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In Reply to: RE: Class D amps and power chords posted by fstein on July 18, 2017 at 09:57:17
How Class D amplifier efficiency is achieved may also be it's Achilles heel. The conducted and radiated noise generated from such designs require a lot more attention to shielding and bypassing than traditional A or AB amps.A quality shielded power cord may help with noise being conducted back into the AC mains from the amp AND it may help with radiated noise on the power cord itself. I ended up using a couple PS Audio shielded power cords that helped but didn't eliminate the problem in my setup.
But there's another problem more difficult to address. In many Class D amps, the speaker cables also act as antenna to radiate noise. I know because I owned a couple Class D monoblocks years go that sound wonderful in an audio-only setup, but turn on the TV and half the channels were wiped out by the Class D noise, not to mention noise across the FM broadcast band rendering my tuner pretty much useless.
So if I wanted to use my Class D monoblocks for my TV setup or FM tuner listening, forget it.
Edits: 07/19/17Follow Ups:
"In many Class D amps, the speaker cables also act as antenna to radiate noise. I know because I owned a couple Class D monoblocks years go that sound wonderful in an audio-only setup, but turn on the TV and half the channels were wiped out by the Class D noise, not to mention noise across the FM broadcast band rendering my tuner pretty much useless."
It is probably very specific to those devices. I have used several Class D amps and continue to use one of them. In no instance have any of them had any effect at all on TV/cable performance. (Don't use FM anymore.)
My PLASMA TV was an incredible RFI producer. On AM bands, with no effect on FM out to 136Mhz.
This was with a 'D' amp and later amp(s) with conventional linear supplies.
Too much is never enough
I listen to UK excellent BBC 3 FM and I would not touch a audio class D amp with a barge pole. Seems most well known brands except Marantz are also steering clear.
I don't want to mention the brand here but these were Class D monoblocks from almost 10 years ago with a MSRP of $5000/pr. My TV reception was not over-the-air but via a Cable TV DVR. If I turned ON the Class D monoblocks a number of channels went blank. The Class D monoblocks were in close proximity to the Cable TV DVR just one AV shelf level apart.
As you say, the significant noise problem may have been specific to this Class D design in the monoblocks that I owned. However, I think the issue of minimizing 'noise' is still a bigger concern in Class D amps than other more 'traditional' designs.
My experience, too, was with a cable box for TV but the power amps sat 3 shelves below that box. OTOH, the intervening shelves were filled with other connected equipment.
Of course, unless one makes a careful survey, one cannot know how pervasive this problem is.
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