CD4047

[nedyoung]

Can I use CD4047 to drive MN3205 BBD chip??
I know EH often use CD4047 to drive the BBD chip like MN3207 or MN3007
I was wondering if I can use the same trick to drive the MN3205 chip??

[ExpAnonColin]

You sure can...  Try looking at this schem for help:
http://www.morleypedals.com/sfb.pdf

-Colin

[Mark Hammer]

A number of BBD-based pedals besides the Morley one/s use the 4047 to drive the BBD.  There are plenty of other candidate CMOS chips you will also see driving the BBD clock inputs.  They are all good.

From what I understand, there are a few key features which determine which CMOS chip you see in schematics:

1) Either the chip itself has to be capable of producing a complementary HF clock signal from an LFO input (like a CD4046 or 4047), or else be capable of dividing a HF clock to provide complementary buffered outputs (like a 4013).

2) If the clocking needs are not especially stringent, most of the above-mentioned chips are fine.  Where a BBD chip has to be run at a very high frequency (for flanging), the high input capacitance on the clock input pins of the BBD require lots of current in the clock signal to provide nice crisp square pulses.  In those instances, you are likely to see several paralleled invertor sections in a 4041 or 4049 just ahead of the clock input pins precisely for that reason.  This is most especially true of the Matsushita MN3xxx series of chips.  If the pedal does not aim for ultra-high clock rates (>500khz) usually all you'll see is the typical 4047 or 4013.  The MN3101 and 3102 were intended to replace all the clock generation/division circuitry with a smaller self-contained package.  It works well when aiming for clock rates within spec (e.g., 100khz or less) but needs a little bit of extra help when pushing the envelope.

[nedyoung]

thank for the reply!!
I'll do some research~ :twisted: