background image

11

now, so that the synthesizer "produces" a sound only when you 
have pressed a key. Experiment with various settings of the ENV 
2 controls, and with setting various relationships between the 
VCF frequency control and the knob (#5) that determines control 
signal amplitude.

NOTE: These relationships are the most crucial ones in the syn-

thesizer; until they are mastered, you will not be getting 
the most that you can from your instrument. A quick summary 
of the most important points to learn: (verify each one as 
you read.)

a) in many keyboard setups the filter is either closed, to 

open only under control of ENV 2, or (less often) open, 
to be closed only under control of ENV 2.

b) a highpass filter is closed when its frequency is high; a 

lowpass filter is closed when its frequency is low; a 
bandpass filter is closed when its frequency is either 
high or low; and a notch filter is always open.

c) when the control input attenuator is rotated left, the 

incoming signal from ENV 2 drives the filter frequency 
down; as it is rotated to the right, the ENV 2 signal 
drives the filter frequency up.

d) as the filter resonance is increased, its output level 

will--generally--increase. Compensate by lowering 
slightly the level of the input audio level. At maximum 
resonance a very small input signal is enough to produce 
full output from the filter (in a very narrow band of 
frequencies).

C. INTERRUPTED SOUND

If the filter manual frequency setting is at minimum, and the 
mode control is set for lowpass operation, and the control 
input attenuator is at maximum right, the filter alone will be 
capable of producing "events" under keyboard control. In other 
words, with these settings you will hear nothing until a key is 
depressed, thus gating the ENV 2 "on" which opens the filter to 
allow a signal to pass through.

In many cases, however, you will want to use the filter for 
some other purpose--perhaps controlled by the LFO, or even not 
controlled at all except manually. Good oboe and bassoon tim-
bres, for example, require a resonant filter at a constant fre-
quency.

In all of these cases, you will need to use the VCA to inter-
rupt the continuous source sound and produce "events."

Summary of Contents for Two Voice

Page 1: ...A BRIEF INSTRUCTION MANUAL for the OBERHEIM TWO VOICE SYNTHESIZER prepared by james michmerhuizen director the boston school of electronic music...

Page 2: ...is on voice module two will not be gated until a second key is depressed 3 The PORTAMENTO control normally left fully counterclock wise introduces a lengthening pitch slide between different notes on...

Page 3: ...king the external connection to headphones or ampli fier you may turn the synthesizer on Locate the ASSIGNMENTS switches in the minisequencer section and be sure that they are all down In each voice m...

Page 4: ...scription following applies to the three switch version The first switch on the left selects the source of control voltages and gates for VOICE MODULE ONE In its lowest posi tion voice module one will...

Page 5: ...nt of LAG low frequency filtering applied to the sample hold voltage Turning the lag control to the right produces in other words the same effect on pitches being governed by the sample hold that the...

Page 6: ...he three position switch selects one of three control signals indicated on the panel to be routed through the rotary pot just above the switch If this knob is rotated to the right the selected control...

Page 7: ...ter begins to have some effect on a signal passing through it is called the cutoff frequency of the filter The large single knob labelled RESONANCE determines the filter resonance at its cutoff freque...

Page 8: ...ctly to the output of the NOISE GENERATOR that is part of the sample hold in the minisequencer Noise filtered in various ways is used in the production of wind thunder and motor sounds as well as many...

Page 9: ...e NOTE above In order to simplify the operation of the voice module while learning or whenever it is necessary to hear continuous sound this VCA BYPASS SWITCH can be moved to the on right position Thi...

Page 10: ...nual pulse width controls of each oscillator note that these have no effect on the sawtooth oscillator outputs and finally with the VCF manual controls for frequency resonance and pass mode Do not at...

Page 11: ...by voltage control you are changing the range or area of particular frequencies that are emphasized Try using maximum resonance with a lowpitched sawtooth input open only a little about 10 o clock an...

Page 12: ...s the filter frequency down as it is rotated to the right the ENV 2 signal drives the filter frequency up d as the filter resonance is increased its output level will generally increase Compensate by...

Page 13: ...nd sustain and fairly short decay Now slight changes in the filter frequency control in the range 12 o clock to 3 O clock will produce a wide range of percussive noises In a later section you will lea...

Page 14: ...dinary and conservative results however will come from playing con tinuous legato on the lower voice and a slight nonlegato on the upper voice E TROUBLESHOOTING I Using only the controls we have intro...

Page 15: ...t s how we started you off the VCA BYPASS switch on and the filter open If either of these conditions does not hold then no continuous sound is possible except that with certain envelope settings unde...

Page 16: ...o change the pitch of the oscillator The on off switch for the minisequencer CLOCK has also a lower position labelled step This position is spring loaded and the svitcb will not stay there but every t...

Page 17: ...nspositions will occur with the depression of only a single key if one key is held down while another is depressed to the right of it the sequence will transpose to the higher key only for as long as...

Page 18: ...trol of the s h begin with the two knobs in the s h section rotated maximum counterclockvise and slowly increase the range setting The first voice produces a series of random pitches over a wider and...

Page 19: ...all four to check 4 The beat frequency will always double as you go up by octaves So after you have tuned at 8 go up to 4 and then 2 to check on the tuning of each oscillator read just if necessary If...

Page 20: ...fective range 3 As you increase the filter resonance beyond about the eleven o clock position begin to decrease the audio input levels to the filter until at maximum resonance the audio input level s...

Reviews: