Filters

width: 10hp
Current: +20mA, -20mA
SKU: BLMHRMVCF

Color: Black

Style: Vintage OTA analog Filter.
Modes: High pass and low pass filtering

Technical: JRC13700 OTA IC, saturation IC JRC 4558.

What does this do?
This is an analog filter with a lot of low end. The design uses a JRC 13700 OTA dual vca chip to produce 12db Low pass and 12db high pass filtering. The module can easily self oscillate. There is a trimmer to adjust how much sine wave you want. There is a 2 channel internal mixer, so that you can patch two sound sources. There is a bi polar FM input, and a 'MOD' input with level control. These are used to voltage control the Cutoff knob.

The 'ping' input is a unique trigger conditioner that will send a spike to the filter. This is used to produce percussion type sounds from the output. This is used in combination with the Rez knob. The cutoff knob determines the sine wave frequency.

Price: $115

• blm-hermippe_vcf.pdf PDF

Analog Filter
Width: 10hp
Current: +16mA,-15mA

What does this do?
This product is an analog filter that processes -5v/+5v synth level audio signals. This particular product is using a 10 stage diode ladder circuit influenced from a classic steiner filter.

Features:
-Ping circuit, for easy percussion sounds
-level controls for Low Pass, Band Pass, and High Pass inputs.
-All inputs can be used simultaneous.
-FM bi-polar input
-CV direct input

Price: $135.00

In the store: BLM 10-stage Steiner VCF

Width: 10hp
Current: +89mA -88mA

What does this do?
This module is an analog filter based on the Dwarf Star Semi Modular Synthesizer. This uses 2164 Quad VCA for the filter cells.
Each Filter State is internally patched to three toggle switches to allow any combination of filtering states. Low Pass, Band Pass, High Pass.

The filter is internally patched to a VCA for compact analog voicing. All you need is the following products to complete a mono analog voice.
-BLM Looping ADSR v2.1
-Analog VCO (any one is good)

The Gleba has a 2 stage sub harmonic generator inspired from the SH101. There is also a Diode Limiter Circuit activated by toggle switch
to simulate metallic feedback tones similar to the MS20 vcf.

The front panel has a 'Q' trimmer that allows you to fine tune the self oscillation amplitude. Some people like screaming self oscillation, while others
like the classic soft whistle similar to a moog classic filter. You can adjust the resonance to your liking.

The self oscillation will track 1v per octave. Expect about 3 octaves of in tune tracking. Higher tracking is slightly off.
This is normal behavior.

Features:
(2) Audio Input jacks. One is internally patched to the sub harmonic generators, with level controls for all of those.
The other Audio Input Jack is a direct input.
-Rez Voltage Control
-Bi-polar FM Attenuinverter input.
-VCA with CV input
-FCV (Filter CV) direct input for 1v per octave control.

Cutoff knob is one of the biggest in the industry.

You are paying for the following circuitry:
MIXER+SUBHARMONIC+VCF+VCA.

Price: $235.00

• blm-glebavcf.pdf PDF

In the store: BLM Gleba SV VCF

Width 16hp
Current: +69mA -68mA
PCB Stack: 1 Level, Skiff compatible.

Module type: analog filter, sub harmonic generator, internal vca, white noise generator, (self) oscillator

What does this do?

This particular product is my take on the vintage analog filter found on the Roland SH1 Keyboard. Some key differences from the original
are low end correction on the resonance path (audio level would drop), with voltage control, and I used a modern exponential converter.

The bass frequency will retain nicely on this modern version. No more audio level drop. The 'RCV' can be used to simulate Band Pass sounding tones when used with audio rate external sources..

I also included the famous feedback patch that lucky users of the vintage keyboard would do. Users would patch from the headphone output back into the filter external input.
I duplicated the original discrete headphone circuity and internally patched it for you. All you have to do is turn it up with the 'FBK' knob. Small settings go a long way with this.
It can get strange with too much feedback, in a good way.

24db Low Pass Filter.

Features:

(2) Possible External Audio inputs.
(1) White Noise Generator, Switch Jack internally patched to AIN2 input jack.
(2) Sub Harmonic Generators taken from the SH101 circuitry. Both are accessible by level knobs.
(1) Voltage Controlled Rez, with auto low end level correction.
(1) 1V per octave 'Expo' input.
(1) Linear FM input. Best used during Filter Self Oscillation duties.
(1) Bi-polar FM Attenuinverter. Best used with an external envelope generator.
(1) Internal VCA with 2 possible CV inputs. VCA knob is a manual offset to 'open' the VCA.

What you get:
Mixer+WhiteNoiseGen+Subharmonics+VCF+VCA

All you need is a vco, and envelope generator to complete a compact analog mono voice.
If this was literally your first and only module, it is possible to make sound and noise for entertainment.

Price $225.00

• blm_luck7_vcf.pdf PDF

In the store: BLM Lucky 7 OTA VCF

WIDTH: 6HP
CURRENT: +64mA -64mA

24DB VCF + VCA

This module has the modern 3109 filter chip. The older 3109 chip is found in the vintage Roland keyboards like SH-101.
What I did is add resonance audio drop out compensation and precision resistors for the exponential converter. The module
will easily track 5+ octaves when in full self oscillation. Band pass was also added as a bonus. The band pass steals the
show, as many have not heard an sh101 with band pass.

-24db low pass
-18db band pass

-Internal VCA for easy voice building
-FM Bi Polar CV input for the Filter
-Envelope Input for the VCA
-Dual Audio Inputs, one direct, and the other with over drive.

Price $125.00

• blmans3109vcf.pdf PDF

In the store: Acid N Sons Filter

WIDTH: 10HP
DEPTH: 1 PCB STACK, SKIFF COMPATIBLE

What does this do?
This is an analog filter based on the 1974 SEM filter. The original early design did not self oscillate into a sine wave. This one also does not self oscillate. The sound, however, makes up for that. You get the original notch sweep, and incredible band pass mode at such a low friendly price.

Added Features
-onboard VCA
-onboard envelope generator (decay)
-variable trigger input circuit. Emulates a Vactrol.
-dual audio input possible

• blmsem.pdf PDF

Width: 10hp
Current: 32mA,-32mA

What does this do?
This is an analog filter based on the roland JP6 filter. It uses an OTA-JFET cell for each filter section. I added some modifications and a 'Vactrol' simulation. There is a dip switch on the back, please look up the manual to determine your best needs.

Features:
-LP12,LP24,BP12,HP24 modes
-internal vca
-internal Decay circuit based on the syncussion. Modified to act like a vactrol.
-Bi polar FM Attenu-inverter
-CV on the Rez
-Feedback internal routing.

• blm-jelly_paste_vcf.pdf PDF

In the store: Jelly Paste Filter Factory

Width: 16HP
Current: +65mA,-65mA
PCB Stack: 1 Level, Skiff compatible.

What does this do?
This is an analog filter with a separate 3 channel mono mixer, and VCA combo. There is also an internal envelope generator with Decay. All this product needs is a VCO and a trigger signal to complete a mini voice.

The outputs on the filter are meant to be manually patched into one of the VCA audio inputs on the module to complete the mini voice. You can mix and match to create custom filter types.

The Feedback on the product 'Rez', is what makes this sound like an MS20 filter. There are diodes, used as a limiter, and also to wave shape when in self oscillation mode.

Features:
-2 audio inputs with 2 level control knobs.
-Bi-polar FM for the filter.
-Mod input with level knob for the filter.
-FCV Filter CV direct input for the filter.
All CV inputs for the Filter are 1V per octave, Exponential.

-REZ CV

-VOLT CUT output. +5v/5v output. Used to remote control another filter, with the master 'Cut' knob.
-Internal Envelope Generator, with Level Sends to VCA and Filter.

-Separate VCA circuit, with 3 channel mono mixer input.
-1 CV input for the VCA. 'VCV'.
-1 VCA output.

The filter will self oscillate into a sine wave and does track 1v per octave.

• blm-phrogs-vcf.pdf PDF

In the store: Phrogs FIlter