Hardware questions

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Hi,

I'm doing a pcb for a Teensy 3.5 eurorack module project and I have some questions about hardware.

I plan to have many potentiometers (18), is it better to use a multiplexer or using 18 analog pins is fine ?

Are these schematics right ?

Screenshot 2020-04-18 at 12.21.31.png

Thanks for your responses :)
 
hi @xtreemechill

I'm no expert but a few points just from my experience with pots and audio effects:
- are you using the audioboard as part of your design, if so remember that will take out a few analogue pins
- same for the DACs if you are planning on using them
- is this a one off, if it is and you are ok soldering onto the bottom of the Teensy there are a few extra analogue pins
- what accuracy are you aiming for - I've never needed and external reference board but you may need more accuracy that I've needed
- I've used 10 pots directly onto the teensy (no ref voltage, no multiplexer) with no problems at the same time as running effects and lights etc. 10 wasn't a limit it was just all I needed

cheers, Paul
 
Yes, but use quality encoders. The cheaper ones tend to bounce a lot, so the repeatability takes time and they have to be turned left-right again and again to get the right value...
Or be prepared to add a debouncing technique if necessary...
All in all, some pots might be easier to use. That depends on the accuracy you need.

You can't use the ADC for Audio if you use pots.
 
The problem I've had with encoders for audio effects/applications is the lack of resolution with a single turn - with 24 pulses per revolution you need to turn the knob 10 times to get 8 even bit resolution (256 steps).

My experience is they're good for menu selection and things like that but prefer a pot if trying to adjust frequencies or other audio parameters where you want to cover a large range in a single turn with some accuracy.

If you could get a small and cheap 512 or 1024 step encoder that would be ideal but haven't found any of them.
 
The problem I've had with encoders for audio effects/applications is the lack of resolution with a single turn - with 24 pulses per revolution you need to turn the knob 10 times to get 8 even bit resolution (256 steps).

My experience is they're good for menu selection and things like that but prefer a pot if trying to adjust frequencies or other audio parameters where you want to cover a large range in a single turn with some accuracy.

If you could get a small and cheap 512 or 1024 step encoder that would be ideal but haven't found any of them.
Audio settings are rarely linear. Especially the volume.
Normally logarithmic curves are often used.
 
prefer a pot if trying to adjust frequencies or other audio parameters where you want to cover a large range in a single turn with some accuracy.
I find that the apparent setting hysteresis, drift, and lack of repeatability inherent in using pots outweighs other considerations. But, YMMV.
 
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