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Class D Switching Power Amplifiers and Power D/A conversion

audible hum with two Sure TA2024 boards on same source
audible hum with two Sure TA2024 boards on same source
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Old 23rd December 2016, 12:46 AM   #1
Hybrid fourdoor is offline Hybrid fourdoor  United States
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Default audible hum with two Sure TA2024 boards on same source

I have two boards, trying to make a multi-channel amp. They share 15V power source (the red/black cable). When I plug a source just in to 1 unit, everything is perfect...just the tiniest amount of hiss (ear inches from tweeter). But when I try to hook the same source up to both units I get a very audible buzz from 3-4 feet away.

I though it was my iPod having a shared ground on the 1/8" to RCA. But now I am using the pre-amp outputs from a receiver and I get the same effect.

Any ideas?

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Old 26th December 2016, 01:29 PM   #2
Mayuri is offline Mayuri  Finland
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Maybe the PSU is insufficient for the amplifiers?
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Old 26th December 2016, 02:10 PM   #3
djoffe is offline djoffe  United States
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Default A Guess?

I think it may be due to the fact that these guys are switch-mode amps. There are sum and difference frequencies generated between the two of them, since they don't have synchronized clocks, and that's causing audible birdies.

I looked for data sheets on these boards, but didn't find much detailed info...maybe a 10 micro-Henry inductor in the +15 V supply lead of one would help?
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Old 27th December 2016, 01:36 AM   #4
Khron is offline Khron  Finland
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Are the red & black wires soldered to both boards, and you're basically daisy-chaining the power?
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Old 27th December 2016, 02:04 AM   #5
turk 182 is offline turk 182  Canada
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15 volts supply but no curent rating given....?
two amps with a common ground and no provision for isolating input source grounds....?
sounds like another thread about ground loops...i'm sure the usual debate will insue.....
or research the topic a bit....it's background that you'll need if your eventual goal is to build a multichannel amp....
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Old 27th December 2016, 02:15 AM   #6
turk 182 is offline turk 182  Canada
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and i wish people would stop using low impedance source outputs like Ipods and there ilk as a source device across amp inputs that are designed as line level and wonder why they are having problems or thinking it sounds good.

and what makes you think the pre out's on the receiver are isolated?

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Old 29th December 2016, 12:59 AM   #7
Hybrid fourdoor is offline Hybrid fourdoor  United States
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Quote:
Originally Posted by Khron View Post
Are the red & black wires soldered to both boards, and you're basically daisy-chaining the power?
Yes, I don't see any functional difference between having the same PSU connect to each of them separately. It's a direct connection through the board, there are lugs on either side, so you can connect on each side.
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Old 29th December 2016, 01:01 AM   #8
Hybrid fourdoor is offline Hybrid fourdoor  United States
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Quote:
Originally Posted by djoffe View Post
I think it may be due to the fact that these guys are switch-mode amps. There are sum and difference frequencies generated between the two of them, since they don't have synchronized clocks, and that's causing audible birdies.

I looked for data sheets on these boards, but didn't find much detailed info...maybe a 10 micro-Henry inductor in the +15 V supply lead of one would help?
I was also thinking it had to do with the frequency generation of each one. But the only thing I can think of that would attempt to fix that would be op-amp buffers.

I will try separate power supplies and see what happens.
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Old 29th December 2016, 01:04 PM   #9
turk 182 is offline turk 182  Canada
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does connecting your "source" across the two input of one board result in the same hum/noise?
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Old 29th December 2016, 02:00 PM   #10
Grib is offline Grib  France
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You should probably try to split the ground of the PSU before reaching any of the boards.
So that each board has a ground wire coming to it, and no board act as a ground splitting point.

Simply make a Y with you PSU cable a connect each branch to your boards.
I guess you could do the same thing for the + wire, but its probably less important
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