How to design a BBD flanger?

[ElectricDruid]

Dead electric organs from the 1970s are a decent source of pedal mechanisms. The volume pedal on such instruments usually has a longer travel than a wah pedal and can be wired up as an expression pedal pretty easily in most cases. I've seen that uses a light bulb shining on a photocell with a moveable shade to control the volume which wouldn't be so easy to adapt, but mostly it's not too difficult.

You'll definitely get support from me for a 0-5V expression pedal/CV input standard.

[anotherjim]

Somebody somewhere did use both halves of a 4013 in parallel instead of buffering the clocks. Worth doing if it's going spare, but probably not going to equal dedicated buffers for highest speed. I'm not entirely convinced the 4049UB is the best choice -  its output can sink more current than it can source so the switching is asymmetric. However, I'll bet by this stage in the development, somebody must have tried everything. If you wanted to go to a lower supply voltage, it's worth noting that most 74HC logic is good for up to 7v.

An unused D-type can handle electronic momentary latch switching, be the mosfet in a Millenium bypass (it can drive a LED directly if you do with high-efficiency LED and large CLR). It can be wired as a non-inverting buffer and be the Schmitt trigger in an LFO. Or be an extra divide by 2 to drop the BBD master clock down for a longer delay range.
I don't think it can make coffee.

Mark said...

Let's clear this up.  NOTHING sweeps down to .0001ms.  That's 1/10,000 of a millisecond!! 

Digital can, all the way to effectively zero delay if you ignore converter latency and do the wet/dry mix in the chip. However, for most instrument flanging, the sound of classic BBD based flangers is the benchmark and doesn't impose any latency on the dry signal.

[Digital Larry]

Not sure if someone mentioned it yet.  Most of my perspective is from doing flangers with DSP but I think it still applies.

a) Try inverting the phase of the "dry" signal, OR the "delayed" signal.  This will cut much/most of your low end and you'll get  peaks where previously you had notches.

b) Also try inverting the phase of the feedback signal with or without (a).

[Mark Hammer]

Mark said...

Let's clear this up.  NOTHING sweeps down to .0001ms.  That's 1/10,000 of a millisecond!! 

Digital can, all the way to effectively zero delay if you ignore converter latency and do the wet/dry mix in the chip. However, for most instrument flanging, the sound of classic BBD based flangers is the benchmark and doesn't impose any latency on the dry signal.

As ever, Larry, I defer to you in the digital domain.  That said, analog flangers that do through-zero also don't actually achieve delays much lower than maybe a half millisecond or so.  They achieve thru-zero by imposing a small imperceptible fixed (though sometimes variable) delay on the "dry" signal, such that the swept delay can move "ahead" of it in time, even if it can only achieve modest sweep.  So, for instance, if I delay the dry signal by a fixed delay of 1msec, and the modulated signal gets swept down to 800usec (0.8msec), I pass "through zero" on the way, and on the way back as well.  I think I mentioned in past that I experimented with my two Boss BF-1 flangers by lifting the dry signal in both and patching them between a splitter and mixer.  The two units have a Manual delay control, such that I can use one as the "dry" signal and insert a fixed delay of my choosing.  Perhaps more interestingly, I can let them both sweep, such that with independent LFOs, the thru-zero point occurs in an unpredictable manner, both passing through and coming back.

[Digital Larry]

As ever, Larry, I defer to you in the digital domain.

Hey Mark, it wasn't me who said it. I can neither confirm nor deny blah blah blah... I do "through zero" flanging by having a fixed tap which is "wherever" you want it so long as the varying part sweeps through it.  My own experiments with multiple LFOs on modulation haven't been all that satisfying but maybe there's a magic formula in there. 

[Toynbee]

Some BBD patents

https://patents.google.com/patent/US3866505A/en?oq=US3866505
https://patents.google.com/patent/US4438525A/en?oq=US4438525
https://patents.google.com/patent/US4535368A/en?oq=US4535368

[Mark Hammer]

Thanks for those patent links.  The first two are interesting, especially the first one.

[anotherjim]

That first one is somewhat cheeky of Yamaha since the somewhat earlier Eminent organ Ensemble effect is just that (it essentially became the chorus used in the Arp Solina). It isn't Flanging because the modulation for parallel BBD's is the same only with a phase lag between LFO waves so the mixed delay times never cross each other.
Note that unlike guitar chorus, the dry signal is not used which is easier to get away with in a synth since the dry signal does not have to be heard as a signature sound while we still expect guitar chorus to sound of the guitar, and the same may be true of many other modulation FX.

[Mark Hammer]

As soon as I saw three BBDs in the document, "Solina" was my first thought. 

I don't know if I agree with you regarding the relative necessity of a dry signal.  The chorus effect relies somewhat on two aspects: the sense that there is a second "voice" which lags a bit in time  behind another voice, and the sense that the two voice are very close in pitch but not identical.  The triple-BBD example in the patent document nails the first aspect well, providing not only a 2nd voice, but a third as well.  And while they are not modulated relative to an unmodulated clean signal, they ARE modulated relative to each other, so you do get that not-everybody-at-the-exact-same-pitch thing.

I'm looking at a bunch of 3207/3102 sets in my BBD drawer at the moment.  Hmmmm.  But, worth noting it would make a crappy flanger, rather than a good one, which is the focus of this thread.

[anotherjim]

I think the triple chorus was originally intended to be a rotary speaker emulation. In fact, the Eminent organs using it had 3 separate amps and speakers running off each BBD. No dry signal and no cross-mixing.  Back then, the effect was traded as "Orbitone". The BBD's then were TCA350Y with only 185 stages. I don't think they sounded anything like flanging, even when mixed down to mono in the later string ensembles, but there is a gentle phasing sweep effect.

By the time the effect was used in the Arp Omni (essentially a Solina with a mono-synth), the BBD's had changed to SAD512. Still 3-phase and no dry. They added a Phaser mode with different modulation settings - so finally going for peaks and troughs between the BBD channels. I think that in an electronic keyboard, especially with slowish attack sounds like a stringer, the fact that there is always the latency of the fastest BBD goes without notice. I'm not sure it would for guitar.
Anyway, since multi BBD has existed since the end of the 1960's, I think its telling that no guitar effects followed the same ideas with multiple delays used in the keyboards.

An interesting new product, is the TC June-60. Supposedly only inspired by the Roland Juno synth dual BBD chorus but not a true clone. The designer said things had to change to make it work for guitar. That might be because they don't have any 256 stage BBD as per the original so it's got the common CoolAudio 1024 stage chips, I'm not sure. Still it has a 180deg opposite sweep mode (I + II) - unfortunately, in that mode, the LFO rate goes up to something like 8Hz (if that stayed the same) so you can't tell if it's really flanging between the 2 delays. I have an original in a Juno-6 synth and that don't sound like flanging either. Note that in that Chorus the dry signal is always used and only one LFO rate modulates the clocks -  only the speed and depth is changed.
Anyway, despite most of the June-60 being SMD (except the BBD and clock chips) and since it's cheap and based on known circuitry it might be possible to hack it about to try for a Flanging effect?

[duck_arse]

attention Rob Strand:

Back then, the effect was traded as "Orbitone". The BBD's then were TCA350Y with only 185 stages. I don't think they sounded anything like flanging ....

[Mark Hammer]

I think the triple chorus was originally intended to be a rotary speaker emulation. In fact, the Eminent organs using it had 3 separate amps and speakers running off each BBD. No dry signal and no cross-mixing.  Back then, the effect was traded as "Orbitone". The BBD's then were TCA350Y with only 185 stages. I don't think they sounded anything like flanging, even when mixed down to mono in the later string ensembles, but there is a gentle phasing sweep effect.

Look for info on the Roland "Revo", which used stationary speakers, in tandem with some BBD chips and modulated amplifier sections to mimic a rotating speaker cab, but with the weight reduction and omission of mechanical issues coming from not having any motors, rotors, or tube-amp transformers.  They only produced it for a few years, in a few different models.  It never really took off, but the one I heard in a store in 1980 or so sounded nice.

[Puguglybonehead]

If we're looking at building a manually swept flanger then why not look for an existing 'double-tracking' effect design? (one that, hopefully, can use current production 3207 BBDs) I'm just thinking of how to achieve simplicity here. Maybe using two of the double-tracking circuits, with the dry signal removed, leaving one fixed and one treadle-controlled? Then add filtering on a trial and error basis until you find a satisfactory, low-noise, low-whine result.

[gde]

All of that makes me wonder: Maybe I should give the Ibanez FL-9 a go. Reportedly, the Joyo Classic Flanger is a more or less exact replica of that one. Although the sources for this info are highly shaky and the whole theory may be based on little more than the knobs having the same utterly weird names, for all I know. Considering how sacrilegiously cheap the Joyo is, I might just buy that one and mod it and see how it goes. Assuming it is indeed the FL-9 design, then it has a Manual control (called "Delay Time" cause that won't confuse guitar players at all on something that isn't a delay) and the Width knob is positioned such that a switch can be inserted here to disconnect the LFO and/or insert an envelope follower here.

I've been modding some joyo flangers lately and can confirm its an FL9 clone but with true bypass. It uses through-hole components so a lot easier to mod than most Chinese clones that use SMT. You can snip the lfo off the width pot and attach other sources, but the width control and the manual control interact with each other so i have the manual pot wired up similarly to how the trimmer is set up and i wire any modulation the same way. If you dont use a battery you can fit an expression jack right below the in or out jack

[noisette]

https://www.banzaimusic.com/Wah-Pedal-Shells/
great thread!

btw interesting the joyo uses th components

[Fancy Lime]

All of that makes me wonder: Maybe I should give the Ibanez FL-9 a go. Reportedly, the Joyo Classic Flanger is a more or less exact replica of that one. Although the sources for this info are highly shaky and the whole theory may be based on little more than the knobs having the same utterly weird names, for all I know. Considering how sacrilegiously cheap the Joyo is, I might just buy that one and mod it and see how it goes. Assuming it is indeed the FL-9 design, then it has a Manual control (called "Delay Time" cause that won't confuse guitar players at all on something that isn't a delay) and the Width knob is positioned such that a switch can be inserted here to disconnect the LFO and/or insert an envelope follower here.

I've been modding some joyo flangers lately and can confirm its an FL9 clone but with true bypass. It uses through-hole components so a lot easier to mod than most Chinese clones that use SMT. You can snip the lfo off the width pot and attach other sources, but the width control and the manual control interact with each other so i have the manual pot wired up similarly to how the trimmer is set up and i wire any modulation the same way. If you dont use a battery you can fit an expression jack right below the in or out jack

Good to know, thanks! Interesting indeed that they use through-hole. I should expect smd would be easier and cheaper when producing on an industrial scale. But then again, with through-hole, they can just straight up copy the FL-9 layout, no R&D required, as long as they rotate a few components to avoid copyright infringement.

Cheers,
Andy

Andy