[sdiy] 13700 VCA Noise Issue

[Tim Ressel]

Is there a handy schematic for a 2164 based cross fader?

--tr


On 5/17/2017 4:44 PM, David G Dixon wrote:
> Did you remember to use a fairly large voltage divider on the inputs?  The
> input signal to an OTA should only be a few tens of millivolts (unless you
> use the linearizing diodes, which I never did).  I think those dividers
> generate a fair bit of noise.
>
> I stopped using OTAs years ago, once I discovered the beauties of the 2164
> VCA, so you know my advice....
>
>   
>
>> -----Original Message-----
>> From: Synth-diy [mailto:synth-diy-bounces at synth-diy.org] On
>> Behalf Of Tim Ressel
>> Sent: Wednesday, May 17, 2017 1:13 PM
>> To: *SYNTH DIY
>> Subject: [sdiy] 13700 VCA Noise Issue
>>
>> Hi,
>>
>> So I did a design with a pair of 13700 VCAs in series and I
>> am getting a lot of white noise on the output. With the first
>> VCA closed and the second wide open I get 100-200mV of noise.
>> I made a png; where do we share these again?
>>
>> Does anyone have experience with 13700 and noise?
>>
>> Here's a wonk question: if I use an opamp as a transimpedance
>> amp (oh Ghod I hope I'm using the right term) on the output
>> of the 13700 to convert current to voltage, how do I
>> determine the amp's input current noise contribution to the
>> output noise? Assuming it does contribute. Or would it be
>> better to do a resistor to ground and have the amp be a non
>> inverting buffer?
>>
>> Thanks!
>>
>>
>> --
>> --Tim Ressel
>> Circuit Abbey
>> timr at circuitabbey.com
>>
>> _______________________________________________
>> Synth-diy mailing list
>> Synth-diy at synth-diy.org
>> http://synth-diy.org/mailman/listinfo/synth-diy
> _______________________________________________
> Synth-diy mailing list
> Synth-diy at synth-diy.org
> http://synth-diy.org/mailman/listinfo/synth-diy
>

-- 
--Tim Ressel
Circuit Abbey
timr at circuitabbey.com