BrianGT's LM3886 Kit
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 1st March 2005, 04:54 AM #1 scott_jcp   diyAudio Member   Join Date: Feb 2005 Location: Richardson, TX BrianGT's LM3886 Kit Got the kit, and everything is great, until I went to put it together. Which Resistor is which? R1, R2, R3, etc mean nothing without something to tel me which is which!
jeff mai
diyAudio Member

Join Date: Aug 2002
Location: Melbourne
Re: BrianGT's LM3886 Kit

Quote:
 Originally posted by scott_jcp Which Resistor is which? R1, R2, R3, etc mean nothing without something to tel me which is which!
You could try Brian's web site...

Or try a forum search...

 1st March 2005, 05:06 AM #3 scott_jcp   diyAudio Member   Join Date: Feb 2005 Location: Richardson, TX I spent about an hour doing that actually.
BrianGT
diyAudio Moderator Emeritus

Join Date: Jan 2002
Location: near Atlanta, GA
Re: BrianGT's LM3886 Kit

Quote:
 Originally posted by scott_jcp Got the kit, and everything is great, until I went to put it together. Which Resistor is which? R1, R2, R3, etc mean nothing without something to tel me which is which!
Components:

Board pic:
http://www.briangt.com/gallery/lm388...886_019?full=1

Amp board:
R1 - input resistor = 1k (2 - black on the resistors packed)
R2 and Rf - input-to-ground resistor = 22.1k (4 - uncolored)
R3 - feedback-to-ground resistor = 681 (2 - blue)
Rm - mute resistor = 10k (2 - red)
picture of 2 ways to wire feedback resistor:
http://www.briangt.com/gallery/lm3886amp/3886_037
with and without the feedback capacitor, notice the resistor placement
C1,C2,Cm - 100uf
C3,C4,Cz - 0.1uf
Ci - 47uf

Power supply board:
R1,R2 - 1 ohm resistors for snubber network
R3,R4 - 2.2k bleeder resistors for power supply caps (mount on bottom)
R5 - 10k or 22k resistor for LED (10k might be too bright, so try 22k to lower the current supplying the LED to reduce brightness)
C1-C4 - snubber caps = 0.1uf
C5,C6 - power supply caps = 10,000uf
C7 - 10uf cap for LED (extra included in bag with diodes)
D1-D8 - power supply diodes = MUR860

I am working on a manual now, and will try to finish it soon.

--
Brian

 1st March 2005, 05:11 AM #5 scott_jcp   diyAudio Member   Join Date: Feb 2005 Location: Richardson, TX Thank you so much!
troystg
diyAudio Member

Join Date: Apr 2004
Location: In a dream... Please don't wake me.
Re: BrianGT's LM3886 Kit

Quote:
 Originally posted by scott_jcp Got the kit, and everything is great, until I went to put it together. Which Resistor is which? R1, R2, R3, etc mean nothing without something to tel me which is which!

Thanks Brian for the post! I was going to ask the exact same question but found this post in the search. Remarkable timing on Scott's part! May I suggest you post the color code on your web page?

Scott-

Rchdn TX... I'm up in McKinney. Want to meet up for amp listening sessions one day?

Thanks,

Troy

 2nd March 2005, 11:21 PM #7 dsavitsk   diyAudio Member     Join Date: Jan 2005 Location: Hartford It is a good idea to have a multi meter if you are building amps. Even a \$20 one from radio shack will do fine. At the very least, it is good to know if it safe to plug your speakers in. That said, resistors are easily measured. -d
troystg
diyAudio Member

Join Date: Apr 2004
Location: In a dream... Please don't wake me.
Quote:
 Originally posted by dsavitsk It is a good idea to have a multi meter if you are building amps. Even a \$20 one from radio shack will do fine. At the very least, it is good to know if it safe to plug your speakers in. That said, resistors are easily measured. -d

Only Brian knows the color coding of the resistors he shipped. (I assume he has a master plan with the markers ).

The resistors he shipped are NOT the factory spec'ed values so proper placement is a guesstimate until he confirms. (Which he did).

I think Scott's original post was directed towards Brian even though he does not state so.

PS, I have an ORIGINAL Fluke 87 and the 10k probe I bought myself for graduation back in '87. I use it at LEAST every other day and it's still in "close to mint" condition.
__________________
Troy
Thinking positive doesn't make things better, it makes you a better person.

 3rd March 2005, 11:36 PM #9 budwiser   diyAudio Member   Join Date: Jan 2004 Location: dark side of the moon Look at the pictures posted for the power supply. Gold stripe with 3 red stripes go on the bottom (R3 and R4). Black stripe with 2 gold stripes goes on the top (R1 and R2). My guess on the led is longer leg goes where arrow is pointing marked on board. On the led resistors they are so small even with my magnifying glass I can't read them. I see though that on has a red tab and the other does not so this must mean something. Any corrections anyone. Cheers, Pete
 4th March 2005, 01:41 AM #10 troystg   diyAudio Member     Join Date: Apr 2004 Location: In a dream... Please don't wake me. Hi budwiser- Thanks for the post, but Brian already got us straightened out.. He is EXCELLENT on support and his kits aren't half bad either . I would recommend his kits to anyone, newbie or experienced, to try for ease of assembly and excellent sound. __________________ Troy Thinking positive doesn't make things better, it makes you a better person.

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