Introducing the Nodular Desktop Synthesizer - Two Sided Analog Monophonic Semi-Modular Synthesizer

Note: Auction links are affiliate links for which the site may be compensated.

via this auction

Update: the maker/brand name for this synth is ndlr.synths. I created a new channel label for them. We have a new synthesizer manufacturer in town.  See second "Update" at the bottom of this post for additional notes on the design.

via the auction:
"Up for sale: one monophonic analog synthesizer. I've been making analog synthesizers for about 15 years now, but this is the first I am offering up for sale to the 'general public'. I am hoping to make a business out of selling this particular model, and you could be my very first customer.

The pictures show the same unit that is up for sale. The cabinet is made from 3/4" natural cherry boards, except for the base, which is made of 3/4" MDF. Both instrument panels are made of 1/8" thick anodized aluminum. The panels have been mechanically engraved and the engravings filled with chemically hardened black enamel paint. The whole unit measures about 18" wide by 18" deep by 12" tall. It weighs about 40 pounds. This is a very well made unit, with sturdy instrument panels that'll last a lifetime.

This synthesizer has its own +15/+10/GND/-10/-15 volt power supply and will only run on 120VAC 60Hz. It consumes about 45 watts of power at full bore.

All the modules in this synthesizer have been designed to work together seamlessly, and all use the same standards: 1 volt per octave, 10 volt peak-to-peak signal voltages, and 5 volt peak-to-peak gate, trigger, and control voltages. All patches are made among the modules via banana jacks. And a few different ways of interfacing to external modules or instruments are offered via 1/4" phone jacks.

A description of the different modules follows:

(1) ring modulator

(1) white and pink noise and random voltage source

(1) sample/track & hold

(1) voltage comparator

(2) low frequency oscillators (LFOs):

(1) headphone amplifier

Both offer voltage controlled frequency, variable offset and symmetry, and sinusoidal, triangular, and pulse wave outputs. By adjusting the speed knob, the frequency can be changed from about 20Hz down to really, really, slow. This range can be extended through voltage control.

(3) voltage controlled oscillators (VCOs):

All three offer 1 volt per octave frequency control, voltage controlled pulse width modulation, ac-coupled linear frequency control, hard sync, and sine, triangle, sawtooth, and pulse wave outputs. They'll track to within .2% over at least 8 octaves with basically negligible temperature drift once the enclosure is warmed up. And they'll operate from below audio to above audio frequencies.

In addition, the first VCO offers a frequency range switch and fine tuning.


The other two VCOs offer a switch to either couple to the range switch of the first VCO,or operate independently. Each of these has a coarse tune and fine tune control. Another feature of these is a detune control which allows all three oscillators to be tuned just slightly off from each other. This produces a very animated sound at low frequencies without becoming a nuisance at higher frequencies.

(1) low pass filter (LPF):

This is a discrete version of the infamous SSM2040 filter chip. It offers simultaneous outputs for 12db (2-pole), 24db (4-pole), and 48db (8-pole) cutoff responses, and voltage controlled cutoff frequency and resonance. The filter has been designed so that output levels do not decrease when resonance is increased.

This module has its own 3-input AC-coupled audio mixer.

(1) high pass filter (HPF):

Another discrete SSM2040. This one has simultaneous outputs for 12db and 24db cutoff responses, and voltage controlled cutoff frequency but NO resonance.

This module has its own 3-input AC-coupled audio mixer.

(1) filter coupler:

This unit couples the 24db low pass and 24db high pass filters to make either one band pass or one band stop filter, according to a switch. These offer voltage controlled center frequency and width control.

(2) audio quality voltage controlled amplifiers (VCAs):

These are exceptionally low noise amplifiers with negligible CV bleedthru at normal levels. They offer simultaneous linear and exponential control.

Each VCA has its own 3-input audio mixer. One is AC-coupled, the other DC-coupled.

(3) linear contour generators (ADSRs):

Each offers attack, decay, sustain, and release phases. The attack, decay, and release times are adjustable from about 200 micro(not milli)seconds to a few minutes. The sustain level is adjustable from 0 to 5 volts. These are activated by a gate voltage and are retriggerable.

One is hard-wired to control the LPF, another to control the HPF/band stop/band reject filters, and the other to control both VCAs. But they act independently from these modules and can be patched elsewhere.

(1) midi to control voltage converter:

This module accepts MIDI information and converts it to the appropriate control voltages using a PIC microchip and a DAC. It is monophonic with a ten note stack and last note priority. MIDI notes are converted to a 1V/OCTAVE signal which is accurate across all 127 notes to within .2%. Pitch bend messages are used to modulate this signal, with a modulation range adjustable from nil to +/-1 octave. Velocity messages are converted to an ACCENT signal which varies from 0 volts at maximum velocity to -5 volts at minimum velocity and is hard-wired to control both VCAs. Each new note on message generates a TRIGGER output, with a GATE output whenever there is any active note on message. Modulation wheel messages are converted to control two separate amplifiers, allowing the level of any two signals to be adjusted via a modulation wheel from nil to unity. In addition, this module provides two banana jacks which are wired directly to two separate 1/4" phone jacks for communication with the outside world.

There is also a glide knob on the front panel which adjusts the amount of glide or portamento between notes generated by this module. This function can be defeated with a shorting switch.

(1) external signal processor:

This module amplifies any line level or microphone level external signal and extracts pitch, contour, gate, and trigger information. The microphone input is a Tip-Ring-Sleeve balanced input designed to amplify signals from a typical dynamic microphone. No phantom power is supplied. The signal at this input is amplified by 100X and passed along to the line level input if no other jack has been inserted there. The line level input is a Tip-Sleeve mono input designed to get most line level signals up to the standard 10 volt peak-to-peak levels. The signal at this input is amplified by either 1-10X or 10-100X according to the position of a switch and the PREAMP knob.

After amplification, the signal is sent to a pitch extractor which converts the frequency of the sound to a 1 volt per octave signal accurate to within .2%. It works pretty well with any fairly clean, pitched sound that has a strong fundamental frequency. As with all pitch extractors, YMMV.

The information from the pitch extractor is used to sample and dump the amplified signal once every cycle to provide a loudness contour signal which is exceptionally accurate. If the pitch extractor is doing its job, the contour signal will be a very close replica and will not suffer from the problem of voltage droop versus slow response time that is inherent with most envelope followers. And if the pitch extractor is struggling, the circuit has been designed with a fail-safe to provide a pretty good contour signal even still.

The information from the contour signal is used to provide a gate signal whenever it exceeds an adjustable threshold, and a trigger signal whenever its rate of increase exceeds an adjustable threshold.

(1) dual matrix mixer:

Your typical matrix mixer with some exceptions. There are two banks of inputs directed to two separate outputs, meaning one knob controls the level of two different inputs. The knobs are bipolar, meaning the input levels can be adjusted from inverted unity to nil to unity. And two linear VCAs are provided within the matrix.

This module also provides +5 volt and 440Hz reference signals.

(1) transient shaper

This module is modeled after the marvelous universal slope generators found in the Serge systems. This is the Swiss army knife of synthesizer modules. It can be used as another VCO or LFO, a voltage controlled ARSR contour generator, a voltage controlled Delay-AR contour generator, a gate delay, an envelope follower, and a slew limiter with separately adjustable and voltage controlled rise and fall times, among other things.

(1) audio quality voltage controlled panner/cross-fader/stereo output

This module takes one signal and pans it between two outputs. Or two signals, and cross-fades them between two outputs. This is an equal power amplifier, meaning the response is not linear, but more like sinusoidal. In other words, if one signal is being panned from left to right, when it is midway between it will be -3db down at each output, rather than -6db down (or 1/2X). This is done so the signal does not appear to lose volume as it is moving across the stereo field.

Both left and right outputs are provided at the standard synthesizer level via banana jacks and at the standard -10 dBV line level via 1/4" phone jacks. This will allow the synthesizer to interface with most audio equipment.

Also, the left and right outputs are fed into the headphone amplifier.

That about covers the basic functions of the different modules. This synthesizer has been designed as a performance synthesizer, with the Korg MS-20 as an inspiration. As you can see from the pictures, the modules represented on the front panel are mirrored on the upper panel. So all patching is done on the upper panel, away from most control knobs on the front panel. This reduces the amount of spaghetti you have to work around once a patch is set up. And it makes tweaking so much more enjoyable.

In designing this synthesizer, I have tried to keep the quirks to a minimum and have the "parameters of sound" be as transparent as possible. I realize it is the quirks which give the most loved synthesizers a lot their character, but the idea here is to insert the quirks yourself. So, if you're looking for "that" sound, while you may not be able to replicate it exactly, you can get very close. As a really good example of this, one of the things which gives the minimoog its punchy bass is the contour generators hang for a little bit at the top of their attack. You can mimic that on this synth with a patch between one of the ADSRs, and the track & hold, +5 volt reference, matrix mixer, and comparator. Can you see how? It's this openness and versatility which gives you an enormous palette of sounds. And I don't think musicality has suffered much as a consequence. All this is to say, while it doesn't have the magic of a [insert your favorite synth here], it does have its own magic.

After all this you're probably wondering how it sounds. Well, it sounds great. In terms of the typical VCO->LPF->VCA patch: The VCOs are very similar to the old Moog sawtooth-core oscillators, only with much better tracking and less temperature drift. With three VCOs and careful detuning, they'll produce some sweet sounds all by themselves. The SSM2040-style LPF is a very versatile and musical filter. With the 12db response and its aggressive resonance, you can get some really harsh, acid effects. With the 24db and 48db responses and their tamer resonance, you can get that fat bass sound. And the VCAs are as quiet and responsive as anything that's out there. Of course, there's much more to this synthesizer than that old patch and it will just plain run circles around any vintage synth that costs twice as much.

If you'd like to actually hear what it sounds like, send me an email with a reasonable amount of specific patches and I will record them and send them to you as soon as I am able. Or, if you prefer, I live in Milwaukee, WI and you are welcome to come by and check it out for yourself. Also, be sure to click on the photos to see the larger, zoomable jpegs.

Short of finding an ARP 2600 at a garage sale, this is the best deal you'll ever find on an analog synthesizer. If it were "branded" I estimate it would cost around $6000, and the quality is every bit as good. Making synths is a labor of love for me. I'm not doing this to make a quick buck or get rich. I'm 100% committed to your satisfaction. You will be very happy with this synthesizer. And if you have a problem I will work with you to fix it. Since it's the first one I am offering for sale, I'm selling it with a lifetime warranty against any defects on my end and one free tune-up/calibration. If you find there is something wrong with it, contact me, then ship it back and I'll fix it and pay for return shipping. If you want it calibrated, I will do the first one free of charge but you must pay for shipping both ways.

The fine print: I will ship only to the lower 48 states in the USA. You must have a good history on eBay as a buyer for your offer to be accepted. Otherwise, your purchase will be canceled. This unit comes with one power cord and that is all. Nothing else is included. You WILL need other things to use it. At minimum, you will want a MIDI cable to interface to a MIDI device, several 1/4" phone cables to interface to other modules, instruments, and amplifiers, and some banana cables. 20 is a good start: five 4", five 8", five 12", five 18", all of different colors. This will be adequate for most patches. The 18" cables will not quite stretch across the diagonal, so you may want a couple 24" cables just in case. You shouldn't need these, though, since you can make longer cables by connecting them if you have stackable cables, which I strongly recommend. Mouser Electronics sells some decent ones for about $5 a piece depending on length. I use Mouser part number 565-B12-6 and similar. Or you can roll your own for slightly less."

Update:  additional notes on the design via ndlr.synths: Some notes on the design: "All the actual circuit layout and artwork is mine. As far as the designs go, some modules are based heavily on other designs with a good deal of modifications and, sometimes :), improvements by myself: the VCOs are based on the famous Electronotes VCOs, the ring mod is based on the CGS real ring mod design, the filters are discrete SSM2040s for which I'd give a lot of credit to Jurgen Haible, the LFOs are based on the Korg MS-20, and of course the transient shapers are at heart the same as the Serge modules but have a different 'front end' and more personally 'mine' implementation. Others modules, like the MIDI converter, the external signal processor, and the panner, are designs which I would call my own. Although, of course, I haven't reinvented the wheel. I've always been much more of a tinkerer than a designer, and most of my work has been finding designs I like, building them on a breadboard to see how they work, and trying to make them new."