LM1972 Audio Attenuator and XLR Balanced to Unbalanced

dbbaker2007 · 3rd June 2011, 08:17 PM

First off...Has anyone gotten the LM1972 working properly from a microcontroller? I am going to be using this in my project and would like to know if there is any pop when going from 100% to MUTE? I am going to use the suggested LF412ACN buffer on the output, but if anyone has any other suggestions that would be great.

Next thing is how do we take a XLR balanced and make it unbalanced. And then take that unbalanced signal and transform it back to balanced? Reason being, I want to take the XLR signal and attenuate it and it would be easier if it was unbalanced.

Moset · 3rd June 2011, 09:17 PM

I'm running the LM1972 from a PIC16F84 (iirc) and have no problems with pops, except when doing sine wave tests. I haven't tested it from 100% to mute in one step, since it would be waay too loud. If it turns out to be a problem, you could always ramp the volume down to mute over a couple of steps, and the same when returning from mute.

I had to buffer the LM1972 inputs and lower the input voltage to avoid clipping (halved it), which is something to be aware of. It is possible I've made an error in implementing the LM1972, but I got the hint from some page online, so I am not the first to have that problem. The dpot outputs need to be buffered anyways, so you can easily regain the lost gain, though it might be suboptimal.

3rd June 2011, 08:17 PM	#1
dbbaker2007 diyAudio Member Join Date: Aug 2010	LM1972 Audio Attenuator and XLR Balanced to Unbalanced First off...Has anyone gotten the LM1972 working properly from a microcontroller? I am going to be using this in my project and would like to know if there is any pop when going from 100% to MUTE? I am going to use the suggested LF412ACN buffer on the output, but if anyone has any other suggestions that would be great. Next thing is how do we take a XLR balanced and make it unbalanced. And then take that unbalanced signal and transform it back to balanced? Reason being, I want to take the XLR signal and attenuate it and it would be easier if it was unbalanced.

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3rd June 2011, 09:17 PM	#2
Moset diyAudio Member Join Date: Jun 2009	I'm running the LM1972 from a PIC16F84 (iirc) and have no problems with pops, except when doing sine wave tests. I haven't tested it from 100% to mute in one step, since it would be waay too loud. If it turns out to be a problem, you could always ramp the volume down to mute over a couple of steps, and the same when returning from mute. I had to buffer the LM1972 inputs and lower the input voltage to avoid clipping (halved it), which is something to be aware of. It is possible I've made an error in implementing the LM1972, but I got the hint from some page online, so I am not the first to have that problem. The dpot outputs need to be buffered anyways, so you can easily regain the lost gain, though it might be suboptimal.

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