[sdiy] Hardware convolution box?

[cheater00 cheater00]

Any pc-based solutions will have quite a lot of delay as well as will be
very expensive for what they do.

On Wed, 8 Feb 2017 00:44 Travis Thatcher, <recompas at gmail.com> wrote:

> I imagine with a Bela + BeagleBoneBlack you could do it in PureData. Maybe
> I'll give it a try.
>
> On Feb 7, 2017, at 17:25, analogheaven at hushmail.com wrote:
>
> I keep coming back to this as processors get cheaper and faster. If I was
> better at Linux scripts and the Linux enviroment, I think a convolution
> system could be cobbled together pretty quickly with Jack, JConvolver, a
> standard audio interface and some hardware controller.
> Until then, I am pretty happy with the Logidy EPSi:
> http://www.logidy.com/
> Crappy interface, but have used it with all sorts of IRs.
>
> On 2/7/2017 at 10:30 AM, "Mikko Helin" <maohelin at gmail.com> wrote:
>
> This XMOS board designed (for stompbox use mostly) by an XMOS employee
> might be a good alternative for DSP chips and better than generic
> ARM's:
>
> http://www.diystompboxes.com/smfforum/index.php?topic=114354.0
>
>
>
> On Tue, Feb 7, 2017 at 8:12 AM, <rsdio at audiobanshee.com> wrote:
> >
> > On Feb 6, 2017, at 9:20 PM, cheater00 cheater00 <cheater00 at gmail.com>
> wrote:
> >> I understand FFT domain convolution introduces latency, which is not
> wanted in hardware.
> >
> > There are a few considerations regarding latency:
> >
> > 1) Most convolution represents a reverberation, especially convolutions
> of impulses that last a couple of seconds. In nearly all cases, the reverb
> involves a pre-delay before the signal appears in the impulse response. In
> such cases, the latency can be subtracted from the pre-delay and then there
> won't be any perceived latency.
> >
> > 2) All 24-bit converters have hundreds of samples of delay. Or at least
> it seems that all 24-bit converters are built on delta-sigma technology
> with tons of digital filtering. Unless you're going to based your design
> around a 16-bit or perhaps 20-bit codec, you won't be able to remove all
> latency regardless of the convolution algorithm used.
> >
> > 3) One of the responses mentioned overlap-add FFT. That technique allows
> for significant reduction in latency, provided that the processor has the
> power to calculate many more FFTs per the time available.
> >
> > That said, I support all designs which strive to reduce latency in
> hardware! It's just not as easy as you might think. You certainly want to
> start with a DSP, though, for the best chances.
> >
> > Brian Willoughby
> > Sound Consulting
> >
> >
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