New Low-Cost AOUT (MBHP_AOUT_LC) under development

[moebius]

Hi,

Actually, SIP/DIP r2r ladders do exist - at least the Bourns has 'em.. the ones I've looked at had only 2% resistor matching ;)

their way of doing D2A conversion is simple and elegant.

Now, let me get this straight - PAiA way of An 8-bit dac, followed by a CMOS mux, followed by S&H/CV-buffers is a simple and elegant design? Well, it works and it's definitely a cheap one, but elegant?

Bye, Moebius

[Tanstaafl]

it's been something i have folowed for a few years... and seems to work for me.. (the hardware i have on hand)... i have had very good luck with the analog designs of PAIA.  I must admit.. I am an old analog guy from the 70's.  I guess the difference in this topic is you guys are talking about controlling envelopes...and not vco ? is that right?

[moebius]

it's been something i have folowed for a few years... and seems to work for me.. (the hardware i have on hand)... i have had very good luck with the analog designs of PAIA.  I must admit.. I am an old analog guy from the 70's.

I have to admit I admire PAiA designs too, they did what they could with the technology they had within the reach. (8031's, eproms, cheap 8-bit dacs.. and hey, they have all design documents online so we can build them DIY if we like, but PAiA is also still selling kits, so they probably don't their stuff to be "cloned" and released in public) and you're doing just fine for an old analog guy from the 70's ;)

  I guess the difference in this topic is you guys are talking about controlling envelopes...and not vco ? is that right?

No, this is planned to be a better "all around" AOUT solution, than some specialized DAC chips..

Bye, Moebius

[Synthhead]

Hi.

in my book... the r2r ladder thing is the best way... but has some caveats.

1. space... (it takes a lot of space)

Good point, but how big are we talking here? postcard? paperback book?

Given that a lot of people are going to use the AOUT with analogue gear - hardware synths/modules and modular synths etc, size may not be that much of a problem, except of course, bigger pcbs = higher cost.

When adding the SHX8, the panel area will have to be  large anyway, if sockets are installed for all 64 CV outs. I guess including LCD and programming controls, it would fit in a 19" 2U panel, if using 3.5mm jacks or banana plugs. Modular synths are often the size of a bookcase, so no problem if mounting there.  ;D

One way might be to build-in thru holes for stacking pcbs, like the CORE and DIN into the AOUTs pcb. This way they could be mounted on spacers above the board, reducing the overall footprint for all the pcbs, although the height will increase of course. 

I know that plenty of people will want to keep their midibox design small as possible ( me included) and that there may be many other uses other than just analogue gear.

But given that a midibox + SH board should easily outperform either the PAIA midi2CV8 ( US $92, 16.5cm x 10cm), or Doepfer MCV24, (US$ 500, 1U 19" rack), personally I'd put up with a bigger board than usual, especially in terms of the cost difference.

Not knocking either product, (I have  2 Paia boxes) but the midibox CV looks like a killer!

Incidentally, Vishay may be worth a look, as they seem to do a large range of resistor networks, but their web page keeps crashing my computer every time I look. 2nd time writing this post!  :(

cheers all,

Dave

[Duggle]

hi,

Using SMD resistors, the R2R DAC's resistor chain should take up no more that the same real estate as the Dout SR.

I suggest folks dont be scared of SMD. Its really not that hard to handle. If vision is a problem there are illuminating magnifiers that overcome this problem. SMD (particularly discrete components) have some distinct advantages:

-no holes to drill or stuff components into

-no leads to clip

-much less board space required

Heres my tips:

-resistors can be nudged into position with tweasers or jewellers screwdriver

-surface tension of molten solder can actually be used to "suck" resistors into position.

-if the resistor is not correcty in position, apply heat and nudge into correct location, then solder the other side.

With a little practice the process can be really efficient, and the results are really pleasing (and tiny!)

cheers

[Martin_Haverland]

Hi,

my 5 cent to smd resistors? i use them on my surplus breadboards/veroboards i got ultracheap at ebay.

these boards are so small...

it's absolutely right, there's nothing to it to use them. really easy.

and i'm absolutely NO solder god...

it's right that it's really easy to get them in position, really worth a try. smd for analog circuits is always a good try.

(but i'm not kd so i will not try to explain why, don't wanna blame myself ;))

Martin

[atomsize]

ok... i dont know the status of this low cost AOUT, but i've looked in to the PDF that KD made, the circuit seems to be very simple and easylly made. As i'm a analogue synth user i'm very interested in this design, mainlly for its parts availlability, as for the MAX's and other DAC's are very expensives or hard to get here in my country. I'm going to breadboard the circuit KD shows to give it a try, and i'll let you know my results later on... i would be great to use this new module with my almost finished MBSeq!

i'll try to post some pics of the sequencer soon ;)

Thank you KD and TK!