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 Forum index » DIY Hardware and Software
CV Quantizer PCB Layouts
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loss1234



Joined: Jul 24, 2007
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PostPosted: Wed Jun 04, 2008 5:30 am    Post subject: Reply with quote  Mark this post and the followings unread

i got mine for 12 from digikey
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Etaoin



Joined: Jun 30, 2005
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PostPosted: Wed Jun 04, 2008 5:37 am    Post subject: Reply with quote  Mark this post and the followings unread

loss1234 wrote:
i got mine for 12 from digikey


Digikey price is not the issue, their shipping to Europe is.

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fluxmonkey



Joined: Jun 24, 2005
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PostPosted: Wed Jun 04, 2008 8:38 am    Post subject: Reply with quote  Mark this post and the followings unread

guitarfool wrote:
ericcoleridge wrote:
However, I've recently discovered an option that I didn't previously know of. There is a quantizer built into the Blacet "Improbability Drive" module. The kit is $150 (which is still high, but much better that buying a doepfer quantizer for $250, and then putting it behind a new panel).

The quantizer on the Blacet has a switch for chromatic, major, minor and diminished. Plus the rest of the Improbability Drive looks pretty cool and useful. Similar to the Wogglebug or Buchla Source of Uncertainty. I'm leaning in this direction.


I have one. It works pretty good, but the scale is selected by a trimmer on the board. I plan on having this done from the panel.

He used a PIC, DAC0800 and a couple of op amps for it - pretty simple actually. You could petition John Blacet to produce a board with just his quantizer on it. Or at least the programmed PIC with a schematic. If there was enough interest, he might do it. Very Happy


i asked john about this when the Imp drive first came out... he said the resolution of the PIC as implemented was pretty low, not good enuf for a stand-alone quantizer. I did bring the scale selector pot to the front panel, tho... and I've seen other folks have modded theirs to accept an external signal into the quantizer.

I have 2 Miniwaves, both with ScaleQuantizer chips in the B ROM socket. Works great.

bbob
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BananaPlug



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PostPosted: Wed Jun 04, 2008 9:57 am    Post subject: Reply with quote  Mark this post and the followings unread

Here's a link to my post about the ID2510, including that mod. It really is a very nice module for a whole host of reasons. Perhaps not the ultimate in quantizer.
http://electro-music.com/forum/topic-25179.html
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Etaoin



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PostPosted: Thu Jun 19, 2008 10:59 am    Post subject: Reply with quote  Mark this post and the followings unread

I've been wondering; what is so special about the AD7245A that it can't be replaced? We are only using 7 of the 12 bits, we are not using the double buffer. One would say that any flash D/A with more than 7 bits would do.
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zthee



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PostPosted: Fri Jun 20, 2008 2:42 am    Post subject: Reply with quote  Mark this post and the followings unread

I second that thought! Why does it have to be a AD7245?

I'm in "desperate" need of a quantizer. Even thought about learning to program AVR just to get one..
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Clack



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PostPosted: Fri Jun 20, 2008 4:03 am    Post subject: Reply with quote  Mark this post and the followings unread

sorry about the layout thing - I still have it but I dont have a electronics space to work in at the moment wich has made me loose my enthusiasm for cad stuff - I also question the DAC but it has just been well tested and tweaked by scott sites - to do it properly somone should get into it and work it out with a cheaper IC - maybe a discrete one may be more universal!

i.e along the lines of - http://www.ucapps.de/mbhp_aout_lc.html

Im planning this summer to really get my head technically in gear ( I spend way to much time just copying schematics without understanding them ) and this may be one of the projects

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Etaoin



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PostPosted: Fri Jun 20, 2008 7:59 am    Post subject: Reply with quote  Mark this post and the followings unread

One advantage of the AD7245A is of course that it generates it's own reference voltage. But that's nothing a seperate reference won't handle.

By the way, does someone know why Scott uses two 4516's instead of just a single 4024 or even a 4040?

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Clack



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PostPosted: Fri Jun 20, 2008 8:09 am    Post subject: Reply with quote  Mark this post and the followings unread

I beleive he seperated parts of the schematic to go through different chips due to bleedthrough but im not sure if that applies to the cmos
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bearblock



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PostPosted: Fri Jun 20, 2008 9:55 am    Post subject: Reply with quote  Mark this post and the followings unread

Quote:
I'm in "desperate" need of a quantizer. Even thought about learning to program AVR just to get one..


that's what i did!: http://www.electro-music.com/forum/topic-26667.html

i found the a/d a bit glitchy though. maybe on a proper pcb with a ground plane it would be ok, but alls i have is stripboard....
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funkyfarm



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PostPosted: Sat Jul 19, 2008 8:35 am    Post subject: Reply with quote  Mark this post and the followings unread

looking at pin4 of DAC AD7245A highlights analog ground, represented by a white triangle and a capitol A next to it.

They are several points like this on scott stites' schematic.
I'm sure they have to be connected altogether, i guess the shortest/most meticulous to be required...
but I wonder about linking this analog network to main ground. the trick is to have only one common point between ground (zero/voltage reference) and analog ground ?

this is the way to avoid interference here ?

cheers,

ff


http://mypeoplepc.com/members/scottnoanh/birthofasynth/id15.html


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Etaoin



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PostPosted: Sat Jul 19, 2008 8:40 am    Post subject: Reply with quote  Mark this post and the followings unread

Indeed, you need a single point where analog and digital ground come together and that point usually needs to be as close to the power supply as possible. So if you're building a module, the power connector would probably be the best point.
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funkyfarm



Joined: Jan 21, 2007
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PostPosted: Sat Jul 19, 2008 8:45 am    Post subject: Reply with quote  Mark this post and the followings unread

thank for that prompt and clear explanation.

Farnell has 28 AD in stock...


edit : ooopps, now, only 26 left.
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widdly



Joined: Jun 25, 2007
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PostPosted: Sun Jul 20, 2008 7:32 pm    Post subject: Reply with quote  Mark this post and the followings unread

I would have thought you could use a DAC08 instead. They are really cheap in my part of the world.
Last edited by widdly on Thu Aug 05, 2010 10:11 pm; edited 1 time in total
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okvern



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PostPosted: Sun Jul 20, 2008 7:57 pm    Post subject: Reply with quote  Mark this post and the followings unread

widdly wrote: "I would have thought you could use a DAC08 instead. They are really cheap in my part of the world."

Agreed!

Actually, an R2/R ladder DAC works pretty well, too (at least as well as a DAC08/DAC0808 in my tests). For a *quantizer*, what I want are notes--not all of the voltages in between. So what I do is use the upper 6 bits of an 8-Bit DAC and 0-63 note values over a 5.229 volt range, adjusting the output amplifier for .083v per note. If I need to expand the range, I can go to 7 bits and 0-127 note values.

If I need better speed, I can use an AD558 or similar, again limiting the input to 6 bits. This is the approach used in the Pro-One--an early microcontroller synth design that is well worth studying. (That said, this DAC is a little more expensive than I like, at $10-12.)

The point is: for quantization, you do not need the accuracy of a 10, 12, or even 16 bit DAC. If you *do not care* about the voltage values in between--which is why you're building a quantizer in the first place--then why not create a DAC where every value in equals a note out in 1v/octave scaling?

If you attach this DAC to a microcontroller--my experiments have been with an Arduino, but just about any will work--you can limit the quantization to specific scales or modes, as well.

If what you need is continuous controller voltages--then, yes, higher resolution DACs are better. But I think we sometimes get hung up on the notion that more bits in a DAC will give us better accuracy, and end up spending *way* more than we need.

Thanks,

Ole
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Rykhaard



Joined: Sep 02, 2007
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PostPosted: Sun Jul 20, 2008 9:38 pm    Post subject: Reply with quote  Mark this post and the followings unread

My current desires (with NO DAC experience period) are to have a sequencer where each step is controlled by a set of ON/OFF switches, acting literally, as BITS. Smile

Now - I DID verify a set of resistors to 1% for myself, to build an R-2R 'DAC' for 4 switches. With only 1 resistor (or pair of) being very close to 1% edge, did I have a slight tuning problem. Otherwise, the other 3 switches in the set of 4, did give me proper 1V/oct notes. Smile

Now my question is - whether to setup to 6 switches per step, for an 8 step sequencer, going with a DAC chip (using the 6 upper bits as you'd stated) or bring home a high resolution HP tester from work, to match myself 1% resistors to 0.1%.

Any thoughts on this? My only desires, are for the standard 1V/oct. notes, for the sequencer. All other aspects (pitch bend / etc.) are taken care of externally.

Thanks for any thoughts on this. Smile

BTW - if I'm going with a chip - what else do I have to worry about with using it? An external clock, if I'm not mistaken - anything else?
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widdly



Joined: Jun 25, 2007
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PostPosted: Mon Jul 21, 2008 7:57 pm    Post subject: Reply with quote  Mark this post and the followings unread

Rykhaard,

You might want to check out Ken Stone's Diatonic Converter. It looks almost exactly like what you want.

It has 6 digital inputs, 3 bits for octave and 3 bits for notes. It outputs a v/oct signal.

here...

http://www.cgs.synth.net/modules/cgs41_diatonic_converter.html

Last edited by widdly on Thu Aug 05, 2010 10:11 pm; edited 1 time in total
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Rykhaard



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PostPosted: Mon Jul 21, 2008 9:15 pm    Post subject: Reply with quote  Mark this post and the followings unread

widdly wrote:
Rykhaard,

You might want to check out Ken Stone's Diatonic Converter. It looks almost exactly like what you want.

It has 6 digital inputs, 3 bits for octave and 3 bits for notes. It outputs a v/oct signal.

here...

http://www.cgs.synth.net/modules/cgs41_diatonic_converter.html


OMFG!!! Why the heck didn't _I_ think of that????? Embarassed Embarassed Thankee greatly for including the link, Widdly! I just went off and read the whole thing and sent a confirmation question about my idea and the Diatonic to Ken. I don't see a problem with it, but wish to read 'yes' from Ken before I order 1 or 2 of them.
THAT module could take care of all of my design troubles that I've had over the last couple of years! Very Happy
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widdly



Joined: Jun 25, 2007
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PostPosted: Mon Jul 21, 2008 10:41 pm    Post subject: Reply with quote  Mark this post and the followings unread

Ken's site is like that. You think of some idea you think is cool and new. Then you check cat girl and Ken's built it already and made it more betterer.
Laughing

Last edited by widdly on Thu Aug 05, 2010 10:11 pm; edited 1 time in total
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Rykhaard



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PostPosted: Mon Jul 21, 2008 11:10 pm    Post subject: Reply with quote  Mark this post and the followings unread

widdly wrote:
Ken's site is like that. You think of some idea you think is cool and new. Then you check cat girl and Ken's built it already and made it more betterer.
Laughing


Definitely! Ken was the first chap that I started buying from in late 2005 or early 2006. Smile I now only build basically, what I come up with myself, or a modified version of someone else's or something very simple. Otherwise, I'm now buying from Ken and Ray Wilson and happy as heck. Smile

Wondering whether to start expanding from my 4 channel MIDI to CV limitation of my Roland MPU-101. I'm going to need more channels eventually.
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funkyfarm



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PostPosted: Thu Aug 07, 2008 5:58 am    Post subject: Reply with quote  Mark this post and the followings unread

Quote:
Only minor error I've found in scott schems : with TL074, +input is pin 12, not pin 13... (see page 3of3, IC U11D, quantizer channel #4) Smile
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philpeery



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PostPosted: Sat Aug 09, 2008 9:28 am    Post subject: Reply with quote  Mark this post and the followings unread

I have been looking at Scott's quantizer design since I am in need of a couple of quantizers, and don't want to go the whole miniwave or quantix route at this point. I really just need a couple of standalone quantizers to keep things simple. I've got too many irons in the fire right now with my modular so I don't want to go totally crazy here. As a side note, I am also working on a CNC panel engraving machine (wink, wink Wink ).

So my quesiton is, has anyone built Scott's design, on breadboard, stripboard, or pcb? I'd be curious about anyone's experiences with the circuit (since he designed it, I'd like to hear from Scott's too!). I see that the AD chip is available from digikey, and the other parts are already in my parts bin! It looked like there was some PCB design work going on from Mr Clack, has anyone else gotten anywhere with this other than him? If not, I might take a swing at a single sided PCB later in the summer.

Thanks for any input!

Phil
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ALH84001



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PostPosted: Tue Aug 12, 2008 2:20 pm    Post subject: Reply with quote  Mark this post and the followings unread

zthee wrote:
I second that thought! Why does it have to be a AD7245?


Just scanning quickly thru this thread, I'd like to suggest the Texas Instruments TLC7524 8-bit multiplying DAC, about $4.50 from Mouser. I find them convenient to use.

If you're not using all 12 bits of the AD7245, you can save some $$.
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Coriolis



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PostPosted: Wed Aug 13, 2008 12:28 am    Post subject: Reply with quote  Mark this post and the followings unread

Quote:
Texas Instruments TLC7524 8-bit multiplying DAC


...which futurlec has for 1.90$... Cool

C

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Etaoin



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PostPosted: Wed Aug 13, 2008 3:00 am    Post subject: Reply with quote  Mark this post and the followings unread

Biggest difference seems to be that the 7524 doesn't provide it's own reference voltage, so it will require some extra circuitry if used in Scott's design.
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