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Application circuit for SSM2018T arranged as dual output VCA's?

Question asked by Davis65 on Sep 24, 2012
Latest reply on Oct 15, 2012 by ColemanR

I have been using thousands of Analog Devices SSM2018T, since 1999, in guitar pedals I manufacture. I feed the guitar signal into an OP Amp designed as a pre-amp, before it enters the SSM2018T, VCA, at pins 6 and 7.  I use the "Typical Application Circuit" from page 3 of the Analog Devices Data Sheets. The "Typical Application Circuit" from page 3 only shows one output--who's connections are Vout, (coming from pins 3 and 14) and V-, (coming from pins 16 and 10).  On the first page of Analog Devices SSM2018T Data Sheets there is a picture of the Functional Block Diagram.  This Functional Block Diagram shows two outputs. My questions are as follows; I would like to see an Application Circuit using these two outputs?  Will both of these outputs act as a VCA, as in the Typical Application Circuit with one output?  In  the SSM2018T Detailed Functional Diagram on page 9 of Analog Devices SSM2018 Data Sheets, A3 appears to be an internal OP Amp. The "Typical Application Circuit" from page 3 shows an 18K resistor from pin 14 to pin 3.  Is this like the feedback loop of an non-inverting OP Amp, where you can increase, or decrease the resistor between pins 14 and 3?  When I try to change the value of the 18K seems to me I have had negative audio results, I wonder why?  Should I be able to alter the gain of A3 by resistance between pins 14 and 3, or should it always be 18K?  If hooked up as a dual output VCA-- as it appears by the Functional Black Diagram on page 1 of the data sheets, A4 appears to be the other output.  If that is the case, what resistance value would go between pins 4 and 16---(if)--that resistance is acting like a feedback loop in A4?  From the data sheet diagram on page 9, logic tells me A3 and A4 are two VCA controlled outputs, is that correct? I may be wrong, but it appears to me both A3 and A4 gains can be, "individually", increased or decreased by resistors in the feedback loop.  Is this correct?  Again, I would like to see an application circuit as the Functional Block Diagram on page one of the data sheets with two VCA outputs? Would the two outputs make this stereo since the feedback loop gains could be controlled individually?

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