From: tmoravan@netcom.com (Tom Moravansky) Subject: Roland IR3109 Date: Thu, 24 Aug 1995 05:43:29 -0700 (PDT) As one of my last posts here, I thought I'd toss up some data I found on the IR3109 filter chip. Someone was asking before if there was any application notes for this chip. Well, the only thing I've found was a picture and some short information in a Juno-6 service manual. There's a nice picture of the chip with the pins labelled: 1 - Ground 2 - In 1 3 - Cap 1 4 - Out 1 5 - In 2 6 - Cap 2 7 - Out 2 8 - -V ee (substrate) 9 - V cont 10 - In 3 11 - Cap 3 12 - Out 3 13 - In 4 14 - Cap 4 15 - Out 4 16 - +V cc "The IR3109 contains four variable transconductance amplifiers designed for VCF applications in electronic musical instruments. The device is equipped with four high input impedence buffers, and anti-log circuitry (V-in to I-out) which controls conductances of four amps." - wide transconductance vaiable range (1 - 10 micro{upside-down Ohm symbol}) - low input offset voltage (less than +- 3mV) (transconductance amplifier) - high input impedance. MOS P-Channel (buffer) There are 4 sets of the following configuration: Note that there is only 1 function generator per chip - it drives all four sets - |\ G n |\ B n In n ------------------| \ | \ | \_______| \__________ Out n Exponential + | / | | / Function ----/\/\/-----| / | | / Generator |/ | |/ | Cap n -- _______________________________________________________________________________ Tom Moravansky tmoravan@netcom.com ambulation From jdm@synthcom.com Fri Feb 16 13:25:08 1996 16 Feb 96 16:25:04 +0500 16 Feb 96 16:22:57 +0500 Date: Fri, 16 Feb 1996 12:17:59 +0000 () From: "J.D. McEachin" Cc: analogue@hyperreal.com Subject: Re: Roland IR3109 Filter Chip On Fri, 16 Feb 1996, Mattachine wrote: > Hello, > Spring is almost here and I'm comming out of my winter depression, that > means back to working on my project!... I'm currently building a LARGE > modular system, and I've just ripped apart my old MC202 (don't cry, it was > badly damaged in a fire!) The filter chip is marked as Roland IR3109, any > clues to what it *really* is 24, 18, 12 dB or what? It has 4 transconductance gain stages. Therefore, you can wire it up for 6, 12, 18, or 24 dB response, depending on your preference, and how many gain stages you want to waste. If you want to get really clever, you could adapt the multimode filter switching circuit from the Xpander SM to make a 15 mode Roland filter. JDM From mdma@primenet.com Sat Feb 17 16:56:06 1996 17 Feb 96 19:56:01 +0500 16 Feb 96 23:41:39 +0500 Date: Fri, 16 Feb 1996 21:20:38 -0700 (MST) From: Adam Muntner Cc: analogue@hyperreal.com Subject: Re: Roland IR3109 Filter Chip > > Is it 24 by default in the 202? My 202 sounds VERY different than my 101... > > Any way for me to turn it into an 18 and keep it IN the 202? :)_ > > Don't be fooled into thinking that any ol' 3 pole/18 dB rolloff filter is > going to sound like a 303. There's more to a filter than the # of poles > - there's also the matter of where those poles are located, which is what > determines whether or not the filter oscillates when you crank up the res > (the 303 filter doesn't). Besides, I think the 303 filter is SUPPOSED to > be a 4 pole filter, and it's rolloff is only 18dB at certain frequencies, > probably due to the chee-ziness of the design. > Well, I dont want it to sound like a 303, and I dont want it to sound like any other 202. I still want to change the 202's filter, and my 101 too while im at it. Im convinced the 101 and 202 filters are configured differently.... and I want to be able to reconfigure them myself!