David Kronemyer

AC Power to the Electronic Music Studio

January 18th, 2010 by David Kronemyer · 1 Comment

DAVID KRONEMYER: It’s astonishing how many synth studios ignore the requisites of proper AC power.  Power behind the racks typically is an afterthought.  It ends up as a confused jumble of cables.  This not only is conceptually offensive, but also results in marked degradation of audio sound quality.

Here is the solution we have implemented (see picture).  We have six separate 20-amp AC lines coming into the studio from the main power service.  First they go to Tripplite power conditioner-line stabilizers.  These maintain the incoming voltage at a steady 120 V and also filter out noise, spikes and other undesirable artifacts.  Then they go through a metering panel, which shows amperes – volts – watts.  This gives a ready indication of each circuit’s capacity and status.  Then they go to balancing transformers manufactured by Equi=Tech.  Usually AC line voltage is 0 V on one leg and 120 V on the other.  What balanced power does is change this to 60 V on both legs.  This promotes common-mode rejection (analogous to balanced audio cabling) and lowers the noise floor by at least 10dB.  It also eliminates ground loops (audible as 60 Hz hum) and complex star-grounding schemes.  We can turn our main mixing system all the way up without audible hiss or noise.  Oversized cabling is used throughout to reduce impedance and promote headroom.  We also have uninterruptible power supplies for computers (not depicted).

Here are a few other observations:

1.  Most studios have at least three separate cabling systems (AC, audio, MIDI).  Power cabling should be physically separated from audio and MIDI.  If they run parallel, there should be space between them; if they cross, they should do so at right angles.  These same principles apply to digital cabling, computer cabling and time-code cabling.

2.  Power to anything but sound-producing keyboards or modules must be on a completely separate AC circuit.  Lighting and computers, for example, always should be on their own lines (as seen in the picture, four circuits are devoted to audio and two circuits to non-audio).  It is difficult to over-emphasize the importance of this step.  Back in the days of 24-track analog tape recorders, we even went so far as to rewire them, segregating power to the electronics from power to the motors.  This considerably improved the sound of the electronics, because they did not have to deal with motor factors such as torque and slew.  It also improved the performance of the motors, because now they could have a consistent power source without also worrying about powering electronic components.

3.  Multiple wall-warts of the same power type (e.g. 12 VAC) easily can be replaced with a single, larger AC transformer.  This provides consistent power to all of them and results in significantly improved sound quality.  Many modules are 9 or 12 VDC.  We have two large transformers (made by Acopian) to make these conversions, then distribute the power along separate lines, to the same effect.

In conclusion, studios typically spend thousands of dollars on gear while at the same time ignoring basic principles of how to make it sound good.  This doesn’t make a lot of sense because the way things sound is constrained by the least-satisfactory variable.  It’s important to optimize every step of the process in order to achieve a desirable outcome.

Studio power supply medium rez