Volume control on PA-100 amp

Adam M. · 12th April 2004, 12:35 AM

I was looking at the an-1192 application note and was thinking about how to implement a volume control on the parallel config. There is a 47k resistor from the input to ground, and any volume control put in front of it will have at least some of volume control resistance in parallel with the 47k resistor, decreasing the resistance to ground. Is this a problem? I'm just trying to conceptualize how this will work. THanks for any suggestions.
-Adam

Hybrid fourdoor · 12th April 2004, 05:29 AM

Probably a buffer would be best bet.

Adjust the signal going into an opamp (NE5532 type), then the opamp signal goes to the main amp.

You can get NE5532's, or OPA627's and UA7912/UA7812's from TI through samples, so your only out a couple resistors and caps.

Adam M. · 13th April 2004, 12:18 AM

Looking at the spec sheet for the OPA627 it looks like that if using it as a buffer it can just be hooked up as a non-inverting amp connecting the output back to the negative input, but that gives a gain of 2...

Is that typically acceptable for an input buffer, or would it be better to run it inverting so the gain would be 1?

Where to the resistors and caps come in building a buffer? In school I saw a lot of math, and not a lot of practical apps.
THanks for the help.

12th April 2004, 12:35 AM	#1
Adam M. diyAudio Member Join Date: Feb 2004 Location: Pittsburgh	Volume control on PA-100 amp I was looking at the an-1192 application note and was thinking about how to implement a volume control on the parallel config. There is a 47k resistor from the input to ground, and any volume control put in front of it will have at least some of volume control resistance in parallel with the 47k resistor, decreasing the resistance to ground. Is this a problem? I'm just trying to conceptualize how this will work. THanks for any suggestions. -Adam

12th April 2004, 05:29 AM	#2
Hybrid fourdoor diyAudio Member Join Date: May 2003 Location: Ft. Worth, TX	Probably a buffer would be best bet. Adjust the signal going into an opamp (NE5532 type), then the opamp signal goes to the main amp. You can get NE5532's, or OPA627's and UA7912/UA7812's from TI through samples, so your only out a couple resistors and caps. __________________ I enjoy my organic shapes.....

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13th April 2004, 12:18 AM	#3
Adam M. diyAudio Member Join Date: Feb 2004 Location: Pittsburgh	Looking at the spec sheet for the OPA627 it looks like that if using it as a buffer it can just be hooked up as a non-inverting amp connecting the output back to the negative input, but that gives a gain of 2... Is that typically acceptable for an input buffer, or would it be better to run it inverting so the gain would be 1? Where to the resistors and caps come in building a buffer? In school I saw a lot of math, and not a lot of practical apps. THanks for the help.

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