Dual Double Function Generator -- B281 Euroclone

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AlanP
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Dual Double Function Generator -- B281 Euroclone

Post by AlanP » Fri Feb 14, 2020 10:11 pm

I'm releasing the Eagle files for this project with a few strings attached.

Firstly, please don't sell either the boards, or the finished project, for profit. Group buys are fine, as are selling your spares to cover costs. Doing one for someone who hates soldering is fine. Doing a few dozen and charging a few hundred bucks a pop each is not. Secondly, please don't email or PM me for help. This is a complex project. Each Eng board has two channels. Take each thing step by step and be careful. Post in this thread if you want a hand. I do not guarantee a working build, that is up to you.

This is a Eurorack clone adaptation of the Buchla 281 Quad Function Generator. Unlike other Eurorack clones, AFAIK, this has all four channels.

As far as I know, all of the parts used for this should be commercially available and in current production. The BOM for the Panel PCB is incorrect for the two Peak Out pots -- they are both 100kB, not 10kB. The build document is contained in the attached zip file, as well as the Eagle SCH and BRD files for each board as well as the panel.

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SyndieBot2000XL
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Re: Dual Double Function Generator -- B281 Euroclone

Post by SyndieBot2000XL » Fri Feb 14, 2020 10:39 pm

Thank you for this! :love:
It began as a mistake.

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SphericalSound
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Re: Dual Double Function Generator -- B281 Euroclone

Post by SphericalSound » Sat Feb 15, 2020 3:57 am

Wow, triple sandwhich. Yumm!

Thank you, Alan.

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Noodle Twister
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Re: Dual Double Function Generator -- B281 Euroclone

Post by Noodle Twister » Sat Feb 15, 2020 4:34 am

Brilliant. Thank you Alan :goo:

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squarewavesurfer
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Re: Dual Double Function Generator -- B281 Euroclone

Post by squarewavesurfer » Sat Feb 15, 2020 8:14 am

I just built this earlier in the year and it is fantastic!

Aside from the slight discrepency in the potentiometer specs in the BOM (clarified by alanp above), the build document is perfect and easy to follow. This is an excellent project!!

Also remember to buy dip sockets and male/female pcb headers for making the pcb sandwiches.
WTB: Sputnik Valve Multiplier; Verbos Scan & Pan; 0603 Ears pcb and/or panel

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SphericalSound
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Re: Dual Double Function Generator -- B281 Euroclone

Post by SphericalSound » Sat Feb 15, 2020 4:43 pm

I think I understand everything that the module does except the right side. Could anyone explain what atten B, peak out and quad on/off switches does?

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squarewavesurfer
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Re: Dual Double Function Generator -- B281 Euroclone

Post by squarewavesurfer » Sat Feb 15, 2020 8:32 pm

SphericalSound wrote:
Sat Feb 15, 2020 4:43 pm
I think I understand everything that the module does except the right side. Could anyone explain what atten B, peak out and quad on/off switches does?
The quad switch syncs channel B to channel A so that B gets triggered at the end of channel A's attack phase.

The B atten pot attenuates channel B's signal going to the Peak output which is an OR logic gate (ouputs whichever singal is highest from A or B)
WTB: Sputnik Valve Multiplier; Verbos Scan & Pan; 0603 Ears pcb and/or panel

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SphericalSound
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Re: Dual Double Function Generator -- B281 Euroclone

Post by SphericalSound » Sat Feb 15, 2020 9:59 pm

squarewavesurfer wrote:
Sat Feb 15, 2020 8:32 pm
SphericalSound wrote:
Sat Feb 15, 2020 4:43 pm
I think I understand everything that the module does except the right side. Could anyone explain what atten B, peak out and quad on/off switches does?
The quad switch syncs channel B to channel A so that B gets triggered at the end of channel A's attack phase.

The B atten pot attenuates channel B's signal going to the Peak output which is an OR logic gate (ouputs whichever singal is highest from A or B)
Thanks!

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AlanP
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Re: Dual Double Function Generator -- B281 Euroclone

Post by AlanP » Sat Feb 15, 2020 10:24 pm

https://modularsynthesis.com/roman/buch ... 81_qfg.htm

Dave Brown's page on the 281 has a lot of good scope shots explaining how the module works.

kevin0
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Re: Dual Double Function Generator -- B281 Euroclone

Post by kevin0 » Sun Feb 16, 2020 7:17 am

this looks great :o

Thanks Alan !

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