Resonant Lopass Gate
Here's a little project that I am offering the PCB for, inspired by and approved for (but not officially endorsed) this small run by legendary synthesizer designer Don Buchla himself. To buy a PCB, simply hit the PayPal button to the left. PCB's are only $15 each, with shipping included to anywhere on the globe. Boards are ROHS approved "lead free" materials and have a silver finish to them instead of lead. The board size is 3.8 x 2.5 inches and they should fit most cabinets. RLPG's are compatible with nearly all modular formats, but work particularly well with all the popular 3U and 5U high modules like those from Synthtech, Blacet, Doepfer, Synthesizers.com and all of the modern Euro format makers out there.
RLPG rev.3.2 PCB's are $15 US each (currently out of stock)
(includes shipping to anywhere in the world via USPS)
 Features of the RLPG:
- Up to 3 Audio Inputs Up to 3 Control Voltage Inputs
- Offset (Frequency) Control
- Resonance Control
- VCF/VCA/Both Modes (Rotary or 3PDT Option)
- "Deep" Switch to set lower freq range
- Inverted CV Out (From CV Mixer)
- Jumper points to bypass mixer or remove resonance circuit
- MOTM Pot Spacing
- Compatible with www.bridechamber.com panels and parts kits
- MOTM (MTA-156), Synthesizers.com (MTA-100), and Euro/Doepfer Power Connector options
- +/-15v or +/-12v
- PCB Mounting for Alpha, Bourns, TT, or Vishay/Spectrol pots
- Ability to use 2 Single or 1 Dual Vactrol (see below)
- "Cool" people use Vactrols
This is a distant cousin PCB project that is a derivative version of the famous Buchla 292c Lopass Gate. Don Buchla himself gave approval to this endeavor for us all to learn a bit more about analog synthesizer module design, and for this we owe him a debt of gratitude as a true scholar and gentleman. This is not the first, nor will it be the last Lopass Gate module to come out to the world. People have become transfixed on the magic of Vactrol's (Light Dependent Resistors or LDR's) which are a combination of a resistor and LED in a light-tight package that seals out the light of the world yet somehow glows with an internal magic, that for the Synth_DIY crowd becomes hard to. Many have contributed to this PCB project and to the research supporting Vactrol integration to modular synthesizer design through various designs and ideals made public through the wonders of the modern Internet.  These people include Don Buchla, Peter Grenader, Chris MacDonald, Mark Verbos, Grant Richter, electro-music.com members and others. We would like to thank them for their valuable contributions to our Synth_DIY community and for their brilliant projects which have helped to spawn a crowd of Vactrol addicts.
Building this PCB requires the same fundamental practices which we have generally put in practice with our other personal modules we have built. If this is your first module, or your 100'th I hope you find the documentation and support offered within to be satisfactory. However, if this "is" your first module I highly recommend you to find and frequent the dirty Internet watering holes for us synth junkies otherwise known as www.muffwiggler.com and www.electro-music.com
Watch the YouTube videos, search the web, email me with questions. If this project suits your needs or triggers your interest you will find PCB's to be avilable through my PayPal cart linked here and on the store page. Many thanks!
Project Documentation:
- RLPG rev3.2 Project Documentation Download (zip format)
Notes: Nearly all project documents in this zip file are in Abobe PDF format. Part numbers for parts on the Mouser part list are very outdated and will likely need to be updated. Some users have mentioned using a "Log" pot for the Resonance control provides better control over the total resonance amount.
 Single or Dual Vactrols?
You can use a variety of LDR/Vactrol parts for this including 2 single vactrols, 1 dual-vactrol or homemade units if you are really up for a challenge! Here is a great diagram showing how the recommended VTL5C3/2 (dual LDR) fits to the board instead of 2 single parts.
User Community:
Dave Brown has a great build report, mods, and updated parts list at: modularsynthesis.com
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