Compatible Digi Pot IC Replacement for MCP42xxx

[leowatso]

Is there a Compatible Digi Pot IC Replacement for MCP42100 that will plug into the current IC mount sockets without having to do any rewiring for a different IC pin configuration? I'd like to replace them with an IC that has a higher impedance value like: 250k, 500k, 1M, or 2M.

Please advise me on this IC...I see that it has very high audio quality characteristics, but I am limited in my knowledge of IC design and implementation. Most everything I design is discrete for simplicity.

This is a VCA so I'm a little confused. :o
http://www.thatcorp.com/2181-series_Trimmable_Blackmer_IC_Voltage-Controlled_Amplifiers.shtml

Thanks,
Lance

[John]

Hi Lance,

The MPA is designed specifically for Microchip MCP42xxx digital pots, which only come in 10k, 50k, and 100k values. It's not possible to plug in a different type of digital potentiometer IC.

Depending on how you're using the potentiometers in your circuit, there are strategies for getting larger effective values by connecting the pots in series...

[leowatso]

Thanks John:)

Yes, I felt running them in series would to be a possible solution, but wanted to avoid having to deal with multiple CCs for one composite audio signal. (i.e. application PanPot: Left CC0 and CC1, Right CC2 and CC3).

Thanks again John, you've been a great help! :)

[John]

Thanks John:)

Yes, I felt running them in series would to be a possible solution, but wanted to avoid having to deal with multiple CCs for one composite audio signal. (i.e. application PanPot: Left CC0 and CC1, Right CC2 and CC3).

Thanks again John, you've been a great help! :)

You can assign the same CC to multiple output pots, if you want. ;) You could even configure all four to respond to the same CC...

[Psyfi]

Hi. I understand you can use multiple pots in series to create higher values of pot resistance but if you were needing to create a 1Mohm pot you would need many connect many in series just for the 1 pot.

Would it be possible to use one of the 5v logic outs to control another brand of digital pot IC and if so would it involve some reprogramming of the microcontroler? I was looking at these ICs
http://www.farnell.com/datasheets/60081.pdf
http://www.analog.com/static/imported-files/data_sheets/AD5222.pdf
One uses a serial input and the other a click input.

Would that be possible or would there be another more elegant solution to dealing with these larger values? useing the 100k digi pot to control a 1M digi pot?

[Psyfi]

Any thoughts on this?

[John]

Hi Psyfi, welcome. Sorry for the slow response.

Using a different variety of digital pot would definitely require some custom procedural microcontroller programming. If you really want to do this, it's probably best to undertake a from-scratch project.

I think there may be other approaches to getting a variable resistance from an analog value produce by the lower-value pot on the MPA, but I'm not sure what the typical approach would be. Perhaps another electronics forum will give you an answer for how to generate a "variable resistance from analog voltage".

Sorry for not having a better answer. If you find something out, please let us know.

Hi. I understand you can use multiple pots in series to create higher values of pot resistance but if you were needing to create a 1Mohm pot you would need many connect many in series just for the 1 pot.

Would it be possible to use one of the 5v logic outs to control another brand of digital pot IC and if so would it involve some reprogramming of the microcontroler? I was looking at these ICs
http://www.farnell.com/datasheets/60081.pdf
http://www.analog.com/static/imported-files/data_sheets/AD5222.pdf
One uses a serial input and the other a click input.

Would that be possible or would there be another more elegant solution to dealing with these larger values? useing the 100k digi pot to control a 1M digi pot?

[Jim McDougall]

It would be helpfull if you could post the circuit segment where the 1M pot is used. If it is directly in the audio path, a VCA might well be a viable solution

[Jim McDougall]

V+ through the MPA digital pot gives you a control voltage to drive the VCA

[Psyfi]

Thanks for the reply guys. VCA approaches had sprung to mind but hadn't looked in to the exact application of it. Was hoping any digi pot that uses a serial input like the MCP42xxx digital pots might work :( The pot in question is the decay pot of a TB-303 details on page 5 of the service notes. http://www.dinsync.info/2010/02/roland-tb-303-service-manual.html

All other values are 50k 'apart from the devil fish mods' so a few MPA's would do the trick, its just this one pot holding me back.