[sdiy] Re: Inexpensive 16 bit DAC?

[Scott Gravenhorst]

Harry Bissell Jr <harrybissell at prodigy.net> wrote:
>As drawn, no advantage. Possiblt a little better
>symmetry, have to check the source / sink currents
>of the buffer to see if it would be truly
>symmetrical...

I can't speak for the 4066, but I know that the 4069UB is
spec'd as having symmetrical transistors.  It's one of the
reasons I like them.

>By extension, you sould replace the "+12V" going
>to the switches with a precision reference... or even
>a variable reference... making a multiplying DAC.
>(of course negative voltages are out).

Truly.  For me, it was mental gymnastics.

>
>Back to my ORIGINAL complaint and name of the
>thread... with 1M and 2M resistors you are going to
>not, NO WAY make your own 'inecpensive' 16 bit
>converter.  The archetecture is there, but the
>implementation is NOT !!!

I am so out of touch, is this because they must be precision
resistors and prec. resistors of that value range are more
expensive?



>--- Scott Gravenhorst <music.maker at gte.net> wrote:
>> 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.
>> 
>> 
>

---------------------------------------------------------
- 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.