Frequency Shift Register

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andrewF
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Frequency Shift Register

Post by andrewF » Mon Mar 08, 2010 7:37 pm

Have been toying with this circuit for a couple of months. The basic idea seems to work although don't expect this to be useful for 'Switched on Bach' covers when granny visits.

I would appreciate any suggestions/comments/mods.

Still not sure about the signal input circuit, may need to adjust the resistors on pins 11 & 12 of the 4046 which set the operating frequency range of each chip. Maybe pots or trimpots here?

from my homepage -

The Analog Shift Register is well known, where voltages are shifted over three stages. This is the same in concept except it shifts frequencies and uses 4046 PLLs to do it.
Which means you have to be very optimistic to expect to see the frequency you fed into stage 1 to appear at stage 4.
For a single audio input and a clock signal, it produces 16 audio (or possibly CV/gate/trigger) outputs of related frequencies.

March 2010: Here is an UNTESTED draft of the full schematic. The circuit has been breadboarded with two 4046 stages and certainly put on a performance.
The clock ticks over the 4017 decade counter which enables the 4046 PLLs to shift their frequencies to the next stage.
first clock shifts PLL3 to PLL4, 2nd is PLL2 to PLL3, 3rd is PLL1 to PLL2 and 4th allows a new frequency to be introduced to PLL1.
Or you can feedback one of the outputs from PLL4 and get a loop going....oh yes:-)
But don't expect any kind of perfect tracking, these are 4046s. Your loops will drift horribly at best or just generally misbehave.
The frequencies are shifted by connecting the comparator outputs to pin 9 of the 4046s. The 4017 counter allows each 4066 switch to close in turn. The frequency from the comparator is smoothed to a voltage by the 10k resistor and 0.1u cap.
Once the 4066 switch opens, the voltage in the cap is held thanks to the hi-Z input on pin 9.
This voltage on pin 9 determines the frequency of that PLL's VCO.


schematic vers2 [72kb] pdf

MP3 demo

edit 18/3/10 updated link to vers2 of schematic
Last edited by andrewF on Thu Mar 18, 2010 7:40 am, edited 1 time in total.

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neandrewthal
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Post by neandrewthal » Mon Mar 08, 2010 7:42 pm

Very exciting :goo:

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falafelbiels
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Post by falafelbiels » Mon Mar 08, 2010 8:02 pm

interesting indeed, but I'm not going to try and break my brain over this one again I think. I don't understand PLL anyway. But I did get some extra 4046 in the mail when I ordered for the CGS digital noise. In fact I have all the parts needed I believe...

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andrewF
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Post by andrewF » Mon Mar 08, 2010 10:19 pm

Don't worry - PLL functions and behaviour are often the source of much animated discussion on electronics forums.

Generally for synths, they are good for noise/cacophony, as in the CGS digital noise or wogglebug.

this module won't be much different :party:

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Post by DGTom » Mon Mar 08, 2010 10:56 pm

neandrewthal wrote:Very exciting :goo:

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falafelbiels
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Post by falafelbiels » Wed Mar 10, 2010 8:23 am

andrewF wrote:Don't worry - PLL functions and behaviour are often the source of much animated discussion on electronics forums.

Generally for synths, they are good for noise/cacophony, as in the CGS digital noise or wogglebug.

this module won't be much different :party:
Well I kind of get the workings, just not the magic.
PLL = the new vactrol maybe? both being seemingly magical...

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Post by wetterberg » Thu Mar 11, 2010 3:54 am

DGTom wrote:
neandrewthal wrote:Very exciting :goo:
PLLs AND shift registers in one thing? Sign me up, buddy!

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Post by BugBrand » Thu Mar 11, 2010 4:41 am

Tuneful demo!

Sounds like a very fun concept!

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Post by DGTom » Sun Mar 14, 2010 8:32 pm

I was just looking at a partly disassembled lunetta PLL module... & remembered I'd used Pin 1 (SD or whatever the datasheet calls it) as a neat little indicator. I think the pin goes high when the VCO frequency locks to the incoming signal... or something like :hmm:

Not sure how much use it would be here, but, may provide some sort of visual feedback?

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Post by andrewF » Sun Mar 14, 2010 9:24 pm

okay will give it a try
might make an interesting display

F.Mims had some FSK circuits with pin1 NORed to pin2, will try and find them.

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Post by DGTom » Sun Mar 14, 2010 9:39 pm

I'm pretty sure Doepfer uses pin 1 in some way for the LED on the A-196 as well... or at least the way the 196 blinks at me is very similar to the way my lunetta PLL does the same.

My module was just straight from the TI datasheet with pretty similar values as you have for the cap / resistor inbetween VCO out / VCO in.

With 4 of em all going & some LEDs for the 4017 outs that'd be some tasty blinken :banana:

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Post by andrewF » Mon Mar 15, 2010 11:16 am

don't suppose you could have a look at the Offset pot and range switch of the A-196?
I'm guessing it is 1M and the switch will select different caps.
After reading Scott R. Gravenhorst's PLL article maybe a max freq pot for each stage would be interesting......so would range switches and LPF damping pots, but maybe the feature bloat would be a bit much

cheers

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Post by neandrewthal » Mon Mar 15, 2010 12:04 pm

The offset pot is C50k.

Range switch has 3 caps attached. From small to large marked:

.1
10n
105

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Post by andrewF » Mon Mar 15, 2010 6:22 pm

Thanks
looks like this circuit will need some refinement to work out the best functions to bring to the panel.

which of these controls and the frq pot are used most often?

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Post by DGTom » Thu Mar 18, 2010 2:35 am

damn, thought I replied... autumn heat must be getting to me :confused:

I'd say the range switch would be usefull in addition to the pot, altho, with a 1M pot you can get quite a range out of the 4046.

A pot would be cool for the LPF, but, that could be a switch as well, Fast / Slow or Tight / Slewy :D

The other thing I was thinking, instead of having so many outputs, maybe multiplexing those? a pair of 4052s & you could have 4 outs or maybe 2 4051s... still, it'd need another counter (or 2) then I guess :hmm:

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