Quantizers and sequencers

Coriolis · Joined: Apr 11, 2005 Posts: 616 Location: Stilling, Denmark

Hi there.
Ive been looking at various sequencer-designs for my Soundlab (and a modular, if I get around to it), and it strikes me, that in order to tune each step to a note in a scale, a stepped voltage would be needed. Otherwise one would need finetuners to find a specific note, and that wouldnt be to performance-friendly. After looking at the quantizer-project at Scott Stites' page, I realize that these things already exist (of course), but what I'm not sure of, is how to connect the two - quantizer and sequencer? Which comes first, or how are they interfaced? Does anyone know of simpler projects like it, or is the Stites project a basic design?

Where can I find basic explanations of various modules in synthesizers (logic and cv - stuff)?

Thanks,
C

Scott Stites · Posted: Wed Mar 01, 2006 10:35 am Post subject:

The quantizer on my page is a bloated version of a basic design. It certainly works, and works well, but I'm not happy with the parts count of my convoluted comparator/S&H trigger scheme. It just works better than anything I had at hand to try.

I've got a link to David Brown's design on that page (which may work quite well) and another one that I don't think would work quite well at all (though is a good starting point). Reason I'm not wild about it is that it uses a ripple counter to clock the DAC - not the best situation there (been there done that).

Another thing - I think 5 octaves (or even less) rather than 10 octaves would be more than enough - figure 128 steps for a single pot, and that sets you up for a very narrow little slice of the pot per step. The 10 octaves was a requirement for a project that may be on hold now, for unrelated and unhappy (sad) reasons.

You might check out the Oberheim sequencer schematics or ARP 1601 schematics for other ways to do it as well.

A different approach is to eschew the staircase/comparator method altogether and use an EPROM to store the DAC values. In this case, it would be a matter of using an analog to digital conversion on the input signal to address the EPROM with the output of the ADC, and then decoding the output of the EPROM with a DAC. This would give you the advantage of storing different tunings.

The Blacet/Wiard Miniwave, for example, can fulfill this function.

The actual connection of a quantizer is quite simple. Sequencer->Quantizer->VCO. That's of course if you wish to use a sequencer to control a VCO. Any other CV source or destination could be used.

Cheers,
Scott

Coriolis · Joined: Apr 11, 2005 Posts: 616 Location: Stilling, Denmark

Thanks a bazillion! Very Happy

I love long answers!

I did have the thought myself, that an EPROM or similar might be used (have no clue about those things), but I would I would need to learn about programming first, right? Although, that might be worth my while to get stuff like different tunings and such. As a user of software sequencers, I am probably rather spoiled in the features department... Wink

Your advice on limiting the octave range is noted (btw, my best wishes and hopes for that undisclosed sad matter you refer to).

I may go the programming route, but for now, i think i'm going to try a couple of the easy 4017 based designs I've seen floating around...

Thanks again,

Christian.