PT2399 feeding a BBD chip for analogue (sounding) delay

[Auke Haarsma]

Say we take the Rebote 2 utilizing the PT2399. We filter the signal to be as 'clean' as possible. Next the delay out of the PT2399 is  fed into a BBD circuit (eg mn3007+clock+filtering).

The BBD circuit is set to a fixed low delay time (<10ms), the PT2399 delay time is the 'base' delay (upto 500ms). The BBD Delay out is then mixed back with the dry signal.

Maybe add a SA571-type compander ala pt80.

Among plenty of interesting sounds/mods/variations with added modulation, parallelling the pt2399 delay and bbd delay, taptempo of the pt2399 delay etc etc ...

My main question is:
Would this give us BBD/analogue (sounding) delay? Would the BBD chip cause/force the analogue-ness warmth / filtering of the highs on the delayed signal?

Or, is this a waste of the BBD?

[svstee]

Wow, nice idea. I know next to nothing about BBDs but I think this could be a really cool project. Would you want the BBD delay time fixed? If you could set it to adjust between, say 0-20 ms you might be able to manipulate the timbre a bit more than with just a wet/dry mix, right? Or am I talking out of my tail end here?

[Mark Hammer]

It won't do what you think.  First off, what a lot of folks attribute "analog tone" to is really the filtering that is required to make analog delays behave themselves, and not the BBD.  Yes, I know there can be an "analog tone" inherent to BBDs under some circumstances, but in the majority of circumstances, the "warmth" that people like is the lowpass filtering.  Which is why so many PT2399-based pedals and projects produced these days can describe themselves as having "analog tone", merely by sticking the same sort of lowpass filtering in.

Second, to the extent that there IS something one might call an "analog tone" that arises out of having essentially infinite resolution in the samples that the bucket brigade chip passes along (as opposed to the resolution imposed by an A/D convertor), you lose that by passing the signal through a digital chip first, where it will be quantized and converted using the A/D/A conversion internal to the PT2399.  It's not a "bad" convertor, but it is also not possible to somehow over-ride what the conversion has already done, and somehow wipe the slate clean with a BBD.  So, no, I strongly doubt it will have the effect you are hoping for.

Will it have a negative effect?  To the extent that there are two independently-clocked chips in the same circuit, there is always the risk of heterodyning and resultant clock noise, but since the clock ranges of the two categories of chips are so far apart, the risk of audible sum and differences products is small.  That being said, you still have to worry about two clock signals bleeding in, so layout will be important.

Is it a "waste" of a BBD?  Not necessarily.  Adding a small amount of delay in the regeneration path can eliminate the boxey standing-wave tone of a delay that has a single fixed delay time.  If you modulate the BBD a little, that could make the sound a little more interesting.

[Auke Haarsma]

Thanks a lot Mark.

Is it a "waste" of a BBD?  Not necessarily.  Adding a small amount of delay in the regeneration path can eliminate the boxey standing-wave tone of a delay that has a single fixed delay time.  If you modulate the BBD a little, that could make the sound a little more interesting.

I'll keep this in the back of my head. Your posts somehow always trigger one or two ideas

[Processaurus]

http://www.diystompboxes.com/smfforum/index.php?topic=31886.0

It is a good idea.

[Auke Haarsma]

Thanks for the link Ben! Great info there. Seems the idea is worth at least a try.

[RonaldB]

I did this with my PT80.
I have a CE-2 (in vibrato mode) to create modulation on the delayed signal  and it sounds really great.

Ronald

[jpwilksch]

Sorry to resurect this old thread, but I just noticed over at http://stinkfoot.se/archives/1289 something very similar to the OPs idea - the Seymour Duncan deja vu does the reverse, with BBD delay first, which is the extended by digital delay.