Recording - December 2015 - 58

By Michael Lauter

So you've acquired, or dusted off, a vintage keyboard or
drum machine, and you'd like to connect it with your DAW to
record alongside virtual instruments... but things don't seem to
sync up well, if at all. It's not always easy to bridge the gap
between modern software and vintage or "nouveau analog"
gear; maybe you've seen terms like "latency" and "clock jitter" but you don't know what they mean.
Sync can be scary, but it's important to understand-proper
sync can make the different between a sloppy beat and a tight
groove, a flop or a hit. So let's get started.
Connections and goals
First, assess what connections your hardware has (especially inputs if your DAW will be the tempo master). These may
include USB, MIDI, DIN Sync, CV/Gate/Trigger,
Timebase/Sync/Clock/Ext Clock, Arp Clock, or Tape/FSK.
There are three typical goals you might have when connecting
your vintage gear to the computer: you'll want to sync a drum
machine to the DAW's timeline, control synth notes or trigger percussion sounds from the DAW, or sync a hardware arpeggiator
to the DAW. Which signals are needed for each task?
Synching a drum machine or sequencer requires some form
of timebase (clock) and possibly transport signal. (Some vintage gear, like the Roland TR-606 or MC-202, requires both.)
If you want to play vintage synths from your DAW, you will
need some way to send CV (control voltages) and gate or trigger signals, and if you want a keyboard's arpeggiator to sync
with your DAW, you may need either a timebase or a trigger
signal, or a specialized "arp clock".
Timebase vs. Triggers
Although different devices may call it different names,
almost every piece of gear you want to sync has a timebase:
a clock signal that's related to the tempo of the song. We usually express this in pulses per quarter note (PPQN or just PPQ).
Think of it as the ticking of a clock, but one that follows the
song tempo rather than actual time.




Many machines have differing internal and external timebases,
one for the minimum "distance" between events (resolution) inside
the box, and one for the resolution of timing with respect to externally connected devices. See Figures 1 and 2, which we'll talk
about in detail below.
The most common internal timebase is 96 PPQN, the resolution
of Ableton Live, the DSI Tempest drum machine, LinnDrum, and
Roland MC-202, among many others. The most common external
timebase in 24 PPQN-the resolution of MIDI Clock messages
and Roland DIN Sync. Figure 2 shows how smaller PPQN values
are more like note lengths (suitable for arpeggiator steps) and
higher ones provide high-resolution timing for use inside DAWs
and sequencers.
On the other hand, triggers are used to communicate the occurrence of singular musical events, so they don't have to have regular timing. One trigger pulse is for one event only, sent when a
note is played. The polarity and length (usually 2 to 10 ms) of trigger pulses varies by manufacturer and era. Some vintage gear
uses gates rather than, or in addition to, triggers. A gate signal
turns on when the note starts and stays on until the note stops. You
may also see inputs labeled CV; that's for control voltage, which
determines the pitch of notes played on older analog keyboards,
but isn't directly relevant to sync.
Understanding transport and location
If all you have is timebase (clock) signals, it's still possible to
start, stop and sync vintage drum machines. For example, the
classic LinnDrum can synchronize to an external 48 PPQN timebase clock. When a machine uses timebase alone for sync, it
starts from the beginning when it sees the timebase signal and
stops when the signal goes away. That's all the control you have.
It is preferable to have a separate signal for transport control.
Roland's and Korg's DIN Sync scheme includes separate timebase and transport signals contained within a 5-pin (non-MIDI)
DIN cable. DIN Sync can allow for not only Start and Stop, but
also Continue (from last stopping location). MIDI also has separate timebase, transport, and cueing (location) mechanisms.

Table of Contents for the Digital Edition of Recording - December 2015