK4241, 2nd is IRS2092/ IRFI4020H-117P 250W Class D Amplifier and 3rd is TDA8954 Class D Amplifier. I need to run those 3 Amplifiers at once.
But the problem is in put signal. I have one stereo audio input signal. When i divided this in to 3 Amplifiers parallel, there will be a hum noise from all the Amplifiers.
So i need your help to remove the Hum from Amplifiers. Pls let me know if there any audio split circuit for the same.
I have 3 separate Home made Stereo Power Amplifiers. One is STK4241, 2nd is IRS2092/ IRFI4020H-117P 250W Class D Amplifier and 3rd is TDA8954 Class D Amplifier. I need to run those 3 Amplifiers at once.
But the problem is in put signal. I have one stereo audio input signal. When i divided this in to 3 Amplifiers parallel, there will be a hum noise from all the Amplifiers.
So i need your help to remove the Hum from Amplifiers. Pls let me know if there any audio split circuit for the same.
This is due to ground loops.
You might be able to lift the safety grounds on one or more ofthe power plugs (AC Mains).
You might be able to insert small resistors between the input jacks and the ground wire going to that jack, or to the chassis (if they are connected to the chassis mechanically, you can't do that).
Or you may want to build up a box with three buffer amps, they can be ICs, each feeding one amp (2 channels per, or technically 6 buffers total). The output jacks should be floating WRT each other, ideally.
Alternately you could use (6) 1:1 or similar transformers to do the job.
Again the output jacks are not connected to each others grounds.
You might be able to lift the safety grounds on one or more ofthe power plugs (AC Mains).
You might be able to insert small resistors between the input jacks and the ground wire going to that jack, or to the chassis (if they are connected to the chassis mechanically, you can't do that).
Or you may want to build up a box with three buffer amps, they can be ICs, each feeding one amp (2 channels per, or technically 6 buffers total). The output jacks should be floating WRT each other, ideally.
Alternately you could use (6) 1:1 or similar transformers to do the job.
Again the output jacks are not connected to each others grounds.
Wouldn't this work? The input Impedance of each amp should be some 50K...running them in parallel is going to be loading down the pre-amp some...so why not this? I'd say 10K would work fine.....just hope you have some gain control on the three amps to make up the difference. The 20K (min) should effectively isolate one from the other.
______________________________________________________Rick..........
______________________________________________________Rick..........
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Thanks Friends. I will try and come back with Results. Mean time can you pls give me any buffering circuit if you have?
I think removing the safety ground is not a great idea. Not sure what country the unit is in, and I'm not a power guru, but here in the US one of the 2 power pins is neutral - essentially ground. Even if I'm wrong, floating a unit with respect to earth can be a safety concern.
The transformer will shape the signal in the frequency domain especially loss of low frequency. If not a concern, then it's good. I think the opamp is a good idea, and better yet, use a fully differential opamp.
Maybe the connections are not correct (reversed + and -) between all of the loads. Maybe the preamp has a high output impedance, in which case buffering is required.
I'd check all the polarity first, make sure everything is plugged into the same power strip, and no unit is floating (e.g. the ground pin on the plug has been removed). Try divide and conquer approach - attach the preamp to each amp individually. Maybe only one of the amps is at fault. Then add the 2nd amp, then the 3rd. You may be able to isolate the problem.
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