[sdiy] nice Digi Pot

sleepy_dog at gmx.de sleepy_dog at gmx.de
Mon Jun 27 21:21:28 CEST 2016


"No zipper noise?"

Oh, I only used that on prototype boards, and yeah it had some noise there.
I hadn't thought about that coming from the switching, I assumed it was 
SPI and my "wild wire" board and that a proper PCB layout may cure that.
Also I personally don't care that much at least for the simple synth 
designs where I don't modulate resonance, so the noise would be only 
there on setup, not playing, and since it's not commercial and does not 
need to seem super polished, oh well ;-)

So I guess that reduces the use of that for some people, unless such 
noise can be alleviated with some external circuitry.

Steve

Am 27.06.2016 um 20:50 schrieb Vinicius Brazil:
> Hi Steve,
>
> No zipper noise?
>
> On Mon, Jun 27, 2016 at 2:06 PM, <sleepy_dog at gmx.de 
> <mailto:sleepy_dog at gmx.de>> wrote:
>
>
>     Reading the thread "non-mechanical switching solutions",
>     I just remembered a nice series of digital potentiometers which I
>     discovered some months ago,
>     which are SDIY friendly ( for those not afraid of TSSOP ;) ), as they
>     - support +/- 18V dual rails
>     - digital voltage: 2.7 ... 5.5V (or even 1.8V)
>     - cost less than 2 bucks
>
>     I have used, as an experiment, digi pots in some VCFs to easily
>     control resonance from an MCU, but before I found those here, I
>     only knew similar products in a price range of 8...12 US$ or
>     something like that.
>
>     So I just thought, I'll throw that in here, maybe someone else
>     also only knew the expensive ones.
>
>     MCP41HVx1 series, where
>     http://www.tme.eu/de/details/mcp41hv31-503e_st/digitalpotentiometer/microchip-technology/
>
>     available in 5k, 10k, 50k, 100k
>
>     datasheet
>     http://www.tme.eu/de/Document/8b361619149495099964ddab197bebfe/mcp41xvx1.pdf
>
>
>     regards,
>     Steve
>
>
>     Am 27.06.2016 um 16:27 schrieb Vladimir Pantelic:
>
>         On 27.06.2016 16 <tel:27.06.2016%2016>:15, Pete Hartman wrote:
>
>             First thought: CD4052, but that doesn't work well in
>             practice at all.
>
>             Second thought: DG409, better characteristics, but that
>             still doesn't
>             work sufficiently well.
>
>             Dig around a while for why.... aha, the on resistance for
>             both is
>             significant, especially for the capacitive stages of a
>             ladder filter.
>             The DG409 has on the order of 100R - 120R.  Too much, and
>             confirmed to
>             be the issue by comparing physical connections with wire
>             to physical
>             connections with 100R resistors.
>
>         ADG1414, R_on = 9.5R and 8 switches inside one package - but
>         needs SPI
>         so you need to add a 50¢ uC to control it
>
>
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