[sdiy] Frequency shifted from BBD?

[Gordonjcp]

On Fri, Oct 04, 2024 at 06:55:43PM -0700, brianw wrote:
> Thanks! Very nice to have that Eventide article.
> 
> One advantage of the H910 is the RAM. The glitch cannot be avoided, but it's much shorter. In the H910, the sample rate being written into RAM is constant. The sample rate being read out of RAM is also constant, but different, so when it wraps around the circular buffer there is a glitch, but that glitch only lasts for one sample.
> 

They used a similar technique in the olden days of the 1990s for "radio phone-in" delays.

What you used to do was put in a fixed delay of maybe ten seconds. When you patched the delay in - it used to be tape but eventually digital took over - you dropped a cart the same length as the delay like maybe a station ident, and immediately start the introduction to your programme into the delay line. By the time the cart was finished the delay had filled up.

In the mid-90s some bright spark realised that you could make ten-second digital delays easily with just a few hundred quid's worth of RAM, and if you played out ever so slightly slower you could make it "ramp" into a ten-second delay. So maybe about 15 minutes before the phone-in programme started you'd hit the button on the delay - the time was adjustable - and it would slowly delay programme-to-air more and more with an imperceptible pitch shift. When you were done, hit the button again, and it'd speed up and telescope the delay back in.

I don't think they even bother with that these days. Certainly BBC Radio Scotland and BBC Radio 4 don't!

-- 
Gordonjcp