A low cost ($579) 50 watt rms (20 Vrms) self contained sound system from Japan designed for use in dry indoor classrooms only with optional Palca air speaker. This unit has not been approved through UL, UL-C, CSA, ETL, or any other safety laboratory, and may not be used with underwater speakers. Features variable-pitch cassette, transport logic controls, microphone input, 50W/8 ohm (20 Vrms) mono amplifier with switch-mode power supply, 10" internal 8 ohm speaker, line output jack, and switched/unswitched speaker output jacks. External unswitched speaker jack for use with 8 ohm Palca air speaker only.
WARNING: DO NOT USE WITH UNDERWATER SPEAKER UNDER ANY CONDITION -- AMPLIFIER AND CIRCUITRY IS NOT DESIGNED OR UL 813 CERTIFIED FOR INTERCONNECTION TO UNDERWATER LOUDSPEAKERS USED IN SWIMMING POOLS!
POWER OUTPUT TEST
Although a Lubell LL916 and its transformer box (AC203/4, AC205) could theoretically connect to this unit in a isolated test tank without any living creature in the water, and the amplifier output voltage of 20 volts would remain at 20 volts rms (AC203/4) or 16 volts rms (AC205) on the LL916 underwater speaker cable, it is still not permissible under any condition to connect an underwater speaker to this amplifier since its construction is not designed or UL 813 certified for underwater speaker pool audio applications.
- Test Tone: 1kHz sine wave
- Load: 8 ohm dummy resistor (HEI FTV-100-8-1%) or internal 8 ohm speaker
- Output voltage with no audible or visible distortion on scope: 20 volts rms
- Output voltage with slight clipping (~1% THD): 22 volts rms
- Rated Output power: 50 watts rms @ 8 ohms
VOLTAGE OUTPUT WITH AFTERMARKET TRANSFORMER (XFMR) CONNECTED
Question: What if an internal or external audio isolation and matching transformer (xfmr) was connected to the Palca PA-7550's output circuitry by a manufacturer -- what output voltage would appear on the output of the transformer and attached speaker cable if the amplifier was driven to full undistorted 50 watt (20 Vrms) rating @ 1kHz?
*WARNING: EXCEEDS WORLDWIDE 30 VOLT RMS LEGAL SAFETY LIMIT allowed on underwater speaker cables! This is a theoretical example, since the Palca PA-7550 is not UL Listed and cannot be used with an underwater speaker for swimming pool audio applications.
8 ohm to 8 ohm (1:1) xfmr: 20 volts rms in = 20 volts rms out on speaker cable 8 ohm to 16 ohm (1:2) xfmr: 20 volts rms in = 28.28 volts rms out on speaker cable 8 ohm to 32 ohm (1:4) xfmr: 20 volts rms in = 40 volts rms out on speaker cable* 8 ohm to 128 ohm (1:16) xfmr: 20 volts rms in = 80 volts rms out on speaker cable* 8 ohm to 512 ohm (1:64) xfmr: 20 volts rms in = 320 volts rms out on speaker cable* 8 ohm to 2048 ohm (1:256) xfmr: 20 volts rms in = 1280 volts rms out on speaker cable* (is this YOUR system?) 8 ohm to 4096 ohm (1:512) xfmr: 20 volts rms in = 2560 volts rms out on speaker cable* (is this YOUR system?!)
1881-9, Iriya 5-chome
Zama City, Kanagawa 228-0024 Japan
Contact: T. Katoh - http://www3.ocn.ne.jp/~palca/enquete1.htm
Valiant IMC, (d.b.a. Hamilton
1010 Sherman Ave.
Hamden, CT 06514
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