[sdiy] Now tube type (6SN7) flip-flop circuit.. Follow up...

[Tony Allgood]

If you are creating pulse waves, or a pulse like wave, from the output 
of the flip flop, it is important to consider the phase relationship of 
the flip-flop outputs all together. Phase matters not if you listen to 
these derived pulse outputs individually, but on an organ, or string 
machine, octaves are mixed together, either by playing octaves on the 
keyboard or using the footage mixers. If you don't have the correct 
phase relationship the resultant mix will sound weak.

Using a cascade of flip-flops to divide down will result in a set of 
square waves. If the pulse is being created by a standard 
differentiator, a high pass CR circuit, then it is the position in time 
of the leading edge of the output square wave that is important. Those 
leading edges must line up, so that the leading edge of the lowest 
frequency must be synchronised with all the others. That is, when the 
lowest octave square wave goes up, then so must all the others.

Note that the propagation delay within the chip itself is minimal and 
can be ignored.

How do I know this? I designed a SAJ110 octave divider replacement board 
for string machines. The scope outputs looked perfect. But it sounded 
like pants because every other octave when played together destructively 
interfered and sounded wrong. It used the 4520 to divide the octaves.

The problem was solved when I ensured the leading edges of all the were 
synchronised. I could have done this with additional invertors, but it 
was smaller to do it with a couple more 4520 stages. Now when you mixed 
octaves the sound become louder.

At this point I should present a diagram to show this. But I've lost my 
original sketches I did on graph paper to show how the waveforms add 
together. If I find it I'll post it.

Tony

www.oakleysound.com