281 Quad Function Generator Question

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emergencyofstate
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281 Quad Function Generator Question

Post by emergencyofstate » Thu Jun 04, 2009 3:47 pm

Hi all. I have a 281 clone in my future and I'm starting to get more and more curious as to what to expect. I know some of it functions as multiple EGs...but beyond that I don't know much else.

Can anyone offer insight? For example, how it differes from my Doepfer Quad ADSR...

:bug:
Last edited by emergencyofstate on Thu Jun 04, 2009 3:54 pm, edited 1 time in total.

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Post by consumed » Thu Jun 04, 2009 3:51 pm

are you talking about the topp 281 function generator?

im just finishing an FPE panel for euro up on it now
it is an A/D circuit, but also has an ASR mode and cycle mode
there is an additional circuit in there called the "peak out" circuit if you build them in pairs
it is an ANALOG OR (max) function between the outputs of the two ADs.
the B amount knob controls the amount of B envelope in the peak out
so if the B amount is all the way down, peak out = A out
let me know if that makes sense

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Post by emergencyofstate » Thu Jun 04, 2009 4:24 pm

consumed wrote:are you talking about the topp 281 function generator?

im just finishing an FPE panel for euro up on it now
it is an A/D circuit, but also has an ASR mode and cycle mode
there is an additional circuit in there called the "peak out" circuit if you build them in pairs
it is an ANALOG OR (max) function between the outputs of the two ADs.
the B amount knob controls the amount of B envelope in the peak out
so if the B amount is all the way down, peak out = A out
let me know if that makes sense
Yeah that 281. PCB from topp on the electro-music forum.

I treid to understand your explanation but I don't totally get it. I bought 4 PCB's. So that's a pair right?

So:

A/D circuit = Attack Decay circuit?
ASR = Attack Sustain Release?
Cycle mode (switch between them?)

I don't quite understand ANALOG OR thing. :despair:

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Post by parasitk » Thu Jun 04, 2009 4:36 pm

4 PCBs = a quad. The A/B pair, and C/D pair.

Cycle = basically an LFO mode.

The OR outputs the highest (peak) signal of a pair at any given time.

Some reading: http://www.sdiy.org/toppobrillo/twoeightyone.html

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Post by consumed » Thu Jun 04, 2009 4:37 pm

emergencyofstate wrote: Yeah that 281. PCB from topp on the electro-music forum.

I treid to understand your explanation but I don't totally get it. I bought 4 PCB's. So that's a pair right?
thats two pairs. by a pair, i mean two pcbs
building two pcbs permits you to build the 'peak' circuit as well
EDIT: and the quadrature function
So:

A/D circuit = Attack Decay circuit?
ASR = Attack Sustain Release?
Cycle mode (switch between them?)
yes,
yes,
no. cycle as in looping, like an oscillator

I don't quite understand ANALOG OR thing. :despair:
ANALOG OR is the same thing as MAX.
take two voltages and feed them into a maximum function
you will only get the highest value of the two voltages at any moment
ill post a couple pics to make some sense of it

EDIT: parasitk beat me to it
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Post by consumed » Thu Jun 04, 2009 4:38 pm

parasitk wrote:4 PCBs = a quad.
dont get this terminology confused with the "quadrature" function

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Post by parasitk » Thu Jun 04, 2009 4:40 pm

consumed wrote:
parasitk wrote:4 PCBs = a quad.
dont get this terminology confused with the "quadrature" function
Ah, good point. "Two pairs" then. :cloud:

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Post by emergencyofstate » Thu Jun 04, 2009 4:47 pm

ahh thanks much :banana:

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Post by Luka » Thu Jun 04, 2009 4:53 pm

the peak out is just a enelvepe mixture so you can get complex shapes
if you have 4 it is good to have an external input to your peak circtuit too so you can go even more complex by adding more A/D stages

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Post by consumed » Thu Jun 04, 2009 5:13 pm

Luka wrote:if you have 4 it is good to have an external input to your peak circtuit too so you can go even more complex by adding more A/D stages
i am designing my panel with an external input on the peak circuit but i need a tiny schematic or hook up guide. do you know how to do this already?

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Post by emergencyofstate » Thu Jun 04, 2009 5:24 pm

consumed wrote:
Luka wrote:if you have 4 it is good to have an external input to your peak circtuit too so you can go even more complex by adding more A/D stages
i am designing my panel with an external input on the peak circuit but i need a tiny schematic or hook up guide. do you know how to do this already?
How is your panel coming? I'm euro as well so I'd love to know how you chose to artwork etc... :sb:

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Post by consumed » Thu Jun 04, 2009 6:14 pm

sure, here's my 20HP in-progress layout.
im uncomfortable with a couple parts of it still
(location of a/d text and how the cv inputs graphically relate to them) and the function graphics are wrong
here's my logic

separate the quadrature function since it is not related to anything else
separate the peak circuitry since it is mostly not related to anyting else
outputs on the right side, inputs on the left-ish side, knobs down the center column
i gave each AR two outputs since this module will be really useful
the big hole above the end (pulse output) is for the leds i am now using in my builds (they are meant to be prominent)


when im finished ill post an FPE panel if you want it.

EDIT: posted improved/corrected panel design farther down in thread
this is the 'bad' design with errors, unfinished graphics, bad feel to the spacing
Image
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Post by emergencyofstate » Thu Jun 04, 2009 6:57 pm

Excellent!! Thanks. :tu:


So if I'm doing the ABCD module would I need twice the panel?? wait, or did you just repeat A&D twice in the mockup?
Last edited by emergencyofstate on Thu Jun 04, 2009 6:58 pm, edited 1 time in total.

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Post by consumed » Thu Jun 04, 2009 6:58 pm

emergencyofstate wrote:So if I'm doing the ABCD module would I need twice the panel??
yes.

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Post by Luka » Thu Jun 04, 2009 7:46 pm

i think if you add a external input you want to have an attenuator
so you have an amount B and an amount X pot

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Post by wetterberg » Thu Jun 04, 2009 7:50 pm

to me the biggest advantage of these, apart from perhaps the Cycle mode is that you can CV the A and D stages... Set one AD to cv the D of another, and then back again... lovely feedback scenarios will unfold from just that one feature. Add in the peak circuitry, the quadrature mode, etc. etc. etc... I'm really looking forward to getting mine built - meaning; when I can afford the parts again... :despair:

Consumed: As always, AWESOME panel. Does it use the board mounted pots?

And also, the rare parts in this one (I forget, there's a few in there) - anyone looking into group buys? I'd be in for 6x anything if that could happen.

Oh, btw Bridechamber can do parts kits for 25 bucks each - great for the lazy among us! :sb:

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Post by consumed » Fri Jun 05, 2009 5:26 pm

wetterberg wrote:Consumed: As always, AWESOME panel. Does it use the board mounted pots?

And also, the rare parts in this one (I forget, there's a few in there) - anyone looking into group buys? I'd be in for 6x anything if that could happen.
thanks! no board mounted pots--i recently discovered 3/4"x3/4" aluminum l-bracket material (easy to cut and drill)

i think the only hard to find part is the CA3080 which bridechamber sells

i printed the design out and took it home, laid the knobs down on it and didnt like the spacing
so here's the most recent FPE design, corrected from above, close to final
the light circles centered around the pot holes represent the footprint of the 1900h knobs
its really helpful to get a sense of how it will feel with knobs on it

Image

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Post by toppobrillo » Sat Jun 06, 2009 12:50 am

hello dudes- i made up an 18HP layout that looks like it would work- let me know what you think about it- the pic just shows placement nothin fancy!

josh
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Post by consumed » Mon Jun 08, 2009 10:42 am

hi josh! just noticed you arrived here--welcome!
nice looking panel design there
i originally laid an 18hp panel out but abandoned it for a little more finger room
i had thought to lay out a vertical panel but never got round to it--thanks for posting that

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Post by toppobrillo » Mon Jun 08, 2009 4:20 pm

oh hey thanx i think i may build one with this panel as inow am getting euro stuff. the quadrature switch might get bumped down inline with the others tho.

cheers!

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Post by consumed » Sun Jun 14, 2009 11:35 am

finally got the boards completely populated
building them in an A/B pair for quadrature and peak circuitry
the A board is on the right, where the power comes in
here's a pic to help encourage those of you getting started on this
in building this project, it is apparent to me this is NOT a beginner project :lol:
i had to correct a few mistakes i made already

Image

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Post by panda30y » Sun Jun 14, 2009 11:43 am

Nice work! Can't wait to see your boards mounted and running though. Please do post audio samples when you get it running!

I purchased four boards myself and plan to wire all four together on the same panel. I'm pretty sure I can wire 4 boards together and get sufficient power. I'm just waiting to get some more money before I order parts so I'll be sure to have money for my best of CGS panel from Zthee.

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Post by pickleinn » Sun Jun 14, 2009 12:13 pm

i just got my four boards working together.....finally! i made some dumb mistakes combined with sloppy wiring. i havent used them much yet because i am working on the rest of the panel.

i had a hard time fitting four boards behind the panel space i allotted. it would have been much easier if i didnt have to go back in and check everything after i mounted and wired all the boards.

i have four more boards that i dont have plans for yet.

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Post by consumed » Sun Jun 14, 2009 12:45 pm

pickleinn wrote:i just got my four boards working together.....finally! i made some dumb mistakes combined with sloppy wiring. i havent used them much yet because i am working on the rest of the panel.

i had a hard time fitting four boards behind the panel space i allotted. it would have been much easier if i didnt have to go back in and check everything after i mounted and wired all the boards.
congrats! id love to see your build. did you post it over at EM already?
i have a stupid question--did you have to run +15v AND -15v AND +10v from your power entry board to your B/C/D boards? in looking at the B schematic i think this is correct, but its funny that i cant find where 10v connects on there (or maybe im just not seeing it).

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Post by panda30y » Sun Jun 14, 2009 12:55 pm

consumed wrote:
pickleinn wrote:i just got my four boards working together.....finally! i made some dumb mistakes combined with sloppy wiring. i havent used them much yet because i am working on the rest of the panel.

i had a hard time fitting four boards behind the panel space i allotted. it would have been much easier if i didnt have to go back in and check everything after i mounted and wired all the boards.
congrats! id love to see your build. did you post it over at EM already?
i have a stupid question--did you have to run +15v AND -15v AND +10v from your power entry board to your B/C/D boards? in looking at the B schematic i think this is correct, but its funny that i cant find where 10v connects on there (or maybe im just not seeing it).
I have the same question myself!

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