TM
THE MATCHBOX HD
IHF<>PRO STEREO INTERFACE AMPLIFIER
DESCRIPTION
THE MATCHBOX HD is an active interface amplifier that properly interfaces unbalanced “consumer” IHF-standard
or Semi-Professional audio equipment with professional studio gear. THE MATCHBOX HD is a bi-directional unit,
with four independent amplifiers providing stereo input and output audio interface. Two amplifiers convert a stereo
HI-Z unbalanced source to LO-Z balanced outputs at studio level. A second pair of amplifiers converts a stereo
balanced studio line source to unbalanced compatible outputs. All four output levels are adjustable. The special
"HI GAIN" mode increases the system gain to accommodate exceptionally low unbalanced levels. All circuitry is
active and direct-coupled for absolute sonic transparency, making THE MATCHBOX HD ideal for use with digital
audio sources such as DAT recorders and computer-based digital sound editing systems.
INSTALLATION
1. Connect the UNBALANCED inputs of the Matchbox to the outputs of an unbalanced device, e.g., the
"line outputs" of a DAT recorder.
2. Connect the UNBALANCED outputs of the Matchbox to the inputs of an unbalanced device, e.g., the
"line inputs" of a DAT recorder.
3. Connect the BALANCED inputs of the Matchbox to the outputs of a balanced signal source, e.g.,
the line-level outputs of a professional audio console. NOTE: If the source feeding the Matchbox
is unbalanced, install a jumper between pins 1 & 3 on the male XLR plug.
4. Connect the BALANCED outputs of the Matchbox to the inputs of balanced studio equipment, e.g.,
the line-level inputs of a professional audio console. NOTE: If the Matchbox is used to feed an
unbalanced load, connect to pins 1 (Gnd) and 2 (HI) only! DO NOT short pin 3 to ground.
All XLR connectors should be wired as follows: Pin 1=Gnd Pin 2=HI Pin 3=LO
All audio grounds are isolated from the AC ground, which is connected to the Matchbox chassis.
The Matchbox is shipped with all level controls set so that unbalanced input/output levels of -10dBv will produce
balanced input/output levels of +4dBu. If other output levels are required, the Matchbox gains may be readjusted
via the OUTPUT ADJ controls on the front panel. Use a small screwdriver to carefully adjust the trimpots.
HI GAIN MODE: Some unbalanced equipment, such as computer-based digital audio editing systems, use
unbalanced audio levels that are lower than IHF standard. In this case, the HI GAIN mode should be used.
Remove the Matchbox cover, and locate JP1 and JP2, near the right side of the PC board. Move JP1 and JP2 to
their HI GAIN positions. This will increase the unbalanced input gain by 6dB. It may also be necessary to reduce
the unbalanced OUTPUT levels (on front panel) to prevent overdriving the audio inputs of the device being used.
SPECIFICATIONS UNBAL input to BAL output BAL input to UNBAL output
INPUT LEVEL -10dBv nom (HI GAIN: -20dBv) 0dBu to +8dBu nominal
INPUT IMPED 10K ohms (HI GAIN: 5K ohms) 20K ohms
GAIN +6 to +20dB (HI GAIN: add 6dB) -6dB to infinity (off)
OUTPUT LEVEL 0 to +8dBu nom, +26dBu max -10dBv nom, +20dBv max
OUTPUT LOAD 600 ohms or higher, balanced 2K ohms or higher, unbalanced
FREQ RESPONSE DC to 20 kHz, +/- 0.25dB DC to 20 kHz, +/- 0.25dB
NOISE LEVEL -100dBu, 20 kHz b/w -90dBv, 20 kHz b/w
DYNAMIC RANGE 122dB, 20 kHz b/w 120dB, 20 kHz b/w
DISTORTION .008% at any frequency .008% at any frequency
POWER INPUT 115/230 VAC, 50/60Hz, 3 W
PHYSICAL DIMEN 5.70”w X 1.65”h X 5.60”d; 2.5 lbs
Specifications subject to change without notice. Rev. 10/03
HENRY ENGINEERING
503 Key Vista Drive
Sierra Madre, CA 91024
Tel: 626.355.3656
Fax: 626.355.0077
www.henryeng.com
of
11Monday, September 29, 2003
1
1
503 Key Vista Drive
Sierra Madre, CA 91024 USA
telephone - (626) 355-3656
FAX (626) 355-0077
HENRY ENGINEERING
NOTE: UNLESS OTHERWISE SPECIFIED
L-UNBAL OUT
4
J1
5
RCA-413
2
1 3
R24
5K POT
U3A
LF353N
1
2
R16 4.99K, 1%
-15V
-
2
+15V
+
8 4
3
1. ALL RESISTORS ARE 1/4W, 1%.
R-UNBAL OUT
J1
6
RCA-413
4
2
R23
5K POT
U3B
LF353N
7
-15V
R11 4.99K, 1%
-
6
+15V
+
8 4
5
3110 B
SCHEMATIC: MATCH BOX II
Size Document Number Rev
B
Date: Sheet
Title
1 3
2
123
R22
R12 10.0K, 1%
C7
.001uF
C8
.001uF
NC3FAH2
4.99K, 1%
LED
3.9K, 5%
TP1
LED1
1
C5
.1uF
C3
.1uF
-15V
1
3
TP3
+15V
TP2
R21
1
C6
.1uF
C4
.1uF
R25
4.99K, 1%
R13 10.0K, 1%
J6
R-BAL IN
123
R14 10.0K, 1%
C9
.001uF
C10
.001uF
NC3FAH2
R15 10.0K, 1%
3
J5
1
LEFT CHANNEL
J7
123
NC3MAH
L-BAL OUT L-BAL IN
RIGHT CHANNEL
J8
R-BAL OUT
123
NC3MAH
OUT
IN
Q1 LM7815
3
GND
GND
2
IN OUT
Q2 LM7915
1
2 3
4
5
C2
2
R19 50K POT
1 3
JP1
R28
10.0K, 1%
47pF, NPO
3
2
1
NORMAL HI GAIN
-15V
R6
R20 10.0K, 1%
R7 47, 1%
U2B
7
-
6
NE5532
+
5
10.0K, 1%
C14
+15V
8 4
.001uF
R10 47, 1%
R2 47, 1%
R5 47, 1%
C12
330uF 25V
+
D1
1N4004
+
C11
330uF 25V
4
C1
1N4004
687
D3
1N4004
47pF, NPO
C15
R8 2.00K, 1%
R9 2.00K, 1%
U2A
300pF, NPO
1
NE5532
-15V
+
-
3
2
C16
300pF, NPO
-15V
U1A
-
2
1
+
NE5532
3
U1B
NE5532
7
+15V
8 4
2
R17 50K POT
-15V
-
1 3
6
+15V
+
8 4
R3 2.00K, 1%
R4 2.00K, 1%
5
D2
1N4004
+15V
8 4
D4
5
T1
SPW-061
BIPOLAR POWER SUPPLY
5
JP2
R27
10.0K, 1%
HI GAIN
3
2
1
NORMAL
R1
R18 10.0K, 1%
10.0K, 1%
C13
.001uF
1
PRI SEC
E6
230V
E7
342
E9
115V
E8
J1
RCA-413
2
1
L-UNBAL IN
D D
J1
3
1
BLK
F1
WHT
RCA-413
R-UNBAL IN
E1
AC
115V: 250 ma; 230V: 125ma
E2
AC
E4
E5
GROUND TIE
C C
B B
A A
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