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the fundamental and second harmonic at equal amplitudes when the pitch bend signal is close to zero. Otherwise 
only the fundamental frequency can be heard. Therefore, you can find the ideal situation when there is zero voltage 
at the pitch bend input - and it thus has no effect on the note - by adjusting 

adjust 1

 when 

slider 16 

is up until you 

hear both. If you need to adjust the pitch bend offset so large that only the fundamental is heard, then you have to 
remember that disconnecting pitch bend will change the tuning.

Grounding, shielding and RF interference

Inputs

The Eurorack community is diverse, therefore the common grounding and signal shielding practices may not be 
obeyed in all environments. There should be only one common ground between the different modules in a rack, the 
bus ground strip. Multiple grounding points may generate ground loops that add noise to sensitive inputs. However, 
typically patch cables also carry a signal ground in their sleeve contact. This is usually not a problem for such low 
output impedance, large amplitude signals that are applied to e.g. the envelope inputs within the same rack. 
However, in a case when signals from a remote rack are connected to the HG-16 inputs, large ground loops may be 
created. The unwanted additional ground usually comes from a common power jack safety ground connection, so 
the obvious remedy is to use systems with fully isolated power supplies. The secondary remedy is to use the HG-16 

ground lift switches

. Note that there should still be at least one common signal ground, and hopefully close to the 

most sensitive input. Therefore it may not be a good idea to lift all the switches, because then the possibly remaining 
common ground may be close to some noisy power supply lines. The HG-16 ground lift switches correspond to 
three regions in the circuitry. If you keep the circuit board positioned so that the ground lift switches are up, and 
look from the backside of the system, the leftmost switch (no. 3) is connected to the 

Modulation 1

  input ground, 

the middle one to 

Modulation 2, CV pitch

, and 

CV velocity

 grounds, and the third to all the 

envelope input 

grounds. The switch levers are very short, so use a small sharp tool for lifting the levers.

Outputs

The HG-16 outputs have their signal grounds permanently connected. Because the signal output has a balanced 
differential output, it does not necessarily need a separate signal ground, so if there are noise problems, use the 
receiving amplifier ground lift switches. Or, if there are none, you can even disconnect the signal cable shield from 
the ground  (but only at the output side). 

RF/EM Interference

The HG-16 has high speed digital circuitry, therefore special concern has been paid to prevent high frequency 
emission to sensitive analog circuitry inside the same rack or outside it. All the inputs and outputs have RF filters 
tuned to block high frequency signals. The module has grounded metal shielding on both sides: the front panel has a 
grounded copper layer, and the backside has an iron grille. The exposed front opening at the sliders has the slider 
support bars also grounded. When connecting the module in a (metal) rack, the attachment screws also connect the 
chassis to the rack metal parts that are typically grounded, but separately from the signal ground.

PM vs FM

The HG-16 has two different periodic modulation methods, phase modulation (PM)  used in several modes, and 
frequency modulation (FM) used only in Mode 14. The difference of these methods in terms of resulting signal 
characteristics is described in the following.
As the name suggests, PM varies the  instantaneous phase of the sinusoidal signal by the modulating waveform. The 
result is a controlled distortion that can be heard as increasing harmonics with increasing modulating signal 
amplitude. Because several of the operating modes have the possibility to add independent modulation to distinct 
harmonics, each harmonic will correspondingly be distorted, therefore creating very spectrally rich signals within 
separately controlled spectral areas.  Because the modulation is limited inside the base frequency period, all the 
distortion components will remain harmonic (except for some modes that allow signal folding/aliasing with extreme 
modulation).
FM adds frequency shifting modulation over an arbitrary period that is not limited within the modulated signal 
period like in PM. Therefore the resulting spectrum is not limited to harmonics of the modulated signal. Most 
percussion instruments have nonharmonic spectra, therefore FM is useful for generating percussive sounding 
signals, e.g. when the modulation comes from an envelope generator signal with steep amplitude variations. In fact, 
many instruments that  are periodic in their steady state, have complex nonperiodic spectra within their attack and/or 
decay periods. Such periods can easily be generated in the HG-16 because the modulation parameters can be 
controlled with external envelope generators, even independently for each generated harmonic.

10

Summary of Contents for HG-16 black

Page 1: ...external voltage gate trigger and preferably several external envelope generators These instructions cover the power requirements external connections common operating characteristics and then instructions for each of the 14 synthesis modes These instructions are quite detailed and for experienced users there is a more compact section at the end for quick setup of different operating modes see Qui...

Page 2: ... Mode 3 Base note with selectable intervals 14 Mode 4 Pseudo VCF with noise control 15 Mode 13 Pseudo VCF with PM control 15 Mode 5 True chorus with 10 chorus members each having a maximum of 8 harmonics Also the possibility to generate non harmonic overtones 17 Mode 10 16 harmonics with two parameter noise control 18 Mode 11 8 harmonics with individual two parameter noise control 18 Mode 12 Harmo...

Page 3: ...s line that is the bottom terminal in the bus connector The 5V in the bus is not a standard feature in many racks so please check that your rack has this option installed The system diagnostics is run at power up and to show that everything is ok the two red leds one right to the volume knob and the other left to the mode select knob will blink successively and then both should go off Dimensions T...

Page 4: ...ming Mostly used in the off position see the mode instructions and virtual switchboard instructions for details tune fine tuning typically not needed for user adjustment volume main volume adjustment adjust 1 and adjust 2 mode specific adjustments multi turn digital encoders D C out constant voltage output useful in many modes as a constant envelope output 4 x envelope inputs inputs for external e...

Page 5: ... microphone input mic that accepts a differential 3 5mm TRS i e stereo jack and used only in the vocoder operating modes The main output has a balanced 3 5mm TRS jack Only connect to an amplifier that also has a balanced differential input otherwise the noise level is unacceptable Non balanced stereo or mono inputs are not compatible not suitable for headphone connection either The external requir...

Page 6: ...t panel are the following volume a typical output volume potentiometer adjust 1 and adjust 2 are multiturn rotary knobs that have control functions specific to each operating mode Three position toggle switch gate on off envelope select The HG 16 black assumes that the modular synthesizer gate signal is connected through front panel plug contrary to the original HG 16 that had it bus connected In ...

Page 7: ... control for each common modulatable PM synthesis and phase noise for each harmonic Mode 1 8 harmonics with individual envelope control for each and individual modulation depth control noise and or PM for each using the remaining 8 sliders Mode 2 Harmonic filtered noise bands from a voltage controlled comb filter with individual envelope control for each Mode 3 Base note with selectable interval n...

Page 8: ...toggle the switch back and forth between single slider programming events Note that only the last moved slider is activated therefore if you accidentally move more than one slider at the same time you need to check back that all channels are in the desired order If you leave the moved slider at the very minimum or maximum after selecting channels such accidents are not likely to occur Note that in...

Page 9: ...a trimmer for fine adjustment for compensating possible input scale error This is typically sufficient for normal situations If not there is a software facility for adjusting both the offset and scaling errors Errors can also occur in the pitch bend signal CV pitch input so they can also be compensated in software This is described in the following Software tuning For software tuning turn the mode...

Page 10: ...l ground so if there are noise problems use the receiving amplifier ground lift switches Or if there are none you can even disconnect the signal cable shield from the ground but only at the output side RF EM Interference The HG 16 has high speed digital circuitry therefore special concern has been paid to prevent high frequency emission to sensitive analog circuitry inside the same rack or outside...

Page 11: ...in the typical way i e the former for pitch bending and latter for key velocity based amplitude control These signals are available from typical MIDI input modules not included Note that adding simultaneously both noise and PM is also possible However in that case also some constant band low frequency noise will be added in addition to the band limited voice around the selected harmonic Some of th...

Page 12: ...idually be adjusted using the corresponding sliders 9 16 i e they can be used for weighing the input fed to modulation1 modulation 2 The individual adjustment allows creation of complex spectra that have sections of noisy or clean areas when the noise adjustments are used The individual phase modulation on the other hand adds variable spectra that are harmonics of the selected overtones instead of...

Page 13: ...oise is slow because the comb filter stabilization takes some time When moving to the opposite direction the rate is fast modulation 2 has no effect in this mode Furthermore the Eurorack gate signal is not used in this mode even if the toggle switch is in the on position Therefore the output level is all the time controlled by the external envelope inputs linked to the corresponding sliders Notice...

Page 14: ...the chord elements can be modulated by one of the 4 selectable envelopes as described before you can make e g quite complex glissando type effects when using envelope controls with different durations for the different chord notes or even make a transition from one chord to another during the activation of a single base note In the case of rapidly varying envelopes such activation would be quite t...

Page 15: ...vity for that input is zero Only when you rotate the adjust 2 knob the sensitivity for the external modulation increases When rotating CW an increasing modulating voltage at modulation 2 will shift the pseudofilter center frequencies higher Correspondingly rotation of adjust 2 CCW from the reset state will shift the center frequencies lower with increasing modulation voltage As usual you can alter...

Page 16: ...ions and adjustments 1 Connect envelope generator outputs to all those of the envelope inputs that you have activated for the desired harmonic sliders 1 8 and for the filter amplitude sliders 9 16 Remember that on power up all are connected to input 1 2 Connect envelope generator output to modulation 2 to do the center frequency modulation of the pseudofilters use adjust 2 to control its sensitivi...

Page 17: ...des The adjustment using adjust 2 advances stepwise generating audible clicks therefore not useful during live performance A drawback from the true chorus operation is that such close frequencies inevitably will interfere i e make beating effects with their periods varying inversely proportionally to the frequency difference If the amplitudes are identical there will be periodically almost complet...

Page 18: ...random frequency hopping of the harmonics rather than noise The hopping period is increased with increased CW turning of adjust 2 so the signal spends more time at the random frequencies Notice that the range of adjust 2 is several tens of full rotations so you can hear the frequency hopping slowly slow down when you turn it CW Again it is convenient to connect modulation 1 to the D C out terminal...

Page 19: ...n be selected The selection is done exactly in the same way as selecting one of the external envelope inputs in the basic mode i e by turning the toggle switch down to the position envelope select and then moving the selected slider up and down until one of the lit leds next to the 4 envelope inputs shows the desired delay The delay length corresponds to the order number of the input so if the led...

Page 20: ...al to the gate input and optionally connect the CV pitch and CV velocity inputs to the corresponding MIDI input module outputs 5 Keep the toggle switch in the gate on position to trigger the internal envelopes alternatively use modulation 1 as the trigger input but leave it open if gate is used for triggering 6 Check the harmonic slider virtual link connections to the envelope inputs 1 4 because t...

Page 21: ...raised and live envelopes or D C Out connected to modulation 1 2 and to all the envelope inputs that you have linked to the activated sliders In this mode the modulating signal is not added raw to the note determining voltage in the same way as the typical pitch bending signal of a keyboard would do Instead each of the 6 harmonics are separately frequency modulated using the same modulator defined...

Page 22: ...plitude The chain of possible modulation amplitude controls may appear overly complex but it allows dynamic control of all the signal aspects 1 Global modulation amplitude through modulation 2 2 Individual modulating signal harmonic amplitude modulation through the virtual switchboard inputs linked to sliders 7 8 3 Individual base note harmonic modulation strength through the virtual switchboard i...

Page 23: ...velope inputs that you have linked for the sliders 7 8 Adjust sliders 7 8 to set the relative amplitudes for each of the modulator harmonics 3 Connect envelope generator outputs to all those of the envelope inputs that you have activated for the individual harmonic frequency modulating signal amplitude defining sliders 9 14 Check the correspondence of sliders 1 6 and 9 14 4 For modulating signal f...

Page 24: ... which typically is noisy increased clipping also removes lower spectral contents for sound coloring Slider 7 Spectral shaping exaggerates the differences of spectral peaks and valleys when shifted upwards from the default off position Slider 8 Control of the interpolation between the analyzed spectral bands This is an on off control and its change only comes into effect after system reset or mode...

Page 25: ...both versions the maximum harmonic frequency is limited below 10kHz therefore notes whose fundamental is more than 10kHz Nmax will have less harmonics than indicated above Also note that only if the adjust knobs are rotated towards the small singer i e shifting the spectrum upwards the output spectrum contents exceeds the analysis filterbank upper limit of 5200Hz Practical operation tips A short l...

Page 26: ...tor has very rapid response This vocoder has not been intended to be used as a high quality autotune This is because the output pitch follows faithfully the note played rather than just trying to correct off key singing and the voice quality changes more than in a dedicated autotune processor Its use is mainly in special effects due to the versatile means to modify the spectral parameters and the ...

Page 27: ...imultaneously switching the mode selector from 6 or 8 to 7 Now the spectrum at the switching moment will be frozen and you can continue playing in the same way as in Mode 6 except that no microphone is needed any more Leave envelope input 3 open or grounded 2 Transient capture Keep the three position toggle switch in the middle position gate off and leave envelope input 3 open or grounded Then mov...

Page 28: ... limitations in instrument replay are due to the fact that non harmonic nature of the signal is not retained which means that most percussion instruments are not reproduced well Also the overall spectrum envelope may vary drastically for musical instruments with the key played and the vocoder only stores the instantaneous spectrum for the specific key used in the recording This is in contrast to a...

Page 29: ...n off automatic manual noise control If off or fully down the noise characteristics can be adjusted using sliders 2 5 otherwise automatic noisiness decision made in the vocoder Slider 2 If Slider 1 is off adjusts the noise level at the frequency band corresponding to the fundamental otherwise adjusts the sensitivity for automatic noise generation for the band Slider 3 Corresponding noise adjustmen...

Page 30: ... noise gate adjustment with Slider 6 also the input microphone A D has noise gating The default gating from system reset can be varied using these sliders If you want to increase the gating threshold move Slider 15 to the maximum position and move 16 up and down between the minimum and maximum positions Each sweep up or down increases the threshold by 3dB Correspondingly when Slider 15 is at the m...

Page 31: ... modulation strength using adjust 1 Phase modulation strength using adjust 2 Mode 1 8 harmonics individual modulation control 1 Connect envelope generator outputs to all those of the envelope inputs that you have activated for the desired harmonic sliders Only 8 harmonic sliders used in this mode 2 If you want to use the noise and or PM modulation features connect also envelope generator outputs t...

Page 32: ...level for noise Mode 4 or PM Mode 13 Use Sliders 1 8 to set the harmonic spectra Use sliders 9 16 to set the pseudofilter spectral response If you want to use the 4 highest bands connect a signal source also to envelope input 3 Mode 5 True chorus with 10 chorus members each having maximum of 8 harmonics Also possibility to generate non harmonic overtones 1 Connect envelope generator outputs to all...

Page 33: ...the gate input and optionally connect the CV pitch and CV velocity inputs use adjust 1 to control the envelope shape see Figure 4 use adjust 2 and slider 16 to control the envelope duration and relative delays between the 4 possible trigger events Mode 14 Frequency modulated harmonic generator 1 Connect envelope generator outputs to all those of the envelope inputs that you have activated for the ...

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