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

[Tony Mowbray]

Jean-Pierre,

 

Simply, if the flip-flops are feeding each other sequentially, this will
naturally be out of phase on successive sections. There will also be a
propagation delay. As the oscillators are running at a relatively high
frequency and then divided to produce the frequency required, the human ear
will be unable to discern the phase or delay within.

 

Furthermore, if it does, it becomes as “effect” that characterises the type
of instrument.

 

The odd flip-flops will be roughly in phase and the even flip-flops will be
in phase also. The odd and even flip-flops will be roughly 180° out of
phase. Your ears are pretty slow to operate in comparison, so will not
discern much difference. Hope this helps.

 

 

Kind Regards

 

Tony Mowbray

 

From: Synth-diy <synth-diy-bounces at synth-diy.org> On Behalf Of Jean-Pierre
Desrochers
Sent: Thursday, February 1, 2024 8:31 AM
To: synth-diy at synth-diy.org
Subject: [sdiy] Now tube type (6SN7) flip-flop circuit.. Follow up...

 

I  asked this question about flip-flops because I have a new project in
mind..

I once had a vintage Hammond RT2 organ with a wide church type pedal board.

This pedal board sounded amazingly beautifull !

This pedal board sound was produced by a bunch of successive flip-flops made
out of 6SN7 triode tubes

In a chain distribution.. Producing all the needed pipes sounds (1’, 2’, 4’,
8’, 16’, 32’).
I thought I could reproduce these sounds using a simple CD4040 counter,

Or best, a PIC micro that would have MIDI input and take care of all the
push buttons/leds

That select the actual footages, AND generate all the successive square
waves (yes, these flip-flops have roughly shaped square waves output)
to be filtered using Hammond’s filters design.
Have a look at the below ‘Hammond RT2 PedaL Solo’ schematic ..

As you will see the actual waveforms kept to be filtered are derivated going
down short pulses

>From each flip-flops output like this :



 

These pulse are filtered by successive low pass filters and mixed together
to the final output.

But to be a good Hammond pedal simulation I need to know the actual phase of
each flip-flop outputs

Against each others..

Are these FF’s changing states on each preceding FF on going down or going
up situation ?

I did not measure these waveforms in the past BUT I do know
each FF change state on the ‘going down’ pulse of its pre-driver.

I think using all the 6SN7 tubes output (always inverting their inputs)

I could figure out all the waveforms in this schematic but I’m not sure at
all..

 

BTW, I made a LTSpice simulation using this schematic with all the same
components
including all the necessary 6SN7 (and the two 6J5’s V1 & V6)

And had very bad results.. noisy unreadable waveforms on many places..

 

What do you think about the actual phasings of all the FF’s square wave
output against each others ?

 

JP

 



 

De : Synth-diy <synth-diy-bounces at synth-diy.org
<mailto:synth-diy-bounces at synth-diy.org> > De la part de Jean-Pierre
Desrochers
Envoyé : 31 janvier 2024 10:43
À : synth-diy at synth-diy.org <mailto:synth-diy at synth-diy.org> 
Objet : [sdiy] Transistor type flip-flop circuit.. What makes the 'power up'
state of it ?

 

Hi list,

I have a question about the behaviour of transistor type flip-flop circuit

When the DC power is applied to it..

The following schematic of Boss CE-2 pedal shows the flip-flop at the bottom
right.

Why when the DC power is applied :  collector of Q6 goes high (to make the
pedal in the ‘no effect’)

And it’s not Q7 that goes this way instead ?

I know that C23 (.01uf) pull down the trigger input when DC is applied
to put the pedal in the ‘no effect’ position, but why is Q6 selected ?

This is a ‘balanced’ flip flop circuit and both sides should behaves the
same

But some kind of selection is done here.

 

Could someone explain that behaviour ?

 



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