Matching impedance for replacement faders

[musika]

I am looking for faders for an Allen & Heath MOD2 desk. They are 2k2 ohm and 45mm stroke.  These are the monitor channel faders for the console - 2 on each sub group output module.  There are 16 channel monitor mix faders.  I cannot seem to locate any suitable direct substitution.  P&G has 1k and 5k. And I think they are log audio, but not certain. So, I am wondering about how I could incorporate one of these into the design?

A&H Output Module Schematics:

http://www.flickr.com/photos/76115376@N08/6830065193/in/photostream/

 

[musika]

I should note that the second drawing shows the faders marked 2k2b in their respective boxes, labeled as 'Monitor' and 'Aux Monitor'.  I included the first drawing to show the 2004A amplifier ahead of the faders. 

Oh, and the board runs on 21V.

Hope this helps.

 

[musika]

added Allen & Heath MOD2 schematics.....

http://www.flickr.com/photos/76115376@N08/6830065193/in/photostream/

 

[MagnetoSound]

The value of these faders will be chosen in order to present a suitable source impedance to the pan circuit that follows, while placing an acceptable load on the preceding buffer stage.

1k will probably work. 5k will be a better load for the buffer, but will alter pan law slightly,  though you may not notice. Any higher is likely to have an adverse affect on pan law, so I wouldn't exceed 5k.

 

[musika]

Dan,

Thanks... I will be trying both the 1K and 5K absent the 2K2B fader.  I will look and see what value the pan pot is since it is not noted on the schematic.  Do you think this will matter?

Thanks again for the info!!

Dave 

 

[MagnetoSound]

I would expect to see dual 10k pan pots there.

If the pan pot is 10k you will be good with the 5k fader. 4k7 pan might work better with 1k, but check for distortion at the group output and and after the L/R summing amps.


EDIT: I meant the L/R monitor amps.

 

[musika]

The pan pots are dual 4K7 linear A.  So I guess I'll go with the 1K P&G fader as suggested. 

All that is marked on the old Radiohm faders is 2K2 so I'm not sure if it's a logarithmic or linear, but I saw a test somewhere to determine that with a simple Ohm meter watching the values change as you slide the fader up.

 

[MagnetoSound]

They will be log faders.

 

[musika]

Thanks Dan,  I guess the only thing left is to get that credit card out, buy these, and put them in.  The originals had seen their day.  They were only about 40 years old....  Ivor and Andy put together a pretty nice mixer back then.