GAI-Tronics 700 Series 120 V AC Page/Party Systems - Manual (Page 2)

Pub. 42004-139D
GAI-Tronics 700 Series Page/Party
®
Systems Page: 2 of 10
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Installation Procedure
Step 1 — Electrical Noise Considerations
When planning your system, consider the following suggestions to avoid electrical noise caused by slip
rings and silicon control rectifier (SCR) power supplies.
Slip Rings -
Use a radio frequency (RF) alternative and avoid using slip rings as audio conductors. Slip
rings are a source of electrical noise and are not reliable.
SCR Power Supplies
- If the Page/Party ® system will be installed in areas where SCR power supplies
are used to power motors or other heavy equipment, consider using one or all of the following four
recommendations to reduce electrical noise.
1. Separation—Locate the Page/Party
®
system cables as far as possible from the SCR power supply
input or output cables. Electrical coupling between cables is reduced by the square of the distance
between the cables.
2. Shielding—Use shielded (armored) system cables if the cable must be run in the same bundle or cable
tray with the SCR power supply cables. Shielded cables reduce capacitive coupling between SCR
power supply cables and Page/Party
® audio cables.
3. Isolation—Two methods of power source isolation can be used to avoid electrical noise:
A. Use a low capacitance (primary to secondary) isolation transformer between the Page/Party ® system
and the ac supply to the SCRs. This electrically isolates the Page/Party ® system’s ac power from the
noise generated by the SCR on the ac power feed. Also use an isolation transformer to isolate the
Page/Party
® ac power from an ungrounded ac power source. Note: The neutral side of the
transformer output must be grounded in all instances.
The size of the isolation transformer should be based on the number of amplifiers used in the system.
If ten or less amplifiers are used in the system, a 500 VA transformer is sufficient. If 11 to 20
amplifiers are used in the system, select a 1000 VA transformer. For systems with more than 20
amplifiers, the transformer should be sized to accommodate a load of 50 VA per amplifier.
B. A battery powered 24 V Page/Party ® system can be used as an alternative to the standard 120 V ac
system. In this instance, the battery/battery charger provides isolation from the SCR noise on ac
power systems. Cable shielding and separation as mentioned above still apply.
N OTE : Avoid battery chargers that utilize SCRs in their design.