Sub 37 Has A Digital Modulation Buss

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Uvula_Fluorentine
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Sub 37 Has A Digital Modulation Buss

Post by Uvula_Fluorentine » Mon Jan 28, 2019 7:31 pm

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.

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Yes Powder
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Post by Yes Powder » Mon Jan 28, 2019 9:03 pm

digital modulation buss
Yeah, so what?

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sduck
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Post by sduck » Mon Jan 28, 2019 9:48 pm

Ok.
flickr cloud of sound touyube NOT A MODERATOR ANYMORE

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Uvula_Fluorentine
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Post by Uvula_Fluorentine » Mon Jan 28, 2019 11:31 pm

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.

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Post by chvad » Mon Jan 28, 2019 11:33 pm

sduck wrote:Ok.
:tu:

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Franktree
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Post by Franktree » Tue Jan 29, 2019 12:19 am

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.

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Post by ObsoleteModular » Tue Jan 29, 2019 3:04 am

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!

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Post by toxoplasma_gondii » Tue Jan 29, 2019 4:12 am

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.

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Post by latigid on » Tue Jan 29, 2019 4:49 am

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

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Post by franktropez » Tue Jan 29, 2019 9:50 am

Plus it prevents confusion with the vehicle/mode of transportation.

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Post by anselmi » Tue Jan 29, 2019 10:09 am

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
Last edited by anselmi on Tue Jan 29, 2019 4:05 pm, edited 1 time in total.

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Post by ObsoleteModular » Tue Jan 29, 2019 11:10 am

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.

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Post by GuyaGuy » Tue Jan 29, 2019 2:20 pm

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.

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Post by jzwoopwoop » Tue Jan 29, 2019 4:32 pm

Nothing much to add on the topic of Sub37, but this is a fantastic video about DCOs


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