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Joseph1 14th January 2013 12:10 AM

LM1875 Trebles Modifications
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I have built my own 2.1 subwoofer system using 3 LM1875.It is a locally available kit.Also I corrected some mistakes on it.

The design works nicely.The only problem is the two satellite amps trebles is not enough.

I uploaded the schematic by tracing the KIT.You can go through the red covered area.

What modifications to be done to gain more trebles.


hitsware 14th January 2013 01:15 AM

remove R24 and C14

attach input to C15 .........

Joseph1 14th January 2013 01:22 AM

1 Attachment(s)
Hi thanks for the help.

I corrected the mistake.Here is the corrected one :)

Joseph1 14th January 2013 10:41 AM

Hi I removed the R24 and C14 & checked the system.The gain increased much.

I mean from the two satellites its coming too much sound comparing to sub amp,so when hearing I cannot hear much bass from the sub amp.

Is there any gain ratio between satellites & sub amp in 2.1 systems?

Here is my system gains

Satellite amp Left = 20
Satellite amp Right = 20

Sub preamp TL072 gain = 12
Sub Amp = 20

When listening to music I always put BASS level in subamp to half way mark in linear potentiometer.

basi 14th January 2013 10:44 AM

Hi!!!Reduce R26 to 24k.

Joseph1 14th January 2013 11:01 AM

Hi I increased the value of R27 to 3.3K so the new gain will be -11.8.

Now the two satellites have -11.8 each.Now I can hear balanced sound.

But still the sub amp has these gains.

Sub preamp TL072 gain = 12
Sub Amp = 20

Is it ok?

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