Swiss-Army Knife type functions geared towards audio processing:
Manual signal attenuation from null to +6dB
Switch-selectable diode waveshaper with full VC
White/Pink Noise Source
Linear VCA w/velocity port
DC coupled Ring Modulator
Analog White Noise Source • Attenuator • +6dB Amplifier • Wavefolder/Waveshaper • Voltage Controlled Amplifier • Ring Modulator • Fuzz Distortion
The M25 is one of two Swiss Army Knife processors that, along with it's counterpart, the Model 26 Control Signal Processor, provides a bank of essential audio synthesis functions within a single module: a Manual Attenuator, a Waveshaper, a White/Pink analog Noise Source, a Dual-VC Linear VCA and a DC coupled Ring Modulator and Fuzz Distortion -- all under a single 10HP faceplate.
The functionality of the M25 is broken down into three sections:
1)Wave Attenuator / Waveshaper / Noise Generator
With it's Mode switch set to the right, the top section of the Model 25 provides an often overlooked audio synthesis function - Manual Attenuation of both audio and control signals. It's range travels from full attenuation (no signal), through unity gain to +6dB, so that signals can be amplified from their input level by a factor of 2.
With the Mode switch thrown to the left, the M25's diode-based Waveshaper is put into the signal path. The level pot at that point effects both the signal amplitude and the amount of folding. Along with the manual pot, the Waveshaper has a dedicated voltage control input.
WIth no input present in the Attenuator/Waveshaper, the output of the returns a manually-adjustable analog White Noise source. When the Mode switch is thrown to left , the White Noise is shaded Pink. There is also a dedicated unity gain noise output. .
2) Linear VCA
The center section of the M25 hosts a standard linear VCA. Unlike the M13, no filtering is applied to the signal path and both AC and DC sources may be gated. There are two control voltage inputs provided - the first will take the output from full attenuation to unity gain. The second VC input is preescaled for the velocity output of a midi to CV converter.
3) Ring Modulator
The bottom section of the M25 is a 1496-based balanced dual sideband four quadrant multiplier - a Ring Modulator. Boasting over 65dB of carrier suppression, it features a unique corss-modulation Feedback switch not found in other Ring Modulators that introduces harmonic content with minimal sidebanding.
By running the same signal through both the X and Y inputs of the M25 Ring Modulator and engaging the Feedback Switch, the output is fuzzed (in a very big way). Have a listen to sound sample 3 below.
Click HEREor scroll down for the Model 25 calibration/set-up procedure
1) The following soundbite consists of two sine VCOs, both controlled by the same M24 output, which are run through the M24's Ring Modulator with the FEEDBACK SWITCH being turned on and off at regular intervals. click
1) There's another example of the Ring Modulator's Feedback option, this time with the same signal (two Ramp VCO's) being fed into both the X and Y inputs. The Feedback is engaged throughout. A second voice is added halfway through the soundbite, then a third with a shorter envelope. click
3) Fuzz Distortion - This sample gives an example of using the M25 to produce Fuzz distortion. The identical signal is run through both the X and Y inputs of the Ring ModulatEDDBACK switch is engaged. click 4) 2 examples of the Waveshaper on a single sine wave VCO. The first is a manual sweep of the attenuation pot click, the second is the effect from a fixed setting of the pot when the sine is gated through a VCA prior to being being run through the waveshaper click
5) One patch, four rmodules involved -- none of them filters: Two Model 15's (both sine) into the M15's Ring Modulator set with a closed feedback loop, then through it's VCA with that output routed through the Model 25's Waveshaper, them to the speakers (with a little TC4000 reverb added). One Model 10 controls both the VCA and Waveshaper. Again...no 'filter' in this patch. click
6) An even simplier patch, but no less interesting: Sine into Waveshaper, one hand on the VCO freq knob, the other on the Model 25 attenuator, which is opening and closing the wavefold function click
Model 25 Demo's from REwire:
Model 25 Demo's from REWIRE:
Sine to Waveshaper - LFO to WS CV input click here
Saws to Waveshaper - Theremin Control of WS CV click here
Ringmod to Waveshaper - Sync LFO to WS CV click here
Ringmod to Waveshaper - Repeating Env to WS CV click here
Ringmod to Waveshaper - Env and LFO to WS CV and OSC CV
Ringmod to Waveshaper - Theremin Control of WS CV click here
Ringmod to CV input of Waveshaper - Triangle to WS Audio Input click here
Ringmod to Waveshaper - Env to WS CV - Flip Feedback Switch click here
Sine to Waveshaper - WS to Ringmod - LFO to WS CV click here
Calibration -- Care and feeding of the Model 25:
Something that makes the Model 25 such a useful module is the Ring Modulator's carrier supression. Great lengths were made to assure the least possible bleed of the input signals at the sum and difference output - the Ring. This may need to be checked periodically, when the unit is installed initially or when it's moved to another location in your system. Because it's balanced (thus, BALANCED Modulator), and much like being on a tightrope, that balance can be upset with bumps or knocks.
There is an easy two step calibration procedure to check and adjust the supression of the X and Y inputs. When performing this calibration, make sure the Feedback is not engaged (switch set to the RIGHT):
STEP A) Insert a unrprocessed, non-gated signal into X input of your Module 25's Ring Modulator, indentifued in the diagram as A. Connect a second patchcord from the Ring's output to your speakers. Adjust the Trimpot labeled A in the diagram until that signal is as low in amplutide as possible (it's a touchy adjustment, take your time!)
STEP B) Repeat the same operation, this time moving the same sound source into the Y input (labeled B in the diagram) and adjusting it's associated trimpot (also labeled B)
Your Ring Modulator is now calibrated!
Notes: The intent is not to adjust the amplitude of the X and Y input so they are the same - the intent is to adjust each independently so each are as low as their associaed trimppot's will allow them to be. This may not mean they are adjusted to the same level as one another. As a general rule, the Y input tends to ride a bit hotter than the X. This is normal
No damage can be done to the module by adjusting these trimmers.
STEP C ) OPTIONAL - The trimpot labeled C in the diagram sets the maximum distortion the Waveshaper can produce. We adjust this at the factory so that the signal begins to flatten out (square) slightly when the attenuator pot is fully CCW. Feel free to try other settings of the trimpot - you may prefer it a bit more agressive or little more tame. No harm will come of the module by adjustng this pot. This adjustment is not required for calibration.
Model 25/17 demos by Thighpaulsandra with Peter Forrest shot at Aeriel Studios