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digital attenuator


kevin gilmore
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max williams should be joining us soon.

His entire thing was 3 pages of code.

And one entire page of the code is to control the

preamp inputs (of which there aren't any in the

volume control only version) and to flip the

MSB and LSB because he got the bits upside down.

How someone else can turn this into 10k+ lines of

code, i just cannot fathom :D

Now as to morse code, we can certainly do that

as long as you have 2 keys. One for clock and the

other for data.

Edited by kevin gilmore
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max williams should be joining us soon.

And here I am!

His entire thing was 3 pages of code.

My code is here:

http://nospecifictop...eamp-relay.html

Feel free to use it! I don't claim to be good at coding though, I just learn enough to get what I need done.

And one entire page of the code is to control the

preamp inputs (of which there aren't any in the

volume control only version) and to flip the

MSB and LSB because he got the bits upside down.

That was by design, not a mistake wink.gif

Interesting project!

I'm curious why you chose that resistor package? Isn't it hard to get all the values right from the same range and make? I used 1206 sized which also fits MMA0204 (both pretty common) and it was still tough to get the right values all within one range/make! I settled for +/-2.5% of the correct value using 1% metal film resistors:

IMG_0235.JPG

Also someone mentioned using thick film resistors, wouldn't metal film be a better choice?

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Glad you're here Max!

I'm currently looking at thin film resistors in a 1206 package (similar to GoldPoint). The boards will support both 2512 and 1206 sizes. I'm not against metal film either.

I'm actually on vacation now, but will sneak in some geek time and see if I can find the required values :)

I know this is opening up a can of worms, but it might be possible to have a 10K version and one other like a 50K or 100K. Could possibly impact price a bit, but I just wanted to float this out there to get some feedback.

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Well, it's just swapping the resistor set for another one. It shouldn't be too hard if we include some preset values on the BOM for people with blank boards. OTOH, for people with assembled boards maybe we should have a single version to keep the price down? What do people think?

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PLEASE SEE POST FOR THE LATEST COUNTS.

Another updated list:

Name - Assembled - Bare Boards

grawk - 4 - 0

Driftwood - 4 - 2

luvdunhill - 0 - 2

ujamerstand - 4 - 0

deepak - 2 - 0

cetoole - 0 - 10

manaox2 - 2 - 0

el_doug - 2 - 0

DouglasQuaid - 2 - 2

jgazal - 2 - 0

Lil Knight - 4 - 0

nattonrice - 0 - 4

kevin gilmore - 4 - 0

looser101 - 4 - 0

chinsettawong - 2 - 0

Kerry - 2 - 4

Fing - 4 - 0

blubliss - 4 - 0

n3rdling - 4 - 0

guzziguy - 2 - 0

Pars - 0 - 2

Nebby - 4 - 0

Flyingsparks - 0 - 4

morphsci - 4 - 0

dwhat - 4 - 0

minivan - 2 - 0

Craig Sawyers - 2 - 4

MASantos - 2 - 0

Vortex - 0 - 10

Beefy - 0 - 4

Samuel - 2 - 0

deadlylover - 0 - 6

TOTAL - 72 - 54

Again, if anyone is interested please PM me and I'll add you to the list.

Edited by Kerry
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Well, it's just swapping the resistor set for another one. It shouldn't be too hard if we include some preset values on the BOM for people with blank boards. OTOH, for people with assembled boards maybe we should have a single version to keep the price down? What do people think?

I am ok with what the majority want for assembled boards. Guessing 10k?

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Hi everyone,

this is my first post here, though I have been reading Head-Case for quite some time.

Would you consider shipping to France? If yes, I am definitely in for 2 boards assembled, plus relays.

regards,

sam

I don't want to speak for Kerry, but I would assume that won't be a problem as I'm in Europe as well.

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The boards will support both 2512 and 1206 sizes. I'm not against metal film either.

So you will have pads for both? Nice!

I know this is opening up a can of worms, but it might be possible to have a 10K version and one other like a 50K or 100K. Could possibly impact price a bit, but I just wanted to float this out there to get some feedback.

That will depend on what people are using for sources and whether they are happing driving 10K. Folks could always use an input buffer though, or buy their own resistors! This calculator is handy for calculating values:

http://www.amb.org/a.../delta1/r2r.cgi

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2050/38.3k (silk has 38.8k)

3650/16.9k (silk has 3050)

This http://www.charcroft.com/site/pdf/data/Charcroft.SCAR.04.09.Is2.pdf could be an interesting resistor option - the SM form of the Vishay/Charcroft Z-foil resistors. Not sure about availability though. Unless anyone knows of an easy source already, I'll make enquiries.

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This http://www.charcroft...R.04.09.Is2.pdf could be an interesting resistor option - the SM form of the Vishay/Charcroft Z-foil resistors. Not sure about availability though. Unless anyone knows of an easy source already, I'll make enquiries.

They look amazing but foil resistors are usually really expensive, for example:

http://uk.farnell.com/vishay-foil-resistors-vpg/s102c-20k000-0-01/resistor-metal-foil-0-6w-20k/dp/1692579?Ntt=1692579

blink.gif

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ok, 2 final versions.

4 layer version with 99.9% controlled impedances

http://gilmore.chem....nuatorsmt10.pdf

and 6 layer version with 100.0% matched impedances

(2 ground planes added)

http://gilmore.chem....nuatorsmt11.pdf

:D

Perhaps the process of exporting to PDF messes with the clearances? It looks like some clearances are inconsistent, example attached!

post-3041-0-50394900-1303056778_thumb.pn

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They look amazing but foil resistors are usually really expensive, for example:

http://uk.farnell.com/vishay-foil-resistors-vpg/s102c-20k000-0-01/resistor-metal-foil-0-6w-20k/dp/1692579?Ntt=1692579

blink.gif

Well, yes - the Z-foil resistors with leads from (eg) Parts Connexion are $16 to $17 each. So the SM versions are likely to be about that too. But if this attenuator is to match up to the KG Blowtorch, it's gonna need some pretty fancy resistors.

I'll get a quote and see how nuts this option is likely to be.

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