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  • MikeDB's Avatar
    11-17-2019, 12:54 PM
    If you're a beginner it's always best to build someone else's design first. Google for existing projects such as https://www.pjrc.com/polymod-polyphonic-digital-modular-synth/...
    9 replies | 352 view(s)
  • MikeDB's Avatar
    10-31-2019, 11:27 PM
    You do indeed cross mix reverbs. You often also use anti-phase additions to give the reverb extra width.
    3 replies | 180 view(s)
  • MikeDB's Avatar
    10-11-2019, 04:36 AM
    You don't state what bandwidth you need between each node, but if not too high one possibility would be to make a mesh of Teensy4.0s using the I2S ports, with IN1, OUT1A, OUT1C, OUT1D, IN2 and OUT2 reprogrammed as...
    8 replies | 387 view(s)
  • MikeDB's Avatar
    09-29-2019, 03:55 PM
    Rather than using a single FFT, you might like to consider using the lower portions of multiple FFTs. The low frequencies would be based on possibly the last one second of audio input, but for higher frequencies you...
    77 replies | 11872 view(s)
  • MikeDB's Avatar
    09-28-2019, 10:05 PM
    Sorry - I only use the Teensys as I/O processors.
    29 replies | 1541 view(s)
  • MikeDB's Avatar
    09-28-2019, 09:00 PM
    I totally agree - getting the maths right is far more important than optimising the odd instruction out of the code. And when I want autotune, I start with wavelets, not short FFTs as selecting the correct algorithm...
    29 replies | 1541 view(s)
  • MikeDB's Avatar
    09-28-2019, 01:29 PM
    Yes I was assuming filtering before you get to the NE5532s. They are there as output drivers.
    5 replies | 149 view(s)
  • MikeDB's Avatar
    09-27-2019, 10:12 PM
    I think most things are at least 64 bit integer internally nowadays - ARM 64 bit processors are so cheap that using anything else is silly. Some use 80 bit floating point, most notably PC based apps.
    6 replies | 150 view(s)
  • MikeDB's Avatar
    09-27-2019, 10:03 PM
    Figure 1 in the link Sin-Phi gave is fine, only use NE5532s and the correct value of output resistors (300 Ohm?) for your application.
    5 replies | 149 view(s)
  • MikeDB's Avatar
    09-27-2019, 09:48 PM
    There's only one good way for polysynths - a 32 bit DAC and run the signals at about 24 bits which still gives a good signal to noise ratio. Yes I realise 32 bit DACs aren't really 32 bits because of their noise floor,...
    6 replies | 150 view(s)
  • MikeDB's Avatar
    09-26-2019, 01:33 AM
    MikeDB replied to a thread Audio over Serial in Audio Projects
    From Paul himself last month : There is the small matter of (so far) no software support for Teensy 4.0's S/PDIF peripheral in the audio library. Given the power of the Teensy4.0 for audio, I wouldn't think...
    4 replies | 139 view(s)
  • MikeDB's Avatar
    09-25-2019, 09:16 PM
    The Teensy 4.0 has far more horsepower for synthesis and any I2S->audio card can be patched onto the output pins so no need to stay with the one suggested. Loads on Aliexpress and elsewhere. My personal preference is...
    9 replies | 352 view(s)
  • MikeDB's Avatar
    09-25-2019, 08:10 PM
    Thanks Paul. That's a pity. Looks like I'm back to the STM32H7 MCU series then as that can multiply the LRCLK by up to 256 with extremely low jitter - but is an absolute PITA with dreadful support :-( I'd assumed...
    9 replies | 273 view(s)
  • MikeDB's Avatar
    09-25-2019, 07:47 PM
    Not quite - to sound the same as most analogue ones you want to sweep them up and down with equal logarithmic spacing. Still easy to do, just choose the ratio you want and then multiply the base notch frequency by...
    4 replies | 121 view(s)
  • MikeDB's Avatar
    09-25-2019, 07:43 PM
    MikeDB replied to a thread Audio over Serial in Audio Projects
    The Teensy 4.0 chip supports SPDIF which is exactly what you want for point to point as that is what it was designed for. But I believe you'd have to write your own drivers for now for the Teensy. The second...
    4 replies | 139 view(s)
  • MikeDB's Avatar
    09-23-2019, 09:40 PM
    I'm afraid I read it as SAI1 offers 8 in, 2out through to 2 in, 8 out, i.e. 10 channels in total, not 16. But I think you can have these at 384kHz if you want. But you can use the SAI2 for another 2 in and 2 out and...
    22 replies | 583 view(s)
  • MikeDB's Avatar
    09-23-2019, 02:06 PM
    Thanks Richard Those links are very useful. Will try the tool and see if it does what I want. Given there are so many PLLs in the Teensy MCU I was hoping not to add an external one, but that's always a possibility....
    9 replies | 273 view(s)
  • MikeDB's Avatar
    09-22-2019, 01:55 PM
    Yes about 95% gets through okay, but when they charge you it hurts. I don't mind the VAT but their 'handling charge' strikes me as excessive. I also had an argument with customs over something that shouldn't be...
    25 replies | 1658 view(s)
  • MikeDB's Avatar
    09-22-2019, 12:52 AM
    Careful if anybody is ordering these to the UK as even a single unit exceeds the 15 product + postage customs limit and so could incur VAT plus a 10 mail handling fee. It's pot luck whether this gets applied or not,...
    25 replies | 1658 view(s)
  • MikeDB's Avatar
    09-21-2019, 01:36 AM
    Thanks Richard All studios just distribute a 96kHz (or 192/384 if you've a lot of hard discs you want to fill up :-) clock to sync everything. Sending MCLK everywhere would be a nightmare and wouldn't actually...
    9 replies | 273 view(s)
  • MikeDB's Avatar
    09-21-2019, 01:03 AM
    In the first case, the data setup time of 15nS makes this unlikely to work as you are thinking. In fact SAI1 outputs 8 channels as 4 streams of 2 channels over the 4 active outputs (or active inputs if you prefer) so...
    22 replies | 583 view(s)
  • MikeDB's Avatar
    09-21-2019, 12:56 AM
    Not that I use it, but I'm pretty sure you'll find PulseAudio does work ok on a Pi nowadays.
    22 replies | 583 view(s)
  • MikeDB's Avatar
    09-20-2019, 05:18 PM
    I want to supply the Teensy just with the studio Master Clock (96kHz in our case) and have it generate it's own I2S LRCLK and BCLK (and MCLK if possible) from it. I've read through the whole iMXRT Reference Manual but...
    9 replies | 273 view(s)
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Board advice for synth project. Does 4.0 make sense? 11-17-2019 12:54 PM
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