Aphex 124B Owner`s Manual

 -10/+4 AUDIO INTERFACE
MODEL 124A
APHEX SYSTEMS LTD.
10/4 INTERFACE MODEL 124
POWER/CLIP -6dB +6dB
CHANNEL 1
CHANNEL 2
TERMINATE
-6dB +6dB
OWNER'S GUIDE
1.0 INTRODUCTION
The Aphex 10/4 Audio Level Interface, Model 124, is a dual, bi-directional buffer amplifier designed to provide level and
impedance matching between consumer hi-fi equipment and professional, as well as industrial, audio systems. Many
consumer electronic devices can be very useful in the professional environment, but interconnection is difficult due to
differences in operating levels, impedances, and unbalanced line operation. The Model 124 solves these problems
through its simple, high-quality interface design without the added noise, distortion and instability that can result from
an improper hookup. A block digram, shown in Fig. 1, illustrates the signal path used in the design of the Model 124.
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CHANNEL 1 3 : OUTPUT LED 4
INPUT 1-43
+!- 608 GAIN
OVERLOAD
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Aa LEVEL 2
CHANNEL 2 e—_ = |
LOLEVEL = отт
INPUT ll 3
«- 60H GAIN
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CHANNEL 1
HI-LEVEL
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HI LEVEL o
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B00 OHM TERMINA TE
) INTERNAL SELECT
CHANNEL 1
LOLEVEL
OUTPUT
+15 VDC
15VDC
a rin ) INTERNAL SELECT
AAA
Fig. 1. Block Diagram of Aphex -10/+4 Audio Level Interface, Model 124.
Strict attention to details, such as exceptionally wide bandwidth and dynamic range, flawless square wave response, good
common-mode rejection and low distortion, make the Model 124 ideal for interfacing with the new digital disc and tape
machines in the studio. Other consumer devices that may be used in the professional environment are video cassette
recorders, audio cassette recorders, graphic equalizers, reverb and ambience devices, noise reduction systems, electronic
crossovers and power amplifiers.
2.0 FUNCTIONAL DESCRIPTION
2.1 IHF (Unbalanced) Inputs
The -10 INPUTS, 1 and 2, are designed for a standard IHF Input level of -10 dBV, unbalanced, with headroom of +15
dBV (Ref: 1.0 VAC). These low-level inputs are RF filtered for minimal interference pickup with an impedance of 18
kOhms for minimal loading of the source. Standard RCA type phono connectors are used, as shown in Fig. 2
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MODEL 124 10/4 INTERFACE APHEX SYSTEMS LTD NORTH HOLLYWOOD, CA
Fig. 2. Rear Panel Layout of Aphex -10/+4 Audio Level Interface, Model 124.
2 Model 124 Owner's Guide
2.2 Balanced Outputs
The corresponding +4 OUTPUTS, 1 and 2, are high-level, balanced outputs at a nominal level of +4 dBm. Recessed front
panel adjustments, labelled CHANNEL 1 and CHANNEL 2, provide level control of each output over a range of +6 dB,
as shown in Fig. 3. These outputs are transformerless for improved transient response with a peak output level of +25
dBm. Because of the servo-balance circuit design, the outputs can be used unbalanced (single-ended) at any time by
simply grounding the unused pin, much like a transformer. The circuitry assures there is no 6 dB loss that typically
results when other types of balanced outputs are grounded at one pin. However, peak headroom is reduced to +21 dBm
when used in this manner. The low output impedance of 65 Ohms perfectly drives 600 Ohm loads with minimal hum
and noise pickup and will drive long lines effortlessly. XLR-type connectors are used, with pin 2 in phase with the
RCA jack.
LEVEL CONTROLS FOR BALANCED OUTPUTS
APHEX SYSTEMS LTD. ON 10/4 INTERFACE MODEL 124
CHANNEL 1 CHANNEL 2
O a
TERMINATE
&dB +5dB 4d8 +608
POELE 6 AN
N 600 OHM TERMINATION
FOR BALANCED INPUTS
LED IS GREEN FOR POWER ON
LED TURNS RED SdB BELOW
SIGNAL CLIP
Fig. 3. Front Panel Layout of Aphex -10/+4 Audio Level Interface, Model 124.
2.3 Balanced Inputs
The +4 INPUTS, 1 and 2, are high level, balanced differential inputs which are RF filtered and exhibit high common-mode
rejection. The input impedance of 100 kOhms allows bridging over 600 Ohm balanced or unbalanced lines with
negligible loading effects. When required, the 600 OHM TERMINATE switch (front panel) can be depressed to place a
600 Ohm load across each individual input. Servo-balancing prevents high common-mode voltages from interfering
with peak headroom. NOTE: Overload is greater than +30 dBm!
XLR-type connectors are used, with Pin 2 in phase with the RCA jack. For phase integrity, use the same polarity standard
for inputs and outputs. The input operating level is factory set at +4 dBm, but may be easily changed to +8 dBm via two
jumpers on the printed circuit board.
2.4 IHF (Unbalanced) Outputs
The -10 OUTPUTS, 1 and 2, are low level outputs at a nominal level of -10 dBV (Ref: 1.0 VAC), with a peak level of +18
dBV (Ref: 1.0 VAC). Because of the low 150 Ohm impedance, audio signals will not be affected by cable capacitance or
loading effects when feeding two or more inputs.
3.0 APPLICATIONS
3.1 Two-Way Interface Amplifier
The most obvious application of the Aphex Audio Level Interface, Model 124, is to level match consumer IHF equipment
to professional audio gear. An unbalanced device (i.e. cassette deck, equalizer or CD player) is connected to the IHF
inputs and outputs. The balanced inputs and outputs are connected to the studio console, patchbay or other line level
equipment. The different gains and impedances are matched for optimum performance. The Model 124 is compact and
inexpensive enough to travel with a dedicated piece of equipment, and may be fastened directly to it for convenience.
3.2 Line Driver
The servo-balanced input and output stages of the Model 124 can be used as a very effective line driver for driving long
lines. The output stage provides a short circuit proof, low impedance source that is relatively unaffected by the
impedance of the cable. If needed, adjust the gain controls (front panel) to boost signal level. In this application either the
unbalanced IHF or balanced high-level inputs may be used. For the latter, simply jumper the IHF inputs and outputs
with a short phono cord.
Model 124 Owner's Guide 3
3.3 Signal Splitter
The Model 124 may be used to provide two high quality balanced outputs from a single unbalanced mono signal. Simply
use a “Y” connector to split the incoming signal to each of the IHF unbalanced inputs.
3.4 IHF Distribution Amp
The very low output impedance of the Model 124 enables it to drive a considerable number of unbalanced devices such as
cassette decks, VTR's, power amps etc. By patching the various inputs and outputs, you can select a balanced or
unbalanced input.
4.0 INSTALLATION
4.1 Unpacking and Mounting
Your Model 124 was carefully packed at the factory, and the container was designed to protect it. Nevertheless, we
recommend careful inspection of the box to determine if any damage occurred in transit. Save the box, so the Model 124
can be repacked in case it should ever need repair. Due to its compact size, the Model 124 can be placed almost
anywhere. Rack mounting one or two Model 124 units (or other Series 120 unit) is easily accomplished with the optional
rack mounting kit, Aphex Part No. 44-008. Complete instructions are included with the kit.
4.2 Input Level Set
The Model 124 comes set from the factory to operate at +4 dBm at the balanced inputs. If +8 dBm operation is desired,
remove the top cover and locate the two +4 /+8 jumpers on the printed circuit board (between the power transformer and
female XLR connectors). Note that the center post is jumpered to the +4 post. Remove the jumpers and reposition each
one so that the center post is jumpered to the +8 post.
4.3 AC Line Voltage and Fuse
The AC line operating voltage on the Model 124 is NOT user-selectable. A desired voltage (100, 120, 220 or 240 VAC)
must be specified at time of purchase. Due to the low current draw, the Model 124 uses a thermal fuse built into the
power transformer. This should only fail due to a catastrophic problem in the PCB or transformer itself. If failure occurs,
the unit must be returned to Aphex or an authorized distributor for repair.
5.0 SPECIFICATIONS AND WARRANTY
[HF Inputs RCA jacks
[HF Outputs RCA jacks
Balanced Inputs XLR type
Balanced Outputs XLR type
IHF Input Level 10dBV, peak +15dBV (Ref: 1.0 VAC)
[HF Input Impedance 18 kOhms
[HF Output Level 10dBV, peak +18dBV (Ref: 1.0 VAC)
[HF Output Impedance 150 ohms
Balanced Input Level +4 dBm (+8 dBm via internal jumpers), peak +30 dBm
Balanced Input Impedance 100 kOhms (front panel switchable 600 ohm load)
Balanced Output Level +4 dBm (front panel adjustable +6 dB, peak +25 dBm)
Balanced Output Impedance 65 Ohms
THD 0.005 %
Dynamic Range 99 dB
Bandwidth 5 Hz to 100 kHz, +0, -05 dB
Common Mode Rejection >45 dB
Power 100, 120, 220 or 240 VAC
Fuse Thermal
Dimensions 1.775" Hx8.25“ Wx7.25 “D
Weight 3.5 165
Aphex Systems is constantly striving to maintain the highest professional standards. As a result of these efforts, modifications may be
made from time to time to existing products without prior notice. Specifications and appearance may differ from those listed or shown.
Aphex Systems warrants parts and labor for the Audio Level Interface, Model 124, for a period of one year from the date of purchase.
If it becomes necessary to return a unit for repair, repack it in the original carton and packing material, if possible. For warranty repair,
enclose a copy of proof of purchase and send package to:
Aphex Systems Limited, 11068 Randall Street, Sun Valley, California 91352
(818) 767-2929 e FAX (818) 767-2641
4 Model 124 Owner's Guide