BBD Chips - Which FX To Build ?

[spudulike]

Ok, I just liberated a 3102/3207 pair from a 1980's RadioShack "Karaoke-mate" (car boot sale £1 ). I'm after recommendations for a chorus/flanger project to use them for. All the projects Ive checked use the 14 pin SAD1024 chip.

Any suggestions ?

[Mark Hammer]

Some folks seem to like the Arion Stereo Chorus, and there is a schem floating around for that.  Several of the Ibanez choruses (CS-5, CS-9) also use an MN3207, as does the Pearl Chorus.

Francisco, how amenable is your CE-2 layout to using an MN3207/MN3102 combo instead of a 3007/3101?

[spudulike]

Thanks Mark, not much other interest though
These chips seem pretty inexpensive anyway.

After searching I found the Boss BF flanger uses these chips. Before I dive in and hack one, anyone know of a layout ? pcb ?

[Mark Hammer]

Note that the 3207/3102 combo can't normally be clocked fast enough to get dramatic jet plane flanging (though all the other classic flanger sounds are not affected by this limitation).  If the clock lines (i.e., the path between the clock input pins on the 3207 and the source of the complementary clock pulses) are buffered, the 3207 can be clocked much faster to achieve much shorter delays.  Whether you can push it into A/DA terrain is another thing (there are several other noteworthy circuit/design differences between the A/DA and BF-2), but you'll be able to achieve delay times shorter than the 1msec the pedal is spec'd for.  The normal method for buffering the clock lines is to take a hex invertor, and parallel three invertor section for one clock line and 3 other invertors for the other clock line.  You can see some examples in the various Morley flangers.

[spudulike]

I'm going to breadboard this first, get it working then try your suggestions Mark (thanks )
Never played with a flanger before so the mods should be fun, and Ive got a couple hex inverters in the spares bin ... laters 

[RickL]

Mark, is the buffering something that could be retrofitted to a BF-2? Cut the traces, send clock signals to the buffers then on to the BBD? I assume you'd also have to drop the value of the cap on the driver to increase the clock speed.

Rick

[Mark Hammer]

I suppose you could, but never having looked inside the box, I can't speak to whether there is enough room.  Of course, if one's intent is to retrofit it inside a different chassis, then I suppose all bets are off.

But to answer the question by example, I completely overlooked the Hollis Ultraflanger.  Take a gander at the schem for that over at RG's site, and you'll see an example in action.  It's a 4049, with 3 sections paralleled on one clock line and 3 on the other.  That's it.  Near as I can tell, the supply voltage differences between the 3207 and 3007 should not make a difference.

All of that being said, it is common practice to snuggle the clock chip right up against the BBD, so the clock lines are kept blessedly short, and any stray clock whine kept to a minimum.  Though a person is TECHNICALLY able to cut the traces discussed and find a way to shove a 4049 in there and run leads from all the "heres" to all the assorted "theres", whetrher you end up with anything you'd wanna play to your mother is a completely other question.  I'm not saying it will necessarily turn into a whining monster (especially if the changes permit the clock frequency to be increased into the >500khz zone), but I suspect one will need to be careful about layout and putting things in the locations that avoid stray signals.

[Fp-www.Tonepad.com]

Mark,

I don't really know. If you had a schematic, I'd like to see it. I suppose it's possible with a few modifications.

Fp

[Mark Hammer]

Look here: http://www.geocities.com/CollegePark/Library/1355/Bf2.gif

[Fp-www.Tonepad.com]

OK.

I was thinking more along the lines of what exactly needed to be done in the schematic!...

I'll look into it in some free time, but if you can help sorting it out, that'd be great help!

Fp

[Mark Hammer]

Let,s hope either Ton, Mike, or Steve has a few moments to leap in here and give some *solid* advice on what needs to be done.

[Fp-www.Tonepad.com]

I have a few of those chips, I may experiment with them some time.

Fp

[StephenGiles]

Nothing to suggest here other than replacing the clock for the 4007/4047/4049 from the ADA, but that would need a separate board.
Stephen

[Mark Hammer]

As far as "re-tuning" a chorus goes, I'm not sure how much the circuitry of a variable Manual control would add over and above a simple range switch, such as the Zombie has (and as people have done with their Small Clones).  Maybe the DOD unit I have is simply a lousy chorus, or the manual control is a lousy implementation of that function.  What I do know is that on my Zombie, and on my Washburn chorus, I can think to myself "I want that sound.  I'll flick this switch here".  On the DOD, I tend NOT to think "I know what sound I'd like.  I need to shift the Manual control THIS way."  The continuously variable manual control certainly lets you experiment more, and custom tailor, but tends to NOT foster mental images of sounds that easily suggest control settings.  The preset ranges may not provide as much precision, but they are contrasting enough from each other that you can imagine which of sounds 1, 2, or 3 you really want/need at this moment.

Six of one, half dozen of the other.

On the other hand, if a continuously variable Manual control allowed one to modify a chorus pedal so that it could gracefully move between flanger and chorus modes (or straddle them), that would be added value in my view.