Halving stages in a BBD

[Bucksears]

Is there a way to use just half the number of stages in a BBD? I was wondering if that's what designers are doing when they modify a unit (particularly flangers) to use an MN3007 (just guessing).

How is that done, exactly? I'm asking because I'm having problems finding a particular 512-stage IC for a new project and was wondering if I could get the same results by using a 1024-stage IC and halving the stages.

thx

[marauder]

Run it at twice the speed.

[Scruffie]

With the Flangers using MN3007s that were originally designed for 512 stage chips, what's happening is the clock that pushes the BBD is being buffered so that it can push itself past the capacitance inside the BBD and drive it further than it was designed for. The clock is happy delivering those Frequencies, it's the BBD that wont let it and the buffer overcomes that to a point.

You can't physically half the number of stages though.

What project is it out of interest? There may be other options.

[Bucksears]

What project is it out of interest? There may be other options.

Thanks.

The project is (deep breath) an Ibanez FL99 Classic Flanger (the big one in the silver box, four knobs, made in the late 90's). I've owned two and they are fabulous units, but a bit large and pricey; I sold each at different times when I really needed the money. I was going to build one for a 1590Q enclosure (same length as a 1590BB, but square). I want to rewire it so the 'Filter' toggle is on the 2nd footswitch instead of 'Intense' (which I never used).
I've already worked out most of the other parts of the layout, but stopped working on it when I couldn't find ANY leads on a 3210.

The problem is, the original takes an MN3210 (dual 512-stage IC), which is harder to find than the FL99 itself. I was going to get two MN3204's (single 512 ICs) and design the BBD part of the PCB so they make the same connections as the dual stages of the 3210.
I've been able to find MN3204's, but they're pricey too but still cheaper than an FL99. (For two 3204's, it would still be less than 1/3 of what an FL99 might cost when they come up). I was going to see if the MN3207 (1024-stage) could be halved, then use two of those. They're all in the MN32xx family, so they should all be able to run on the MN3102 clock driver and same voltage polarity.
I think using two MN3204's would be the easiest solution, but finding a way to use two MN3207's would be cheaper.

What do you think?

[Scruffie]

What project is it out of interest? There may be other options.

Thanks.

The project is (deep breath) an Ibanez FL99 Classic Flanger (the big one in the silver box, four knobs, made in the late 90's). I've owned two and they are fabulous units, but a bit large and pricey; I sold each at different times when I really needed the money. I was going to build one for a 1590Q enclosure (same length as a 1590BB, but square). I want to rewire it so the 'Filter' toggle is on the 2nd footswitch instead of 'Intense' (which I never used).
I've already worked out most of the other parts of the layout, but stopped working on it when I couldn't find ANY leads on a 3210.

The problem is, the original takes an MN3210 (dual 512-stage IC), which is harder to find than the FL99 itself. I was going to get two MN3204's (single 512 ICs) and design the BBD part of the PCB so they make the same connections as the dual stages of the 3210.
I've been able to find MN3204's, but they're pricey too but still cheaper than an FL99. (For two 3204's, it would still be less than 1/3 of what an FL99 might cost when they come up). I was going to see if the MN3207 (1024-stage) could be halved, then use two of those. They're all in the MN32xx family, so they should all be able to run on the MN3102 clock driver and same voltage polarity.
I think using two MN3204's would be the easiest solution, but finding a way to use two MN3207's would be cheaper.

What do you think?

Wow, I never even knew they'd made a low voltage version of the MN3010, learn something new every day.

Well looking at the schematic through exhausted eyes, it seems that there are 2x512 stage delay paths connected to the same input that both have identical output stages except for the value of one filtering cap but the output of one looks like it's fed back in to the input of the other so I assume that the 'intensity' switch is allowing selection between 512 stages or 1024 stages.

If this is the case and my tiredness isn't making me not think, I think it'd be quite simple to use 1 x MN3207 with a 4049 buffer and one output with a DPDT wired to switch between that one cap value in the filtering and to double the clock frequency to imitate the 512 stage outputs sweep. Assuming the LFO & VCO can cope.

[Bucksears]

Thanks again - get some rest and have another look whenever you have time. I've got a few other projects to finish up first, but would really like to take a serious swing at this one.
I don't necessarily NEED the 'intense' mode, if that helps any. I just want the flanger and the filter option.

I'm in the process of finishing up an Ibanez CS-505 Chorus (mono) that I rev-engineered using the original PCB layout. Instead of using an 18V power supply externally, it has a RoadRage board internal to double the 9V to 18V.
I was about to do the same on an FL-301 Flanger and decided to take a look at the FL99 again first.

Take care,
Buck

[Scruffie]

Thanks again - get some rest and have another look whenever you have time. I've got a few other projects to finish up first, but would really like to take a serious swing at this one.
I don't necessarily NEED the 'intense' mode, if that helps any. I just want the flanger and the filter option.

I'm in the process of finishing up an Ibanez CS-505 Chorus (mono) that I rev-engineered using the original PCB layout. Instead of using an 18V power supply externally, it has a RoadRage board internal to double the 9V to 18V.
I was about to do the same on an FL-301 Flanger and decided to take a look at the FL99 again first.

Take care,
Buck

As far as I can tell, i'm right, it would explain why on the 1024 stage line the 560pF low pass filtering cap is increased to 1n2 to keep the clock noise out.

So as long as there are no other changes necessary, changing the 30pF between 30pF (1024) & 15pF (512) with the 4049 buffer in conjunction with the 560pF (512) and 1n2 (1024) should emulate the original... it probably will need some tweaking though, you'd probably be better off asking on DIYStompboxes as there's quite a few guys who are more focused on BBD technology than me.

You may as well keep the intensity switch if you can!