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Sub 37 Has A Digital Modulation Buss
MUFF WIGGLER Forum Index -> General Gear  
Author Sub 37 Has A Digital Modulation Buss
Uvula_Fluorentine
They never make any claims here. The audio path is fully analogue, but those are DCO's, not VCO's.

This is a statement to promote discussion about such things.
Yes Powder
Quote:
digital modulation buss

Yeah, so what?
sduck
Ok.
Uvula_Fluorentine
It just gets messy. Set the filter to 12 dB and full oscillation, then try to tune to a specific note. With 1:1 keyboard tracking the filter will track within an octave or so.

Here's the problem: Once you get near the note, small adjustments become "stepy" and tuning becomes difficult.

My point would be that small annoying problems like this would not crop up in the fully analogue world. Of course, achieving the great versatility of this instrument would become far more complicated.

I would encourage you to try tuning that filter, though.
chvad
sduck wrote:
Ok.
thumbs up
Franktree
Having a digital modulation bus isn't the same as having DCOs, is it? It has VCOs and a digital modulation bus. As in, the oscillators are controlled by voltage, they're not digital controlled.
ObsoleteModular
A digital modulation bus doesn’t imply DCOs. Digital electronics have been used in synthesisers pretty much from the outset to do stuff that’s too complicated or expensive otherwise. Where it creates controversy is when it’s directly involved in the audio path such as oscillators, LFOs, envelopes and filters.

VCOs and DCOs both create a waveform but differ in how the time period of that waveform is generated. Broadly speaking, a transistor grounding a charging capacitor at a given threshold versus a subdivision of a high frequency crystal.

Historically the latter is far more consistent than the former resulting in more stable tuning. Developments in VCOs over the years have narrowed that gap to the point where instability or slop is added back in, often digitally - oh the irony!
toxoplasma_gondii
Part of the problem is the ambiguity inherent in the term DCO. A VCO consists of an oscillator core (usually sawtooth, generated by charging and discharging a capacitor in a comparator circuit), which is then fed into a waveshaper to produce additional waveforms. As far as I know, the Sub 37 contains what could be described as digitally-controlled VCOs, in which the oscillator control voltage (this determines the frequency of the capacitor discharge) is generated by a DAC. In contrast, a standard DCO, such as is found in the Roland Junos, uses a master clock of very high frequency, which is then fed into a digital counter that functions as a frequency divider (to produce the desired pitch), and the resulting pulse is fed into waveshaper.

Ultimately, however, it is rather a moot point if the end result is the same: ultra-stable, lifeless oscillators. I used to own a Sub 37, but always felt there was something lacking in the core tone.
latigid on
Some people spell buss with one 's'. Personally, I prefer to use two esses (if I remember) as it's more closely associated with the idea of a signal running along a distribution line, able to be tapped at multiple points.

Buß
franktropez
Plus it prevents confusion with the vehicle/mode of transportation.
anselmi
it´s full digital, Amos confirmed it to me in a message years ago when I asked him about aliasing when trying to modulate stuff at audio rates...ir´s digital even at the CV input levels...everything is converted twice (A/D, then D/A) before reach the analog voice board

he said that they decided this because this way you have a full modulation matrix where any modulation can reach any destination

while this is OK for slow modulations, it´s not so go for audio-rate ones...personally I´d prefer to go with less destinations and have a full analog modulation path...this is the only thing I always dislike of this synth...well, this and the menu system that is kinda messy
ObsoleteModular
anselmi wrote:
it´s full digital, Amos confirmed it to me in a message years ago when I asked him about aliasing when traying to modulate stuff at audio rates...ir´s digital even at the CV input levels...everything is converted twice /A/, then D/A) before reach the analog voice board


The input control voltage may be derived from a digital soure (ie a dac) but that doesn't make the oscillator a DCO. The osc is still voltage controlled. That is to say, the oscillation is derived from a capacitor/comparator topology not a high frequency clock. As toxoplasma put it, it's a digitally controlled VCO.
GuyaGuy
ObsoleteModular wrote:
anselmi wrote:
it´s full digital, Amos confirmed it to me in a message years ago when I asked him about aliasing when traying to modulate stuff at audio rates...ir´s digital even at the CV input levels...everything is converted twice /A/, then D/A) before reach the analog voice board


The input control voltage may be derived from a digital soure (ie a dac) but that doesn't make the oscillator a DCO. The osc is still voltage controlled. That is to say, the oscillation is derived from a capacitor/comparator topology not a high frequency clock. As toxoplasma put it, it's a digitally controlled VCO.

I don’t believe anselmi is saying that it’s A DCO—just that the CV input and analog mod sources are converted A>D>A, which would mean that the conversion is the same whether routing to the VCO, VCF, or anything else. It’s not been a problem for me on the Subsequent but I don’t use it a lot for FM.
jzwoopwoop
Nothing much to add on the topic of Sub37, but this is a fantastic video about DCOs

http://www.youtube.com/watch?v=mqY6cVJS9fo
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