TDA1097 Chorus unit

[Mark Hammer]

Old news to many, I suppose, but I stumbled onto this in an old issue of Electronics Today, found here: http://www.americanradiohistory.com/Archive-Electroncis-Today/Electronics-Today-1985-11.pdf

Decent cymbal synthesizer in the same issue.

[roseblood11]

Looks interesting! Has anybody here built it?

It would be nice to have a pcb for this project from madbean or someone else...

[Ice-9]

Thanks Mark,  I love old project magazines like this, quite a nice article in there about switching regulator power as well. When I was about 15 I was always excited when the next edition of 'Practical Electronics' was due out to see what projects were in it.   

[Scruffie]

I spy your favourite shape Mark... new one for a chorus.

Nothing too exciting otherwise but still a decent looking design.

[samhay]

Can anybody still find TDA1097s?
There aren't likely to be any drop-in replacements as it uses 1536 stages. However, an MN3207 is probably close enough, seeing as the design runs it off 5V.

http://www.datasheetarchive.com/dlmain/Datasheets-X/DSA842000-532.pdf
http://www.diystompboxes.com/smfforum/index.php?topic=96684.msg840672#msg840672

[bloxstompboxes]

Found this: https://www.avspares.com/parts/search?parts=TDA1097 .

Looks wrong to me though because it looks like they are listing them for $.01 a piece. Surely even if it was a few thousand on a reel it wouldn't be that cheap. I must be missing something.

[duck_arse]

I think EIS are using "0.01000" as a placeholder or clik-bait. they show the same price for ca3080.

interesting buck supply in that mag, too.

[Luke51411]

Found this: https://www.avspares.com/parts/search?parts=TDA1097 .

Looks wrong to me though because it looks like they are listing them for $.01 a piece. Surely even if it was a few thousand on a reel it wouldn't be that cheap. I must be missing something.

Avspares shows up in results for just about any aircraft part number you type in google, I doubt they are very reliable to actually find the parts you are looking for.

[StephenGiles]

Thanks Mark,  I love old project magazines like this, quite a nice article in there about switching regulator power as well. When I was about 15 I was always excited when the next edition of 'Practical Electronics' was due out to see what projects were in it.   

So were we all!

[StephenGiles]

Thanks Mark - this is one I don't remember!

[Mark Hammer]

Actually that was a pretty good issue overall.  A number of interesting things in there.  I mistook the cymbal project for one I had already made.  This one is different, and simpler.

I will also note that the chorus unit uses a hypertriangular LFO, and sweep rates go as low as 0.1hz, which seems kind of bleah when the shortest delay time is apparently 7ms.  If there was a way to shorten that delay a little more, the LFO shape and slow sweep would be more interesting.

[bloxstompboxes]

I found the bbd on ebay for $20 something bucks but I just can't justify that for such a chip. Is there a simple way to drop in another one? I know this one is 1536 stages, the mn3007 is 1024, and so is the mn3205. I can't seem to find the datasheet for the TDA1097, so I'm unsure of the pinout. I am also not that good with BBDs or how to set them up and what changes would be necessary, or if you could drop one of these others in, would it change much if everything else was left as is?

[armdnrdy]

Years ago I contacted Mr. Hammer inquiring about a data sheet for the TDA1097.

Mark was gracious enough to send me the pin out that someone had figured out from a 1097 circuit.

The info Mark supplied helped out immensely in double checking the Infinite Flanger 1097 to 3007 BBD conversion.

Since that time...I did find some additional info that almost resembles a data sheet.

[antonis]

Old news to many, I suppose, but I stumbled onto this in an old issue of Electronics Today, found here: http://www.americanradiohistory.com/Archive-Electroncis-Today/Electronics-Today-1985-11.pdf

Old news indeed but with also a very comprehensive and practically helpful article about Designing Transistor Stages..!!
(there is more than enough interpretation not only for how to bias a transistor but also for why to do so..)

[bloxstompboxes]

Cool! Thanks, armdnrdy. So based on that, I could either make an adapter board or just change up the board layout. At first glance, it seems that there might not be any other changes necessary.

[armdnrdy]

At first glance, it seems that there might not be any other changes necessary.

Take a second glance!

There's a 2M2 potentiometer for the rate control! 

Not to worry though...

I successfully redesigned the LFO section of the Tycobrahe PedalFlanger to a more easily sourced 1M control.

The redesign is outlined in this thread, reply #6:
http://www.diystompboxes.com/smfforum/index.php?topic=110562.msg1034365#msg1034365

[bloxstompboxes]

Steve at smallbear has 2M linear pots.

[armdnrdy]

Steve at smallbear has 2M linear pots.

I know that a linear pot is called out for in the original BOM but...that was probably due to reverse audio pots being extremely difficult to source at the time this circuit was published.

A linear pot for the speed/rate control would cause either the fast or slow end of the control to be bunched up. There would be too much of one on the one side, and not enough control of the other on the other side.
That's why you almost always see reverse audio pots for the rate/speed control.

Now if this doesn't bother you....then you're golden.
I happen to think that an incorrect taper pot makes the speed adjustment seem like it's not working correctly.

You can breadboard the LFO with a 2M linear control and a LED rate indicator to see how the control behaves.

[StephenGiles]

There is a circuit which gets round this problem - part of HSR dual gate. Will find it later!

Here  - see Attack pot circuitry and relevant description.
https://www.dropbox.com/sh/2aedsoafmaa3bc7/AACiigi5aVYTjrPP1ybQMO_oa?dl=0

I've had a PCB for this beast for over 30 years, I must solder it up sometime!

[bloxstompboxes]

Hmmm. The small clone uses a C1M pot and the CE2 a B100k. If I had time to breadboard these days, I would try all 3. Looks like I may just have to pick one and go with it.