Paralllel configuartion LM3886 - adjusting variable resistors

[jmillerdoc]

I am looking for some assistance with adjusting the variable resistors on a LM3886 parallel configuration. I recent purchased a prebuilt amp PCB from Nemo-e-store on eBay and I was very impressed with the sound from this configuration. I subsequently purchased the PCB's to DIY the design but, although the PCB came with a schematic it did not explain how to balance the 3 chips by adjusting the 3 variable resistors. I have come up empty handed searching the web and asking the guy I bought the PCB from.

The PCB I bought is here:
http://cgi.ebay.com/lm3886-3-Parall...34.c0.m14.l1262&_trkparms=|301:1|293:2|294:30

Can anybody help me with this problem?
Thanks for all y'alls help.
Sincerely,
Jeff M.
Lawton, USA

 

[pacificblue]

Without a schematic it is guesswork, but they are probably there to adjust the DC offset to zero.

 

[deepthrob]

I purfed up a 3*3886 non inverting and balanced it by lifting the three output resistors and adjusting each chip individually to the lowest dc offset. Then I adjust the two lowest to match the highest (8 mv).


Frank
http://www7.taosnet.com/f10/

 

[deepthrob]

Ooops, meant to write 'inverting'

 

[jmillerdoc]

Where exactly do you take the measurements? Across pin 3 and GND on each chip? Or is there another way to measure the DC offset? Also, how do you put a load across the output and GND of each individual pin or is it even neccessary?
Jeff

 

[deepthrob]

A load is not necessary and yes, from 3 to ground but the resistors must be lifted so the outputs are isolated.

 

[jmillerdoc]

i am sorry but this is a first for me....which resistors must be lifted? What is the general value of the resistor you are speaking of? There are several resistors, I am not certain which you are speaking of.
Thanks,
Jeff

 

[pacificblue]

The big ones R2, R5, R11 on the PCB you linked to.

 

[jmillerdoc]

I got it, thanks! Anybody know of a source to buy similar PCB's. I have tried to email www.Shine7.com several times with no response. I would love to get a few of the PCB's found at their website!

Thanks again for all of your assistance!
Sincerely,
Jeff

 

[AndriyOL]

I purfed up a 3*3886 non inverting and balanced it by lifting the three output resistors and adjusting each chip individually to the lowest dc offset. Then I adjust the two lowest to match the highest (8 mv).


Frank
http://www7.taosnet.com/f10/

Sorry, but I can't understand. Could you explain how exactly you adjusted each chip individually to the lowest dc offset.
Thanks.