Recording - December 2015 - 38

B Y PA U L V N U K J R .

When I reviewed the Ingram
Engineering MPA575 back in our March
2015 issue, I noted that with the dozens
upon dozens of available 500 Series modules on the market, there are very few fullfledged channel strips. Presumably this is
due to the limited space of the 500 Series
format both externally and internally. It
takes some serious engineering chops to
cram a genuinely comprehensive feature
set into such a small box.
With that in mind, I was very curious to
try out the new EL-Rx 500 Series channel
strip from Empirical Labs, affectionately
named the DocDerr after company
founder and head designer Dave Derr.
Dave has been rewriting the book on how

change the input from line level to instrument level. The DocDerr originally
debuted about 4 years ago at NAMM as
the Smart Ax, where it was marketed as
a 500 Series channel strip for acousticelectric guitar.
Of course it's not just for acoustic guitar; the DocDerr's instrument preamp
works well for anything with a pickup. I
had great results with a Fender Jazz
Bass, a Fender Telecaster, and a Martin
acoustic-electric guitar. On my Fender
Rhodes 73 electric piano, I loved the
onboard compressor/saturation circuit
(spoiler alert-see below)!
To facilitate using the DocDerr as an
instrument preamp, the company

Empirical Labs EL-Rx DocDerr 500 Series Channel Strip
It's almost scary how much power is packed into this little module
studio processors are supposed to work for
nearly 20 years now; the Distressor® is
considered a desert island dynamics
processor by engineers around the world.
What's in a channel strip?
The term "channel strip" refers to the
functions you would find on a single input
channel of a mixing console. Depending
on the mixer, this may or may not include
a mic or line input, high- and lowpass filters, 3- or 4-band EQ, and maybe even a
compressor. Most modern 19" channel
strips are similar, with the most common
varietals being an input (mic/line) > EQ
> compressor > output, or just the input
stage and a fuller-featured EQ.
To make this happen in the 500 Series
realm, one or more of these sections is
often simplified. You may only get a simple
bass/treble style EQ, or a single-knob compressor; often the module will include a
mic preamp but skip the instrument input.
Despite the 500 Series size limitations,
the DocDerr is impressively full-featured. It
does make a few simplifications/concessions, but it does so with the circuit
designs and elements of many of the
other Empirical boxes. In a way it's a bit
of an Empirical Labs "Best Of" box!
The DocDerr will see you now
First up, the DocDerr does not have a
microphone preamp on board. It does,
however, offer a set of internal jumpers to




includes a locking Neutrik 1/4"-to-XLR
adaptor for the back of your 500 Series
rack enclosure; you plug your instrument
directly into that. You can also use a
patchbay with similar results, or consider
the EL500 enclosure (see the sidebar).
Per its original design intent, the
DocDerr also works with a guitar, bass,
or any instrument amplifier. Another internal jumper changes the output from a
fully differential output to a single-ended
output; the net effect of this is lowering the
output gain by 6 dB to avoid unnecessary
clipping of the amplifier's input.
Filter and EQ
Following the line in/preamp section is
an 18 dB/octave (3rd order) highpass filter
with a selectable corner frequency choice
of 70 Hz or 100 Hz. This is a good place
to note that all band selection on the unit is
digitally controlled and handled by one of
three buttons. As a result, a few functions-
such as engaging and choosing the HPF
settings-require dual button presses.
Reading the manual and looking at the unit
makes it sound confusing, but it's quite intuitive and you get the hang of it quickly.
Speaking of the manual, it is a worthwhile read, even if you are not a manualtype person. It offers handy tips, tricks,
and settings suggestions beyond the usual
"this is how this works".
The main section of the DocDerr is the 3band parametric EQ. This reminds me of a

simplified version of what is found on
Empirical's Lil FrEQ (reviewed April 2009).
Unlike the fully variable Lil FrEQ, though,
here each band makes use of seven preselected frequencies:
~ Low: 80, 125, 160, 200, 300, 400,
500 Hz
~ Mid: 250, 500, 750, 1k, 2k, 3k, 4k
~ High: 3.5k, 5.2k, 6.5k, 8k, 10k, 12k, 15k
The low bands are fixed Q while the
mid band has two selectable Q ranges
(again a multiple button press), and each
band can be boosted or cut by 14 dB.
Dynamics control (and saturation)
You may notice that there are only two
more controls on the DocDerr, labeled In
and Mix. While placed before the EQ section, the In knob actually sends signal into
the compressor's threshold and is a postEQ process. This is, in fact, one of those
single-knob compressors I mentioned
above (attack and release are fixed at
roughly 1 ms and 200 ms), but it draws
heavily on the compression technology of
the Distressor and the Fatso (reviewed
May 2011). In fact, it even includes the
tape-style saturation circuit also found in
the Fatso!
As you push the signal into the compressor, it starts to saturate and tame the
highs like a vintage tape machine might
do. It does not sound exactly like tape,
but it is a beautiful, warm, slightly gritty
effect just the same.



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

Contents
Recording - December 2015 - Intro
Recording - December 2015 - Cover1
Recording - December 2015 - Cover2
Recording - December 2015 - 1
Recording - December 2015 - 2
Recording - December 2015 - 3
Recording - December 2015 - 4
Recording - December 2015 - 5
Recording - December 2015 - Contents
Recording - December 2015 - 7
Recording - December 2015 - 8
Recording - December 2015 - 9
Recording - December 2015 - 10
Recording - December 2015 - 11
Recording - December 2015 - 12
Recording - December 2015 - 13
Recording - December 2015 - 14
Recording - December 2015 - 15
Recording - December 2015 - 16
Recording - December 2015 - 17
Recording - December 2015 - 18
Recording - December 2015 - 19
Recording - December 2015 - 20
Recording - December 2015 - 21
Recording - December 2015 - 22
Recording - December 2015 - 23
Recording - December 2015 - 24
Recording - December 2015 - 25
Recording - December 2015 - 26
Recording - December 2015 - 27
Recording - December 2015 - 28
Recording - December 2015 - 29
Recording - December 2015 - 30
Recording - December 2015 - 31
Recording - December 2015 - 32
Recording - December 2015 - 33
Recording - December 2015 - 34
Recording - December 2015 - 35
Recording - December 2015 - 36
Recording - December 2015 - 37
Recording - December 2015 - 38
Recording - December 2015 - 39
Recording - December 2015 - 40
Recording - December 2015 - 41
Recording - December 2015 - 42
Recording - December 2015 - 43
Recording - December 2015 - 44
Recording - December 2015 - 45
Recording - December 2015 - 46
Recording - December 2015 - 47
Recording - December 2015 - 48
Recording - December 2015 - 49
Recording - December 2015 - 50
Recording - December 2015 - 51
Recording - December 2015 - 52
Recording - December 2015 - 53
Recording - December 2015 - 54
Recording - December 2015 - 55
Recording - December 2015 - 56
Recording - December 2015 - 57
Recording - December 2015 - 58
Recording - December 2015 - 59
Recording - December 2015 - 60
Recording - December 2015 - 61
Recording - December 2015 - 62
Recording - December 2015 - 63
Recording - December 2015 - 64
Recording - December 2015 - 65
Recording - December 2015 - 66
Recording - December 2015 - 67
Recording - December 2015 - 68
Recording - December 2015 - 69
Recording - December 2015 - 70
Recording - December 2015 - 71
Recording - December 2015 - 72
Recording - December 2015 - Cover3
Recording - December 2015 - Cover4
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