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Note that the ubiquitous PC COM port generates RS-232 with ± 12V logic levels, and can-
not be connected directly to the board (although no damage will occur). An RS232-to-TTL
level converter such as BB Electronics Model 232TTL is recommended, along with a suit-
able test cable.
If the RS-232 input is chosen, there are a couple of things to be aware of:
— the input buffer is only 34 characters long, so any command strings sent to the eq. PCB
must insert a pause of at least 10msec between blocks of 34 characters to allow time
for the microcontroller to act.
— communication is half-duplex, which means that while the board is transmitting, it can-
not be receiving. In practice, this requires the user to pause after each single line com-
mand and wait for the reply, instead of sending multiple commands one after the other.
2.3
Signal Inputs
Signal Name
Left Input
Right Input
gnd. ref.
SPDIF in
SPDIF gnd
Serial Data
In
Serial Data
Out
Turn-on
Ground
Protect
Clip
Notes:
1.) The analog inputs are diode-clamped to the ± 12V rails. Do not exceed peak signal
levels of ±12V.
2.) The serial data input uses MOS logic levels (approximately 1.5V/3.5V), and is diode-
clamped and current limited.
Framingham, MA 01701-9168
Location
J5 Pin 9
left channel analog signal input 2Vrms max. input level (note 1)
J5 Pin 1
right channel analog signal
input
J5 Pin 5
input ground reference
J5 Pin 4
digital bitstream input
J5 Pin 3
ground return for SPDIF in
J5 Pin 12
5V logic input
J5 Pin 11
5V logic output
J5 Pin 7
10V logic input
J5 Pin 2, 6,
grounds
10
J8 Pin 6
input
J8 Pin 14
± 12V logic input
SIZE
FSCM
A
32108
Characteristic
CLASS
DWG NO.
TS
264695
Notes
2Vrms max input level
connect to measurement
ground
75W input impedance (note 4)
(note 2)
RS-232, 4800 baud (note 3)
power on/off
(note 5)
(note 6)
SHEET
5 of 16
REV.
39
00
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