Osc 3 as a LFO
Posted: Fri Mar 31, 2006 4:17 am
It seems like the Voyager's implementation of Osc 3 as a LFO is a little more complicated than the same implementation on the Minimoog Model D. The Minimoog Model D offers a single band of LFO frequencies while the Voyager offers 6 bands of LFO frequencies.
If you want to use Osc 3 as a LFO on the Minimoog Model D, you would:
1) Flip the "Osc 3 Control" rocker switch to "off". (Not only does this disable keyboard tracking, it also expands the range of Osc 3's "Frequency" pot from "1 octave" to "6 octaves".)
2) Set the "Osc 3 "Range (or Octave)" selector switch to "Lo". (Setting the "Range (or Octave)" switch to "Lo" specifies a single range of low frequencies that Osc 3's "Frequency" pot can select from.)
3) Tune in the desired frequency using Osc 3's "Frequency" pot.
On the otherhand, if you wish to use Osc 3 as a LFO on the Voyager:
1) Flip the "3 KB Cont" rocker switch to off. (Disables keyboard tracking of Osc 3 and expands the range of Osc 3's "Frequency" pot.)
2) Set the "3 Freq" rocker switch to "Lo" (Configures Osc 3 as an LFO as opposed to an audio oscillator)
3) Select one of 6 low frequency bands using the "Octave (Range)" selector switch (32', 16', 8', 4', 2', 1')
4) Tune in the desired frequency using Osc 3's "Frequency" pot.
Does anybody know if there is a technical spec that specifies the low frequency range for each of the 6 low frequency bands (32', 16', 8', 4', 2', 1'). If not, perhaps somebody has measured the frequency range of each band using a frequency counter.
I have made some rough estimates of various values within each of the 6 ranges by making audible comparisons with the existing LFO. Although I don't claim that they are very accurate, I'll post some of these values (below) in order to facilitate discussion on this matter. Hopfefully, somebody will post factory specifications or actual measurements for the entire range of each band.
32': 0.2 Hz (-4.5*); 0.8 Hz (0); 3 Hz (+7)
16': 0.4 Hz (-6); 1.3 Hz (0); 3 Hz (+4); 5.5 Hz (+7)
8': 0.6 Hz (-7); 3 Hz (+1); 10 Hz (+7)
4': 1.2 Hz (-7); 3 Hz (-1); 12 Hz (+4.5)
2': 2.25 Hz (-7); 6 Hz (-1); 12 Hz (+2)
1': 3.5 Hz (-7); 12 Hz (-1); 25 Hz (+1)
*Note that the value in parenthesis is the dial position for Osc 3's frequency pot using the scale written on the front panel of the Voyager.
The advantage of having 6 frequency bands as opposed to a single frequency band is it increases the resolution of the Osc 3 Freq pot for the entire low frequency range. However, one observation that is readily apparent from the estimates above is that there is considerable (if not excessive) overlap between adjacent bands. For example, when comparing the 16' and 32' ranges, the 16' range only expands the maximum frequency range from 3 Hz to 5.5 Hz. This corresponds to about 20% of the frequency pot's range: dial positions +4 through +7 for the 16' range.
If you want to use Osc 3 as a LFO on the Minimoog Model D, you would:
1) Flip the "Osc 3 Control" rocker switch to "off". (Not only does this disable keyboard tracking, it also expands the range of Osc 3's "Frequency" pot from "1 octave" to "6 octaves".)
2) Set the "Osc 3 "Range (or Octave)" selector switch to "Lo". (Setting the "Range (or Octave)" switch to "Lo" specifies a single range of low frequencies that Osc 3's "Frequency" pot can select from.)
3) Tune in the desired frequency using Osc 3's "Frequency" pot.
On the otherhand, if you wish to use Osc 3 as a LFO on the Voyager:
1) Flip the "3 KB Cont" rocker switch to off. (Disables keyboard tracking of Osc 3 and expands the range of Osc 3's "Frequency" pot.)
2) Set the "3 Freq" rocker switch to "Lo" (Configures Osc 3 as an LFO as opposed to an audio oscillator)
3) Select one of 6 low frequency bands using the "Octave (Range)" selector switch (32', 16', 8', 4', 2', 1')
4) Tune in the desired frequency using Osc 3's "Frequency" pot.
Does anybody know if there is a technical spec that specifies the low frequency range for each of the 6 low frequency bands (32', 16', 8', 4', 2', 1'). If not, perhaps somebody has measured the frequency range of each band using a frequency counter.
I have made some rough estimates of various values within each of the 6 ranges by making audible comparisons with the existing LFO. Although I don't claim that they are very accurate, I'll post some of these values (below) in order to facilitate discussion on this matter. Hopfefully, somebody will post factory specifications or actual measurements for the entire range of each band.
32': 0.2 Hz (-4.5*); 0.8 Hz (0); 3 Hz (+7)
16': 0.4 Hz (-6); 1.3 Hz (0); 3 Hz (+4); 5.5 Hz (+7)
8': 0.6 Hz (-7); 3 Hz (+1); 10 Hz (+7)
4': 1.2 Hz (-7); 3 Hz (-1); 12 Hz (+4.5)
2': 2.25 Hz (-7); 6 Hz (-1); 12 Hz (+2)
1': 3.5 Hz (-7); 12 Hz (-1); 25 Hz (+1)
*Note that the value in parenthesis is the dial position for Osc 3's frequency pot using the scale written on the front panel of the Voyager.
The advantage of having 6 frequency bands as opposed to a single frequency band is it increases the resolution of the Osc 3 Freq pot for the entire low frequency range. However, one observation that is readily apparent from the estimates above is that there is considerable (if not excessive) overlap between adjacent bands. For example, when comparing the 16' and 32' ranges, the 16' range only expands the maximum frequency range from 3 Hz to 5.5 Hz. This corresponds to about 20% of the frequency pot's range: dial positions +4 through +7 for the 16' range.