Duncan A E C User manual

SEYMOUR DUNCAN RESEARCH
A E C™
Acoustic Environment Control™
Preamplifier
OWNER'S MANUAL
5427 Hollister Avenue
Santa Barbara, CA 93111-2345, USA
Tel. [phone]
Fax. [phone]

Introduction
Congratulations on your purchase of the Seymour Duncan Acoustic Environment
Control™. In one compact battery-powered package we have combined the functions of:
• FEEDBACK ELIMINATOR
• An activeDIRECT BOX
• A PREAMPLIFIER with gain and tone controls
This multi-purpose product has been crafted specifically to fill the needs of the acoustic
guitarist.
Every feature has been specifically chosen to give you an unprecedented amount of
control over your sound while allowing the flexibility to handle virtually any playing
situation.
Anti-feedback controls have been optimized to allow high sound pressure levels without
annoying feedback. There are two separate 1/4" inputs (one with 6 dB extra gain) with
extremely high input impedance to improve the sound of unbuffered piezo saddle-type
pickups from Martin/Fishman/Baggs. One of the 1/4" outputs will drive a power amp to
full power. The other 1/4" output is instrument level, so you can plug it into a combo
amplifier or a mixing board. The high quality, transformer coupled, direct (XLR) output
gives you a quiet balanced output for recording or to use as a house feed for sound
reinforcement. You can use the A E C preamp as a battery powered direct box with tone
controls! The notch filter with sweepable frequency and variable depth will allow you to
get rid of annoying acoustic feedback in almost any room. In short, we think you will find
your Acoustic Environment Control preamplifier has the flexibility to handle any playing
situation, from solo club gigs to studio work.
A Discussion on Feedback
An acoustic guitar, which sounds warm, rich and responsive when, played without
amplification can feedback annoyingly when amplified. The sound from the speakers
interacts with the guitar's natural resonance to cause feedback. There are two dominant
resonant sources, the air cavity and the soundboard. The air cavity is the lower of the
two, generally falling around 10OHz. The soundboard, which produces 90% of the
guitar's acoustic output, resonates around 20OHz.
Our A E C™ preamplifier has several features, which are designed to control unwanted
feedback. The phase switch is used to knock out the air cavity resonance of the guitar
and the notch filter is used to control the soundboard resonance. The phase switch
inverts the polarity of the amplifier's output relative to the resonance of the guitar.
Changing the phase of the output signal can effectively control the low frequency air
cavity resonance, although in very loud settings you may actually need to block the
sound hole. The notch filter is extremely useful in controlling sound board feedback.
Once the notch filter is "tuned" to your guitar's soundboard, the depth control can be
used to cut more or less depending on how loud you are playing. You only want to notch
out "just enough" to control feedback so that the guitar retains as much of its acoustic
characteristics as possible. Proper use of the phase and notch controls will allow you to
play at high volume levels without feedback and without unduly compromising the
natural timbre of your instrument.

Controls & Features
Your Seymour Duncan A E C preamplifier has a wide range of useful features for
getting the best sound out of your acoustic guitar and making the preamplifier
extremely versatile in all types of performing and recording applications.
Balanced Line Out -This output is for Direct Input into a mixer or recording console.
This output is derived from a low noise, wide bandwidth transformer. With a nominal
1OOmV input signal, the output level is -20 dBm or -14 dBm depending on which input
jack you use. When phantom power is present, the AEC automatically switches from
battery to phantom power and lights a green LED on the front.
9 Volt Battery Eliminator Input -Plug in a standard 9 Volt battery eliminator with a 2.1
millimeter plug. Current consumption is less than 1.5 milliamps. The shell is positive.
Check this out before you plug in. Some battery eliminators are the opposite polarity.
The AEC is internally protected against damage from reverse polarity. It just won't work.
Line Level Output -Use this 1/4" output to directly drive a power amplifier to full power.
This output may be used simultaneously with the instrument level output. Either or both
outputs can be used depending on the demands of the playing situation.
Instrument Level Output -Use this 1/4" output to play a combo amplifier or any other
high gain unbalanced input. This output can also be plugged into a tuner, an effects unit,
or used as monitors send.
Instrument Inputs -The instrument inputs are ultra high-impedance (5 Megohms). The
very high impedance of the instrument inputs allows for better impedance matching with
piezo-crystal and piezo-vinyl acoustic pickups, which characteristically have very high
output impedances. When the input impedance of an amplifier is much lower than the
output impedance of the pickup, the pickup may sound tinny and brittle. One of these
inputs is 6 dB hotter than the other for use with low output pickups.

Notch Filter -The notch filter is very useful in combating regenerative feedback (see
section on feedback). It reduces the signal at a particular frequency where the feedback
is occurring (such as your acoustic guitar's sound board resonant frequency). The notch
filter has two controls: notchDEPTH and FREQUENCY. The notch frequency control
varies the notch from 70Hz to 340Hz . The depth knob controls how deep the notch is,
up to -25 dB!. Turning the knob clockwise deepens the notch. You should use the depth
control to notch out "just enough" of the feedback frequency to stop the feedback, while
preserving the natural timbre and characteristics of the acoustic guitar. Although most
acoustic preamplifiers and amplifiers do not offer it, the depth control is essential in
maintaining a transparent, flat response.
Bass and Treble-These are a shelving type controls with ±10 dB and ±7 dB of
adjustment, respectively. The 12 o'clock position on the pots is "flat" The sound of brittle
piezo-ceramic pickups can be improved by boosting the bass and treble and turning
down the volume slightly. This has the effect of "cutting" the midrange, which helps
some piezo pickups sound more natural. As room acoustics change from gig to gig,
these controls can be used to get a good sound regardless of quirks in the room.
Volume -This potentiometer is the overall output control for the entire preamplifier. It
adjusts the level of the two 1/4" output jacks. The level of the XLR balanced output is
determined by which input jack is being used.
Phase Reverse Switch -This switch reverses the phase of the amplified guitar signal
coming out of the preamp, and thus the speaker, relative to the guitar. This can be an
extremely helpful one-shot cure for feedback. Keep in mind that the air-cavity resonance
feedback depends on the distance and direction of the guitar in reference to the
amplifier. For example, if the air-cavity resonance is IOOHz, there will be a
feedback-canceling "node" every 11.2 feet. Halfway between those nodes are the
feedback nodes, where it'll be the worst. Flipping the phaseswitch changes the
feedback nodes into feedback-canceling nodes and vice versa. Direction of the acoustic
guitar in relation to the speaker will also affect air-cavity resonance feedback, so the best
way to keep this kind of feedback under control is to stay in relatively the same area and
facing the same direction.

Setting Up for Optimal Performance
A simple step-by-step procedure is outlined below for setting up the amplifier for optimal
performance.
1. Reset Controls -Turn down the volume, set the Bass and Treble flat, and turn notch
Depth control all the way counter clockwise (no cut).
2. Set Tone -Turn the Volume up to a low listening level and set the Bass and Treble to
taste.
3. Eliminate Feedback -Mute the strings with your right hand by the bridge. Turn up the
instrument volume until the guitar almost, but not quite, breaks into feedback. Now tap
the soundboard with your finger on your right hand while continuing to mute the strings,
and you should hear a "ping". Set the notch-filter Depth control at 12:00. Now slowly
rotate the notch Frequency control from about 12:00 to 5:00. At some point the "ping"
should disappear and you'll just hear a dull "thunk" every time you tap the top. Now the
notch filter is tuned to the soundboard resonance of your guitar. Another technique is to
let the guitar actually feedback (if you can stand it) while dialing in the frequency. The
feedback will stop when you've got it tuned correctly. If you use this method, set the
Depth control to 2 o'clock help make the notch obvious. Now bring the master volume up
to playing volume. If you get a low rumble or roar when you try to turn up, push the
phase button to cancel the air cavity resonance. The correct phase depends on the
position and direction of the instrument, relative to the amplifier; so make sure you check
the phase in the location where you'll actually be playing. You'll also find that the louder
you turn up, the deeper you'll have to notch out the sound board resonance using the
depth control.
Even though these instructions are simple, it takes a little practice to get the hang of
setting up quickly. After a few times through the process you'll be amazed at how easy it
is to get a great sound.

Specifications
Input Stage: Ultra low noise J-FET
Signal-to-Noise Ratio: >80 dB referenced to 100 millivolt input,
20-2OKhz
Wideband Noise: -83 dBV @ line level output
-103 dBV @ instrument level output
-101 dBV @ balanced output
Hum and Ripple: 120 Hz: -113 dBV
60 Hz: -103 dBV
Maximum Available Gain: 50 or 34 dB (using the +6dB input and the
line level output)
Bass Control Shelving: ± 10 dB
Treble Control Shelving: ± 7 dB
Input Impedance: 5 Megohms
Notch Filter Frequency: 70 -340Hz.
Notch Filter Cut: 0 -25dB cut
Balanced Line Out: Transformer coupled, capable of driving
600ohm load
Instrument Level Output: 100 mV nominal, 200 mV max
Line Level Output: I Volt nominal, 2 Volts max.
Power Requirements: 9 volts DC @ 1.5 milliamps
Can be powered from: Internal 9 volt alkaline battery
9 volt battery eliminator with 2. lmm
female, shell is positive
48 volt phantom power
Weight: 12 Ounces
Dimensions: 7.3" x 4" x 1.75"

Warranty Information
FOR YOUR RECORDS:
SERIAL NUMBER______________________DATE OF PURCHASE_______________
DEALER_______________________________________________________________
KEEP YOUR BELL OF SALE IN A SAFE PLACE.
Please read carefully:
Seymour Duncan amplifiers (hereinafter referred to as the Product) are warranted
against defects in workmanship and materials, excluding tubes and speakers covered
separately, for a period of one year from date of purchase by the original purchaser.
Tubes and speakers are warranted for 90 days from date of purchase. Speaker warranty
will be subject to inspection by the Seymour Duncan Factory. Obvious over-powering or
abuse will result in warranty denial. This warranty is transferable.
Defective parts will be repaired or replaced without charge if the product is returned to a
Seymour Duncan Authorized Service Center. In the event a product is to be returned to
the Seymour Duncan Factory for repairs, A RETURN AUTHORIZATION MUST BE
OBTAINED PRIOR TO SHIPPING BY CALLING OR WRITING THE COMPANY FOR
THE RA NUMBER.
When returning, make certain to include a copy of the bill of sale and a detailed
description of
the problem. Any product shipped must be returned in the ORIGINAL SHIPPING
CONTAINER WITH ORIGINAL PACKING MATERIAL and freight prepaid.
Transportation charges involved in warranty service are the sole responsibility of the
owner.
This warranty does not apply to damage caused by misuse, mishandling, negligence in
use or maintenance or storage, and is voided if repairs or adjustments are made after
purchase by anyone other than the Seymour Duncan Factory or a Seymour Duncan
Authorized Service Center. Seymour Duncan reserves the right to be the sole judge as
to the misuse or abuse of the product.
The company assumes no liability for incidental or consequential damages which may
result from the failure of this product. Any warranties implied by law are limited to the
duration of this express limited warranty.
Some states do not allow limitations on how long an implied warranty lasts or the
exclusion or limitation on incidental or consequential damages, so the above limitations
may not apply to you. This warranty gives you specific legal rights, and you may also
have other rights, which vary from state to state.
Please return the enclosed warranty card so that we can give you the best warranty
service possible.