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Audio Sector Kits & PC boards from AudioSector

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Old 2nd April 2020, 07:48 PM   #2251
slungu is offline slungu  Germany
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Ok, so I tried to build an stereo amp based on Peters kit and unfortunately I'm afraid that for whatever reason I have fried one of my chips, One of the channels went up in smoke for whatever reason and the smell and the sparks came from the chip. I have no idea if I can source another chip, but I would be interested to know if anybody would make an educated guess as to what went wrong:


Click the image to open in full size.

Click the image to open in full size.

On the back one can see the 3 black coloured pins of the chip



Thank you,
Stefan

Last edited by slungu; 2nd April 2020 at 08:05 PM.
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Old 4th April 2020, 11:23 AM   #2252
slungu is offline slungu  Germany
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On the channel that did not went up in smoke I measure 25V on input and on output with nothing connected to the amp - can that be ?!? Somehow I am seriously puzzled by this project of mine. P.S.:I did not use any insulation when fixing the chips to the aluminum profile used as cooling.
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Old 28th April 2020, 05:00 PM   #2253
Jmo is offline Jmo
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Default LM4780 Amplifier

I've built these modules but need heat sinks. Can anyone suggest an appropriate heat sink and source?

Thank you.
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Old 28th April 2020, 05:23 PM   #2254
Peter Daniel is offline Peter Daniel  Canada
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Quote:
Originally Posted by slungu View Post
On the channel that did not went up in smoke I measure 25V on input and on output with nothing connected to the amp - can that be ?!? Somehow I am seriously puzzled by this project of mine. P.S.:I did not use any insulation when fixing the chips to the aluminum profile used as cooling.
No need for insulation when mounting the chip, as the case is self insulating plastic package.

It could go in smoke because the supply voltage was reversed, or you had some sort of short circuit? Can you post picture of your rectifier board?

25V at the input could be caused by bad solder joints or resistors mixed up?
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Old 13th May 2020, 05:44 PM   #2255
jrhansen is offline jrhansen
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I just recently found this site, and been reading about this kit.

Would this be a good kit to mod an existing speaker set into a couple active speakers, primarily used as keyboard monitor ? since its designed as a mono block.

Also where would I find info about using 2 in either paralell or bridged mode ?
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Old 15th June 2020, 06:25 PM   #2256
Peter Daniel is offline Peter Daniel  Canada
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Yes, it would be perfect kit for that.
For parallel or bridge mode LM4780 is preferred. The info can be found here: Kit arrived
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Old 9th July 2020, 04:09 PM   #2257
gille is offline gille  Denmark
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Quote:
Originally Posted by Peter Daniel View Post
Yes, no problem using 1000uF Panasonic caps.
C1/C1 are not recommended to be used any longer.

The main caps, Panasonic FC 1500/50, are sometimes on backorder, and then I need to substitute them with something else not to further delay order shipment.

Some people tried those 2700uF Chemicons in the past and claimed they sounded better then stock caps.
Do you mean that C1 and C2 on the rectifierboard no longer are required?
If so for what reason and should i remove them from my assembled kit ?

Kind regards
Edwin
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Old 14th July 2020, 01:35 PM   #2258
Ryelands is offline Ryelands  United Kingdom
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I've been successfully using AudioSector LM3875 kits for several years with stepped attenuator VCs but would now like to re-site the amps, shorten the perhaps over-long speaker leads and use longer leads between the VC and the amps.

The snag is that, when I try longer signal leads, the amps oscillate in an, er, lively manner. I'm reasonably sure a buffer circuit would fix the issue but I'd prefer (also) to try and fix the oscillation.

The signal leads use a quad-core geometry that, as you know, is rather more capacitive than alternatives. I omitted the 1K input resistor R1; the SA's serial resistor in on the low side (5K6). (I accept that low-value resistors do not help stability but the amps' sound quality is noticeably better than it is with higher values.)

Any suggestions as to what I might do?

TIA,

Dave
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Old 8th September 2020, 08:17 AM   #2259
Georgeged is offline Georgeged
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Default LM3875 genuine or counterfeit?

Hi everybody,

I have purchased pair of LM3875 chips on ebay, which according to seller are genuine National Semiconductor. Cant find much info in internet how to identify counterfeit. Will appreciate help.
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Old 8th September 2020, 08:20 AM   #2260
asuslover is offline asuslover  Romania
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I believe they are fake fake...
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