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Old 28th October 2005, 07:48 PM   #1
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Default Schematic for LM3875 wanted fast, as soon as possible

I have boards, parts and others....but do not know what is CZ....and other strange codes.

The sistem used is too much intelligent to me....have R1...R2, CZ.... in the place of the resistor value...so i have to find some inform related what is the R1 value.....i am not clever, why not the direct value over the board?...less one step in construction!

Yes, i understand electronics a little...but when people complicate too much i turn confused!

I want an schematic to assemble, as some guys use 680 ohms, others use 1K..... the black Gate capacitor, the adequated value,...the Feedback...i could see that this is not a simple question...hehe

Hey guys!..help!...i want to make it now, as i will travel latter.

regards,

Carlos
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Old 28th October 2005, 07:53 PM   #2
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Did you try to read Brian GT's very well made handbook???

Steen

PS. CZ is a Zobel filter, not necessarily needed!
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Old 28th October 2005, 07:57 PM   #3
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Default Oh boys!,... i am terrible sorry!...my mistake...here is Solid State!

Please moderators!...change this to Chip amplifiers forum!

thanks, and sorry

regards,

Carlos
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Old 28th October 2005, 08:02 PM   #4
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Default Directly under my nose...page 3 Brian bell pages.

It is all rigth...already doing.... in 5 minutes will be done.

bye

thanks

Carlos
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Old 28th October 2005, 08:08 PM   #5
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Page 3 does not show Zobel yet, here's the current version:
Attached Images
File Type: jpg lm3875.jpg (23.2 KB, 1208 views)
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Old 28th October 2005, 08:33 PM   #6
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Hi Carlos,

I have attached a schematic which is a bit closer to the PCB than the one in the instructions. As you can see Rz and Cz are the zobel that was added to BrianGT version 2 PCB. I have found on my system the zobel had no effect but others have reported a worthwhile improvement.

What is not shown on my schematic is the connection on the PCB of the signal and power earths. This is important if you were thinking of using "normal" star earth arrangement. My advice is not to it the normal way but follow the instructions and you will have no hum.

The little 4uF blackgates go on the PSU PCB.

A little history may help. (as I remember)

BrianGT and Peter Daniel both sell very similiar NIGC LM3875 PCBs. Both were involved in the design of this PCB. BrianGT has 3 versions that I know of and Peter has sold a couple of versions, originally the same as BrianGT but now I believe Peter does his own version.

The documentation was written by Brian and Sandy and reflect the version 1 of the PCB more closely. A few addition notes were added to cover the addition of the zobel in version 2.

There is a confusion between the web sites and documentation regarding the values of the zobel.

BTW: It looks like I was a little slow in responding. !!!

EDIT: Fixed schematic to reflect correct location of R1
Attached Images
File Type: gif nigc lm3875.gif (11.0 KB, 1112 views)
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Old 28th October 2005, 08:34 PM   #7
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Quote:
Originally posted by Peter Daniel
Page 3 does not show Zobel yet, here's the current version:
Why in this shematic, you aren't put a capacitor in + signal?
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Old 28th October 2005, 08:40 PM   #8
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Because it sounds better without it.
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Old 28th October 2005, 08:42 PM   #9
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Quote:
Originally posted by Peter Daniel
Page 3 does not show Zobel yet, here's the current version:
Page 3 (and my schematic) also shows the 220 ohm series input resistor in a different location.
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Old 28th October 2005, 08:44 PM   #10
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I know, and so far nobody pointed that out. The schematic drawn by me here, reflects the actual location of R1.
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