[sdiy] Help deducing the internal resistor values of the IR3109?

[Jack Jackson]

I built up half of the IR3109 schematic using 470ohms for the internal resistors. It made a pretty tasty filter and sounded very much like IR3109. I used the external capacitor and resistor values from the Jupiter 8 schematic. Unsurprisingly I implemented it with a LM13700 for the gain cells, TL072 for the two buffers instead of the 13700s internal buffers, and used the standard Thomas Henry current source expo converter made with another TL072

Here it is:
https://soundcloud.com/dot/ir3109-12db-ota-build

Compare to my recording of the real IR3109:
https://soundcloud.com/dot/ir3109-jupiter-filter-made



> From: jackdamery at hotmail.co.uk
> To: synth-diy at dropmix.xs4all.nl
> Date: Mon, 7 Oct 2013 12:28:40 +0100
> Subject: Re: [sdiy] Help deducing the internal resistor values of the IR3109?
> 
> Yes, that's correct. Where did you get the 560 Ohm figure? I realise my tests were perhaps invalid because I forgot to apply a voltage to the CV. Will try again tonight.
> 
> Jack
> 
> 
>> Date: Sun, 6 Oct 2013 17:40:46 -0600
>> From: sounddoctorin at imt.net
>> To: jackdamery at hotmail.co.uk
>> Subject: Re: [sdiy] Help deducing the internal resistor values of the IR3109?
>> 
>> Did I understand correct that you want the value of the resistance 
>> hooked from non-invert of the OTA's in the IR3109 to ground? 560 ohm is 
>> the value I believe. Not sure if you saw my post
>> 
>> 
>> -- 
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