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Old 23rd August 2009, 08:48 PM   #1
rtill is offline rtill  United States
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Default lm3886 no mute option

hello,
curious if I don't want the mute option with the lm3886, do I just connect pins 4 and 8 together to the V- rail?
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Old 23rd August 2009, 10:08 PM   #2
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hello,
curious if I don't want the mute option with the lm3886, do I just connect pins 4 and 8 together to the V- rail?
No, leave pin 8 disconnected from pin 4.
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Old 24th August 2009, 01:02 AM   #3
djoffe is offline djoffe  United States
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Default No mute for LM3886

Be careful...as I read the data sheet, to disable the mute, you must pull at least 0.5 mA from the mute pin. You probably don't won't to pull a whole lot more than 1 mA. There is a note and equation that describes the resistor value you should use.
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Old 24th August 2009, 12:17 PM   #4
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Be careful...as I read the data sheet, to disable the mute, you must pull at least 0.5 mA from the mute pin. You probably don't won't to pull a whole lot more than 1 mA. There is a note and equation that describes the resistor value you should use.
The datasheet shows a cap across the MUTE input and a resistor to a switch.
You dont need the resistor or the switch for none mute mode if I read the data sheet correctly.
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Old 24th August 2009, 12:38 PM   #5
AndrewT is online now AndrewT  Scotland
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pin8 open circuit leaves the Mute function ON. This mutes signal from the output.

Pin8 needs current (~1mA) to turn Mute function OFF. This allows full signal from the output.

One can permanently connect a resistor from Pin8 to Vee but the amp will switch ON, on power up and may produce a start up noise as the circuits come alive.
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Old 24th August 2009, 01:08 PM   #6
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pin8 open circuit leaves the Mute function ON. This mutes signal from the output.

Pin8 needs current (~1mA) to turn Mute function OFF. This allows full signal from the output.

One can permanently connect a resistor from Pin8 to Vee but the amp will switch ON, on power up and may produce a start up noise as the circuits come alive.
You could add an RC network to hold off the amp on power up.
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Old 24th August 2009, 01:17 PM   #7
rtill is offline rtill  United States
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it is working great, I put a 10k resistor between 4 and 8, powers up fine. Thanks guys.

I am having an issue though. I am using this power amp coupled to a tube preamp. I can't turn my volume past 2. If I do the amp cuts out. I am assuming I am putting too much of a load on the power amp. Could I couple these together with maybe a 470k resistor to try and remedy the issue?

The preamp is http://www.freeinfosociety.com/elect...iew.php?id=507
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Old 24th August 2009, 01:32 PM   #8
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You can decrease the gain of the LM3886.
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Old 24th August 2009, 01:32 PM   #9
AndrewT is online now AndrewT  Scotland
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Hi Rtill,
what is the gain of the pre-amp?
What is the gain of the power amp?
What is the attenuation of the pot at position 2?
What is the load on the power amp?
What is the supply voltage to the power amp?
You have to give us some information if you want us to be able to offer informed advice.
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