Need Your DAC Recommendation

I am in the process of designing/building a home-brewed midi controller for an analog synth (analog except for the midi controller, that is). I have an ATmega168 chip reading midi messages, and now I need to generate a Control Voltage (CV) that is related to the note's pitch.

I need at a minimum 12-bits of precision for the digital to analog (voltage) conversion. Speed is not critical, as this will be at best approx 64 beats (pitch changes) per second or less.

The problem I keep running into is that once I select a part, I find out that it is either unavailable or that it is now obsolete. There are numerous parts that exceed my requirements (with say 24-bits etc.), but come at a high price. Or they are not available as a DIP package. Also DSPs are out for this project.

I must insist on a DIP package format, as I am un-equipped for any surface mount stuff. My eyes can barely focus on the DIP pins as it is.

So what I am looking for is a recommendation:

for a 12 to 20 bit DAC chip.

It must not obsolete or hard to find, and hopefully is reasonable. ;-) I suppose anything less than $20 US would be "reasonable" enough (

Reply to
Charmed Snark
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DIPs are falling off the edge of the world. I suggest getting a good soldering iron and one of those head mounted magnifying setups. With a bit of practice you can work on surface mount parts with big pins. (That's relatively big.)

Go to Digikey. Poke DAC into their search box. Scroll down until you get to the Integrated Circuits header. Click on the Digital to Analog Converters link (mine says 8,920 items) On the Package selection area, select 8-DIP and 8-DIP (300 mil) (I use shift-left-click or ctrl-left-click to select multiple items) Poke Apply Filters That reduces things to 205 items. Some of them are 8 or 10 bits, So select 12, 13, 14, 16 under Number of Bits. Poke Apply Filters again. That reduces things to 156 items.

You can now do a linear search or reduce the search some more by selecting a manufacturer or number of bits or ...

Many of them will be Non-Stock. There are several that are in stock.

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Reply to
Hal Murray

Hal Murray expounded in news:mYGdnRVYrOHTTrzUnZ2dnUVZ snipped-for-privacy@megapath.net:

I am resisting... ;-)

I've been there before, but I guess I never thought of trying the "8 pin DIP" filter. That seems to net what I was after, thanks.

Yes, many many parts out of stock.

However, I just discovered that they have a filter for eliminating the out of stock items. Man, that really helps! I don't know why I didn't see it before? Probably the same reason I avoid surface mount parts..

Thanks

Reply to
Charmed Snark

Charmed Snark wrote in news:Xns9B599672487D4SnarkCharmedFerSure@194.177.96.26:

I've had no problems with the MCP4922-- two channels on 14 pin DIP.

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Scott
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Reply to
Scott Seidman

Scott Seidman expounded in news:Xns9B59AF5789E52scottseidmanmindspri@

130.133.1.4:

..

Hey, that is not bad! You gotta like the price and the features. And you get two for the price of one.

I especially like the fact that it has buffered output, although I should probably build a bipolar buffer for it anyway.

I haven't had time to fully digest the specs yet, but do you think that the chip's buffering would be suitable to drive a VCO and/or possibly one or two other signal driven synthesizer modules? These are all signal level inputs. My only other concern is static damage due to patch cord insertion/removal.

Thanks

Reply to
Charmed Snark

Charmed Snark wrote in news:Xns9B5A6C9FA57FDSnarkCharmedFerSure@194.177.96.26:

I always end up buffering these because the outputs are 0v-Vref, and my apps usually call for a bipolar signal. Buffering and subtracting out a precision voltage ref of Vref/2 is usually my route-- easier than running through an AC coupled design!! For transients, you can use zener diodes on the output.

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Scott
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Reply to
Scott Seidman

Scott Seidman wrote in news:Xns9B5A7A67A82CEscottseidmanmindspri@130.133.1.4:

With a small capacitance too. That combination will protect laser diodes so it's good for most things. You could also use varistors, 6V and 12V types often come up cheap on eBay, though they're usually surface mount types. And Robin Bowden told me that the zener/cap combination works better anyway. From what I've seen, I agree. A varistor might be worth it if you're protecting an input that frequently has long lines patched to it.

Reply to
Lostgallifreyan

Lostgallifreyan expounded in news:Xns9B5ACAD50C296zoodlewurdle@216.196.109.145:

My application is fairly simple. I just need a 0-4.x volt control voltage to select a pitch from the VCO (voltage controlled oscillator). Given that keyboard pitch changes are less than say 100/second, I am not too concerned about speed and transients etc. The VCO signal is turned on/off by a "gate" signal which is separate, and there are also signals "bend" and "pressure", which go to other modules for filtering and envelope modulation.

Thanks again for the chip tip.

Warren.

Reply to
Charmed Snark

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