Buffered Audio Inputs/Outputs

[AsyncResonance]

Reading up on the voltage requirements for the ElkPi hat, especially the warnings on CV IO ranges, I was curious if there was anything that the hardware design team wanted to comment on in terms of IO buffers.

Does the hat design include ample buffering such that we could use simple voltage dividers/amps to change voltages when necessary, or should best practice include a buffer amp either at unity or gain?

[Stefano]

Hi @AsyncResonance,
apologies for the slow response in this.

I’m reporting here the information about this (I’m not a HW guy):

the CV input channels have an Input impedance of 122 kOhm, and the input voltage range goes from -5 to +5V. If you exceed the voltage the input opamp will clamp it, but you would put the opamp in a stress condition, so please stick with ±5V. Output Impedance of CV output is 47 Ohm and the range is 0-10V. You don’t need any buffer for basic CV, or for voltage dividers you can treat it as a non-ideal voltage source with an impedance of 47 Ohm. the output opamp will be able to drive loads down to 500-1000 ohm (or even lower depending on how many pins you are using). if you need to pull more current an extra buffer opamp wouldn’t hurt of course, but not required.

Hope this helps.

[AsyncResonance]

Hi @Stefano -no worries. I’d perused that section of the documentation as well, but was curious if folks who’d done actual implementation had any observations.

I’m at the spreadsheet design portion of this exercise - I’m looking at both Serge and Eurorack-ish options for IO so voltage dividers and low-gain op-amp designs, and panel work it is. Thanks!