#Noise Gates
5 messages in this thread
Rick,
Do most synths (Amiga?) output any noise even when not playing notes?
I'm wondering if it would be worthwhile to have a noise gate between the Amiga
and a mixer; or between my FB01 and mixer. When I have the Amiga hooked up to
my powered speakers, I seem to hear some garbage sometimes.
Thanks, George
/ex
Hi George!
The "absolute" answer is, I suppose, yes, all synthesizers [read audio devices]
generate noise. In practice, if the level is below your particular noise
floor, it might as well be silence. Some synthesizers are remarkably quiet; I
had an old patchable analog synth that never made a peep unless you opened the
VCA. Others tend to generate more hiss and hum and squeal; the DX7 (and,
therefore, its young cousin the FB01) is famous (er, infamous) for being noisy.
The Amiga seems to fall near the noisy end, though some units are apparently
quieter than others.
As to the noise gate being worthwhile, it depends on what you need/want. If
the noise doesn't bother you, if you're just playing for yourself (or in a
band, where the noise would be swamped anyway), there's no sense in spending
the money. If, on the other hand, you are making demo recordings to cassette
or, even worse, doing multi-track recordings, the noise could be a serious
problem.
If you're handy with electronics, building up a multi-channel noise gate can be
fairly straightforward. If you only need one or two channels, it's probably
best to just buy one. On a personal level, I prefer downward expanders and
especially adaptive filters over noise gates… but go with your gut feelings,
George.
Rick
Rick,
Thanks for the reply. I am bouncing some tracks on my 4-track so a
noise gate might be a good purchase. Alesis has a new micro-rack model out for
$125 list (stereo input); one or two of those would be all I'd need. What are
downward expanders & adaptive filters?
George
Rats, I should have known that that was a leading statement. 8)
An expander increases the dynamic range of a signal. A normal amplifier
applies a fixed gain, say *2. An expander is a variable gain amplifier, and
the gain is controlled by the input signal. The larger the input signal, the
larger the gain and vice versa. The upshot of this is that the loud signals
are made louder and the soft signals are made softer.
Now downward expansion is one half of this. From the above, it's obvious that
at some signal level, the amplifier's gain will be one. Downward expansion
works only on the signals below this. In other words, soft signals are made
softer, but loud signals are left untouched. The threshold is set just below
what your normal signal level would be. Net result: any time the input level
goes down, so does the gain, just as if you had run the fader down.
An adaptive filter works on a similar principle, except 1) instead of gain
being controlled, it's the cutoff frequency of a lowpass filter, and 2) instead
of watching the raw signal level, it's the high frequencies. When a cymbal
crash comes through, the filter opens up; when there are no high frequencies,
the filter closes down. Since the ear is most sensitive to high frequency
noise (okay, that's a generalization, don't anybody call me on that one 8),
this effectively improves the S/N ratio.
Rick
Oh, I forgot. On the stereo noise gate, make sure each input has its own
control channel; some units use the sum of both inputs to control both gates.
Good for stereo, but bad for multi-tracking. Same goes for the other units I
mentioned.
Rick