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Chip Amps Amplifiers based on integrated circuits

Neurochrome LM3886DR Build
Neurochrome LM3886DR Build
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Old 20th June 2018, 12:34 PM   #351
Speedskater is offline Speedskater  United States
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Quote:
Originally Posted by scottjoplin View Post
Ground is an ambiguous term, don't confuse it with earth (PE)
That's so, so true!
We have:
  • AC power Safety Ground/Protective Earth
  • Planet Earth
  • Chassis
  • Shield
  • DC power common
  • Audio circuit common
While they all may have continuity to each other, each has it's own tasks.
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Old 20th June 2018, 09:35 PM   #352
tomchr is online now tomchr  Canada
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I have some dirt in a flower pot. Is that earth or ground?

Tom
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Old 20th June 2018, 09:37 PM   #353
chrisb is offline chrisb
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depends how high sea level?
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Old 20th June 2018, 09:48 PM   #354
Speedskater is offline Speedskater  United States
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Quote:
Originally Posted by tomchr View Post
I have some dirt in a flower pot. Is that earth or ground?
Tom
Yes.
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Old 21st June 2018, 02:46 PM   #355
tomchr is online now tomchr  Canada
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Quote:
Originally Posted by 00940 View Post
Which still doesn't fix the tie between earth and the amp gnd. And that's what you want to lift for a while. So R3 has to go.
I have an LM3886DR + SMPS86 on a sheet of aluminum. As far as I remember, it's built accordingly to the project BOM, including the grounding resistors on the SMPS86. It works without issues.

Look. I test the circuits before release. I build them according to the instructions. I do not sell untested garbage. I leave that for the various eBay/Amazon hawks.

If you wish to experiment, you're certainly welcome to. Just keep in mind that the circuits have been designed to work when assembled according to the BOM. This is attested by the various reports here of successful builds.

With the SMPS-86, all you need to do is to use metal standoffs so you ground the mains earth to the chassis. Then use the Molex connectors to hook up the power supply to the LM3886DRs. Connect the two pins in the respective input connectors to the (isolated) shell of the RCA and centre conductor of the RCA, respectively. Similar, the output connections go directly to the speaker connections. Nothing (other than that one mounting hole in the SMPS board) needs to be grounded, blessed, soaked in organic unicorn tears, or otherwise subjected to voodoo.

Pardon my crankiness.

Tom
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Old 21st June 2018, 03:28 PM   #356
00940 is offline 00940  Belgium
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Considering the circumstances and the time/energy you involved in these boards, some crankiness is easily forgiven.

I wasn't suggesting to that R3 should be removed as a general rule. I was just saying that a 0R R3 has to be removed if you want to lift the ground from the chassis/earth (or to install a ground loop breaker), as you suggested yourself to Mixi in order to troubleshoot this particular build.

I'm sorry if I misunderstood you or gave unsound advice. My apologies if it is the case.
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Old 21st June 2018, 05:36 PM   #357
chrisb is offline chrisb
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Indeed, and further, having known Tom for a while now, and seeing the commitment to the "E D R" that is a pillar of his corporate identity and baked into all his designs, being disquieted by second guessing / arm-chair quarterbacking is something to which I think we call all relate?


Tom - let me know if your plans for August might change?
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Old 23rd June 2018, 02:53 AM   #358
matt_garman is offline matt_garman  United States
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Neurochrome LM3886DR Build
Update to post #305 above: I liked this amp enough to rebuild it in a nicer case, and do a clear job on assembly. It could still use a few finishing touches: inline mains fuse, power-on LED, and some right-length black screws for actual LM3886DR mounting. But it's way better than it was. Sorry for the lousy pics; there wasn't much light and I don't like flash photography, so opted for noisy low-light settings instead (except for the rear-end pic, I settled for flash on that one).

Tom, my condolences to you and your family.
Attached Images
File Type: jpg lm3886dr_new_case_birdseye.jpg (805.7 KB, 250 views)
File Type: jpg lm3886dr_new_case_front_3-4.jpg (750.5 KB, 245 views)
File Type: jpg lm3886dr_new_case_rear_3-4.jpg (621.6 KB, 233 views)
File Type: jpg lm3886dr_new_case_side_3-4.jpg (858.0 KB, 234 views)
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Old 23rd June 2018, 08:39 AM   #359
tomchr is online now tomchr  Canada
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I like the slim form factor. That's a pretty nice desktop amp there. Those are some rather phallic mounting screws for the LM3886es, though. If you don't have the ability to drill and tap, I'd consider self-tapping screws. Just a suggestion.

You might not need a fuse. If the IEC inlet connects directly to the SMPS, you should be OK as the SMPS has its own fuse. If you have a power switch in series, I'd add a fuse at the IEC inlet.

I'd leave it the way it is. Enjoy it! Thanks for sharing.

Tom
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Modulus-686: 240W/8Ω @ <0.00025% THD. Modulus-86: 40W/8Ω @ 0.000054% THD. DG300B & Other Tube Circuits.
Neurochrome : : Audio - www.neurochrome.com - Engineering : : Done : : Right
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Old 24th June 2018, 08:49 AM   #360
rsqt is offline rsqt  Germany
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Hello,
I am new here at DIY Audio forum and would like to know, if the" Mouser Electronics Project Link" works also at Mouser Germany?
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