Grimm Audio CC1, Руководство пользователя

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The “lock” LED on the rear indicates the AES3 receiver status:
1. Off: No AES3 signal present.
2. On: AES3 signal present and found to be synchronous with the CC1.
3. Blinking: An AES3 signal is present but it is out of sync with the CC1.
Impedance
The “impedance” DIP switches on the rear allow each individual output to be set
to low-impedance (25 ohms typical) or characteristic (75 ohms) impedance. The
switches are factory set to 75 ohms. Should the receiving device have problems
recognising the word sync signal, you might try the low impedance setting.
Word sync connections are usually 5V square waves transmitted over 75 ohm (vid-
eo) coax cables. Although the word clock frequency itself is relatively low, the tran-
sitions are steep. Taken as a whole, word sync is a wideband signal, necessitating
characteristic termination at least at one end of the cable. Single-terminated lines
are usually terminated on the source end. Better still is series termination on the
transmit end and parallel termination on the receiving end. This minimises reflec-
tions even when the cable impedance is not exact. Double termination like this pro-
duces a 6dB loss, resulting in a 2.5V signal. All Grimm Audio products are designed
to work in this manner.
There is no standard defining word sync connections. As a result, impementations
vary across makes. Outputs may be series terminated or low impedance, DC or AC
coupled. Inputs may be parallel terminated or high impedance. This yields 8 permu-
tations, all of them encountered in the wild. The CC1 input will correctly interpret
all variants without user manipulation, but the impedance of the CC1’s outputs
may need to be set low in some cases. A parallel-terminated input expecting a 4V
input signal will only work with the CC1’s output impedance set low. A fair number
of products were found to have parallel terminated input but stop working around
2.5V which is why the CC1 puts out a slightly higher-than-normal voltage in order to
allow correct operation in the factory preset mode. Nevertheless, some equipment
will only respond correctly when the output impedance DIP switch is set to low.
Phase
Channels 11 to 14 can be polarity-reversed (180º phase shift) to cater for equip-
ment that uses the falling edge to synchronise on instead of the rising edge. Should
you encounter operational problems with equipment, even though it is locked,
check the manual for any mention of clock phase and try the 180º switch setting.