Crown Audio IQ-USM 810 - Manual (Page 22)

©2000 Crown International, Inc.
IQ-USM 810 Service Manual
4-2 Maintenance
130447-1 Rev. A
4.4 IQ Message String Syntax
4.4.1 Host to Device Messages
The following syntax is used for host to device mes-
sages:
Send: XX XX XX XX XX; Description
XX:
A byte of the message explicitly given in hexadeci-
mal.
XX:
A byte of the message as defined by the two-letter
codes in Section 4.2.
Description:
A short phrase to indicate the function of
the message string. The description is added for refer-
ence only. It is not sent as part of the Ucode message.
4.4.2 Device to Host Messages
The following syntax is used for device to host mes-
sages.
Return String: XX XX XX XX XX
XX:
A byte of the message explicitly given in hexadeci-
mal.
XX:
A byte of the message as defined by the two-letter
codes in Section 4.2.
XX:
A byte of the returned message that requires range
testing in accordance to the associated test.
4.5 Standard Initial Conditions
The following tests assume this setup unless stated oth-
erwise.
Unit under test built and programmed as documented,
less top cover and labels.
Preset 32 loaded
Inputs set to line mode.
Input potentiometers set to 0 dB.
Unit under test powered by 120VAC
Unit under test connected to test computer via the
RS232 connector with constant IQ communication at
115.2 K baud.
Output Impedance of Audio Sine-wave Source: 50 W
balanced.
Audio Output Load:
≥ 10 kW balanced.
4.6 Test Procedures
4.6.1 LOAD PRESET 32
Note: Preset 32 is the factory default test preset. This preset
sets the audio paths straight through (no gain, filters, or pro-
cessing) to their respective AUX outputs. Main outputs A and
B are driven from inputs 1 and 2 respectively.
Procedure:
Send the select preset 32 command:
Send: DA DT CT B2 7F 09 20 CS; Select preset 32
Send the load preset command:
Send: DA DT CT B4 7F 09 01 CS; Load preset
Note: The load preset command must be sent within approxi-
mately 2 seconds of the select preset command.
Note: Preset 32 may also be selected using the front panel
controls.
1) Use the “ ∧ ” and “ ∨ ” buttons to select preset 32. (Dis-
play shows P32.)
2) Press “SEL” button.
4.6.2 OUTPUT NOISE
Spec:
LINE mode: ≤ –75 dBu and ≥ –80 dBu, 22 Hz to
22 kHz bandwidth.
Note: The test and printed specifications do not match. The
printed specifications are for an "A" weighted 20-Hz to 22-kHz
bandwidth. Production tests do not use "A" weighted filtering.
Initial Conditions:
Inputs terminated at ≤ 50 W bal-
anced. Bandwidth = 22 Hz to 22 kHz.
Procedure:
Verify each main and AUX output meets
spec.
4.6.3 FREQUENCY RESPONSE
Spec:
+0.1, –0.6 dB from 20 Hz to 20 kHz.
Initial Conditions:
Normalized to a reference of a
1 kHz, 0 dBu signal.
Procedure:
Verify each main and AUX output meets spec with one
of the following methods:
A 10+ point, logarithmically spaced, sweep.
Testing at these frequencies: 20 Hz, 100 Hz, 500 Hz
1 kHz, 5 Hz, 10 kHz, and 20 kHz.
4.6.4 HARMONIC DISTORTION
Spec:
< 0.030 % and > 0.001 % THD+N, with a 22 Hz
to 22 kHz bandwidth.
Initial Conditions:
Input signal: 1 kHz, 0 dBu.
Procedure:
Verify each main and AUX output meets
spec.
4.6.5 COMMON MODE REJECTION
Spec:
>40 dB at 60 Hz in line mode, 22 Hz to 22 kHz
bandwidth.
Procedure:
Input a 60 Hz +18 dBu balanced signal.
Monitor the associated AUX output with a 22 Hz to
22 kHz bandwidth and set the reference.
Change the input to common mode (same frequency
and amplitude)
Verify the associated AUX output is attenuated at least
40 dB below reference with a 22 Hz to 22 kHz band-
width.