CP3PLUS Mixer (by FEEDBACK) [REV2.0 MANUAL ADDED]

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strat-1
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CP3PLUS Mixer (by FEEDBACK) [REV2.0 MANUAL ADDED]

Post by strat-1 »

www.feedbackmodules.com

[UPDATE}
I updated the post with the latest REV2.0 manual.
Plus a BOM list updated to latest parts and what parts to buy from mouser and TME.

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Image

The CP3PLUS is an accurate recreation in Eurorack format of one of the most appreciated vintage mixer for it's rich and beautiful sound.

We know that there are already available projects based on the same famous mixer so probably the question is why we did it. We are musicians and synth DIYers and already built before variations on this theme, but practical experience showed us that there are a few things we wanted to do different to improve it:

- There were many situation we found the 3 inputs were not enough so we decided for four inputs (like the original).

- Previous projects didn't offer both inverted and non inverted polarity outs but a crossfade between the two outs. This has two drawbacks, you don't have access to both outs at the same time (which could be very useful in some patches). Also the distortion pattern is not the same because the harmonic structure of the distortion is affected by the position of the output croossfade pot. We decided for both outputs and to have a similar distortion pattern like in the original mixer.

- Another addition is a four jack multiple (like in the original mixer). It is a very good idea to have a multi close to the mixer. Let's say you want to mix three oscillators for a rich sound and you want to drive them from the same CV source. Having a multi close to the mixer makes easy to distribute CV to all three oscillators.

- Another improvement was to make the module as simple to build as possible without the need of wires. You only need to solder the parts and that's it.

- The last improvement is related to ergonomics. We understand that many modular users try to make compact setups for live performance, so weight and module HP are a big concern. But we find all the crowded modules kill the ergonomics making access to pots and jacks a struggle. So we decided that we will make a version of this mixer that has a good compromise between ergonomics and panel dimensions. Look at this mixer like a module mostly made for your non portable studio modular setup.

This is a comprehensive build document for our CP3PLUS project and we hope it will make soldering and assembling this project an easy task.
We tried to make the whole experience as easy as possible and give as much information as needed to avoid confusion. We also provide additional documents like BOM lists
(PDF and XLS), images with part values, and photos of the construction in various stages. Feel free to download the whole pack and have fun.

This document assumes that you have a decent knowledge about electronics, soldering, using tools and measurement instruments.
The CP3PLUS is an easy project so we recommend it even if you are relativelly new to electronics.
We built some modules from this construction manual so we are confident we ironed out any errors, but we are human and if you discover any problem, feel free to give us a feedback.
Attachments
CP3+ - Front.jpg
CP3+ - Front.jpg (65.41 KiB) Viewed 1071 times
CP3+ Build Files 2.0.zip
(12.3 MiB) Downloaded 52 times
CP3+ Build_500.jpg
CP3+ Build Files.zip
(24.86 MiB) Downloaded 226 times
Last edited by strat-1 on Sun Feb 06, 2022 1:04 am, edited 17 times in total.
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strat-1
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Post by strat-1 »

KIT 1 :


Image


KIT 2:


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BARE BONES
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Post by BARE BONES »

Kit 1 with postage to the UK please! :)
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Bamboombaps
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Post by Bamboombaps »

Yah man kit 1 and uk shipping
DJBRUTAL
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Post by DJBRUTAL »

PM sent for 1x kit 1 with shipping to the USA.
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strat-1
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Post by strat-1 »

There's a print error on the silkscreen, I forgot to mention in the main text. R7 is printed twice, R12 is printed twice.
All the build files are correct, so this print error have no impact in the build.
sammy123
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Post by sammy123 »

I'd like a kit 1 please.
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Stides
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Post by Stides »

Pm'd for kit 1. :yay:
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yan6
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Post by yan6 »

1 x Kit 1 for me please, shipped to Canada
acilator
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Post by acilator »

One KIT1 for me, shipping to The netherlands
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Zaibach
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Post by Zaibach »

I'd like a KIT 1, please! Shipping to Germany.
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strat-1
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Post by strat-1 »

I recorded some demos for the CP3PLUS project.

In the first track I change continuously the mix between 3 waveforms from 3 System-X VCO's. Saw, Square and Sine.
When I raise one channel near the maximum you can hear the characteristic sound of CP3 mixers, the transistors starts to add harmonics to the sound. You can here it especially on sine waveform.
The setup is basic vco's to CP3PLUS to vca.

https://soundcloud.com/strat1/cp3plus-capabilities

In the second demo I play again with the waveforms volume, but the mixer is patched to a vcf>vca>chorus 106.

https://soundcloud.com/strat1/cp3-to-106-noodle
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spneca
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Post by spneca »

I would like a Kit 2, please. Shipping to USA.
Styrofoam
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Post by Styrofoam »

Kit 2 please, shipped to Belgium (I sent you a PM).
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pix
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Post by pix »

I got a dual gang pot from mouser but the shaft is too large and doesn't fit the panel hole.

Now I'm in a dilemma, either I try to enlarge the hole (with very high changes to F it up) or try and source another pot.

Has anyone found a pot that works well?
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strat-1
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Post by strat-1 »

pix wrote:I got a dual gang pot from mouser but the shaft is too large and doesn't fit the panel hole.

Now I'm in a dilemma, either I try to enlarge the hole (with very high changes to F it up) or try and source another pot.

Has anyone found a pot that works well?
As I specified in the manual you have to enlarge the hole. You have pictures also of the making process in the zip file.
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pix
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Post by pix »

As usual...RTFM!

thanks!
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strat-1
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Post by strat-1 »

I had some time to spent and I sawed to size the double gang pots
with professional tools. So the last kits I sent had already prepared pots :).
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HipDestroyer
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Post by HipDestroyer »

I've been a naughty boy: I used film caps for this build.

Anyways, it sounds amazing. To be honest, when I ordered it I wasn't 100% sure the "characteristics" mentioned would be audible but the harmonics are definitely there and sound beautiful. :yay:

Image
Image
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InfraXpert
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Post by InfraXpert »

2 x Kit 2 for me please, shipped to Denmark
Really good music starts with a solder iron
purple_elk
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Post by purple_elk »

Hi,
Could I order kit 2 to the UK please?
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squarewavesurfer
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Post by squarewavesurfer »

pm'd for two of the CP3+ mixer kit 2
kashmir
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Post by kashmir »

Hi, PM'd for one CP3 kit 1
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strat-1
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Post by strat-1 »

UPDATE : KIT2 WILL INCLUDE MATCHED PAIR 3904, 3906 TRANSISTORS AT NO CHANGE IN KIT COST.
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Addam
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Post by Addam »

Any info on that two59 waveshaper? :hyper:
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