A bit about the ARP 2600 filter.
The 2600 VCF is a low pass filter.
The top slider is labelled "initial filter frequency".
This is more commonly calked the "frequency cutoff.
(Range is between 10hz & 10kHz)
You can fine tune this frequency with the next slider : Fine Tune.
The next slider is Resonance.
When the slider is fully to the right, it will self oscillate. ... this usually creates a sine wave.
There one filter output and 8 inputs.
The inputs are divided into
5 audio & 3 CV
The audio inputs are:
+ Ring mod
+ VCO 1, 2, 3
+ Noise
The Control section:
keyboard, ADSR, VCO2.
These inputs control the filter frequency (or cutoff)
To test the keyboard input, put the filter into self oscillation mode ( resonance slider to the right)
and play your keyboard.
Re the VCO 2 input: remember, this VCO can be audio or Low Freq.
When you first use the filter its important to make a few more settings:
There are 4 basic settings you'll need to make to the VCA & mixer
The audio from the filter needs to pass into the VCA.
Thus, on the VCA section
1. fully open the VCF & AR inputs.
(all other inputs are closed)
2. close the initial gain (slider to left).
The audio then passes from the filter to the mixer.
Thus on the Mixer:
1. Open the VCA input.
Note: the VCF input should be fully closed.
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There are two types of filter circuits available on the ARP 2600 synthesizer:
the 4012 filter and the 4072 filter.
The very early 2600s use the 4012 filter
(up to around 1975)
The filter has a distinctive sound that is often described as slightly brighter, more aggressive when compared to the 4072 filter.
The 4012 filter is a 4-pole low-pass transistor ladder, very similar to a Moog ladder filter.
They were encapsulated to conceal their inner workings.
The 4072 filter, on the other hand, was introduced later in the production run of the ARP 2600, and it has a slightly different tone compared to the 4012 filter. The 4072 filter is also a 4-pole low-pass filter, but it has a maximum cutoff frequency of around 7 kHz. The 4072 filter has a slightly darker and more mellow sound compared to the 4012 filter, and it is often favored by synth enthusiasts for its ability to create warm and rich bass sounds.
Both filter circuits have their own unique characteristics and can be used to create a wide range of sounds on the ARP 2600 synthesizer. Some users prefer the 4012 filter for its brightness and aggression, while others prefer the 4072 filter for its warmth and richness. Ultimately, the choice of filter circuit depends on the sound you are trying to achieve and your personal preferences.
So both versions are 4 pole.
The "4-pole" designation refers to the number of filter stages, which affects the slope of the filter curve. A 4-pole filter has a steep curve, which means that it attenuates frequencies above the cutoff more quickly than a 2-pole filter would.
The filter on the ARP 2600 has controls for cutoff frequency, resonance, and keyboard tracking. The cutoff frequency determines the point at which the filter starts to attenuate frequencies, while resonance boosts the frequencies near the cutoff point, creating a characteristic "squishy" or "squelchy" sound. Keyboard tracking adjusts the cutoff frequency in relation to the pitch of the notes being played, which can be used to create interesting tonal variations across the keyboard.
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Even though its just a LP filter
You can configure it to be high pass & bandpass-ish
https://www.youtube.com/watch?v=kw65oO_nlQ8
https://www.youtube.com/watch?v=Nm7t3jQaOBc
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filter feedback
Patch 1 filter feedback -- patch the output of the filter back into itself via the noise input.
patch 2 - also feed the VCA output back into the VCF
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Some eurorack modules based on these filters which you make like to try:
Steffcorp VCF-12 --- based on the 4012 filter
G-Storm Electro Tonus --- based on the 4012 filter
Studio Electronics 4075
STG Soundlabs Post-Lawsuit Filter -- " not a clone of the ARP 4072 submodule.
It does, however, have an identical topology with the same transistors and operational amplifier array."
More links
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