[A6] This whole tuning business

[Dave Scrimenti]

There seems to be a lot of variability from one A6 to the next regarding how
fast and how well they stay in tune. I find my A6 has more tuning problems
than other analogs, and especially other hybrids, which is what the A6
really is. Here's a little article I found on the web about the unclear
distinction between analog and digital.

Analog, Digital, What's in between?

Analog and Digital Synths - What's in Between?

NOTE:

This article is based on an e-mail I posted to Analog Heaven.

I'll continue from here: As discussed before, there are both analog synths
and digital synths trying to emulate analog synths. However, the division
isn't
that simple. A pure analog synth is totally analog, the sound generating
circuitry is analog as well as the modulators (front panel controls and the
envelopes
and LFOs etc...). An example of a pure analog synth is the MiniMoog.

In addition, there are digitally controlled analog synths, they have analog
sound shaping and sound creation circuitry but the circuitry is controlled
digitally. In other words, usually the modulators: front panel controls,
envelopes and LFOs etc... are controlled using a microprocessor. The pitch
of
the oscillators is often digitally controlled to keep the oscillators
stable. These oscillators are usually called digitally controlled
oscillators, DCOs.
Some synths, although controlling the oscillators digitally, convert the
digital representation to analog voltage actually driving voltage controlled
oscillators,
VCOs (Alesis Andromeda). Whether these kind of oscillators are DCOs or not
depends on the definition of a DCO.

It's also worth mentioning that digital control is required if you are going
to store a patch in memory. That's why many later analog synths are actually
digitally controlled analogs, also called hybrids by some people. AS for
sound, digitally controlled analogs sound very close to pure analog synths
because
the sound generation hardware is analog. However, there are some
differences: the pitch of DCOs doesn't drift like that of VCOs and the
parameters e.g.
filter cutoff are discrete and have a certain range and stepsize. An example
of a digitaly controlled analog synth is Waldorf Pulse.

The third category of "analog" synths is so called analog modeling synths,
which use digital technology (physical modeling) to mimic real analog synths
purely in software run on digital microprocessors. There are two types of
analog modeling synths:
1. Synthesizers running on dedicated digital signal processing (DSP)
hardware. These are often called virtual analogs (though, sometimes the term
also refers
to "software synths")
2. Synthesizers running on generic microprocessors (e.g. Intel Pentium).
These are often called software synthesizers, although hardware virtual
analog
synths, too, are running software.

The only differnces between the two categories are the microprocessor (and
other hardware like DACs and memory) used to run the software and the user
interface
which can consist of real hardware gadgets or there virtual counterparts in
software. Personally I use the term virtual analog when refering to analog
modeling synths with dedicated DSP hardware. I use the term softsynth when
refering to any synthesizer software (analog modeling, FM, sample playback
etc...)
which is run on a "normal" computer (with a generic microprocessor). But why
virtual? Because a virtual synth exists purely as an application on the
computers
hard disc (and memory) and has in a way no physical form. Whether the term
virtual synth refers to an analog modeling synth or to a sampler, for
example,
depends on the context.

The sound of an analog modeling synth may or may not be close to the sound
of a real analog synth. There's a profound difference between "analog
synths"
(purely analog synths and digitally controlled analog synths) and analog
modeling synths. The former normally uses analog components for sound
creation
but the latter does the sound creation purely in software. It's hard to do
analog-sounding digital filters, so filters are often the weakest point in
comparison
to real analog synths or hybrids.

By the way, there are two ways of implementing an oscillator in an analog
modeling synth.
1. the oscillator waveforms are generated on the fly. The generation of the
waveforms takes lots CPU power and requires some math calculations but on
the
other hand the waveforms are easy to modulate in various ways. These kind of
oscillators are often called DSP-oscillators because digital signal
processing
is used to generate the waveforms. An example of a virtual analog with DSP
oscillators is the Roland JP-8000 (and JP-8080).
2. "pre-rendered" samples are used as oscillator waveforms. Sometimes these
pre-rendered oscillator waveforms are called wavetables. I think some hybrid
synths in the 80s used these kind of oscillators and that's why they are
sometimes refered as being DCOs. There are really many ways to impement a
DCO
(for example: it depends on the inplementation whether you need a digital to
analog convertter before the DCO signal goes to an analog filter) and that's
why you shouldn't generalize too much when talking about DCOs.

If we define an analog modeling synth loosely to be a digital synthesizer
trying to imitate an analog synthesizer, it's really hard to say what's an
analog
modeling synth and what's not.

Would you consider the JV-1080 with the vintage synth card to be a virtual
analog synth?

I would, at least theoretically speaking. The JV has many qualities
associated with analog modeling synths. For a start, it has resonant
multimode filters,
ADSR-envelopes (?) and LFOs, portamento, pitch-drifting emulation (analog
feel) and samples from analog synths (remember that the oscillator of a
virtual
analog synth doesn't have to generate the waveforms on the fly). However,
the JV lacks oscillator sync and pulse width modulation, two features common
in analog synthesizers. But then again, not all analog synths hav these
features, the TB-303 has neither of them but is still an analog synth, isn't
it.

OK, we have two extremes here: a purely analog synth and a purely digital,
analog modeling synth. I would define a hybrid synth to be anything between
the
two. There are a number of interesting hybrid synths, let's consider the new
Waldorf Q+. As far as I know, It's otherwise a purely digital synth with DSP
oscillators apart from analog filters. It has real analog filters, that is
it has analog sound generation or shaping circuitry, so it's a hybrid synth.


If you have any questions, comments or suggestions,
drop me a line here
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----- Original Message ----- 
From: "Kim Johnsson" <kim.johnsson at ineo.fi>
To: <a6 at code404.com>
Sent: Tuesday, May 11, 2004 1:42 AM
Subject: [A6] This whole tuning business


> Hi there!
>
> (a few more hours to go before I get mine)
>
> I was wondering...my Waldorf Pulse is synced to digital oscillators in
> order to keep in tune, and it needs to be neither tuned nor warm to
> actually be in tune. So as it's obviously possible to make in-tune
> analog oscillators, why isn't the Andromeda made that way? Is it simply
> because it removes some of the "analog charm", or are there other
> reasons I can't think of?
>
> Cheers,
>
> Kim
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