Hi,

I've had on the forum to find similar problems and although they exist I've struggled to implement what posts have suggested. This is mostly because i am new to Pure Data and finding it hard to understand the language used and the help and tutorials don't seem to help much either.

I'm looking to produce a script that will take a single tone (with frequency variability) and split it into two channels, one of which will allow variation of the amplitude and phase. These two signals then need to be outputed to my audio interface which will allow two channel output.

The variations in phase and amplitude need to occur in realtime which is why i've been guided towards using pure data, otherwise i would have done it in MatLab. An easy to use GUI is needed for test subjects to use but i need to also be able to record the values for phase and amplitude though.

I greatly appreciate any help you can give for any parts of this problem.

Thanks

so you want to take the output from your tone wherever that is, take one signal into a *~ and a phase shifter (which could be accomplished by writing and reading to a variable delay line (delread~ and vd~) or another filter allpass maybe. make a dac~ and then take another cord from the outlet of your tone and plug it in to one of the inlets. take the output from the phase shifter and *~ into the other inlet and they will be sent to your audio interface

Hi, thanks for the reply.

I should have been more clear that the tone would be generated from pure data too rather than from a separate device or program.

Although a delay is a way of producing a phase shift it makes calculating the phase more difficult when i will be switching to different frequencies. Is it possible to phase shift from the signal directly rather than introducing a delay line?

Also how do you map the dac channels to audio devices?

[phasor~]
|
[cos~]

outputs a (co)sine wave

any constant number added to the phasor~ output will change the phase of that sine wave.

so,

[phasor~]
|
[+~0.25]
|
[cos~]

will be 90 degrees out of phase with that original wave.

[phasor~]
|
[+~ 0.5]
|
[cos~]

will be 180 degrees out of phase,

etc...

to vary the amplitude, just use [*~]

*** note: you should use a single phasor~ and split the output signal, like this:

[phasor~]
|\
| [+~ 0.5]
| |
| [cos~]
|
[cos~]

...that will ensure that both your waves keep the same phase relationship.

thanks that's really helpful. The scripts now working and I've tried a few tests.

I've found that i need an extra output channel though so the test will work more effectively, however my audio interface only does 2 channel rather than two stereo which i thought it would do to begin with.

Is it possible to use both the laptop's audio output as well as the audio interface?

I looked through the audio device menu and it gives the option of using multiple devices for audio out but when i come to selecting the number of channels for each device it gives me an warning or error saying,
"separate audio device choice not supported\; using sequential devices."
Does it not allow me to or am i setting it up wrong?

Thanks