So i recently got a Choices Rev. 2 and am currently getting to know it. I had the idea to use the Choices to manually crossfade between 2 audio sources.flight wrote: The signal chain goes as follows:
[*]Input jack to the joystick pot (which is connected as an attenuator),
[*]from the joystick pot to the inverting input of an operational amplifier (opamp),
[*]the Scale pot is the feedback resistor that controls the gain of the opamp (0x-2x),
[*]from the output of the opamp to the inverting input of another opamp (inversion + inversion = no inversion),
[*]the Bias pot applies voltage to the output amplifier to shift the DC level of the signal,
[*]from the output opamp to the output jack.
So, I put the switches to AC and plugged 2 different audio rate waveforms into the inputs. I plugged the Choices outputs into a mixer and I am monitoring the audio output of the mixer. For clarity's sake, before going through the Choices, I first patched the oscillators output directly into the mixer and level-matched them.
My expectation would be that if I set the scale of both the Choices channels to zero, i would get silence at any given position of the joystick, but his is not the case. With scale set to zero, I find that I always have sound in any position. Moving the joystick around does change the relative levels of the 2 inputs.
With Scale turned up, I would expect the far sides of the X and Y to give me full level of one signal (with a maximum level as set by that channel's scale knob of course) and kill the other signal entirely. But, the far sides of both the X and Y axis always still contain some leakage of the other oscillator, although not much it is clearly audible. Does this latter 'issue' (?) have something to do with the bias (or other) calibration? Or is this simply because it is nearly impossible to perfectly set X=100 and Y=neutral/central (and vice versa)?
I did another test, this time with a Maths LFO patched into the left channel (I have Choices mounted with the jacks in the top, to be clear). I left the switches in the AC position of course. The output of the left Choices channel carrying the LFO is patched to 1V/oct input of an osc.
The X-axis doesnt do anything (makes sense because nothing patched in or out). With the joystick in the top position, the Y-axis seems to give me the full, un-attenuated LFO signal to the osc pitch. The bottom position of the Y-axis gives me an attenuated modulation. What I don't understand is that this happens with scaling set to neutral. I'm already lost there... Furthermore, I would expect that with scaling set to full (either = or -), I would get full un-attenuated modulation in the top of the Y-axis, and no modulation whatsoever when the joystick is at the bottom of the Y-axis.
I must say, much like the guy who started this topic viewtopic.php?p=2152756#2152756
, I also find that the manual doesnt exactly describe the relationships between the ins, joystick axis, scaling and what to expect at the output. Some more in-depth explanation would be very useful.