1875 distorts terribly

jarcher12 · 8th May 2009, 01:40 AM

Hi first post here even if I have been lurking for a while. This forum is excellent. Have managed to build 2 very nicely working chip amps . The first with 3876 kits (and one 3886 for subwoofer) the second using 1875 and pcb board with almost p2p wiring. Both sound very good. So i thought I would try my next project a more powerful 1875 used +- 18 v out from trafo and tried 22k/680 ohm as gain. Also bought expensive panasonic 1000 mf as dampers near the chip. Had to add some 10.000 mf after rectifier just to be able to hear the thing trough the distort. wow the sound is horrible !!!

I have tried everything lowered the voltage, lowered the gain to 22/1 nothing works. it distorts like crazy when turned up and the bass really smears and distorts the worst. Any ideas ? will add a pic. Oh yea the whole thing is just on the bench, no box yet. Test setup I guess I have checked the grounding.

analog_sa · 8th May 2009, 07:00 AM

Quote:

Originally posted by jarcher12
Any ideas ?

Yes, it's oscillating. Circuit?

jarcher12 · 8th May 2009, 09:31 AM

HI yes I think I sorted most of it out. Made a small blunder with the grounding, but now everything is separate signal ground and power ground (until they meet of course) and it sounds a lot better. there still seems to be a little brrrrrr in the bass but not sure. Will try to post pic later. thanks

8th May 2009, 01:40 AM	#1
jarcher12 diyAudio Member Join Date: Apr 2009	1875 distorts terribly Hi first post here even if I have been lurking for a while. This forum is excellent. Have managed to build 2 very nicely working chip amps . The first with 3876 kits (and one 3886 for subwoofer) the second using 1875 and pcb board with almost p2p wiring. Both sound very good. So i thought I would try my next project a more powerful 1875 used +- 18 v out from trafo and tried 22k/680 ohm as gain. Also bought expensive panasonic 1000 mf as dampers near the chip. Had to add some 10.000 mf after rectifier just to be able to hear the thing trough the distort. wow the sound is horrible !!! I have tried everything lowered the voltage, lowered the gain to 22/1 nothing works. it distorts like crazy when turned up and the bass really smears and distorts the worst. Any ideas ? will add a pic. Oh yea the whole thing is just on the bench, no box yet. Test setup I guess I have checked the grounding.

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8th May 2009, 09:31 AM	#3
jarcher12 diyAudio Member Join Date: Apr 2009	HI yes I think I sorted most of it out. Made a small blunder with the grounding, but now everything is separate signal ground and power ground (until they meet of course) and it sounds a lot better. there still seems to be a little brrrrrr in the bass but not sure. Will try to post pic later. thanks

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