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Thread: Guitar Multi-Fx Project Feasibility?

  1. #1
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    Guitar Multi-Fx Project Feasibility?

    I recently bought a teensy 3.6. I'd like to use it to make a multi-effect system for guitar, because I've never owned one that I've really liked. (I like the effects built-in to most line 6 products, but I don't like the interface so much.)

    Feature wise, I'm looking to be able to do mostly time-domain effects like reverb, delay, and chorusing, as well as parametric or graphic EQ. I'd like to be able to combine up to 6 effects at once, if possible.

    A massive bonus would be to able to use 2 audio boards at once so I can actually have a fx loop that I can run other effects through as well.

    Does that sound doable? I can't stand latency, so low-latency would be important too.

    I guess my main concern is if the hardware would be up to the task, or if I really need to go with a dedicated dsp solution instead.

    Thanks!

  2. #2
    Senior Member+ Frank B's Avatar
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    Quote Originally Posted by RebeccaBlue View Post
    Does that sound doable? I can't stand latency, so low-latency would be important too.
    What is "low-latency" - what would you accept ?

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    Quote Originally Posted by Frank B View Post
    What is "low-latency" - what would you accept ?
    I generally stand about 6 to 10 feet away from my guitar amp, so I'm guessing I wouldn't notice 10 milliseconds of latency.

    I'm also guessing that the latency would be less noticeable from the time-based effects if the output of the effects themselves were mixed with the inputs.

    It's the EQ-type effects that wouldn't work as well, because you typically want the entire signal to be effected.

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    You can do a lot on this one. Delay and chourus is not that demanding for the CPU. But a reverb will take some more power. Filters and compressors are also good. All in all you can make a lot of things.
    I rather prefer single effects with a good userinterface and cool features instead of having 5+ effects in one box with simple controls. But thats my taste...=)
    Latency is normally around 3-6ms

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    Thanks, omjanger, that's what I needed to know. :-)

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    Senior Member oddson's Avatar
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    I personally don't think the audio library is appropriate for in-series effects because that latency is cumulative.... 3 ms (128 sample block) is fine on its own... But I wouldn't want to chain too many together.

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    Senior Member PaulStoffregen's Avatar
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    Quote Originally Posted by oddson View Post
    ... for in-series effects because that latency is cumulative....
    Unless the objects do extra work to store data (like the delay object, or a filter with time response), or if you instantiate them in the wrong order (not in the order they will process the audio), chaining objects does NOT increase latency.

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    Quote Originally Posted by PaulStoffregen View Post
    Unless the objects do extra work to store data (like the delay object, or a filter with time response), or if you instantiate them in the wrong order (not in the order they will process the audio), chaining objects does NOT increase latency.
    Thats the beauty of it=)

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    Senior Member oddson's Avatar
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    Quote Originally Posted by PaulStoffregen View Post
    Unless the objects do extra work to store data (like the delay object, or a filter with time response), or if you instantiate them in the wrong order (not in the order they will process the audio), chaining objects does NOT increase latency.
    Paul ...my comment was to the suggestion above to make single-function effects as stand alone units and chain the together with audio cable the way guitarists like to do.

    Of course a multi effect Teensy, and even two chained the way OP originally suggested, is fine as the latency is minimal.

    I should have said "separate single-effect Teensys in series."
    Last edited by oddson; 12-06-2016 at 02:27 PM.

  10. #10
    Senior Member oddson's Avatar
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    I should say there are types of effects that would be fine even if chained together as separate Teensy units.

    Lots of effects, especially time effects, mix dry and wet signal together. If this is done in analog then latency isn't really cumulative in any way that matters.

  11. #11
    Senior Member PaulStoffregen's Avatar
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    Oh, yeah, if using a separate Teensy for each effect, then yes each can add 7ms or more latency.

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    I am currently developing multi-effects with the Teensy 3.2 and have had no problems.

    I should add that I use the Audio Board because when trying to use the Audio A/D with the Teensy directly leaves only one other analog input free.
    Last edited by mfratus2001; 12-17-2016 at 10:23 PM.

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