FMR ARC V1.00 Users Manual

FMR Audio A.R.C.

Owner’s Manual

V1.00

T ABLE OF CONTENTS

Acknowledgement

**CAUTION!** . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

Functional Description

A.R.C. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

A Brief History . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

What’s cool about the A.R.C.?. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

What sucks about the A.R.C.?. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

Hooking Up the A.R.C.

Connections. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

Operating The Controls

Control & Indicator Descriptions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

Initial Settings. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

Taking Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

Application Configurations

The A.R.C. as a “boost” pedal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

The A.R.C. as a direct box. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

The A.R.C. as a compressor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

The A.R.C. as a studio effect. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

Closing Thoughts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

Control Descriptions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

Appendix A—Understanding and Using the A.R.C.’s Power Out Feature

Purpose of this Document . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .A-1

Who Should Read This . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .A-1

The Scope of this Document . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .A-1

Power Circuit Details. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .A-1

Operational Precautions

Voltage Polarity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .A-2

Voltage Range. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .A-2

Total Current Draw. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .A-2

Ground Loops . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .A-3

Daisychain Checklist

Preflight . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .A-3

Ground Loop Reduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .A-4

Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .A-4

A CKNOWLEDGEMENT

If you’re anything like me (just smarter and better looking...but I digress), when I get a new piece of audio
gear I get excited and anxious to star t playing with it to see what it can do for the s ound. I hope that you too
are excited and anxious to plug in your new FMR Audio A.R.C.! Before you jump in, however, I’d like to
take a short moment to say something important: I know that you can choose to spend your money on any
of a myriad of other available products. Whether by chance or coercion, you’ve chosen ours. For this, I’m
grateful and would like to express a sincere...

THANK YOU!

I appreciate you putting your trust and hard-earned cash into one of FMR Audio’s products (or at least
giving us a shot by demoing them)! Even though all of us here at FMR Audio are very proud of our prod­ucts, the point of what we do is to give you the opportunity to make music without excessively draining
your bank account or making you feel that you mu st make excuses for the sonic results! I hope that the
A.R.C. helps you realize, at least in some small way, your artistic vision...

Mark A. McQuilken
Designer & Co-owner

**CAUTION!**

The FMR Audio A.R.C. has the ability to daisychain its power connection. Using this
feature correctly and effectively requires specific technical knowledge and should
not be attempted by the casual user without the advice and direction of properly
skilled personnel! Without the proper knowledge and appropriate action, it’s possible to

damage or destroy other devices, property and/or cause minor personal injury. For
example, without the proper knowledge and appropriate action, it’s possible to:

• Damage or destroy the A.R.C. and other equipment such as power
supplies, pedals, amplifiers and speakers!

• Cause loud, ear-damaging noise!

• Blow mains breakers or fuses!

If you are unsure about or do not understand the fundamentals of electronics and
power distribution, DO NOT ATTEMPT TO POWER OTHER DEVICES VIA THE
A.R.C.

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I NTRODUCTION

This is the FMR Audio A.R.C. QuickStart Guide. The purpose of this document is to:

• Describe the overall features of the FMR Audio A.R.C.

• Describe the basic connection of the A.R.C. to your system.

• Describe the top/rear panel controls and connections.

• Present the A.R.C. specifications.

F UNCTIONAL DESCRIPTION

A.R.C. Overview

The FMR Audio A.R.C.—an acronym for “Articulation, Resonance and Clarity”—is named for its per­ceived effects on the sound of many instruments. The A.R.C. allows you to easily alter how more transient
notes “stand out” against sustained ones (articulation, resonance), while increasing the overall perceived
clarity of the sound. The A.R.C. offers sonic performance, along with a unique combination of other fea­tures, that you will find equally useful in the studio or on the stage. Specifically, the FMR Audio A.R.C.
provides:

1) A boost function that buffers and amplifies instrument signals to a higher level.

2) A compressor that enhances your instrument’s tone and dynamics.

3) A direct box to interface your instrument to live or recording studio equipment.

4) A studio effect that may be used to process audio tracks from your favorite Digital
Audio Workstation (DAW) or recorder.

It does all this with a minimum set of controls and a look that entices you to plug it in and turn the knobs!

A Brief History

The FMR Audio A.R.C. is based upon our very yellow and nicely tonal PBC-6A. With the ‘6A, I found that I
could make guitar tracks‚ especially acoustic guitar tracks‚ sound sweeter‚ fuller‚ and punchier with the
right combination of PBC-6A control settings. A friend pointed out that his guitar ’s sustain was being
enhanced in a “totally natural way”—like the guitar amp was just resonating a little more—without the
suck-and-swell characteristics we experienced with stompbox sustainers or compressors. Although I sus­pect that our ‘6A customers are using it on guitar tracks of all kinds (among other things), the ‘6A is a stu­dio effect with a physical footprint that would be awkward for the performing musician outside of the
studio. In addition, the nine adjustable parameters on the ‘6A just might be overkill in a stompbox applica­tion. What to do, what to do...

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We spent many hours head-scratchin’ and prototypin’ to find the right f ea tures. We wore out our fingers and
face muscles pickin’ and grinnin’ to achieve just the right sound. After many long months (and apostro-

phes), the result is the FMR Audio A.R.C....and this manual. With only three controls (plus bypass), it pro-

vides PBC-6A tonality in a more convenient, easy-to-use format, with features more appropriate to
support both live and studio instrumentalists.

What’s cool about the A.R.C.?

This is the part of the manual where I trade-in my design hat for my recordist’s hat by telling you what I
think are the cool aspects of our products...in this case, the A.R.C.:

• 4-in-1 Useful Effects — The A.R.C. provides a really nice sounding, high-

impedance (1M ...to avoid tone suckage) BOOST pedal followed by a special,
tone-extracting and tone-enhancing COMPRESSOR. Pro-level power permits
both the A.R.C.’s usage as a DIRECT BOX for impedance-matching as well as the
ability to drive the relatively low-impedance inputs of recording/live mixing
boards. The pro-level power also allows the pedal to be used as wide dynamic
range STUDIO EFFECT.

• Subtle & Sweet Compression — For many players, pedal-based compressors

are too over-the-top because they exhibit a suck-and-swell type compression. This
works well for some special effects, but d iscourages one of the major us es of com­pressors/dynamic processors: to help balance the tone, pres ence and performance
of an instrument, particularly when it must compete or blend with other sounds.
The A.R.C. works well with electrified acoustic instruments in a live setting—
where the subtleties of the instr uments tend to get lost—by allowing the player to
electronically balance articulation, resonance and clarity of the instrument. If you
love the sound of your instrument in an intimate, solo setting, then you’ll appreci­ate how the A.R.C. helps you achieve that experience in both live and studio per­formance settings!

• Fidelity — Although the A.R.C. is an effect, the audio electronics are designed so

that the statically measured output signal very closely resembles the input sig­nal—a paraphrased definition of fidelity. Each A.R.C. is hand-trimmed for mini­mum distortion, typically to less than 0.005% Total Harmonic Distortion plus
Noise (THD+N).

• Dynamic Range — The A.R.C.’s 110dB dynamic range exceeds the dynamic

range of many recording studio devices, not to mention the smaller dynamic
ranges of the myriad of available stompbox effects. The additional dynamic range
of the A.R.C. means more of your instrument can be heard with less noise and
clipping.

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• Studio Effect Power — Many guitar effects operate with a limited dynamic

range determined by the use of a plain 9V power supply. Such a low voltage lim­its the technological choices for the analog electronics, forcing reliance on noisy
and distorted out-of-date devices. The A.R.C. uses the incoming 9V to create a

30V internal supply ( )! This permits the use of state-of-the-art devices to
achieve low-noise, wide dynamic range performance.

• Many Power Supply Choices — We specify the A.R.C. to work with the indus-

try-standard BOSS PS-120 type power supply. This center-negative, 2.1mm barrel
connector, DC power supply is used by many effect pedals and is quite easily
found on-line or in local guitar shops. The A.R.C., however, goes one better: it will
run from voltages ranging from 9 to 12V, either AC, or DC of either polarity!

• All Analog Signal Path — From the input to output connectors, your instru-

ment’s sound is not converted to digital and back to analog. It comes into the
A.R.C. as analog and stays analog all the way to the output jack! The result is a
richer, higher-fidelity effect. The A.R.C.’s main signal path is all analog and is
only assisted by digital/software processes in the power supply and sidechain
circuits.

• Hard-wired Bypass with a Twist — Many effects pedal users insist that their

pedals have a hard-wired bypass (i.e., “true bypass”). The A.R.C. provides this as
well, but with a twist: in the rare case of a pedal or power supply malfunction, the
A.R.C. will default to a BYPASS condition no matter what the position of the
bypass switch! The idea is to keep things rockin‚ even und er the r are case of a fail ­ure.

• Daisy-chained Power Jacks — To help keep things neat, there are two power

jacks on the A.R.C. that allow power to be fed into the A.R.C., out of the A.R.C.,
and into another effect (see “Control Descriptions” starting on page 11).

• Minimum Controls, Maximum Effect — There are only three controls on the

A.R.C.: preamp gain (INPUT), amplifier output level (AMP), and the drive con­trol (DRIVE). Yet, by using combinations of the INPUT and the DRIVE controls,
you can achieve many unique tones. The AMP control allows you to reduce the
differences between the processed and the unprocessed levels.

• Cool Blue Light-Emitting Diode (LED) — This blindingly-blue light displays the

amount of processing being done to the audio. The brighter the glow, the more
processing. But, does it really matter? It just looks sooooo cool...

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• Perdy Knobs — We designed the knobs to be locally built here in central Texas.

They’re custom-designed. They’re custom-built. They’re solid anodized alumi­num and will last a couple of lifetimes.

• THAT2181 VCAs — These are the same VCAs used in scores of professional

audio compressors, gates and other dynamic processors. We can use these with­out compromise, in part, because of the higher-than-normal power supply rails
(see “Studio Effect Power”, page 3).

• Steel Cabinet — There are a lot of really good effects pedals out there that are

housed in the “standard” Hammond Manufacturing cast aluminum enclosure.
We considered that type of cabinet as well, but decided that the A.R.C. was a little
too different to package it the same ol’ way. Instead, we designed a custom, two­piece cold-rolled-steel enclosure with a sloping front and room for the instrumen­talist with prehensile feet. It’s electroplated and covered in a hard polyurethane­based paint to last a good long time.

• Made in Austin, Texas U.S.A. — We want you to know that we do our own man-

ufacturing here in beautiful Austin, Texas ‘cause: (a) We live here. We’re control
freaks. We need things done to standards that are very specific and loftier than
most. Manufacturing products here helps us to control important costs and
reduce waste. All this helps ensure that your A.R.C. will retain its value and con­tinue working for many years to come, (b) Austin’s resources and culture—from a
very lively music scene to lots of high-tech companies/products—help inspire
and maintain our commitment to music and technology, and, (c) In order to help
others, here and abroad, we believe we’ve got to be vital and capable ourselves.
Our first choice is to employ as many U.S.-based resources as possible in the
design, manufacture and distribution of our products.

What sucks about the A.R.C.?

In each product guide, I try to summarize the product’s strengths (see “What’s cool about the A.R.C.?”
starting on page 2) and weaknesses from my view as the designer and user. This is no exception:

• Few Panel Controls — Many recording studio signal processors have lots of

panel controls to afford maximum flexibility to the recording engineer. It’s almost
a requirement for the studio envir onment. For an ef f ects pedal, lots of controls can
be an unnecessary complication for many musicians. We tried to balance com­plexity of controls and ease-of-use and gave the A.R.C. three rotary controls and a
bypass switch. Some will find this complement of controls to be too few, while
others may find it to be just right.

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• Large & Heavy Enclosure — As previously mentioned, we decided to use a non-

standard enclosure for the A.R.C. This will be a pr obl em for some musicians si nce
it’ll be more difficult to make room on a crowded pedal board for a larger-than­normal enclosure and, for even smaller set-ups, the larger enclosure will add
more weight than most. Despite the se con cern s w e cho se th is path for a cou ple o f
reasons: (1) there are more electronics in the A.R.C. than normal that, without
resorting to more esoteric/expensive electronic assembly techniques, require
more spatial volume, (2) we wanted enough panel space to permit control adjust­ments with your prehensile feet, and, (3) wanted a slanted top to make reading and
adjusting the controls a tad easier.

• Confusing Bypass Indicator — This one will trip up some of you: when the

A.R.C. is engaged, the GREEN light is lit and when the A.R.C. is BYPASSED, the
RED light is lit. Technically, with this kind of presentation, the control should be
labeled SYSTEM STATUS with GREEN indicating ENGAGED and RED indicat­ing BYPASSED. Since SYSTEM STATUS sounds really pompous and nerdy, I
opted to just label it BYPASS. Why the two LEDs? Primarily to combine the
engaged/bypassed indication with an ad hoc power indicator. Besides, watching
the LEDs go off and on in response to the footswitch is cool.

H OOKING UP THE A.R.C.

To use the A.R.C. as intended, there are three things you must do in roughly this order:

• Apply power to the A.R.C.

• Connect the audio source and destination(s) to the A.R.C.

• Play!

Connecting the A.R.C.

Here’s some specific details about hooking the A.R.C. up:

1) Connect the Power Supply — Using a BOSS PSA-120/230 type power source,

plug the power supply into the jack marked “Power In”. We recommend apply­ing power to the A.R.C. before any audio cabling is connected to avoid any
“pops” occurring downstream when the power supply is connected. Although
this is rarely injurious, it is annoying! If you’re thinking about using the “daisy­chain power” feature of the A.R.C., please refer to the section “Control Descrip-
tions” starting on page11. Please be sure to heed all the warnings and only use
this feature with proper consultation/supervision and/or hire someone to config-

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ure it for you!

2) Connect the Source — The A.R.C.’s input is a 1/4" unbalanced, high impedance
(Hi-Z) phone jack. Because of the A.R.C.’s BOOST feature its high-Z nature, we
recommend that your instrument be directly connected to the A.R.C.’s input for
best results. The A.R.C. may also be inserted further along in your instrument’s
signal chain without ill effect. So, for example, if you’ve got your favorite XYZ
pedal that you plug into first, just put the A.R.C. in the chain where you’d like it
to be using a regular 1/4" phone plug cable. Remember, since the A.R.C. has a
wide dynamic range, you may also use the A.R.C. as a studio effect! In that case,
just hook it up with an unbalanced cable as you would any other studio effect.

3) Connect the Output(s) — There are two outputs on the A.R.C.: a 1/4" unbal­anced phone jack and an XLR connector. For a regular instrument set-up, use the
1/4" output to go to your instrument amp. Should you also need a separate feed
for stage monitors and/or front-of-house (FOH) applications, you may addition­ally use the XLR balanced connector by hooking up a regular microphone cable
from the A.R.C.’s XLR connector to a mixing board. You can use the A.R.C. as a
direct box in either a studio or live environment by using the XLR connector to
connect the A.R.C. with a mixer or A-to-D converter.

Y ou don’t have to do things in the order listed above for everything to work. The above or der is only a sug­gestion and has worked well for us.

Figure 1: The A.R.C.’s controls

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O PERATING THE CONTROLS

Control & Indicator Descriptions

There are four top panel controls on the A.R.C. (see Figure 1):

• INPUT LEVEL — This knob controls the gain of the input preamplifier. This con-

trol is used in combination with the DRIVE control to change how the A.R.C. will
affect your instrument’s sound. This control will affect: the XLR output, the 1/4"
output and the amount of input signal to the compressor.

• AMP LEVEL — The 1/4" output jack is intended to drive the input to an instru-

ment amplifier. This control affects only this output and allows you to match the
level coming out of the processing circuits in the A.R.C. with the level you get
when the A.R.C. is bypassed. This control doesn’t affect the XLR’s output level.

• DRIVE — This knob sets the gain and mix levels of the internal compres sor. When

used in combination with the INPUT LEVEL control, this control will change how
the A.R.C. will affect your instrument’s sound. This control will increase the
aggressiveness of the compressor and the amount that the compressor’s output is
blended with the unprocessed signal.

• BYPASS — When the GREEN light is on, the audio at the output connector is

taken from the A.R.C.’s main signal path. When the RED light is on, the A.R.C.’s
internal circuits are not engaged and it’s as though you’ve plugged your instru­ment directly to whatever you’ve got connected to the output jack of the A.R.C.,
typically your amplifier.

• PROCESS LED — Simply put: the brighter this light, the more processing that’s

being done by the compressor. Even though it’s not a multi-segment meter, with a
little practice, this LED becomes a quick and useful indicator to help you judge
how much the A.R.C. is processing your signal.

By the way, you might be wondering about the size of the knob on the DRIVE control: we figure that the
most used control will be the DRIVE kn o b , s o we made it a little bigger than the others!

Initial Settings

Although the A.R.C. can achieve a wide range of sounds with minimum controls, it’s still impossible for us
to specify exact settings for all the possibilities you may have for the A.R.C. Despite this, we can give a r ec­ommended starting set-up. For these initial settings, we’ll assume that you’re using an instrument, such as
a guitar, plugged into the A.R.C and that the output of the A.R.C. is connected to an instrument amplifier.
With this set-up in mind:

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• Set the AMP level to the most clockwise position, the INPUT and DRIVE controls
to the fully counterclockwise positions and make sure the A.R.C. is bypassed (i.e. ,
the RED bypass light is lit).

• Set the volume of your guitar and amplifier as you normally would with the
A.R.C. bypassed. Since the A.R.C. is starting in the bypassed condition, setting the
volume of your instrument and amplifier is as though the A.R.C. is not in your
signal chain.

• Engage the A.R.C. and adjust the DRIVE and INPUT controls to give you the
desired effect (see “Application Configurations” starting on page 8). While play­ing, alternate between bypassed and engaged. When the A.R.C. is engaged, adjust
the AMP control so that the loudest parts of the musical passage are the same in both the
engaged and bypassed conditions.

Now we’re ready to see how the controls vary the depth and character of the effect on your instrument!

Taking Control

As already mentioned, although we can’t give you specific settings for the INPUT and DRIVE controls,
there are a couple of guidelines that we can give you to help you more effectively pilot the A.R.C.:

1) When the DRIVE control is fully counterclockwise (CCW), the A.R.C. acts mostly
like a preamp and the compressor’s effect is minimized. In this configuration, the
INPUT and AMP controls dominate.

2) Regardless of the INPUT control’s position, as the DRIVE control is rotated clock-

wise (CW), the A.R.C.’s compression action will be increased and the balance
between the unprocessed/compressed signals will increasingly favor the com­pressor.

3) The XLR output of the A.R.C. is always active when power is applied. No matter

what you’re functionally using the A.R.C. for, the XLR output is available!

A PPLICATION CONFIGURATIONS

The A.R.C. as a “boost” pedal

In this configuration, we don’t want the A.R.C. to do much more than just amplify your instrument’s sig­nal. To use the A.R.C. as a boost pedal, keep the DRIVE control set to a minimum, the AMP control to “0”
(i.e., fully CW), and use the INPUT control to give you the desired level

.

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AmpBanjo*

Use this control
to give you the
desired "boost"

the banjo is shown for illustrative purposes only. The A.R.C.
works with many instruments, stringed or otherwise, including
the banjo.

* —

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Figure 2: Using the A.R.C. as a BOOST Pedal

The A.R.C. as a direct box

A “direct box”, also known as a “direct input” (D.I.), is primarily used to permit the connection of an
instrument-level device to a line-level device, such as a live/studio mixer, analog-to-digital converter
(ADC) or recorder. The A.R.C. provides this function whenever it’s engaged because the XLR output is
always active. The D.I. signal is affected by both the INPUT and DRIVE controls, but not the AMP control.
The AMP knob only controls the A.R.C.’s output level to the 1/4" output jack.

To set up for the D.I. function, generally you’ll want to get as much signal to the mixer/recorder that’s
required for a good signal-to-noise ratio. With the gain control on the mixer/recorder set to “0dB” (consult
your mixer/recorder’s manual for the details), adjust the A.R.C.’s INPU T control to give you the desired
level.

The A.R.C. as a compressor

Set the A.R.C. up as described in Initial Settings and for either boost and/or D.I. function(s). To add com­pression, merely rotate the DRIVE control CW from it’s fully CCW position until you’re hearing the
amount of compression you’d like. The DRIVE control will both change the amount of compression as
well as the balance of the compressed signal with the uncompressed signal. In general, the settings to the
left of the 12 o’clock position are relatively subtle. Beyond that, the compression effect becomes more pro­nounced and may be too extreme except for a “special effect”. Find the balance that’s good for your cir­cumstance.

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Use this control
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This control DOES NOT
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Turning this CW will
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Figure 3: Using the A.R.C. as a D.I.

F M R A u d i o

The A.R.C. as a studio effect

Hook up the A.R.C. as you would a dedicated studio effect. For example, let’s say you’ve recorded a vocal
track in your DAW and want to process it with the A.R.C. instead of a software plug-in. There are two
parts to this: setting up the software and setting up the hardware (you’ll need to confer with your DAW’s
manual for routing an external “insert”). To use the A.R.C. as an external effect, plug an appropriately con­figured digital-to-analog converter (DAC) channel from your interface into the A.R.C.’s input jack using a
standard 1/4"-to-1/4" phone plug cable. Then, connect the A.R.C.’s output, either 1/4" jack or XLR jack,
with an appropriate cable into a channel on your analog-to-digital converter (ADC).

C LOSING THOUGHTS

The FMR Audio A.R.C. is compact, 4-in-1 effects box that can positively enhance the sound of most sound
sources: from stringed instruments like mandolin, dobro, acoustic guitar and fiddle all the way to drum
tracks, vocals and even the two-mix (!), there’s hardly a sound that doesn’t sound better coming out of it.
Whether you’re a live performer or a studio cat, the A.R.C. can truly add some Articulation, Resonance
and Clarity to your performances!

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C ONTROL DESCRIPTIONS

Figure 4: A.R.C.Rear Panel

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# Control Description

1 Power Out Jack — This jack is actually wired in parallel with the POWER-IN jack and is

intended to permit the “daisy-chaining” of the A.R.C.’s power source to other effects pedals.

Although either may be used as an input or output, BE CAREFUL to observe the detailed electrical
requirements of the other effects you’ll be connecting to.

2 Balanced Output (XLR) — This output will product up to +20dBu of level in a fully balance d,

differential manner. Use this output when you want to interface with equipment that uses XLR
connectors for their inputs. This connector emits a signal whenever the A.R.C. is active (i.e.,
unbypassed).

3 Out (unbalanced to instrument amplifier) — Connect this jack to your instrument’s amp. This

output is affected by all of the controls on the A.R.C.: DRIVE, INPUT, AMP and BYPASS.

4 In (unbalanced ) — Connect your instrument into this jack with a “standard” instrument cable,

i.e., 1/4" phone plug-to-1/4" phone plug.

5 Power In Jack — This jack is wired in parallel with the POWER-OUT jack. See “Power Out

Jack” (above) for more details.

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Figure 5: A.R.C. Top Panel

# Control Description

DRIVE Knob — This control increases both the amount of compression as well as in creases the

1

mix between the compressed signal versus the uncompressed. When turned clockwise (CW),
the unprocessed signal is decreased in relation to the processed signal and the compressor
forced to simultaneously increase compression levels and ratios. In the fully counterclockwise
(CCW) position, no measurable compression occurs.

DRIVE Level Indicator — This bright blue LED proportionally varies its intensity with the

2

amount of signal compression. This featur e is additional pr oof o f the A.R.C.’s utility : the LED is
so bright that with the right DRIVE level and musical performance, the A.R.C. may be used as a
flashlight or, if engaged in official activities with SETI (www.seti.org), as a tool to aid in the
search for extraterrestrial intelligence! We do not warranty the A.R.C. for such uses, however.

INPUT Gain Knob — This control changes the gain of the preamp stage from 0dB to almost

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20dB. This is not an input attenuator. This control actually varies the first amplifier stage’s gain.
In this way, gain is applied only as needed and signal-to-noise ratio can be maximized.

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# Control Description

AMP Attenuator Knob — This is the gain control in the last stage feeding the OUTPUT jack,

4

but it only causes signal attenuation. This control varies the signal present at the “Out” jack sig­nal from 0 to 25dB of attenuation.

BYPASS Indicator — These two LEDs show whether the “Out” signal is coming from the

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A.R.C.’s circuits or from the source signal co nnected to the A.R.C.’s input jack. When the “Out”
signal is taken from the “In” jack, the red LED illuminates indicating a BYPASSED condition.
When the “Out” signal is taken from the A.R.C.’s circui ts , the green LED illuminates indicating
the ACTIVE condition.

BYPASS Switch — This switch causes the A.R.C. to alternate between the BYPASSED and

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ACTIVE conditions.

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Control Descriptions Page 13 of 13

Appendix A:

Understanding and Using the A.R.C.’s

Power Out feature

ARC Quickstart Guide Appendix A.fm FMR Audio, [phone]

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P URPOSE OF THIS DOCUMENT

The FMR Audio A.R.C. offers the ability to provide power to another “downstream” device without
requiring another, power supply. This appendi x wa s w ritten to:

• Inform the user about the A.R.C.’s power circuit in sufficient detail to allow the
successful powering of other pedals via the A.R.C.

• Alert the user about some potential problems when using this feature.

• Recommend a general method for evaluating and properly applying this feature.

W HO SHOULD READ THIS

This is written for those that understand electrical/electronic fundamentals and have a need to power at
least one other device from the A.R.C.’s power daisychain feature. As mentioned in the warning at the
beginning of this manual (see **CAUTION!**), we recommend against using this A.R.C. featur e un less you
are quite skilled-in-the-art of electr onic design, development and/or troubleshooting. If you’re not an elec­tronics professional, please let a professional daisychain A.R.C. power to other devices!

T HE SCOPE OF THIS DOCUMENT

This document assumes that the A.R.C. will provide power for only one additional device. Given the sheer
number of effects pedals available, it’s likely there are other application issues lurking that have not been
anticipated in this document. For this and other reasons, this document is not a substitute for the educa­tion and experience required to safely interface electronic devices!

P OWER CIRCUIT DETAILS

The POWER IN and POWER OUT jacks are actually paralleled connections. Although marked as IN and
OUT, these labels are intended to simplify hook-up for the general user by reducing apparent connection
options. Obviously, IN and OUT designations for parallel connections are either really dogmatic or non­sensical. In this application, either jack may be connected to the power source, while distributing power
from the remaining jack.

There is one ceramic (X7R) cap in parallel with each set of coax jack terminals, physically
located at each jack. The coax jack(s), in turn, feed(s) the AC terminals of a full-wave bridge rectifier
(Schottky barrier type for low forward voltage). The “negative” of the bridge rectifier is the internal refer­ence for the A.R.C., while the “positive” of the bridge rectifier feeds the power converter. The “internal”
side of the bridge rectifier is bidirectionally filtered to tamp down HF noise in both directions. That is, this
filtering is intended to reduce noise signals outside the A.R.C. from adversely affecting the A.R.C., and
also any internal A.R.C. noise from adversely affecting outside devices.

The audio and power references are connected to the A.R.C.’s chassis. Since the incoming power supply
reference and the internal references are connected through the bridge rectifier, there is a mechanism for a

Purpose of this Document Appendix A-1

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potential difference to exist between a downstream device’s audio reference and the A.R.C.’s. Should such
a ground loop exist and should it create problems, the A.R.C.’s power reference connection to the chassis
can be defeated to reduce the effects of such a potential difference (see "Ground Loop Reduction") .

O PERATIONAL PRECAUTIONS

Voltage Polarity

The A.R.C.’s bridge rectifier allows either DC polarity power to be used or, if desired, an AC power source.
Many effects pedals, however, do not allow for such a variety of power types and voltage levels. It’s possi-

ble that a power supply that works fine with the A.R.C. may actually present an injurious voltage and/or polarity to
any other pedal “downstream” from the A.R.C. if connected via the A.R.C.’s daisychained-power feature. For exam-

ple, a power supply whose center pin is positive would work fine with the A.R.C. The A.R.C. would “pass
along” this polarity to the A.R.C.’s other power jack. Clearly, this could be problematic and/or destructive
to an effects pedal requiring a “center negative” connection only! The final voltage polarity for a daisy­chained system should be determined by the downstream device, not the A.R.C.

Voltage Range

The A.R.C. can operate over a range of voltages from 9V to 12V, either AC or DC while many pedals can
only use 9VDC for their power. In general, the final power supply selection must be made for the device,
either the A.R.C. or downstream device, with the most narrow voltage requirement that overlaps with the
A.R.C.’s input voltage range. For a “typical” pedal this would be 9VDC.

Total Current Draw

Since a single power supply in the daisychained configuration would be feeding the A.R.C. in addition to
downstream devices, the total current consumption must be considered. While the A.R.C. is specified to
operate on as little as 200mA, be aware that it may actually require more current depending upon actual
operational conditions. There are two additional considerations for the A.R.C.’s total current draw:

• The A.R.C. uses a THAT1646 line driver that’s capable of +27dBm levels. This out­put level magnitude will obviously impact the total current draw and is not
included in the specified 200mA average. In addition, because the A.R.C. is actu-

ally operating from internally—levels developed by a switching power
converter—one cannot merely add the increased current to the 200mA input cur-

rent. The following simple expression, however, can be used to estimate the addi­tional worst-case input current required for driving a line to +27dBm levels:

In this case, the denotes the change in current seen by the external power
supply due to driving the XLR output to maximum levels into , while

denotes the voltage of the external power supply (i.e., 9 to 12 V).

Appendix A-2 Operational Precautions

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• The A.R.C.’s very blue Drive Level Indicator can also consume significant cur­rents. It’s actually driven by an opamp operating from the internal , so that
the effect on the incoming current is a little more complex to calculate. After fac-

toring power conversion efficiencies and the like, the additional current load on
the incoming power supply is given approximately by:

where, is the additional incoming power supply current resulting from a
maximum brightness LED and is the voltage of the external power supply.

So, these two additional sources should be added to the A.R.C.’s 200mA current consumption at 9VDC
(1.8W) in addition to the total current required by the downstream device that you’re powering.

Ground Loops

Normally, when y ou’re trying to power multiple audio devices from mains voltages, the isolatin g nature
of the internal power transformers (and other circuits) helps prevent multiple ground paths that can r esult
in signal interference and audio performance degradation. For a variety of reasons—including the la ck of
standards, ad hoc assembly practices, and a bare bones “design” approach—the typical effects pedal
doesn’t have isolation between the power terminals and the signal references. As long as the effects pedal
is operated with a separate, isolated power source, interconnecting audio signals wouldn’t create any
problems. However, once you attempt to power two or more effects from a signal supply source, the short­comings of such a powering scheme become evident. The A.R.C.’s daisychaining power can be a conve­nient feature that, unfortunately, can uncover ground-related problems.

The accommodations that we’ve made for dealing with these problems are:

• The A.R.C.’s internal supply not only performs the power translation from the
incoming 9-12V levels to , but adds an increased level of isolation between
the power supply “reference” and the audio reference.

• The A.R.C.’s audio reference is optionally separable from the incoming power
supply reference by a “ground lift” mechanism.

D AISYCHAIN CHECKLIST

Preflight

Before hooking up the A.R.C. to the downstream pedal or the power supply:

• Identify the power requirements of the downstream device, i.e., voltage, voltage
polarity, current and connector characteristics.

• Select the operating voltage for the entire chain by picking the highest down-

Daisychain Checklist Appendix A-3

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stream device voltage that’s within the A.R.C.’s root-mean-square (RMS) voltage
range. This becomes the required .

• Calculate the total additional power required by the A.R.C. as discussed in "Total
Current Draw" of this appendix.

• Add the A.R.C.’s total current requirement to the downstream pedal’s maximum
estimated current consumption. This becomes .

• Make sure that the power supply you’ve sourced is rated to provide at

via a 2.1mm coaxial connector with the polarity required by the down-

stream device.

• Hook up the downstream device with a cable that has a 2.1mm coaxial connector
on one end (to connect to the A.R.C.’s power jack) and whatever connector is
required to interface to the downstream device power jack.

Now, the A.R.C. and the downstream device have their power connections made. At this point, intercon­nect the audio of all devices as you would normally. Carefully power up the system and verify expected
audio performance. If there are any unexpected hums , buzzes or exce ss noise that s eem to be related to the
A.R.C. and the rest of the system, consider the following section, "Ground Loop Reduction".

Ground Loop Reduction

One of the most troublesome noise issues in a given set up can often be caused by so-called ground loops.
This is a category of signal interference caused by the flow of unwanted currents, usually due to multiple
return paths. When all other external mechanisms for reducing ground loop effects have been exhausted:

• Reduce the coupling between the signal and power references in the A.R.C. by
completely removing the screw on the right side of the cabinet. Please note that
“rig ht s i d e ” re f e re n ce i s re l at i v e t o t h e v i ew as seen in the manual with the audio
connections toward the top of the page and the knobs facing you (see Figure 1:
"The A.R.C.’ s controls" on page 6 of the main manual).

• In place of the removed screw, carefully put in the provided Nylon screw. Finger
tighten this screw only.

Conclusion

By applying sound electronic interfacing principles, the following guidelines presented in this appendix
and using the features present in the A.R.C., another effects pedal can be adequately powered while main­taining acceptable-to-excellent audio performance.

Appendix A-4 Daisychain Checklist