Showing posts with label Eurorack. Show all posts
Showing posts with label Eurorack. Show all posts

Tuesday, 27 September 2016

NLC Serious Filter - ARP Odyssey 4023

The Serious Filter it is based on the Arp4023.

 This is what it should look like when finished.
..

The ARP Odyssey mkI (model 2800), has the 2 pole 4023 12db/oct filter

The MkI 4023 been described as the most "Arp-like" sounding filter, because it doesn't try to imitate a Moog. The NLC 4023 also makes a nice quadrature oscillator.
The mkII in comparison, has the 4035 24db/oct filter - with a steeper bass roll-off curve, just like the minimoog filter.

The Korg-ARP Odyssey has all 3 filters. Would be nice to compare this with them when the build is done.

The rear virgin PCB 

Some NLC words of wisdom first: "Sausage Fears"
"Sausage fears": a term to describe the actions of straight men who are afraid of showing any physical or emotional bond to the men they are friends with. (The Urban Dictionary) 
So true... we men are afraid of showing emotion.

Back to the build:
First solder the two SMD TL072 ICs

Now the rest of the SMDs & headers.

Next, the regular caps, variable resistors & through hole diodes & resistors.

The 4 pots I've used are 100k B.
You could use an A pot on the signal input if you really want.

Andrew F usually uses B pots on most of his modules (except on the ADSR module). It is very easy to solder a resistor across 2 pins if you wish to turn a B/linear into an A/log pot. This way, you can also adjust the slope to suit your needs.

Don't forget to connect the ground tabs on the 6 jacks.
The completed module.


 Links:
1. ARP Tech schematics for the 4023 filter
2. NLC Blog
3. NLC Build notes

More links to NLC (nonlinearcircuits) projects.


Tuesday, 13 September 2016

Euro build notes for a Serge Resonant EQ Mk. II

These are my build notes for a Euro format Serge Resonant EQ Mk. II.
Mk. II daughter board and Mk. II panel by Clarke

 First the virgin PCBs.
This Euro version still uses Ken Stones CGS 202 pcb.
http://www.cgs.synth.net/modules/cgs202_reseq.html

Above is a pic of a vintage Serge Res equaliser.
It's the 3rd module from the top. It's very compact in comparison to the Euro version and doesn't have
the extra outs from the 10 filter bands. And pot's are used instead for sliders.

 Official BOM for the daughter board:

SMT Components
[3] TL074 (SOIC-14)
[10] 330R Resistor (0805)
[25] 47k Resistor (0805)
[2] 0.1uF Ceramic capacitor (0805)

Through-hole Components
[18] Kobiconn 16PJ138 jacks
[10] Bourns or Alpha 45mm LED sliders
[2] Alpha 9mm pots or similar, value 50k Audio.
[10] LED Current-limiting Resistors - value varies by slider brand and LED color.
        I'm using 1.2K.
[2] 22uF Electrolytic capacitors
[2] 1N4001 Diode
[1] 2x5-pin Eurorack power header
These are the 330R resistors.... outboard resistors.

Next the 47K SMDs.

[2] 0.1uF Ceramic capacitor (0805)
[2] 22uF Electrolytic capacitors
[2] 1N4001 Diode
[1] 2x5-pin Eurorack power header

SLIDER Pots, jacks, etc.


Now for the main PCB.
Resistors & headers 1st.

What capacitors should I use ???

Ken Stone's site says this:
"Traditionally, polystyrene capacitors are used for all of the smaller value capacitors in this module. I have not tried using other types and cannot say whether using the polystyrene capacitors makes any audible difference. From 10n, up greencaps were used. In modern terms these would be MKT or MKS. Note that there are also 10 x 10n decoupling capacitors. These decoupling capacitors can be MKT, MKS, monolythic ceramic, or anything else that will physically fit."

For this build I'm using ceramics for the 680pf & 220pf. The jury is out on whether axial polystyrene sound better. The price difference is considerable.
I'll use Axial poly's in my next build if I can detect a difference between this build and my vintage
Resonant Filter. .


It's now time to wire up the two PCBs.



Headers can also be used like this:


 This makes for easier trouble shooting.




This is not part of the original CGS build. Took a bit of schematic study and trial & error to work out where
to where to make the connections. they were basically the outs pins of the ten TL072s.. pins 1 & 7




Links:
1. Muff wigglers
2. Ken Stone - CGS
Video 1
Video 2


Friday, 9 September 2016

FK1T - VCF build notes (NonLinearCircuits)

These are my build notes for the NLC FK1T VCF.
This VCF is based on the extremely rare Korg FK-1 pedal.
They are hard to find and often sell on Ebay in the $1000AUD range.
The FK1 is a similar VCF to the ones found in the 800dv, 770 and 700 synthesizers.
These early Korg filters consisted of high pass and low pass stages in series.



The virgin faceplate & PCB.
Labels are based on 70s Korg nomenclature as per the original module.

 Korg 800dv

 ..
Mainly surface mount passive components.  ... just one TL074 opamp.
 ...

  No NLC build would be complete without some words of wisdom
 Contemporary Art Hates You - John Waters.

The point of art is to "wreck whatever came before it," he believes. "That something is pretty and beautiful is probably the worst thing you could say today in contemporary art...unless it's so pretty it's nauseating."

This 074 is hopefully the only tricky part of this build.

Solder all the passive SMD components next then the 5 trannies.
The BC857 are PNP & are labeled "p" on the PCB.
The BC847 are NPN & are labeled "n".

Finally the through hole stuff : Resistors, caps, headers.

I'm using Silonex NSL-32 vactrols. They are cheap as chips. The white dot marks the cathode of the LED part of the vactrol. Andrew has labeled this as "K" on the PCB.

The pots are 100k linear (B).



Initial tests were good except for CV input 1 which was dead.
The connection between the jack and the PCB may be dodgy ???

This spot on the PCB responded to CV and it looks like its one of the feedback 100k resistors for the op-amp.


I'll probably build this module again using different vactrols and then see if the same issue with
my CV1 input occurs. It might just be a poor solder connection somewhere. ???
For the moment, I'll probably leave this mod as is. It sounds great.
 -----------------------------------------------
Edit ... From Andrew F himself.
"the 220k resistor between cv1 jack and the 100k feedback resistor connects the two. There are definitely traces there. It is not really good to connect the jack directly to the feedback resistor with a jumper, way too sensitive for a start and can damage the op amp.

The two pots ( Travel 1 & 2) may seem to affect each other as it will be a bandpass filter at some (most) settings and each pot will affect one side each (hp & lp) but the overall sound will change.
Inputs 1 & 2 are summed together at the 1st stage."
 -----------------------------------------
 So I'll remove my mod.:)

-----------------------------------
Links
++NLC Build notes
++NLC Blog 1
++Muffs... NLC 2016 modules
++ NLC facebook


To Be Continued. JP.

Thursday, 1 September 2016

sidechain compression - eurorack modular

 Sidechain compressors.
 
Compressors are essentially devices used to make loud sounds softer.
They enable a producer to boost the level of a track, thus narrowing the dynamic range.
This type of compression is evenly applied to the tack
 
Side Chaining is a more active type of compression.
It's sometimes referred to as "ducking".

It is a type of compression where the volume level of one instrument is controlled by the volume level of another instrument
That is, the compressor is only triggered when certain sounds appear.
This is the pumping effect  you often hear in electronic dance music.
Here, the compression level on a bass track is controlled by the output volume of a kick or snare drum.
The Bass line volume drops every time the kick is heard.
Another example of its use is when a song suddenly drops in volume when a radio announcer speaks.
 
 Daft Punk - Indo Silver Club (Official Audio)
 
Thus for side chaining, we need an external signal to act as the trigger.
 
To build your own side chain compressor using a eurorack system
we need a 
1. drum source 
2. Baseline
3. VCA
4. EG with an inverted output
 
The EG could be replaced with a Envelope follower & an inverter.
 
 
In this case, the VCAs gain needs to be turned up.
The baseline is passed through the "open" VCA.
Everytime the kick sounds, it triggers the envelope generator.
The inverted CV lowers the volume of the VCA 
 

These two videos are really good to watch.
  
 
They use the MATHs module
 
 
 
This second video is esp good
 
This is my usual setup.
 

 
I'm using the the Make Noise Function instead of a Maths.
I like to set Rise to full anti clockwise & Fall to about 11 0'Clock to get a ducking effect. 
A fast attack & a slower decay. 
Play around with these settings to adjust the amt of ducking.
The bubblesound VCA is set to expo and CV in to around 3 0'Clock

The Doepfer A-171-2 VC slew Processor works very much like Maths and Function
 

 
It's mostly a licensed copy of Ken Stone's vcs (voltage controlled slope)
 which is in turn based on the Serge vcs.
 
The VCS is a really useful module. Quite versitile.
In this instance it's being use as a voltage controlled envelope generator with an inverted output.
The top and bottom pot are the most important parameters to adjust.