Noob Question: What is a volume buffer?

hifimaker · 8th March 2007, 05:53 PM

I'm engaged in learning about buffer circuits. I've come across buffers called volume buffers. What are they?

Thank you!

sreten · 8th March 2007, 06:18 PM

Hi,

no voltage gain. lots of current gain. high input impedance. low output impedance.

/sreten.

KISS · 8th March 2007, 06:59 PM

"no gain", being a gain of +1 idealy.

hifimaker · 8th March 2007, 07:05 PM

Thanks for the help!

-David

vynuhl.addict · 8th March 2007, 11:57 PM

A volume buffer is usually seen before the volue pot, it provides a fixed high impedence input thus making the load seen by your source output easier to drive by isolation from the volume pots isolation from the outside world in a sense .a sole potentiometer is an ever changing impedence based on where you set it and most standard commercial outputs are pretty wimpy on drive capability but they all will work and distort differently. I have always preferred a gain of2 buffer in all my preamp projects, while the second half after the pot is the gain block.

Colin

unclejed613 · 9th March 2007, 05:16 AM

another volume buffer is shown below. the pot acts as a volume control for the stage by changing the feedback ratio of the op amp. the advantage of this circuit is the high input impedance and low output impedance, and also that if the potentiometer fails, there will still be output (although it's probably not a good thing that the volume will be all the way up when that happens)

analog_sa · 9th March 2007, 06:14 AM

Quote:

Originally posted by unclejed613
the advantage of this circuit is the high input impedance and low output impedance, and also that if the potentiometer fails, there will still be output

Do you work for a marketing department? What will the output be if the pot fails? Rail DC?

ReidK · 9th March 2007, 11:25 PM

Isn't pot failure usually an open wiper? That would indeed result in max volume and not a pinned-up output. That's why the pot is wired the way it is.

BTW, I've passed along a copy of your slur to the Marketers' Anti-Defamation League. You'll be hearing from their flying monk..., I mean, attorneys.

Reid

analog_sa · 10th March 2007, 06:15 AM

Quote:

Originally posted by ReidK
You'll be hearing from their flying monk...,

I won't. My pots just failed.

Graham Maynard · 10th March 2007, 07:26 AM

The circuit in post#6 will not reduce output below unity gain, the circuit in post#1 will !!!

10th March 2007, 07:26 AM	#10
Graham Maynard diyAudio Member Join Date: Dec 2003 Location: UK	The circuit in post#6 will not reduce output below unity gain, the circuit in post#1 will !!! __________________ http://www.gmweb1.net/ and http://www.gmweb2.net/

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8th March 2007, 06:18 PM	#2
sreten diyAudio Member Join Date: Nov 2003 Location: Brighton UK	Hi, no voltage gain. lots of current gain. high input impedance. low output impedance. /sreten.

8th March 2007, 06:59 PM	#3
KISS diyAudio Member Join Date: Jan 2007	"no gain", being a gain of +1 idealy.

8th March 2007, 07:05 PM	#4
hifimaker diyAudio Member Join Date: Oct 2003 Location: San Jose	Thanks for the help! -David

8th March 2007, 11:57 PM	#5
vynuhl.addict diyAudio Member Join Date: Mar 2006 Location: Vancouver, BC,Canada	A volume buffer is usually seen before the volue pot, it provides a fixed high impedence input thus making the load seen by your source output easier to drive by isolation from the volume pots isolation from the outside world in a sense .a sole potentiometer is an ever changing impedence based on where you set it and most standard commercial outputs are pretty wimpy on drive capability but they all will work and distort differently. I have always preferred a gain of2 buffer in all my preamp projects, while the second half after the pot is the gain block. Colin

9th March 2007, 11:25 PM	#8
ReidK diyAudio Member Join Date: Jan 2006 Location: Los Angeles (a.k.a. Hell on Earth)	Isn't pot failure usually an open wiper? That would indeed result in max volume and not a pinned-up output. That's why the pot is wired the way it is. BTW, I've passed along a copy of your slur to the Marketers' Anti-Defamation League. You'll be hearing from their flying monk..., I mean, attorneys. Reid