V1.01 SP (Steiner Parker?) Filter Board?

Setting up a Polivoks and I scrolled past it, only to find an SP filter after DLY. The added parameters are LP, BP, AP and Filter Feedback. Is there a Steiner Parker in the works and I missed the announcement? I know I’ve been neck deep in diapers, bottles and vomit, but I surely woulda seen this…

Tubeohm is working on this…

Ah. I remember reading something something SP for the ambika, or maybe that was a polivoks. Can’t keep up anymore. Too busing building and parenting I guess.

Polivoks was done by scannerboy

more info here

Ha, it’s pretty apprent now that having a newborn really screws up forum following. Thanks for the Infos. Got some readings ta do.

Having a newborn screws up almost everything. Then you get a bit of a break, followed by having a teenager screwing up almost everything again.

I actually did a lot of soldering late at night the first year my daughter was born… Suddenly there was al this time I had to fill up staying at home… I probably should have tried to sleep more though.

Just don’t solder while nursing a sleeping infant in your lap…even when using lead-free solder.

Hi, the Steiner Parker for Shruthi is ready,( schematics and prototype works) i must do only the PCB. But the Ambika controller comes first…
Next step is the SP filter for AMBIKA, not so hard but needs a little redesign.


Great, I’m in for a Shruthi filter! I’m going to put it into my Polivoks case, it’ll be a Steinervoks, or a Polyparker or something.

I’m interested in a SP filter as well.

I’ve liked the audio demos so far. I’ve been hoping that the next “special edition” Shruthi would be a Polivox, but an SP filter should tide me over.

Hi, SP is very special and also interesting. I have here a lot to do with the AMBIKA controller.
( fighting with the bits…). So sorry for the delay. But after 5 Month of solder i need to do other thinks like an AMBIKA controller.
The first Betas are out. I must only prog the stepper ready .
SP, here is the SP prototype, looks a little crazy , because of the 39 kHz PWM i must do some tricks like a 24 dB tschebyscheff filter in the input, distortion mode and so on…
HAha, hopefully i have enough space on the PCB…


Hey, its nearly done :wink:

If you need more than one 24 dB tschebyscheff filter, you may consider using the input tschebyscheff as the distortion tschebyscheff too. Mux the inputs together and route the output to the two locations simultaneously. It will add more osc distortion even on lower levels.

Hi, no, this cuts only the 39 kHz PWM and generates the audio signal. The SP filter works with 12…18 db and don’t cut the 39 KHZ complete , specially if it works in higher frequencies.
So it can be that, without the tschebyscheff , you get the 39 Khz direct on the output.
If you distort the tschebyschef, it clips only the Audio signal if the Oscillator had a higher outpot range…
Better is to have a controlled distortion…



I thought all the MI boards just use a simple RC filter on the signals from the Atmega?

I agree that a controlled distortion is better. I was suggesting using this doubling method to save space if you also needed a PWM filter for the distortion input as well. With the way you wrote the above description “24 dB tschebyscheff filter in the input, distortion mode and so on” it sounded like you needed more than one PWM filter. If you only need the one on the input, my suggestion is useless anyway. That is just something I have done to save space in the past - use the same passive filter twice with added distortion.

And learned something again :slight_smile: