SMD DD-1 User manual

Distortion Detector
DD-1
Owner’s Manual

2
Table of Contents
The purpose and benefit of this tool 3
What is included 3
About the design 4
Specifications 4
Power Requirements 5
Measuring a headunit only 6
Measuring a headunit through an amplifier 7
Setting the gain of a full range amplifier 9
Setting the gain of a subwoofer amplifier 10
Troubleshooting 13
Where do I set my crossover frequency 15
Where do I set my infrasonic (subsonic) filter 16
Track list on the DD-1 CD 17
Limited warranty 18

3
The purpose and benefit of the D’Amore
Engineering / SMD Distortion Detector.
The purpose of this tool is to enable the installer to set
the gain of an audio amplifier to match the source unit’s
output level, accurately and quickly. It can also be
useful for detecting distortion in the audio signal caused
by poorly designed or malfunctioning audio equipment.
What is included?
The Distortion Detector (DD-1)
Protective silicon rubber boot
Calibrated Test tone CD
Harness
This manual
Pride of ownership

4
About the design
When you pick up the DD-1, know that you are holding a
precision piece of equipment. If treated as such it
should provide you with many years of reliable service.
We have chosen a 9V battery as a power source for a
few reasons:
They are readily available
Isolating the DD-1 from the vehicle’s electrical
system for power, guarantees that it will only
measure what it is supposed to measure;
distortion in the audio signal, not noise in the
charging system
We also chose an RCA input connector for a few
reasons:
It makes it pretty easy to measure the output of
a headunit directly, if you choose to do so
Should the harness become damaged it is easily
replaceable or repairable in the field
Specifications
Everyone hides these in the back of the book. We are
proud of our specs, they aren’t lies, so we are putting
them up front.
The Distortion Detector’s circuitry is 100%
analog
Distortion Detection trigger level > 1.0%
Harmonic Distortion
Guaranteed operating range of input signal is
1.2Vrms –125Vrms. (15,000 Watts at 1 ohm)
Autoranging
Signal Present LED trigger voltage 750mVrms

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Low Battery LED trigger battery voltage <
5.6Vdc
Auto-shut off timer 8 - 10 minutes after ON
button is pressed
Power requirements
Pull the silicon rubber boot off of the unit by starting at
one end and pulling off towards the other end. On the
back side you will see the battery compartment. Slide
battery compartment cover off towards bottom end of
unit to reveal the 9V battery compartment. Insert a fresh
9V battery, make sure the wires are routed around the
battery. (If they are under or on top of the battery the
door may not close properly) You are ready to go. Do
not run this unit off of any power source other than a
9V battery. Wall adapters are electrically noisy, as
are vehicle electrical systems.

6
Measuring a headunit only
1. This procedure will determine where the
maximum unclipped volume setting of the
headunit is. This is accomplished by setting the
bass, treble, ect, to zero; and any EQs and
crossovers in the headunit to flat. Later, when
you set the amplifier gain(s); you can reset these
to where you feel the customer will set them, or
where you will set them for your own system.
2. Next you need to connect the DD-1 to the
headunit’s outputs. Just plug the RCA outputs
into the RCA input of the DD-1. If you are using
speaker level outputs from the headunit, use the
included harness. Red to speaker (+) and Black
to speaker (-).
3. Play track 1 on test CD, turn the volume control
up until you see the signal detect LED illuminate.
4. Continue turning up the headunit and you should
see the 40Hz Detect LED illuminate.
5. Slowly continue turning up the headunit until the
Distortion LED illuminates, then turn headunit
down slowly until it goes out. Note the volume
setting.
6. Next change the track to track 2. Repeat the
steps 3-5 above, this time noting the 1kHz
Detect LED.
7. Now take the noted maximum volume settings
from the 40Hz test and the 1kHz test and
average them. This is your maximum
undistorted volume setting for the headunit.

7
Measuring a headunit through an amplifier
1. This procedure will determine where the
maximum unclipped volume setting of the
headunit is. This is accomplished by setting the
bass, treble, ect, to zero; and any EQs and
crossovers in the headunit to flat. Later, when
you set the amplifier gain(s); you can reset these
to where you feel the customer will set them, or
where you will set them for your own system.
This time we are going to use the amplifier to
boost the signal of the headunit. The DD-1 can
measure the headunit’s distortion THROUGH
the amplifier!
2. With the headunit connected to the amplifier,
connect the DD-1 input to one of the amplifier
outputs using the included harness. Red to
speaker (+) and Black to speaker (-). (Note on
some amplifiers, usually the right channel of a
multichannel amplifier, the Speaker (-) terminal
is where the signal actually comes out. In this
case you connect the Red to speaker (-) and
Black to speaker (+).
3. Turn the gain of the amplifier to its minimum
position
4. Set crossover switch to Flat. (Note if this is a
subwoofer amplifier and there is no crossover
switch to set to flat, turn the crossover frequency
all the way up).
5. Play track 1 on test CD, turn the volume control
up until you see the signal detect LED illuminate.
6. Continue turning up the headunit and you should
see the 40Hz Detect LED illuminate.

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7. Slowly continue turning up the headunit until the
Distortion LED illuminates, then turn headunit
down slowly until it goes out. Note the volume
setting.
8. If you have a full range amplifier, change to track
2. Repeat the steps 3-5 above, this time noting
the 1kHz Detect LED.
9. Now take the noted maximum volume settings
from the 40Hz test and the 1kHz test and
average them. This is your maximum
undistorted volume setting for the headunit.

9
Setting the gain of a full range amplifier
1. This procedure should only be done AFTER you
have ensured the headunit puts out a clean
undistorted signal, AND you know where the
maximum undistorted volume setting is.
2. Turn the gain setting of the amplifier to minimum
3. Set crossover to full range / all pass/ bypass
4. Disconnect all speakers connected to the
amplifier. (This has already been calculated into
the equation and provides 1- 3dB more gain
overlap on unregulated power supply amplifiers
and 0dB more gain overlap on regulated power
supply amplifiers).
5. Using included harness, connect DD-1 to output
of amplifier. Connect the red harness lead to
the Left Speaker (+) terminal, connect the black
to Left Speaker (-). (Note: Most multi-channel
amplifiers have the signal on Left (+) and Right
(-).
6. Play track 4 or 6 on test CD (Track 4 will ensure
maximum sound quality, Track 6 will result in a
louder system). Your choice.
7. Set the headunit’s bass, treble, EQ’s, crossovers
to flat
8. Set the headunit’s volume to the maximum
undistorted volume setting that was measured
with the DD-1 previously

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9. The Signal detected LED and the 1kHz LED
should illuminate.
10. Slowly turn up the amplifier’s gain setting until
the Distortion detected LED illuminates
continuously, then back down slowly until it just
goes out.
11. You are finished with the gain setting of this
amplifier. Now disconnect the DD-1, connect
the speakers to the amplifier, and set the
crossover to the desired position. See Where
do I set my crossovers section if you need
help with this.
12. Congratulations, you have just set the gain like a
Pro.
Setting the gain of a subwoofer amplifier
1. This procedure should only be done AFTER you
have ensured the headunit puts out a clean
undistorted signal, AND you know where the
maximum undistorted volume setting is.
2. Turn the gain setting of the amplifier to minimum
3. Turn the crossover frequency control to it’s
highest frequency setting.
4. If you have an infrasonic filter (sometimes
erroneously called Subsonic filter) control or
switch, set it to it’s lowest frequency setting or
“off”.