Technical Support
If you require technical support, contact dbx Customer Service. Be prepared to accurately describe
the problem. Know the serial number of your unit - this is printed on a sticker attached to the
bottom panel. If you have not already taken the time to fill out your warranty registration card
and send it in, please do so now.
Before you return a product to the factory for service, we recommend you refer to the manual.
Make sure you have correctly followed installation steps and operation procedures. If you are
still unable to solve a problem, contact our Customer Service Department at (801) 568-7660 for
consultation. If you need to return a product to the factory for service, you MUST first contact
Customer Service to obtain a Return Authorization Number.
No returned products will be accepted at the factory without a Return Authorization Number.
Please refer to the Warranty information on the following page, which extends to the first end-
user. After expiration of the warranty, a reasonable charge will be made for parts, labor, and pack-
ing if you choose to use the factory service facility. In all cases, you are responsible for transpor-
tation charges to the factory. dbx will pay return shipping if the unit is still under warranty.
Use the original packing material if it is available. Mark the package with the name of the shipper
and with these words in red: DELICATE INSTRUMENT, FRAGILE! Insure the package properly. Ship
prepaid, not collect. Do not ship parcel post.
What Does a Direct Box Do?
First, a direct box converts the audio signal originating from an unbalanced device (like a guitar)
to a balanced audio signal for transmission over a longer distance than is recommended for an
unbalanced signal to travel. As audio industry people know, the advantage of a balanced signal
is realized at the receiving end (audio input) of the balanced cable, typically in the form of a
mic pre-amp input on a mixing console. The mic pre input circuitry consists of a “differential
amplifier” whose job it is to “accept” the audio portion of input signal and “reject” the noise
portion of the signal. The noise portion happens to be roughly equivalent on (or “common to”)
both the “+” and “-” balanced conductors in the mic cable, since external electromagnetic fields
are induced onto both conductors in a roughly similar fashion. Since the conductors are always
in a “twisted pair” configuration, they “see” the same noise field. Thus, this is known as “com-
mon-mode noise”. Another type of common-mode noise somewhat evenly-induced onto both
conductors is due to the inherent physics of connecting two pieces of equipment together and the
resulting flow of electrons due to noise voltages present at each piece of equipment. The ability
of a balanced input to reject common-mode noise is measured in dB and called its “common-mode
rejection ratio”, or CMRR.
The second function of a direct box is to convert from a high-impedance output – on an instru-
ment such as electric guitar with passive pickups, for instance – to a low-impedance output. A
cable driven by a high-impedance output is more susceptible to signal loss and noise pickup than
a cable driven by a low-impedance output. Thus, using a direct box again improves, for a dif-
ferent reason, the ability to run longer distances due to the impedance conversion from high to
low-impedance.
Third, at the heart of the direct box is an isolation transformer that allows complete “galvanic”
isolation, if desired, between the equipment plugged into either end. This eliminates the hum
and buzz present in the system due to ground loops.
Example Setup 1: Guitar signal sent to amp and PA/Mixer
Pan
Mute
-10
0
+5
+10
-20
-30
-
-5
L / R
Mute
L / R
Mute
L / R
Mute
L / R
-5
-4
-3
-2
-1 0 +1
+2
+3
+4
+5
Pan
-5
-4
-3
-2
-1 0 +1
+2
+3
+4
+5
Pan
-5
-4
-3
-2
-1 0 +1
+2
+3
+4
+5
Pan
-5
-4
-3
-2
-1 0 +1
+2
+3
+4
+5
Pan
-5
-4
-3
-2
-1 0 +1
+2
+3
+4
+5
Pan
-5
-4
-3
-2
-1 0 +1
+2
+3
+4
+5
Pan
-5
-4
-3
-2
-1 0 +1
+2
+3
+4
+5
Pan
-5
-4
-3
-2
-1 0 +1
+2
+3
+4
+5
1
2
3
4
-10
0
+5
+10
-20
-30
-
-5
-10
0
+5
+10
-20
-30
-
-5
-10
0
+5
+10
-20
-30
-
-5
Mute
L / R
5
-10
0
+5
+10
-20
-30
-
-5
Mute
L / R
6
-10
0
+5
+10
-20
-30
-
-5
Mute
L / R
-10
0
+5
+10
-20
-30
-
-5
Aux 1
0
2
4
6
8
10
Aux 2
0
2
4
6
8
10
Aux 1
0
2
4
6
8
10
Aux 2
0
2
4
6
8
10
Aux 1
0
2
4
6
8
10
Aux 2
0
2
4
6
8
10
Aux 1
0
2
4
6
8
10
Aux 2
0
2
4
6
8
10
Aux 1
0
2
4
6
8
10
Aux 2
0
2
4
6
8
10
Aux 1
0
2
4
6
8
10
Aux 2
0
2
4
6
8
10
Aux 1
0
2
4
6
8
10
Aux 2
0
2
4
6
8
10
Aux 1
0
2
4
6
8
10
Aux 2
0
2
4
6
8
10
Mute
L / R
-10
0
+5
+10
-20
-30
-
-5
INPUT
THRU
PAD
0dB
20dB
40dB
Mixer
Amplifier
Guitar
dB10
Direct Box
From
OUTPUT
on Rear Panel
Example Setup 2: Direct guitar signal and amped signal on two mixer channels
Pan
Mute
-10
0
+5
+10
-20
-30
-
-5
L / R
Mute
L / R
Mute
L / R
Mute
L / R
-5
-4
-3
-2
-1 0 +1
+2
+3
+4
+5
Pan
-5
-4
-3
-2
-1 0 +1
+2
+3
+4
+5
Pan
-5
-4
-3
-2
-1 0 +1
+2
+3
+4
+5
Pan
-5
-4
-3
-2
-1 0 +1
+2
+3
+4
+5
Pan
-5
-4
-3
-2
-1 0 +1
+2
+3
+4
+5
Pan
-5
-4
-3
-2
-1 0 +1
+2
+3
+4
+5
Pan
-5
-4
-3
-2
-1 0 +1
+2
+3
+4
+5
Pan
-5
-4
-3
-2
-1 0 +1
+2
+3
+4
+5
1
2
3
4
-10
0
+5
+10
-20
-30
-
-5
-10
0
+5
+10
-20
-30
-
-5
-10
0
+5
+10
-20
-30
-
-5
Mute
L / R
5
-10
0
+5
+10
-20
-30
-
-5
Mute
L / R
6
-10
0
+5
+10
-20
-30
-
-5
Mute
L / R
-10
0
+5
+10
-20
-30
-
-5
Aux 1
0
2
4
6
8
10
Aux 2
0
2
4
6
8
10
Aux 1
0
2
4
6
8
10
Aux 2
0
2
4
6
8
10
Aux 1
0
2
4
6
8
10
Aux 2
0
2
4
6
8
10
Aux 1
0
2
4
6
8
10
Aux 2
0
2
4
6
8
10
Aux 1
0
2
4
6
8
10
Aux 2
0
2
4
6
8
10
Aux 1
0
2
4
6
8
10
Aux 2
0
2
4
6
8
10
Aux 1
0
2
4
6
8
10
Aux 2
0
2
4
6
8
10
Aux 1
0
2
4
6
8
10
Aux 2
0
2
4
6
8
10
Mute
L / R
-10
0
+5
+10
-20
-30
-
-5
INPUT
THRU
PAD
0dB
20dB
40dB
Mixer
Amplifier
Guitar
dB10
Direct Box
From
OUTPUT
on Rear Panel
Mic
Special Functions
Polarity Invert
The polarity function is used in situations where the direct box is used as a splitter, and two
“sort-of parallel” signals are fed to two mixer channels to be perhaps panned left and right for
a nice stereo sound. Flipping the Polarity Invert function will change the phase relationship
between the two signals and will typically result in significantly different-sounding results.
A typical example would be to plug a guitar into the input of the direct box, then feed the signal
directly back out the Thru jack and into the guitar amp. Then the guitar amp would either be
mic’d and sent to one mixer input channel, or a direct output on the guitar amp would be sent to
the mixer channel. The output of the direct box would be fed into a second mixer input chan-
nel, and the Polarity Invert switch position would then be selected based on preference on how
it sounds. In the situation where the amp is mic’d, the position of the mic away from the guitar
amp speaker also affects the exact phase relationship between the two guitar signals as well.
Filter
When a guitar amp is mic’d, not only does the guitar amp speaker not reproduce high frequencies,
but the mic typically does not reproduce high frequencies well either at these loud levels. Thus,
a mic’d guitar amp has significantly subdued “high-end”. Since the 0 / 20 / 40 dB pad feature
allows input connection directly from the speaker output of a guitar amp or power amp* when
switched to the 40 dB pad position, the Hi-Cut filter is used in conjunction with the 40 dB pad on
an amplifier output signal to roughly duplicate the sound of a mic’d speaker. Otherwise the signal
would have much more high frequency content and would sound “tinny” in comparison.
NOTE: The Filter switch only works when the Pad switch is set to 40 dB.
* See the maximum input level specification.
Specifications
Circuit Type:
Input
:
Number of Connectors:
Connection:
Type:
Attenuation Pad:
Filter:
Max Input Level (0 dB Pad):
(20 dB Pad):
(40 dB Pad):
Input Impedance (0dB):
(-20dB):
(-40dB):
Outputs
:
Number of Connectors:
Main Output:
THRU Output:
Main Output Impedance:
Main Output CMRR (60 Hz):
(1 kHz):
(10 kHz)
Output Polarity:
Performance
:
Bandwidth:
Frequency Response:
Phase Deviation (Input ð Output):
Insertion Loss:
Harmonic Distortion (THD+N):
Noise Floor:
Dynamic Range:
Power Supply
:
Voltage:
Current:
Ground:
Physical
:
Size (L x W x H):
Weight:
Construction:
Finish:
If you want to dispose this product, do not mix it with general household waste. There is a
separate collection system for used electronic products in accordance with legislation that
requires proper treatment, recovery and recycling.
Private household in the 25 member states of the EU, in Switzerland and Norway may return their used
electronic products free of charge to designated collection facilities or to a retailer (if you purchase a similar
new one).
For Countries not mentioned above, please contact your local authorities for a correct method of disposal.
By doing so you will ensure that your disposed product undergoes the necessary treatment, recovery and
recycling and thus prevent potential negative effects on the environment and human health.
Warranty
This warranty is valid only for the original purchaser and only in the United States.
1. The warranty registration card that accompanies this product must be mailed within 30 days
after purchase date to validate this warranty. Proof-of-purchase is considered to be the burden of
the consumer.
2. dbx warrants this product, when bought and used solely within the U.S., to be free from de-
fects in materials and workmanship under normal use and service.
3. dbx liability under this warranty is limited to repairing or, at our discretion, replacing defective
materials that show evidence of defect that are not due to normal wear and tear and/or improper
handling by the user, provided the product is returned to dbx WITH RETURN AUTHORIZATION from
the factory, where all parts and labor will be covered up to a period of four years. A Return Autho-
rization number must first be obtained from dbx by telephone. The company shall not be liable for
any consequential damage as a result of the product’s use in any circuit or assembly.
4. dbx reserves the right to make changes in design or make additions to or improvements upon
this product without incurring any obligation to install the same additions or improvements on
products previously manufactured.
5. The foregoing is in lieu of all other warranties, expressed or implied, and dbx neither assumes
nor authorizes any person to assume on its behalf any obligation or liability in connection with
the sale of this product. In no event shall dbx or its dealers be liable for special or consequen-
tial damages or from any delay in the performance of this warranty due to causes beyond their
control.
Passive
1
1/4” TS (Tip Hot, Sleeve Ground)
Unbalanced, RF Filtered
Switchable: 0, 20, 40 dB
Switchable: Low Pass @ 6 kHz (40 dB pad position only)
+33 dBu
+33 dBu
+33 dBu
80 k
Ω
with 600
Ω
load, 270 k
Ω
with 2 k
Ω
load, 13 M
Ω
with 100 k
Ω
load
65 k
Ω
Typical
70 k
Ω
Typical
2
Male XLR, Balanced, Pin 2 hot
1/4” Unbalanced TS (Tip Hot, Sleeve GND)
600
Ω
typical, balanced
128 dB typical @ 60 Hz
104 dB typical @ 1 kHz
98 dB typical @ 10 kHz
Switchable: Normal / Invert
20 Hz to 20 kHz +/-0.1 dB typical
<10 Hz to 80 kHz, -3 dB
+1 deg @ 20 Hz, -5 deg @ 20 kHz into 2 k
Ω
load
21 dB typical
0.003% typical @ 50 Hz, 0 dBu
0.002% typical @ 1 kHz, 0 dBu
0.002% typical @ 10 kHz, 0 dBu
-120 dBu, 22 Hz to 22 kHz, unweighted
153 dB, 22 Hz to 22 kHz, unweighted
N/A
N/A
Switchable: Ground / Lift
5.82” X 5.44” X 2.20”
1.5 lbs. (0.68 kg)
Metal Casting
Powder Coat
