Coldsnow

Using a dual10K pot on ballanced line level.
« on: September 02, 2008, 11:56:27 PM »
Hi,
Would it work to use a simple duel 10K pot in between a ballanced out to a ballanced in as an attenuator without messing up the phase, sound etc.?


McCroskey42

Using a dual10K pot on ballanced line level.
« Reply #1 on: September 03, 2008, 12:10:06 AM »
In a word, no.

A balanced attenuator is only as good as the matching between the two resistors, and a simple dual pot won't match closely enough.  Many manufacturers will quote you 20% tolerance...you need it to be a whole lot closer.  Doing it with a dual pot would attenuate the signal, but you'd shoot your CMRR to hell.  This is what keeps the nice folks over at Goldpoint in business.  

Do a search here for balanced attenuators...plenty of folks around here have built balanced attenuators like the Goldpoint, albeit with somewhat cheaper switches like Lorlin or Alpha.  For example, the famous (and sorely missed) New York Dave's version

EDIT:  Read on page 2 of that link for PRR's comment about a single pot attenuator, and NYDave's response.  Probably closer to what you're looking for.
Be vague, or be informed.
   --PRR

Natural

Re: Using a dual10K pot on ballanced line level.
« Reply #2 on: May 18, 2020, 04:57:37 PM »

ruffrecords

Re: Using a dual10K pot on ballanced line level.
« Reply #3 on: May 18, 2020, 05:41:11 PM »
A single pot will do fine. We used them at Neve on balanced floating monitor outputs back in the 70s.

Cheers

Ian
www.customtubeconsoles.com
https://mark3vtm.blogspot.co.uk/
www.eztubemixer.blogspot.co.uk


'The only people not making mistakes are the people doing nothing'

JohnRoberts

Re: Using a dual10K pot on ballanced line level.
« Reply #4 on: May 18, 2020, 05:44:47 PM »
you could probally use a LM13700 VCA, not?


http://atosynth.blogspot.com/2015/01/the-xonik-vca-revisited.html

https://sound-au.com/articles/vca-techniques.html

just connect R13 and R14 to Q1
A 13700 is an OTA (operational transconductance amplifier) not a VCA.

Not very quiet or low distortion (trade off distortion for s/n when setting operating levels).

JR
Don't only half-ass tune your drums. Visit https://circularscience.com to hear what properly "cleared" drums sound like.

Natural

Re: Using a dual10K pot on ballanced line level.
« Reply #5 on: May 18, 2020, 11:14:49 PM »
well, the LM13700 is easier to find.

alternately you have the ...

SSM2164
https://www.analog.com/en/products/ssm2164.html

or the newer
cool audio V2164D ... quad VCA

https://www.coolaudio.com/features-page.php?product=V2164D
a Behringer subsidiary


RuudNL

Re: Using a dual10K pot on ballanced line level.
« Reply #6 on: May 21, 2020, 11:54:05 AM »
Nice, but to me it looks like killing a mosquito with a machine gun...
There is a solution for every problem!

http://www.vansteenisaudio.nl

JohnRoberts

Re: Using a dual10K pot on ballanced line level.
« Reply #7 on: May 21, 2020, 12:01:25 PM »
Hi,
Would it work to use a simple duel 10K pot in between a ballanced out to a ballanced in as an attenuator without messing up the phase, sound etc.?
The resistance matching and tracking is not good enough to use in series but in a shunt leg, or legs of an H pad, the tracking will not imbalance the interface.

JR

Don't only half-ass tune your drums. Visit https://circularscience.com to hear what properly "cleared" drums sound like.

RuudNL

Re: Using a dual10K pot on ballanced line level.
« Reply #8 on: May 21, 2020, 02:47:05 PM »
At the radio station I used to work for, we simply did it like this.
And yes, the inpedances are not constant, but as long as the load impedance is high compared to the source impedance, it is no problem.
There is a solution for every problem!

http://www.vansteenisaudio.nl

 

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