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Effects using BBD devices

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5/25/1998 3:16 PM

Effects using BBD devices

Hi !
Over the last months there have been some postings conserning Delay, chorus, flangers and Slap-Back.
I am going to build a guitar effect, that could do as much of it as possible !
Therefore I am looking for som information about cascading or chaining BBD chips.
Most of the BBD chips has 2 outputs.
These are mixed via a potmeter, to trim out any possible left over signal from the clock generator. I have seen one example on 2 of these chips in series, (memoryman at stellans site).
My question is, is it adviceble to use this trimmer for each chip, or is it enough to use one trimmer at the last chip ??
Should I use companding ?
Does anyone have any data on the chip
TDA 1097, a 1536 stage low-noise BBD ??
If so could I get a copy. Who is the maker of this chip ?
Any other informations about BBD chips and the use of them in effects, would be of great help to me. It dosn't matter if it is about the old Reticon chips or the newer Panasonic.
I am planning to make a document,
("Technology of BBD effects") inspired by RG. In this I will describe, as god as possible, the results of my experiments with these chips,(TDA1097).
The reason for my interest is that this area is new to me.
Any reply are welcome.
Preben.

5/26/1998 8:59 AM

There's some data on cascading in some old Reticon SAD1024 data sheets, I think. I'll take a look in the data closet.

I think it is advisable to use a trimpot per section, because the signal out of the first BBD section gets re-sampled into the second BBD section so any unbalance there is inextricably mixed with the audio. That's a guess at this point.

For reducing sampling noise, use companding. This adds only an NE570/571, not a big deal.

"TDA" sounds like Phillips/Signetics parts.

I encourage your efforts on the technology paper. Good luck with the experiments.

5/26/1998 10:13 AM

Yes, you should use the trimmer in between cascaded chips, although some simply use two matched resistors.

The TDA is a Philips/Signetics chip (sounds interesting, too; 1536 stages is long enough for a wide bandwidth chorus). Sorry, no data.

Trust me, you want companding.

I have quite a few documents on delay device design with the SAD-1024, from DEVICE, Radio Electronics, Electronics Today, and even Radio Shack. If you want some info on the 1024, I'd be happy to respond.

5/27/1998 6:29 AM
CJ Landry	I have a data sheet on the SAD1024 from Reticon and also from Radio Shack. I would be glad to share this data if you need. Christian

6/3/1998 1:16 AM

Hello again !
Thank's for the responces so far.
I will use the next months to collect further information about BBD chips and the use of them in effect units.
I have allready found some very nice informations, when i started searching for synth modules. I have seen the advertisment at Midwest Analog, I sure would be very interested in the documentation on the unit using the old SAD4096.
I am also collecting definitions of the terms used for BBD-effects: echo, slabback, and so on.
Flangers: I have read somewhere, that the flanging sound is "more efficient" if the input signal contains harmonics. Some flangers have a opamp stage with back to back diodes in the feedback loop, like the screamer, i guess that gives extra harmonics. Any suggestions to that ?
Data sheets: Any data-sheet or application note would be of great interrest.
Thanks in advance, Preben.

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