I'm planning to build one of these, but with my own 1U panel. Yes, 1U.
It will have three pots, the mode switch, and three jacks per filter
section. No spread feature, though. I'm waiting for Ken's PC board to
become available again.
Richard Brewster
http://pugix.comScott Deyo wrote:
>
>
> Of course, I didn't think of that, so I asked Ken:
>
> "Pin 3 is not a summing node. You can feed a second signal into it via a
> second resistor. The two -CV will AVERAGE with each other, not sum. In
> other
> words, stuff will happen, and it will probably be good enough. The -CV
> won't
> be quite as sensitive as on the other unit, though it probably won't
> be that
> noticable. It will be in keeping with the general "roughness" of the
> module
> though, and that is part of its charm. "
>
> You'd think I'd learn to stop doing mods. At least it only effects one
> of the filters, and it's not a 1V/oct, precise filter anyway.
>
> Scott Deyo
> contact@... <mailto:contact@...>
> The Bridechamber
> www.bridechamber.com <http://www.bridechamber.com>
> Jealous Edison Record Kompany
> www.jealousedison.com <http://www.jealousedison.com>
>
>
>
>
> On Mar 17, 2010, at 8:38 PM, joshdaigleusa wrote:
>
>> I apologize if this is posted twice - I have a difficult time with
>> Yahoo groups sometimes and finding recent posts. Posting again
>> because it doesn't seem to have made it through.
>>
>> Ok, I'm building this now and am confused. I think Ken has his
>> schematic wrong for the CV section:
>>
>> http://www.cgs.synth.net/modules/pic/schem_cgs49_twf.gif
>> <http://www.cgs.synth.net/modules/pic/schem_cgs49_twf.gif>
>>
>> This schematic shows the CV "+" inputs summing into the non-inverting
>> input, pin 3, and the CV "-" input going into the inverting input,
>> pin 2. If you look at the traces on the board this is reversed: The
>> single "CV-" input goes to pin 3, the non-inverting input, and the
>> summed "+" CV inputs go to the inverting input, pin 2, with the 2K2
>> resistor in the negative feedback loop between the output and pin 2.
>>
>> So, correct me if I'm wrong, please, but I'm going to venture that
>> this mod will not work as suggested then, right, because we can't
>> throw another input onto the non-inverting input of the TL072, can
>> we? If, as suggested, I add a wire, through a 200K resistor, to the
>> intersection of the 100K input resistor for the CV- input and the 2K2
>> pull-down resistor, ultimately feed into into the non-inverting input
>> summed along with the "CV-" input, this won't work, will it? Am I
>> off? The way I've understood op-amps is to sum/mix multiple inputs
>> into an op-amp this has to happen via input resistors which sum into
>> the inverting input, with the non-inverting input tied to ground.
>>
>> So, does this mean we either have to sacrifice the CV Invert switch
>> or not have the spread functionality?
>>