Need Your DAC Recommendation

[Charmed Snark]

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 (<= $13
would be better). I need at least two of these initially, but potentially
more down the road.

Parallel or serial interface.

The main suppliers I prefer include DigiKey, Jameco or Mouser. I would
consider other sources, if it is worth my while. ;-)

Much obliged for your collective wisdom.

 

[Charmed Snark]

Hal Murray expounded in

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.)

I am resisting... ;-)

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

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.

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

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

 

[Scott Seidman]

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 (<=
$13 would be better). I need at least two of these initially, but
potentially more down the road.

Parallel or serial interface.

The main suppliers I prefer include DigiKey, Jameco or Mouser. I would
consider other sources, if it is worth my while. ;-)

Much obliged for your collective wisdom.

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

 

[Charmed Snark]

Scott Seidman expounded in 130.133.1.4:

...

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

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

 

[Scott Seidman]

Scott Seidman expounded in 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

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.

 

[Charmed Snark]

Lostgallifreyan expounded in

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.

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.