http://www.futurlec.com/Others/PT2253A.shtml
http://www.futurlec.com/Others/PT2258.shtml
PT2253 looks a lot like the TC9170 used in Marshall's JMP-1. I wonder if they have similar to the TC9176 used in the EQ which is W-taper (S-curve).
this is one of the few digital 'pot's I've come accross that actually provided some means of reading what position the wiper is at ...
How do these chips work?
looking the PT2253A datasheet, looks like they convert to digital bits through a resistor network, do the binary shifts, and then back to analog.
how does it perform, for guitar effect, preamp, etc applications? noise issues, aliasing?...
For the PT2258 it doesnt specify the internals, but looks like a 6 channel version of the former.
Quote from: cpm on April 18, 2011, 12:16:23 PM
How do these chips work?
looking the PT2253A datasheet, looks like they convert to digital bits through a resistor network, do the binary shifts, and then back to analog.
how does it perform, for guitar effect, preamp, etc applications? noise issues, aliasing?...
For the PT2258 it doesnt specify the internals, but looks like a 6 channel version of the former.
There si no AD conversion. Signal remains analog all the way through. It receives a set of pulses (clock + up/down), and sets the attenuation accordingly, plus you can read where the attenuation is with the DCO.
Quote from: potul on April 18, 2011, 12:30:31 PM
There si no AD conversion. Signal remains analog all the way through. It receives a set of pulses (clock + up/down), and sets the attenuation accordingly, plus you can read where the attenuation is with the DCO.
you're right
it has two sections of attenuation resisitors, each with an analog switch for selecting each step.
I have looked at the diagram the wrong way...
looks interesting, and cheap compared to other digital potentiometers for this kind of application.
i am buying one to test it out
gracias!
Could you use this in a feedback loop for a VCA?
Quote from: Hides-His-Eyes on April 18, 2011, 01:35:59 PM
Could you use this in a feedback loop for a VCA?
Since the attenuation is stepped in 2db steps, I would expect you'd get some zipper noise if trying to use it for compression or similar real-time gain control.
Quote from: Taylor on April 18, 2011, 04:36:06 PM
Quote from: Hides-His-Eyes on April 18, 2011, 01:35:59 PM
Could you use this in a feedback loop for a VCA?
Since the attenuation is stepped in 2db steps, I would expect you'd get some zipper noise if trying to use it for compression or similar real-time gain control.
That could be cool. All you need is a 16-bit serial out ADC and some other stuff.
As soon as I typed that, I thought, this seems like an earthtonesaudio kind of circuit. Do it naaoow!!!
Quantised tremolo?
Step filter?
;)
The 2 channel chip looks like the TC9176 (now obsolete and hard to find in retail) used in Marshall JMP-1.