User manual

40
resolution July/August 2014
KNOW HOW
State the case for a ‘standard’ for the 500
series rack.
Another discovery was that there was no
clear standard. We spent months researching
older designs and could not find any clear
documentation that set a clear standard for size,
power, or pin configurations. We even found API
modules that did not fit inside their own racks.
You have to keep in mind that API has gone
through different ownerships since the 1970s
and old designs have been kept for legacy sake.
We contacted API for clarity and they suggested
that we send them our modules for testing to see
if they fit and would not cause problems. This is
the basis for their VPR alliance.
Anyone who has been in our business for any
length of time knows that the audio industry is
extremely slow at developing clear standards. We
have been in the digital world for over 30 years
and still today one digital console cannot always
speak to others. We felt the best solution would
be to suggest a free standard and we posted this
on our website. It includes mechanical designs,
electrical requirements and everything you need
to build a module.
Once the Whos-Doc specification was posted, we then
contacted the AES to let them know that we would be pleased
to support a new standard that all manufacturers could adopt.
A couple of the people from the standards committee have
contacted us and we are now waiting to hear of further
developments. Whether the AES adopts a higher or lower voltage
standard, we are prepared to support it as we believe this to be
the healthiest way forward. We believe that the end user should
be able to buy any brand of module, plug it into a rack and it
should work. If every manufacturer goes about optimising the
power racks for their own modules, the industry will never be
unified.
One of the most frustrating aspects of the ‘non-standard’ is
the way modules must be fit into place. Aligning the 15-pin
card edge connector is painful and can lead to electrical problems
if not inserted properly. To address the problem, we started by
adding a simple slide-in tray that aligns the card edge vertically.
Most recently, we tooled up the trays with special nylon inserts
that align the modules horizontally so that they slide into place
without fiddling around. This makes it easy to quickly plug
in modules and change the recording setup on the fly. Any
manufacturer who adopts the Whos-Doc standard will find that
their modules fit easily, which in turn will reduce service problems.
What are the realistic power requirements of a 500 series rack
and what are they able to power?
The issue with powering is two-fold. On the one hand is the in-rush current
and on the other the actual powering of the modules. We have found some
companies whose products require excessive in-rush current to bring them
up. The workaround is sequencing the modules by plugging them in, one at
a time. A good electronic engineer can design a preamp, EQ or compressor
with less than 100 milliamps of current. With some attention, the in-rush
current can be reduced so that it does not exceed the power of the supply as the
capacitors charge.
How real are concerns that
certain racks do not generate
enough juice for power hungry
modules like valve modules?
When tubes are employed, the power
requirements increase to where 200
to 300 milliamps are required. One
merely checks the power supply for
available current and then adds up
the requirements to ensure you do not
exceed the available current.
We came up with a clever
workaround for the PowerTube
module that pulls current in form
alternating sides of the power supply
to reduce the demands when using several of
these tube preamps together in a rack.
Set out a power consumption and
distribution model for a rack full of
typical modules.
Say you have a Radial PowerHouse 10-slot
rack with 1600 milliamps of current, this
gives you an average of 160 milliamps
per slot. If you have four tube preamps
that require 250 milliamps each, two EQs
that need 100 milliamps and a couple of
compressor that need 150 milliamps, you
add them up and you get 1500 milliamps of
required current — this leaves you with 100
milliamps of headroom. If you plug in six
tube preamps — at 250 milliamps each and
an EQ that needs 100 milliamps — you will
be at the threshold of 1600 milliamps which
means you may not enjoy the maximum
performance. It is probably a good idea to
leave some slots empty if you can so that you
have extra headroom.
How real are people’s concerns about the
power issues?
I suppose most racks will do a
reasonable job when it comes to
powering. We have been told by several
major manufacturers that the Radial
racks are the ones that are truly made
correctly. The real issue in our mind is
safety. When a console manufacturer
is creating a channel strip it is in full
control of all of the signals going in and
out. In the 500 world, you are guessing
and hoping that each of the modules are
properly constructed and safe. This is why
we go the extra mile by incorporating
electronic fuses in each channel. Should
a fault occur, the rack will power down
until the fault is removed and then
simply comes back to life.
What other limitations and
concerns are there about 500 Series
racks and modules?
The standard in itself is limiting. It is
designed around an analogue mono format,
so you cannot easily integrate stereo into a single
wide module. Also, because the standard originated
in the 1970s digital was never part of the design. So
developing a digital strategy is somewhat limiting.
In our view, the best way around this is to incorporate some
sort of digital I-O in the master section. This has recently been introduced by
Aphex in its new rack and we are looking at other methods of implementing
something similar. This would enable the user to go from a laptop computer to
the 500 series power rack and back in order to take advantage of the character
and creative approach that analogue brings to recording. n
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