Flangers: CD4049 Hex Inverting Buffer and Converter, what is it good for?

[chance.lima]

Hi guys,

Can anyone tell me in why I might sometimes see a CD4049 between a BBD and lets say CD4047 or MN3101 CMOS chip; what exactly is it doing to the signals passing through it and what are the benefits and/or disadvantages. I'm just looking at flanger designs and how they work as I am working on flanger projects for the DIY community.

Thanks.

[R.G.]

The CD4049 is a CMOS hex (i.e. six of them in there) inverter/buffer. It is intended to take in a weak-ish, low current input signal and be able to drive a strong, high current output signal with fast rise and fall times in logic systems. It's use in all things using bucket brigade delay chips is to provide a strong, high current output signal to drive the clock inputs of the delay chips, which have high internal capacitances. Less-strong drivers for these inputs cannot drive the high capacitance inputs up and down quickly enough to make them valid logic/clock transitions.

There are other non-standard uses for the CD4049, but logic-signal inverting/buffering is what it's intended for. There are no analog/sound signals passing through it in this use. It just speeds up and cleans up the clock signal for the delay chip. You see it when someone either (1) knows or (2) suspects that the clock signals need strengthening. I suppose you're adding another instance: (3) when someone sees it in other flanger designs and decides to toss one in.

[chance.lima]

Ah brilliant, I have a clearer understanding now, thank you for explaining this to me R.G., cheers mate!

[Mark Hammer]

Flangers that are capable of reaching very short delays (which we will arbitrarily define as less than 0.5msec) often use a CMOS chip of some form to overcome the input capacitance of the BBD clock-input pins.  The traditional MN3101/3007 or MN3102/3207 pairs tend to crap out around 100khz clock rate.  I've seen 3007s clocked to well over 1mhz with the additional support of a hex invertor.
Explained in a little more detail here: https://www.premierguitar.com/articles/25035-behind-the-bucket-brigade
Apologies for the self-promotion.