[sdiy] SSM2164 Phaser - another way?

[David G Dixon]

>From my understanding, the 2164 likes up to 20V peak-to-peak input signals
without clipping.  My understanding was that the 2164 would start to clip
with input currents above about 330 uA.  That's the number I design all my
2164 circuits around.

> -----Original Message-----
> From: Donald Tillman [mailto:don at till.com] 
> Sent: Thursday, February 20, 2014 4:02 PM
> To: Neil Johnson
> Cc: David G Dixon; Mattias Rickardsson; synthdiy diy
> Subject: Re: [sdiy] SSM2164 Phaser - another way?
> 
> 
> On Feb 20, 2014, at 5:29 AM, Neil Johnson 
> <neil.johnson71 at gmail.com> wrote:
> 
> > David G Dixon  wrote:
> >> The 2164 does develop a measureable voltage on its input terminals 
> >> when the gain is increased (I've measured it).  It is not 
> large, but 
> >> will create some error if the design absolutely depends on 
> that voltage being exactly zero.
> > 
> > Which is probably most designs using a fixed resistor for 
> the V-to-I 
> > conversion.  This voltage will cause distortion since the simple 
> > linear relationship between Vin and Iin no longer holds.
> 
> I don't understand what you're saying here.
> 
> 
> > Looking at
> > the shape of the THD_N vs Amplitude curve (irrespective of the 
> > horizontal axis *doh*) you can see the very definite break-point at 
> > the far right at which point distortion shoots up at an 
> alarming rate.
> 
> (Perhaps the horizontal axis should have been labeled 
> "mVrms".  That would be close to consistent with the clipping 
> spec on page 2.)
> 
> This curve looks very much like a typical example of simple 
> clipping.  I wouldn't call it "alarming".
> 
> 
> > I suspect that for many synthesizer modules, where signal 
> levels are 
> > higher than the nominal 775mV used in the datasheet, few designs 
> > attenuate the input to keep the input current within the sweetspot.
> 
> Really?  Why would a piece of musical equipment would *not* 
> be designed for the sweet spot?
> 
>   -- Don
> --
> Don Tillman
> Palo Alto, California
> don at till.com
> http://www.till.com
> 650 888-9632
> 
> 
> 
> 
> 
>