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Old 3rd April 2012, 09:03 PM   #21
Pemo is offline Pemo  Mexico
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Default I agree

Quote:
Originally Posted by copperweed View Post
Hi Pemo.
When it's loud (like, 75/80wpch), there is some compression, but if I had a regulated 30/0/30Vdc PSU @ 10A, or even 35/0/35 @ 10A, instead of a Tx on the end of the supply chain then I'd be a lot more satisfied.
You just CAN'T HAVE too much power supply...
I agree with you, there is not such a thing as "TOO MUCH POWER".
I'm planning on using this board stock, with a 24-0-24 transformer, and I was wondering (because I don´t have much information on this board, schematics or anything) if the PSU in this board is enough. In other projects with LM3886 I´ve used 40,000 mF (4 caps) and liked it very much.

RGDS

PEMO
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Old 3rd April 2012, 09:25 PM   #22
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Quote:
Originally Posted by copperweed View Post
Sometimes, if the output stage has gone short-circuit, it can sound like it's oscillating at 50 or 60 Hz. The power has been transformered, rectified and smoothed, but then, if the smoothing caps are shorted to ground through the speakers, it can sound like a full-power oscillation. I need to know aprox frequency to be sure. Whistling or whining could be osc., but loud buzzing could be a blown chip.
Sorry, just re-read ur post. What I said was true, but not in ur case, I think, because you don't mention any frightening or mysterious noises.

What is your supply voltage? Every 5v extra on the PSU adds nearly 30% to the amplifier cct's dissipation, from +/- 20 to +/-25 to +/-30. And there are four amplifiers on your board!

I know you're confident in your heatsink, but I'd still be tempted to double it or add a fan.
cw
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Old 3rd April 2012, 10:08 PM   #23
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Quote:
Originally Posted by Pemo View Post
I agree with you, there is not such a thing as "TOO MUCH POWER".
I'm planning on using this board stock, with a 24-0-24 transformer, and I was wondering (because I don´t have much information on this board, schematics or anything) if the PSU in this board is enough. In other projects with LM3886 I´ve used 40,000 mF (4 caps) and liked it very much.

RGDS

PEMO
This is what I'm thinking...
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Old 4th April 2012, 12:59 AM   #24
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Quote:
Originally Posted by copperweed View Post
Sometimes, if the output stage has gone short-circuit, it can sound like it's oscillating at 50 or 60 Hz. The power has been transformered, rectified and smoothed, but then, if the smoothing caps are shorted to ground through the speakers, it can sound like a full-power oscillation. I need to know aprox frequency to be sure. Whistling or whining could be osc., but loud buzzing could be a blown chip.
Actually it sounds fantastic with no issue whatsoever in the sound but the chips becomes hot extremely fast. 70-80C in 1-2min... And this even at moderate levels... With my other LM4780 amp they never really get that hot... What's the max safe temp I should be seeing on the top surface of the chip?

This is the reason I thought it was oscillating.

Thanks
Do
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Old 5th April 2012, 01:25 AM   #25
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Originally Posted by pinnocchio View Post
Actually it sounds fantastic with no issue whatsoever in the sound but the chips becomes hot extremely fast. 70-80C in 1-2min... And this even at moderate levels... With my other LM4780 amp they never really get that hot... What's the max safe temp I should be seeing on the top surface of the chip?

This is the reason I thought it was oscillating.

Thanks
Do
OK, doesn't seem like any power-draining parasitic osc I ever heard of. And if it were RF, the output RC network would be BAKING at that sort of power.
I ask again, what is the at-rest supply voltage?
And also, is there more than 0.1V dc at the speakers, also in at-rest condition?
And, are you running those dual-amp chips in single,parrallel or bridge?
U kno, they are pretty bomb proof!!!
SC, under-volts, over-volts, max 250 C internal, dynamic SOAR; u gotta ask, "do they actually NEED a heat-sink?"... but I say just make it bigger. Like PSUs, u can't have a good-enough heat-sink...
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Old 10th April 2012, 12:30 AM   #26
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Default schematics here for lm3886 6n11

Click the image to open in full size.
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Old 10th April 2012, 01:30 AM   #27
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Default risistor replacer

here are some pics i did this for my daughter. she loves the sound. it is quite good no hum dead silent.all

Click the image to open in full size. Click the image to open in full size.

i need to do now is replace the input with a newly developed LDR based mod... link= Build An Amp i cleaned up the wireing since then its been going strong for about six months now without a hiccup Click the image to open in full size.
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Old 10th April 2012, 07:22 AM   #28
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Default speakers

p.s it took me a while to find some deacent speakers for the lm3886+6n11 .i was on a painting job in london i complimented the owner on them and he said he was tossing them out. you like them you can have them. nice bonus they sound out standing.i also added a buffer stage . it has one 12ax7 and one 12au7 which ive rolled a little bit to see witch ones complimented the speakers best for my set up. long plate square getters worked out perfect! i think when im done my surround sound set up im going to buil another one exectlly the same i also notice a few caps could be upgraded to 105c there just cheap caps but the the uprade is more for longevity i didnt notice a difference with expensive caps at all .i also swapped out the 6n11 for a 6922 even sweeter sound .hope this all helps best regards
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Old 28th April 2012, 03:07 PM   #29
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Quote:
Originally Posted by kallel123 View Post
p.s it took me a while to find some deacent speakers for the lm3886+6n11 .i was on a painting job in london i complimented the owner on them and he said he was tossing them out. you like them you can have them. nice bonus they sound out standing.i also added a buffer stage . it has one 12ax7 and one 12au7 which ive rolled a little bit to see witch ones complimented the speakers best for my set up. long plate square getters worked out perfect! i think when im done my surround sound set up im going to buil another one exectlly the same i also notice a few caps could be upgraded to 105c there just cheap caps but the the uprade is more for longevity i didnt notice a difference with expensive caps at all .i also swapped out the 6n11 for a 6922 even sweeter sound .hope this all helps best regards
Wow, fantastic job. And thanks for the 6n11/6922 tip. I'll search out some NOS. And did u have to mod the SP Rx cct like I did? see here; Hybrid DIY cct of LM3886+6N11
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Old 8th May 2012, 12:19 PM   #30
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Thanks for the compliment. no i left every thing as is except 2 caps and if you want a beefier supply, why not piggy back some more caps you can add as many *** you like>id be careful with higher voltage trafos these caps are only 50 volts! im running mine at 22-0-22 so i can run 4ohm speakers or 8 ohms nothing gets to hot if went to 30 volts ac i would change at the very least the big cans 80v 100v they should run nice and cool.. im trying a point to point lm3886 next based on elliot but then i seen this powerhouse http://i47.tinypic.com/11kjxg9.jpg[/IMG]]Photobucket | The most recent pictures on Photobucket
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