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Old 9th February 2010, 03:31 AM   #1
JozzaG is offline JozzaG  Australia
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Default need LM1876 mute mode and standby mode help

i've recently bought the LM1876 IC chip and the datasheet does not offer any help as to what kind of circuit should be used if the person wishes to use the standby and/or mute functions. it also does not show wether to connect it to the positve voltage Vcc ot the negative voltage Vee.

Can anyone help me with a simple schematic and explanation of what to use if i wish to use both mute and standby.

Thanks.
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Old 9th February 2010, 11:54 PM   #2
Minion is offline Minion  Canada
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From Reading the Datasheet it seems that the Mute and Standby functions are controlled by a Logic gate , logic-high voltage will mute it and Logic-low voltage will un-mute it , it is simular for the Standby function .....

Since I don"t have a clue about logic gates I couldn"t tell you how to implement it ......

In appliciation information it talks about the Mute and standby pins but I can"t make heads or tails of it ......

http://www.national.com/ds/LM/LM1876.pdf
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Old 10th February 2010, 12:06 AM   #3
JozzaG is offline JozzaG  Australia
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yes i was much the same. i may end up scrapping the mute idea and just not worrying about it. i did have a simple diagram drawn up whcih i thought may work, but im not too sure.
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Old 10th February 2010, 04:25 PM   #4
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If grounded, both mute and standby are disabled. But you may get unwanted turn on pops. A logic "high" is often 5V, and it says mute and standby must be at least 2.5V to function.
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Old 16th January 2012, 10:04 PM   #5
tuhkam is offline tuhkam  Estonia
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Default how to implement LM1876 mute?

I'm struggling to find a simple way to use the mute function on LM1876. I can't program microcontrollers yet. Also I would not like to use relays if possible.
The easiest thing would be to have a separate switch, but this is not very convinient.
I thought of below switch arrangement.
Click the image to open in full size.

Would this work?
When switching off, one would need to wait in POS 2 for a few sec
The 5V would come from a battery.

Does anyone know some elegant and easy ways to handle mute pins of these kind of chipamps?

I have built a LM3886 gainclone - runs nicely, but pops like crazy (did not use mute pins).
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Old 17th January 2012, 02:17 PM   #6
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It may help if you would describe in what circumstance you are going to use this amplifier . The mute function works just like an lm 3886. I have built quite a few lm3886 amplifiers have never used the mute function and apart from the slightest click not even as loud as the power switch itself i have had no problems. with popping noises like crazy
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Old 17th January 2012, 03:38 PM   #7
tuhkam is offline tuhkam  Estonia
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It will be used as a common stereo amplifier, schematic is almost as the one in the datasheet.
I have added bleeder resistors and snubber to PSU, the LM3886 amplifier doesn't have those. As a side note - the LM3886 amplifier also has a low gain 2 stage preamp with opamps. When changing preamp opamps, the pop characteristics change as well.

Click the image to open in full size.
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Old 17th January 2012, 07:27 PM   #8
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The circuit in post #5 would work.

You could simplify the mute section in post #7. Remove R7 and replace R10 with 100k. Skip G1 and connect SW1 pin 1 to V+.

To eliminate popping, use capacitors (Cin) between pot and R1/R2. Add a resistor to ground between the cap and R1/R2 (Rin).

The muting on the LM1876 does not work the same as the the LM3886. The LM3886 is current controlled. No current means mute, more than 0,5 mA means sound. The LM1876 is voltage controlled. No voltage means sound, more than 2,5 V means mute.
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Old 17th January 2012, 07:51 PM   #9
AndrewT is offline AndrewT  Scotland
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Post7:
I don't understand R3 & R4.
What are they doing?
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Old 17th January 2012, 08:42 PM   #10
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The mute and standby functions are switch-enabled, so convenience only applies to how the switch is implemented. That is a personal preference. If desired, perhaps a simple timer could be added to the power-on switch that would disable the function after a brief pause. That seems to me to be what the goal is here, rather than a "mute 'cause the phone is ringing" feature. The datasheet doesn't go into much detail other than to say a logic-level signal is required; there's umpteen ways to get there from here, so they leave it to the designer.
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