[sdiy] Re: Inexpensive 16 bit DAC?

[harrybissell]

And if you used switches from Maxim or Siliconix etc that allow negative
voltages, you would have invented the "multiplying DAC".

But the 1M resistors are really kind of high, and the noise would KILL
you in a true 16 bit fantasy converter

(and if you went real low, current would probably kill you :^)

So you ask yourself... lady or the tiger ?   If stranded on a desert island...
would Harry prefer to be left with a BBD or the parts to make his own
16 bit DAC ???    :^P

H^) harry

Ray Wilson wrote:

> Yes for a simple A to D convertor the switches are overkill but... wait
> there's more. You could apply an AC signal that was oscillating about vdd/2
> and this would now act like a digital attenuator. So see there was method to
> my madness. Also the switches allow you to adjust the highest voltage output
> by connecting all of the inputs to a regulated voltage lower than the vdd.
>
> But I admit your observation is correct about the simple A to D convertor.
> (my face is a little red).
>
> Ray
>
> ----- Original Message -----
> From: "Scott Gravenhorst" <music.maker at gte.net>
> To: <synth-diy at dropmix.xs4all.nl>
> Sent: Thursday, April 28, 2005 8:22 AM
> Subject: Re: [sdiy] Re: Inexpensive 16 bit DAC?
>
> > It seems to me that the analog switches are overkill and could be replaced
> > by
> > a CMOS inverter gate (or buffer) per bit.  It looks to me that the
> > switches
> > are simply providing a solid 12 volts or a solid ground to one end of each
> > resistor.  I'm really not sure why a 4069UB  wouldn't work as well at less
> > than half the part count.  Ok, you would want to do TTL to CMOS level
> > conversion, but still it would be fewer parts.  A 4066 is a bidirectional
> > device but you are using it as a unidirectional device which is why I
> > think a
> > 4069UB design would work just as well.  The 4069 would be powered from +12
> > and ground, the output of each gate hits the resistor.  If the whole thing
> > were powered by +5 and ground, it would be even simpler.
> >
> > Is there some advantage the 4066 provides that I'm not seeing?
> >
> > "Ray Wilson" <raywilson at comcast.net> wrote:
> >>
> >>Here is a DAC with CD40106 and CD4066 chips. I have demo'd 4 bits but you
> >>could go as many as you had patience to build.
> >>
> >>Ray
> >>
> >>----- Original Message -----
> >>From: "KA4HJH" <ka4hjh at gte.net>
> >>To: "Bob Weigel" <sounddoctorin at imt.net>
> >>Cc: <synth-diy at dropmix.xs4all.nl>
> >>Sent: Wednesday, April 27, 2005 3:24 AM
> >>Subject: Re: [sdiy] Re: Inexpensive 16 bit DAC?
> >>
> >>
> >>> >Usually you have to tell them that you are like working on something
> >>>>where you might actually BUY some chips to get samples...or does Analog
> >>>>just hand them out to anyone?  I could have been getting samples all
> >>>>along for the project I'm working on from microchip but I haven't even
> >>>>had time to ask for them and I feel bad doing it because we really don't
> >>>>need them except that that company is out of money I guess so maybe we
> >>>>do :-). -Bob
> >>>
> >>> They may ask you a few simple questions, like "What's this for?" or
> >>> "What's
> >>> the goal of the project?". So you just answer "experimental interface
> >>> design for musical instrument" or something lofty you've daydreamed
> >>> about
> >>> but will probably never get around to. Talk like a junior in
> >>> college--half
> >>> clueless but you know some buzzwords.
> >>>
> >>> Maxim is another one you want to hit up...they've got good stuff...
> >>>
> >>> --
> >>>
> >>> Terry Bowman, KA4HJH
> >>> "The Mac Doctor"
> >>>
> >>> "You'd PAY to know what you REALLY think"--Dobbs
> >>
> >>
> >
> > ---------------------------------------------------------
> > - Where merit is not rewarded, excellence fades.
> > - Hydrogen is pointless without solar.
> > - What good are laws that only lawyers understand?
> > - The media's credibility should always be questioned.
> > - The only good terrorist is a dead terrorist.
> > - Governments do nothing well, save collect taxes.
> >
> > -- Scott Gravenhorst | LegoManiac / Lego Trains / RIS 1.5
> > -- Linux Rex         | RedWebMail by RedStarWare
> > -- FatMan: home1.gte.net/res0658s/fatman/
> > -- NonFatMan: home1.gte.net/res0658s/electronics/
> > -- Autodidactic Master of Arcane and Hidden Knowledge.
> >