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dual 281 project [build related stuff only!]
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toppobrillo



Joined: Dec 10, 2005
Posts: 766
Location: oakland, ca
G2 patch files: 1

PostPosted: Tue Feb 08, 2011 3:45 am    Post subject: dual 281 project [build related stuff only!] Reply with quote  Mark this post and the followings unread

post build related questions/ comments here, no order related stuff. use the main thread for those.

assembly PDF is up, new BOM to follow:

http://www.sdiy.org/toppobrillo/DOWNLOADS/2812_DUAL/
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ericcoleridge



Joined: Jan 16, 2007
Posts: 885
Location: NYC

PostPosted: Tue Feb 08, 2011 12:08 pm    Post subject: Reply with quote  Mark this post and the followings unread

Fantastic! Thanks Topp! This looks WAY easier to assemble than was the single circuit config. Man, that was a headache : )
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J3RK



Joined: Jun 05, 2006
Posts: 99
Location: Seattle

PostPosted: Wed Feb 09, 2011 2:57 pm    Post subject: Reply with quote  Mark this post and the followings unread

Is there any reason I shouldn't use 4066s in place of 4016s? (I happen to have a ton of 66s that I never used) From what I can tell it should be fine. Haven't consulted the datasheets yet, but will be.
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toppobrillo



Joined: Dec 10, 2005
Posts: 766
Location: oakland, ca
G2 patch files: 1

PostPosted: Wed Feb 09, 2011 3:01 pm    Post subject: Reply with quote  Mark this post and the followings unread

Quote:
Is there any reason I shouldn't use 4066s in place of 4016s?


afaik no should be fine.
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J3RK



Joined: Jun 05, 2006
Posts: 99
Location: Seattle

PostPosted: Wed Feb 09, 2011 3:29 pm    Post subject: Reply with quote  Mark this post and the followings unread

topp wrote:
Quote:
Is there any reason I shouldn't use 4066s in place of 4016s?


afaik no should be fine.


Cool. I just looked at the datasheets, and as I read previously they are just improved (noise, impedance, etc.) It looks like each switch has a few extra components in the 4066, but otherwise similar. Think I'll use them.
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emdot_ambient



Joined: Nov 22, 2009
Posts: 669
Location: Frederick, MD

PostPosted: Thu Feb 10, 2011 2:47 pm    Post subject: Reply with quote  Mark this post and the followings unread

thumb up
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J3RK



Joined: Jun 05, 2006
Posts: 99
Location: Seattle

PostPosted: Mon Feb 14, 2011 11:48 am    Post subject: Reply with quote  Mark this post and the followings unread

I should have my parts today or tomorrow, and will get started on the build. The only thing I didn't grab was a 7810. Will have to run out, and grab one.

Quick question on the 062s. I was going to use 072s in their place, (because I have about a billion of them,) but thought I'd see if there was a specific reason the 062s were used. From what I understand, the 062s are just a bit better with low current/voltage situations, but maybe I'm missing something?

That aside, I think I'll be building tomorrow night. Cool
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gddfp



Joined: Jan 11, 2009
Posts: 21
Location: Belgium

PostPosted: Thu Feb 17, 2011 5:44 am    Post subject: Reply with quote  Mark this post and the followings unread

I assume the pots for Attack & Decay are LOG (in the original) ?
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toppobrillo



Joined: Dec 10, 2005
Posts: 766
Location: oakland, ca
G2 patch files: 1

PostPosted: Thu Feb 17, 2011 4:46 pm    Post subject: Reply with quote  Mark this post and the followings unread

Quote:
Quick question on the 062s. I was going to use 072s in their place, (because I have about a billion of them,) but thought I'd see if there was a specific reason the 062s were used. From what I understand, the 062s are just a bit better with low current/voltage situations, but maybe I'm missing something?


TL06_ are low power opamps, they use like 1/10th the current of the 07_s. they are also around 4x slower. so for this application they're great economy. i haven't measured the current draw of the new dual board, but I would reckon its around 25-30mA orso with the 62s in. if you used 72s/71 you're looking at something significantly higher, maybe 50mA, just guessing, with no advantage other than that you already have the chips Smile you might see the FGs easily soft-syncing in cycle mode with the higher current demand spikes. anyways, I say use sockets, try it and see.

Quote:

I assume the pots for Attack & Decay are LOG (in the original) ?


they would be linear.
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J3RK



Joined: Jun 05, 2006
Posts: 99
Location: Seattle

PostPosted: Thu Feb 17, 2011 5:52 pm    Post subject: Reply with quote  Mark this post and the followings unread

Thanks Topp!

That's more or less what I was thinking. I'll socket them and swap. I'm running a fairly large power supply, so the overall current draw shouldn't be an issue. (especially with the small size of my overall system.) The spikes could still be an issue though. I'll give both a try. I don't see any reason not to order a tube of 062s. Smile
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toppobrillo



Joined: Dec 10, 2005
Posts: 766
Location: oakland, ca
G2 patch files: 1

PostPosted: Thu Feb 17, 2011 7:15 pm    Post subject: Reply with quote  Mark this post and the followings unread

Quote:
I don't see any reason not to order a tube of 062s


I use them alot Smile
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waveselector



Joined: Nov 17, 2008
Posts: 14
Location: chicago

PostPosted: Thu Feb 17, 2011 8:22 pm    Post subject: Reply with quote  Mark this post and the followings unread

on the solder side of the PCB there appear to be pads for some SMD components - can you shed some light on those, topp?
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toppobrillo



Joined: Dec 10, 2005
Posts: 766
Location: oakland, ca
G2 patch files: 1

PostPosted: Thu Feb 17, 2011 8:58 pm    Post subject: Reply with quote  Mark this post and the followings unread

Quote:
on the solder side of the PCB there appear to be pads for some SMD components - can you shed some light on those, topp?


bypass caps, .1uF 0805 sized
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waveselector



Joined: Nov 17, 2008
Posts: 14
Location: chicago

PostPosted: Thu Feb 17, 2011 9:04 pm    Post subject: Reply with quote  Mark this post and the followings unread

doh! i knew i was too hasty when i made that mouser order...

maybe i'll just slap some ceramic disc ones on... sloppy, but it's what i've got!
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toppobrillo



Joined: Dec 10, 2005
Posts: 766
Location: oakland, ca
G2 patch files: 1

PostPosted: Thu Feb 17, 2011 9:28 pm    Post subject: Reply with quote  Mark this post and the followings unread

yeah ive done that too no biggie.. or you could just leave them off for now, i doubt you'd notice a difference.
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gddfp



Joined: Jan 11, 2009
Posts: 21
Location: Belgium

PostPosted: Thu Feb 17, 2011 10:49 pm    Post subject: Reply with quote  Mark this post and the followings unread

gddfp wrote:
I assume the pots for Attack & Decay are LOG (in the original) ?

topp wrote:
they would be linear.


Have a look at the original Buchla panel. The scaling marks around those knobs do not look very linear...
And that makes sense to me. It's far more important to be able to finely adjust the faster rates than the slower rates.
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toppobrillo



Joined: Dec 10, 2005
Posts: 766
Location: oakland, ca
G2 patch files: 1

PostPosted: Fri Feb 18, 2011 1:47 am    Post subject: Reply with quote  Mark this post and the followings unread

Quote:
Have a look at the original Buchla panel. The scaling marks around those knobs do not look very linear...
And that makes sense to me. It's far more important to be able to finely adjust the faster rates than the slower rates.


have a look at the schematic.

from my diy page:
The output function is linear, however, the rate [slope] responds to applied control voltage in an exponential manner. Applied positive voltages will cause the generator to ramp more slowly- while voltages that are less positive than the voltage at the control pot's wiper will cause the generator to ramp more quickly. These voltages average together.

if you used a log pot, you would linearize the time vs. knob rotation relationship.
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gddfp



Joined: Jan 11, 2009
Posts: 21
Location: Belgium

PostPosted: Fri Feb 18, 2011 1:54 am    Post subject: Reply with quote  Mark this post and the followings unread

gddfp wrote:
Have a look at the original Buchla panel. The scaling marks around those knobs do not look very linear...

topp wrote:
if you used a log pot, you would linearize the time vs. knob rotation relationship.


Okay, that makes sense.
All clear now.

Thanks, Topp.
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negativspace



Joined: Dec 25, 2010
Posts: 17
Location: Manhattan, Kansas

PostPosted: Sun Feb 20, 2011 11:19 am    Post subject: Reply with quote  Mark this post and the followings unread

Are the two circle-marked parts near the 3904s trimpots? If so, are they 25-50k as specified in your previous versions?

Thanks!
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toppobrillo



Joined: Dec 10, 2005
Posts: 766
Location: oakland, ca
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PostPosted: Sun Feb 20, 2011 4:39 pm    Post subject: Reply with quote  Mark this post and the followings unread

Quote:
Are the two circle-marked parts near the 3904s trimpots? If so, are they 25-50k as specified in your previous versions?

Thanks!


yep
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mph



Joined: Aug 25, 2007
Posts: 67
Location: France

PostPosted: Wed Mar 09, 2011 4:56 pm    Post subject: Reply with quote  Mark this post and the followings unread

What kind of trimmers do you use please?
And is there a need to match the 3906s?

Thanks a lot.
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toppobrillo



Joined: Dec 10, 2005
Posts: 766
Location: oakland, ca
G2 patch files: 1

PostPosted: Wed Mar 09, 2011 9:51 pm    Post subject: Reply with quote  Mark this post and the followings unread

Quote:
What kind of trimmers do you use please?
And is there a need to match the 3906s?

Thanks a lot.


hi- 2.5mm or 5mm lead spacing will work here, 20-50K or so.

the xistrs- no need to..
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mph



Joined: Aug 25, 2007
Posts: 67
Location: France

PostPosted: Wed Mar 16, 2011 6:45 am    Post subject: Reply with quote  Mark this post and the followings unread

Hello Topp

thanks for your reply, I've found some Bourns trimmer which seem to fit the pcb.

I've one more question; what are the componments labelled "L+" and "L-"?
Are they ferrite beads, or 10ohm resistors?

And please, do you have a current BOM for this version, or should I use the older one?

Cheers
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e-grad



Joined: Sep 12, 2008
Posts: 142
Location: Berlin

PostPosted: Thu Mar 17, 2011 3:24 am    Post subject: Reply with quote  Mark this post and the followings unread

mph wrote:
what are the componments labelled "L+" and "L-"?
Are they ferrite beads, or 10ohm resistors?

I prefer beads but you can use 10 ohm or 22 ohm resistors as well.

Basically even a link will work.
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mph



Joined: Aug 25, 2007
Posts: 67
Location: France

PostPosted: Thu Mar 17, 2011 7:40 am    Post subject: Reply with quote  Mark this post and the followings unread

thanks e-grad

I've made a new BOM for this version, based on the V3 but including the changes with the 3080 and the 13700...
If someone need it I could post here.
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