From Oakley Sound Sent Tue, Jan 9th 2018, 10:37
From Oakley Sound Sent Tue, Jan 9th 2018, 10:37
For Kenny :-) In my mind there are two basic string ensemble topologies, which I simply sum up as the Solina and the Roland. The Solina method uses three sound sources all modulated with a common LFO (or LFOs) but with each sound source frequency modulated +/-120 degrees out of phase with the other. It's almost always mono, but I think the later Solinas were designed for stereo output. The three sound sources are typically fed with a simple sawtooth from the keyboard electronics and then each sound source is created with its own BBD and it associating clock driver. Examples; ARP Solina, Korg Polysix ensemble mode, Yamaha SK20 et al. However, I think the best sounding example of this genre is the Logan String Melody II. The Roland method uses four sound sources each one modulated by either one LFO or a combination of two LFOs; one low frequency triangle wave, and another faster sine wave. Roland used four delay lines with a pair for each side of the stereo channel. Examples: VP-330, RS-09, RS-505. Note their two earlier stringers, RS-101 & RS-202, used different systems. The Korg Lambda and PE2000 use a variation on the Solina method, but unlike the Solina and Korg's own Polysix, they use three sets of high frequency VCOs (and the usual organ divide down technology) with each chain modulated with two LFOs with the usual 120 degrees phase shift between them. This works out to be the most complex of all but generates the least amount of unwanted hiss and noise. Unfortunately, the Lambda's VCOs were placed so close to each other on the circuit board they lock together and the rich ensemble effect can only be heard if you use a large amount of detune or introduce vibrato. The later Roland method tends to produce thinner sounding strings but they do seem to sound better, perhaps more realistic, to my ears at least, when playing monophonic lines. Roland did also use a single LFO in one case, the RS-101, which was then sent to a divider chain to produce half, quarter and an eighth frequencies to drive each of the four BBD lines. It has a mono output but sounds closer to the Solina rather than the later Rolands. The ARP Omni falls into its own category I think. This is simply three separate BBD lines each modulated with its own LFO. The actual ensemble circuit board module allows for the dry signal to be mixed in with the effected signal but this has been left unused in all the production versions I have seen. There are also some very effective string machines that use just two BBDs with the Elka Rhapsody surely being the finest example. Then, of course, there is the daddy of them all, the Freeman. It's probably closer to the Korg Lambda with it's three (or two) divide down chains. As to what modulates them I have no idea. But from the pictures online of the insides of the two channel version it seems to suggest that they have no top octave generator (TOG) but individual high frequency VCOs like the PS3100 and other older organs. That should make it sound marvellous. Tony