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Old 11th November 2012, 07:08 AM   #21
pra3718 is offline pra3718  India
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Accepted solutions.

1) Ground Pin 5,10 shifted to power ground.
2) Zobel shifted to decoupling ground.
3) RF makes low input voltage, So instead of using RF I put 220pf between input pins. Pls. describe RF & 220pf (between input pins) functionality.
4) Lower value resistor sounds good to me. but it cut low bass. with the same value resister Post # 17 I can fit 2.2uf input cap. Anyway, now I have selected standard value resistor.
5) I am using 4R speakers and power supply voltage is 20VDC(+/-) I read datasheet and found if I increase supply voltage it produce heat instead of producing output-power. So I can get 22W of continuous average output power with less than 0.1%THD.
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Old 11th November 2012, 07:24 AM   #22
pra3718 is offline pra3718  India
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Post # 21, is accepted solution, One confusion is there, Rin (47K) is important when Amp played without crossover. But not necessary with active crossover. Amp sounds good without those. WHY ?
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Old 11th November 2012, 07:39 AM   #23
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Some of your caps are in backwards.
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Old 11th November 2012, 07:54 AM   #24
pra3718 is offline pra3718  India
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Quote:
Some of your caps are in backwards.
Sorry, not got it.
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Old 11th November 2012, 11:17 AM   #25
AndrewT is offline AndrewT  Scotland
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Quote:
So instead of using RF I put 220pf between input pins. Pls. describe RF & 220pf (between input pins)
I don't like this solution. It increases the risk of amplifier misbehaviour, due to adding capacitance to the -IN Pin
Quote:
Some of your caps are in backwards.
Power supply or feedback?
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Last edited by AndrewT; 11th November 2012 at 11:20 AM.
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Old 11th November 2012, 06:03 PM   #26
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Quote:
Originally Posted by AndrewT View Post
Power supply or feedback?
I'm sure if you look at the pcb and the amended pcb, both on this page, you can work it out for yourself.
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Old 12th November 2012, 01:47 PM   #27
pra3718 is offline pra3718  India
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Quote:
I don't like this solution. It increases the risk of amplifier misbehaviour, due to adding capacitance to the -IN Pin
Todays Job, RF added 220pf and between input pins removed.
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Old 15th November 2012, 05:56 AM   #28
pra3718 is offline pra3718  India
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Default how to wire dual mono lm1876

Confusing part is 1R resister join clear & dirty ground. Configurable at Chip-amp or power supply. I tried my own way.... Pls comment.
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Old 25th November 2012, 11:37 AM   #29
pra3718 is offline pra3718  India
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One channel Left-only build. Sounds good. There is not turn-on-off Noise detected when source not connected. Turn ON/OFF Noise is there when USB-DAC (Source) connected. So Noise coming from DAC ?
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Old 25th November 2012, 12:20 PM   #30
AndrewT is offline AndrewT  Scotland
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How about adding diodes across the 1r and across the DC blocking cap/s in the NFB and across the the power rails via PG and across the power rails via output/s rail?

Remove that loop in the signal routing. The Signal Return is half a mile from the signal hot !!!!!!!
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Last edited by AndrewT; 25th November 2012 at 12:22 PM.
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