Passive Monitor Controller, just a pot?

to get a near log performance from a linear pot you want to slug the wiper to the CCW terminal with around one sixth of the pots value. So if you have a 50K lin dual gang pot you want to use something like a 8K6 resistor. The only issue with doing this is that the impedance looking into the pot varies all over the shop depending on its position. In 90% of situations so long as the minimum impedance which occurs when the pot is fully CW isn't too low then this isn't a problem.

Your desire to make use of the 50K pot you have needs to be thought about. Is this a really good quality pot with good matching between the two gangs? If not, why bother, grab any cheap arse pot that is 10K log if you plan to implement the approach in the AT article, which is different to most where the pot is forming a variable shunt in a pad arrangement. But also give some thought to the concept of a passive monitor controller where there is little to be gained if it isn't better in performance than any other way of turning your speakers up and down. The Alps pots are getting cheaper ( here in Oz through RS components ), so in the scheme of things it is no big deal to use a good quality part that makes the whole effort worthwhile,

Yes it is just a pot.  As simple as a dual gang Sfernice or as complicated as rotary switched resistors.

When it is time to replace a SSL 4K MINI pot I always get 3 or 4 because they track within tolerance but they could be out of balance.  At the CCW side.  Think I will try a slugged linear next time.
You can do the same thing with any dual-stack log or linear as described.  Buy a few. 
I still like the Radio Shack 100K dual for short run (less than 25 foot) situations.  It was my "dupe rack" monitor pot.  I did tests regarding the changing load when switching between different sources CASS, CD and DAT and it did not change the source signal when switched in and out.

Haven't seen a dupe rack in over a decade.  There was one guy in NYC with a wall of 100 Aiwa three-head decks.  I think that was the only time I did not enjoy being a tech- maintaining those decks motors, pinchrollers, alignments, oikh! 
Mike

Quick question.  Got my monitor controller all wired up and working fine, but I wired up a 3 position rotary switch for  stereo/mono/reverse (as shown in the article) and I'm getting bad clicks/pops between positions.  Mostly in the right channel. 
If I hold the switch between two positions the audio gets significantly louder, so my first thought was that I accidentally ordered a shorting switch, but it's definitely non-shorting: http://ca.mouser.com/ProductDetail/CK-Components/A40315RNZQ/?qs=sGAEpiMZZMvNbjZ2WlReYus8Y6%2fQzAi05bQNaEcIi7A%3d

Is it just a cheap switch or is there a trick to getting rid of the pops between positions?

It's probably working in shorting mode if you listen louder signal between positions... Anyway you could add some BIG pull down resistors, 1M would be fine between signals and ground at inputs and outputs, this will descharge any cap at the feedign output and loading input, I would try first just the input ones that is more likely to have caps and less destructive to CMRR and level tracking, if it keeps poping for the output resistors won't harm to be matched but any 1% wouldn't get trouble.

It usualy work in guitar pedals with true baypass wich use to have trouble of poping because of single supply (4.5V offset) If it low the poping but not dissapear could try smaller resistors at input.

JS

minor_glitch said:

Is it just a cheap switch or is there a trick to getting rid of the pops between positions?

Click to expand...

The key to getting rid of clicks in switches is to ensure the dc conditions at and between each switch position are the same; and the simplets way to do this is to ensure there is NO dc there at all. This usually means that wherever you have an input coupled via a capacitor, you need a bleed resistor to drain any dc on it to ground BEFORE the signal reaches the switch. It can be quite a high values (100K or more) so it does not affect the laws of pots or or filters etc. That should take care of 99% of cases but there will still be a few where there is some leakage and not all the dc values are 0V. To fix this you need to ensure everything connected to the switch is at the same dc level not matter what the position of the switch. The classic way to do this is to connect adjacent switch positions together via a very large value resistor - often around 4.7M to equalise the dc conditions.

Cheers

Ian