Modular Synth Panels

I've got a couple newbie questions for the group (standard disclaimer: I have no EE experience, I'm learning slowly as I build this stuff).

I've got a couple MFOS ADSR's that are waiting to be mounted behind their bridechamber panels, however I have two questions that need answered before I start the wiring.....

1) Regarding the long/short adsr option - determined by switching (SW2) "TSW" between ground or not. When TSW is grounded, are the ADSR times long or short?? I guess I could figure this out after I wire it up, however I'm debating on whether I want to use the extra hole on the panel for a adsr time switch or a manual gate...

2) I purchased the CGS04 DC Mixers so I could invert the output of the ADSR. How do I implement this? I understand that the TL072 is a dual opamp, and in the CGS04 the first opamp in the TL072 inverts the input signal (makes it negative) and then inverts the signal again (making it positive) with the second opamp. How can I safely skip one of the opamps so I can use the inverted signal on my panel? Or, do I use both opamps? I see three possible methods, however I don't know which one is right.
2.1) Can I take the inputs and take them directly (after their 100k resistors) to pin 6 of the TL072 and leave the rest of the circuit as is?
2.2) Can I skip the 100k resistor between the two opamps, taking the signal from pin 1 to the 1k resistor, and then take the signal from the resistor directly to the output (skipping the 100k resistor in the ?feedback loop? of opamp2)?
2.3) Use both opamps as the circuit diagram shows, however use the additional circuitry in Red. << I have absolutely no idea what this stuff is doing. Also, as I won't be using pots on this circuit, I don't know what I'll be connecting to points B & C.......

Here are the URL's for reference
MFOS ADSR:
http://www.musicfromouterspace.com/analogsynth/ADSR001/ADSR001.html

CGS04 DC Mixer:
http://www.cgs.synth.net/modules/cgs04_mix.html

Any help is greatly appreciated,
Jim


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>
> 1) Regarding the long/short adsr option - determined by switching
> (SW2) "TSW" between ground or not. When TSW is grounded, are the ADSR
> times long or short?? I guess I could figure this out after I wire it
> up, however I'm debating on whether I want to use the extra hole on
> the panel for a adsr time switch or a manual gate...

The larger the cap, the larger the time. When caps are wired in
parallel, their values are added together. So, grounding that switch is
for "long" time.

>
> 2) I purchased the CGS04 DC Mixers so I could invert the output of
> the ADSR. How do I implement this? I understand that the TL072 is a
> dual opamp, and in the CGS04 the first opamp in the TL072 inverts the
> input signal (makes it negative) and then inverts the signal again
> (making it positive) with the second opamp. How can I safely skip one
> of the opamps so I can use the inverted signal on my panel? Or, do I
> use both opamps? I see three possible methods, however I don't know
> which one is right.
> 2.1) Can I take the inputs and take them directly (after their 100k
> resistors) to pin 6 of the TL072 and leave the rest of the circuit as
> is?
> 2.2) Can I skip the 100k resistor between the two opamps, taking the
> signal from pin 1 to the 1k resistor, and then take the signal from
> the resistor directly to the output (skipping the 100k resistor in the
> ?feedback loop? of opamp2)?
> 2.3) Use both opamps as the circuit diagram shows, however use the
> additional circuitry in Red. << I have absolutely no idea what this
> stuff is doing. Also, as I won't be using pots on this circuit, I
> don't know what I'll be connecting to points B & C.......

A Bridechamber Inverter PCB would work best : )
It was pretty much designed for this application. And Ken designed it!

>
> Here are the URL's for reference
> MFOS ADSR:
> http://www.musicfromouterspace.com/analogsynth/ADSR001/ADSR001.html
>
> CGS04 DC Mixer:
> http://www.cgs.synth.net/modules/cgs04_mix.html
>
> Any help is greatly appreciated,
> Jim
>
> __________________________________________________________
> Be a better friend, newshound, and
> know-it-all with Yahoo! Mobile. Try it now.
> http://mobile.yahoo.com/;_ylt=Ahu06i62sR8HDtDypao8Wcj9tAcJ
>
>

On 5/9/08, James Elliott put forth:

>I've got a couple newbie questions for the group (standard
>disclaimer: I have no EE experience, I'm learning slowly as I build
>this stuff).

I would recommend taking some time to study an op-amp primer:

http://www.national.com/an/AN/AN-20.pdf

If you do a web search, you will find several others. There are also
virtual labs on several manufacturers' websites that allow you to
plug in different values and see what happens, such as this one:

http://designtools.analog.com/dtAPETWeb/dtAPETMain.aspx?part=OP275#RunAnchor


While all sorts of complicated things can be built using op-amps, by
learning two basic circuits -- the inverting amplifier, and the
non-inverting amplifier -- you will be able to answer all of your
mixer/inverter questions.