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Archangel Electronics LLC
Patterson, Ga. USA
X7
Acoustic Instrument Reference Preamplifier / DI
Revision 7.93
Quick Start Guide
This manual is designed to get you quickly up and running with your new X7 Preamp.
The X7 has several new features and settings to make it the most flexible acoustic processor available.
Please take a few moments to read through this guide before the first use to get the highest level of performance possible,
customized for your signature tone and playing style.
Introduction
The Archangel X7
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Acoustic Instrument Reference Preamp / DI
Thank you for your X7 purchase!
The X7 is from the sixth generation of our highly acclaimed AP series preamps.
They are engineered for accuracy, transparency, and ultra-low noise.
By following this guide, you can expect years of faithful service from your X7
Warnings!
• Always keep, read, and follow these instructions.
• Do not use this device near water.
• Clean only with dry cloth.
• Do not block any ventilation openings. Install in accordance with the manufacturer’s instructions.
• Do not install near any heat sources, or other devices (including amplifiers) that produce heat.
• Protect cords from being walked on or pinched particularly at plugs, and the point where they exit from the device.
• Only use attachments/accessories specified by the manufacturer.
• Unplug this device during lightning storms, and remove batteries when unused for long periods of time.
• Refer all servicing to factory authorized service personnel. Servicing is required when the device has been damaged in
any way, such as power-supply cord or plug is damaged, liquid has been spilled or objects have fallen into the device, the
device has been exposed to rain or moisture, does not operate normally, or has been dropped.
• The device shall not be exposed to dripping or splashing and that no objects filled with liquids, shall be placed opon or
near the device.
• Prolonged listening at high volume levels may cause irreparable hearing loss and/or damage. Always be sure to
practice “safe listening.”
WARNING: To reduce the risk of fire or electric shock do not expose this device to rain or moisture.
The X7 has a high impedance unbalanced input for instruments. The X7 can accept input
from piezo pickups, magnetic pickups, even active electronics like the Sunrise™ active
magnetics, or the Taylor™ Expression System™, It even works with 18V active bass guitar
preamps and iOS devices like iPods™ and iPads™. The gain will need to be set to match
your input source, and your personal playing style. The X7 really shines when used with
SBT (multiple soundboard transducers) like Elevation™ premium transducer sets or JJB™ Prestige
330s. Using those transducers with the X7 reveals tone exactly like a large diaphragm condenser
mic, without the feedback that plagues most piezo systems.
The input jack when unplugged, disconnects the batteries from the power supply to extend battery
life. It does not remove phantom power however, to prevent audio spikes into the PA when
unplugging the input jack.
Tip: Engage the mute switch when disconnecting the input jack when using phantom
power and the XLR out. It minimizes any noise or popping through the XLR line when
swapping instruments or unplugging.
Tuner / Mute
The tuner out is activated with the mute switch. The tuner out is completely isolated from the
audio path unless it is active. For accurate tuning with less false triggering, the tuner out is
processed with a sub-sonic and a seperate low frequency filter.
Input
Aux Direct Output
The Aux out is a high definition unbalanced and isolated direct out. It also has it's own
dedicated volume control. The Aux out is designed for ultra-high quality recording and for
stage monitoring. The Aux output bypasses the equalizer and line driver for a transparent
output that sounds even cleaner than our X5 reference preamp. The Aux output is a low
impedance line out at 4.7k. It is still a high enough impedance to drive most pedals and processors.
Tip: When recording, run the XLR and the Aux output to separate channels and apply
compression to just one channel for parallel compression. This is a trick used in pro
studios to add punch and sustain, without losing the brilliance or attack of the notes. This
technique also works great when using reverb and other effects to keep your transparent tone
intact. You will also find that the Aux and XLR outs are perfectly phase correct, so you may have to
flip the phase of the Aux output at the mixer when using with some pedals that reverse the phase of
the signal.
XLR Balanced Output
The XLR output is a true balanced output so the signal is twice as hot as similar half balanced
devices, and true balanced also means that any induced line noise is canceled out. The XLR
output has it's own dedicated volume control, and is processed by the Isometric Equalizer.
We recommend starting with the volume reduced and bring it up to a strong level on the
mixer with the faders zeroed and the mixer's gain at a low setting, for the cleanest possible signal.
Mute the channel on the mixer when turning on or off phantom power on the mixer and when switching
to phantom power or battery power on the X7 to avoid and spikes in the audio signal.
The impedance of the XLR output is ultra low at 100Ω (200Ω balanced) It is possible to get +4db
signals from the XLR balanced output. Be careful to not clip the mixer's inputs from sending a line level
signal into a microphone input, which causes distortion, and could damage the mixer.
Gain Control
Note: The gain control has 15 complete revolutions in it's travel from minimum to maximum.
The gain control is accedes by removing the 4 screws securing the bottom plate. The gain
control is a blue box with brass adjustment screw. Using a jewelers screwdriver, turn the
screw clockwise to increase the gain and counter-clockwise to reduce it. At the lowest setting
the gain is 0dB for unity gain. At the highest setting the gain is 21dB for 11x amplification.
The gain control is centered when shipped. It must be reduced for single piezo elements mounted
directly to the soundboard (like ukeleles), and for active electronics or heavy percussive playing styles.
To test the gain settings for acoustic instruments with piezos, tap the bridge or soundboard with your
palm using a fair amount of force. For electric instruments and magnetic pickups, play the loudest
passages you will process with the X7. Decrease the gain if there is popping or clipping coming from
your X7. Ipods, keyboards, and similar line inputs may need their master volume level reduced before
processing the signal with the X7.
Mod Switches
The X7 continues one of our most popular features from previous generations. The Mod
Switches allow you to re-wire the X7 circuit and change and personalize several essential
design parameters to suit your personal playing style and tone. There are 6 Mod Switches
inside the X7 which are accessed by removing the bottom plate. Switches 1 & 2 on with
switches 3 & 4 off tune the midrange knob to eliminate feedback (detailed in the EQ section
below) Switches 1 & 2 off and 3 & 4 on tune the midrange filter to a normal midrange frequency of 1.5
kHz. Switch 5 selects the input impedancbetween 11 M when off or 1 M when on (detailed below in
the impedance section). Switch 6 is the bright switch. It lowers the tuning frequency of the treble filter.
On is the bright setting and off is the sweet setting.
Powering Up
There is a power source selection switch on the top of your X7 for selecting phantom, or
battery power. The highest performance is realized in the phantom power setting from the
extra voltage supplied. Phantom powering means you wont need to buy batteries at all, or at
least much less often than with similar products. And the X7 has no annoying wall wart
power supply.
The X7 uses two 9v batteries. Duracells are included, and recommended for use with all Archangel
preamps. The batteries are accessed by removing the bottom plate. Yes, we heard loud and clear when
our customers suggested a battery door to access the batteries. When they make one that we can
warranty for five years, we will include one in every preamp. Until then, removing 4 screws is necessary
to change the batteries. Battery life is estimated by our friends at Duracell to be 450 hours or longer.
This varies with your gain and eq settings. Unlike most preamps that are only 9V DC battery powered
and considered dead at 8 volts, the X7 is 18 volts on battery power and will play well even with the
batteries drained down to below 9 volts on the power rails. If you consider your performance to be
mission critical however, install fresh batteries whenever you change your strings.
The X7 can easily be powered with standard 48v DC phantom power supply. The X7 only draws 1.7mA
of current at maximum. If the phantom power supply from the mixer is substantially below 48 volts, or
the current supply is below the international standard of 10mA, please use the battery setting.
Note: The voltage and current of the phantom power supplied by the mixer can be seriously
affected from using very long cable runs, improper cables or termination, too many phantom
powered devices connected at once, shorted cables and connectors, and home brew XLR to 1/4
adapters. Mixers equipped with phantom power may have a different voltage rating from the standard
48v. Read the owners manual of any product connected to the X7 carefully before use.
Isometric Equalizer ™
The EQ bands all have 26dB of boost and 15dB of cut, so go easy at first. The Isometric
Equalizer design allows for independent tuning of each band, and they are tuned precisely
for acoustic instruments.
The bass filter is tuned to 60Hz for tight and powerful bass response. 60Hz is tuned just
below the low B on a 7 string. When you boost the bass knob it will not cause the low E string to be
louder than the other strings like most EQ designs do. The tuning is still high enough to not cause
subwoofers to move violently, but low enough to really bring the house down when using modern
percussive fingerstyle playing techniques when boosted. It will also cut at 60 Hz to help acoustic
instruments to sit in the mix beautifully with bass and drums without needing excessive additional eq
from the mixer. Bass instruments and harp guitars will benefit greatly from the extended low filter
tuning.
The treble filter is tuned very high and designed as an upward expander. It increases the gain
exponentially as the frequencies get higher. It really allows your instrument to cut a through the mix with
amazing presence and clarity, without any of the shrill and ear piercing frequencies or harsh harmonics
that typical equalizers produce. The bright switch lowers the treble filters frequency by an octave, to
capture more high midrange frequencies that are sometimes needed for darker sounding instruments
and for instruments with laminated tops.
Harmonic Feedback Elimination (HFE)
The Isometric Equalizer's midrange filter is actually two filters in one. The tuning is
selectable with our Internal Mod Switches.
The first tuning is a conventional midrange filter tuned to 1.5kHz, which is the same
frequency that competes with vocals. The second tuning is our remarkable HFE setting.
It is tuned at 237Hz, which captures the first harmonic of the 95Hz to 110Hz fundamental that will
always feedback when acoustic guitars are amplified, especially when using piezo soundboard
transducers.
Acoustic instrument tops have several frequency modes that resonate differently. The fundamental is
the primary resonant frequency of the box. When we analyzed the typical acoustic guitar feedback, we
found that the fundamental frequency and the first harmonic were both excited at the same time at or
near the low G#. The harmonics that cause feedback, resonate primarily at (or close to) 106Hz and
212Hz, with the first harmonic being a little louder than the fundamental from the reinforcement of the
octaves and fifths in the top's upper bouts. We tuned the feedback elimination at 237Hz and it kills the
first harmonic's resonance, but still leaves the lower fundamental note perfectly intact. This stops the
feedback but leaves the bass response strong and powerful. And the frequencies that are cut are in the
typically much louder G string frequency range, and not the low E and A strings.
We don't use a notch filter in the X7 design and you can really hear the difference. The Isometric
Equalizer allows for fast and simple complete feedback elimination, and the bass response is still tight,
loud, and very low.
Features and specications in this manual are subject to change without notice.
Current product information is available online at: www.archangelelectronics.com
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