Feedback potentiometers

MIDIbox SID
1

Hi,

I’m about to start the frontpanel design for a 19 inches rack version of MB6582 and was wondering the following :

Is it any space left in patch structure and DOUT left to use digital potentiometers so that feedback could be driven by the frontpanel encoders and their values could be saved in the patch structure ?

MikePig

2

I’ve found these pots

http://www.maplin.co.uk/Module.aspx?ModuleNo=2207#features

which are available in 470k linear, but I don’t know if they’re physically the right size. Apparently, they require a 10.5mm hole. So, I wonder if someone could tell me the size of the holes for the feedback pots on Wilba’s MB6582 rear panel? I’m at work at the moment, and don’t have access to a PC that I can run Frontpanel Designer on, unfortunately.

a|x

3

Don’t worry- I popped home at lunchtime and measured the panel hole as 7.5mm, so those Maplin ones are too big.

a|x

4

It’s quite ironic that here in Australia I needed to import practically everything to build the prototype MB-6582, but the feedback pots were found in the local electronic store. :)  (No, I am not running a bulk order on feedback pots).

You should be looking for ones with 16mm diameter housing:

If the shaft is too long, that’s fixable, as is cutting the pins to make it fit over the audio sockets… but obviously that threaded bushing needs to fit the panel hole, and the housings must be small enough so they fit next to each other.

I’m not apologizing for anything  :P  but these feedback pots were a last-minute design addition that I put in just because I could… I have no idea why these are harder to find than the bigger ones, or why they bother making the bigger ones at all…

5

Hi,

Sorry I think I misexplained myself :

I was thinking about digital potentiometer (IC) that are controlled by the software.

The IC replaces the mechanical potentiometer and is controlled by rotary encoder.

So the feedback value would be stored into the patch structure.

Regards

MikePig

6

Can be done, but involves quite a bit of asm coding.

7

If you write a digipot driver, it should be implemented as another type of AOUT module.

Then you can use the patch structure’s existing stuff space, and you’re in business. So, no need for any mods to MB6582, just write a digipot driver.