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Rear Panel 

 

 

 

 

 

Connection 

The Adastra A-series mixer-amps and S-series slaves can drive EITHER 100V line OR 4-16

Ω speakers.  

Both types of speaker should NOT be connected together to the same amplifier. 

100V Line Speakers

 

 
100V line speakers must be connected using the “100V” and “COM” screw terminals (23) on the rear panel.  
All 100V line wiring should be run with double-insulated cable rated to the max current for the system. 
 
For example, in a 250W system @ 100Vmax, 250W/100V=2.5A, so the speaker cable should be rated to 2.5A 
minimum 
 
Each speaker must be connected in a parallel chain and the total wattage for all speakers should not exceed 90% 
of the amplifier’s rated output. Please see the diagram below to show an example arrangement. 

25.

 

FM antenna connection 

Cooling fans 

26.

 

OUTPUT – 2 x RCA line output 

27.

 

LINE1 + LINE2 – 2 x RCA line inputs 

28.

 

MIC1 + MIC 2 – 2 x balanced 6.3mm jack MIC inputs 

29.

 

Phantom power switch (32V) 

 

20.

 

IEC mains inlet and integral fuse 

21.

 

Voltage selector 110/240Vac 

22.

 

Mono 6.3mm speaker jack outputs (4-16Ω only) 

23.

 

100V speaker output terminals 

24.

 

Cooling Fans 

 

Summary of Contents for A121

Page 1: ...908 S251 Slave amp 250W 952 911 User Manual Features 2 Mixer amp models and 2 Slave versions Transformer coupled output for 100V or 4 16Ω operation USB FM audio player on mixer amp models Compact 1U rack mount format Dual fan cooled High efficiency toroidal transformers 32V phantom power switchable www avsl adastra com ...

Page 2: ...cover or obstruct cooling vents or fan grilles Placement Keep out of direct sunlight and away from heat sources Keep away from damp or dusty environments When rack mounting secure firmly in place and avoid positioning heavy items directly on top of the unit Ensure adequate access to controls and connections and pay attention to cooling air flow Cleaning Use a soft cloth with a neutral detergent to...

Page 3: ...250W system 100Vmax 250W 100V 2 5A so the speaker cable should be rated to 2 5A minimum Each speaker must be connected in a parallel chain and the total wattage for all speakers should not exceed 90 of the amplifier s rated output Please see the diagram below to show an example arrangement 25 FM antenna connection Cooling fans 26 OUTPUT 2 x RCA line output 27 LINE1 LINE2 2 x RCA line inputs 28 MIC...

Page 4: ...imum impedance of the total speaker load connected to either or both of these sockets must be no lower than 4Ω The impedance is calculated using an inverse calculation as shown below _________1________ _________1________ _________1________ Impedance Speaker 1 Impedance Speaker 2 Overall Impedance therefore for 2 speakers each 8Ω impedance _1_ _1_ _1_ 8Ω 8Ω 4Ω so the overall impedance is 4Ω for bot...

Page 5: ...via the OUTPUT pair of RCA connectors Operation With all volume levels and VOX control turned down connect the amplifier to the mains supply ensure correct supply voltage using a suitable IEC lead as supplied and switch POWER on HIGH and LOW EQ controls should be initially set to the vertical 12 o clock position If microphones are being used turn up the MASTER control approximately half way and gr...

Page 6: ...cking of the other channels when MIC channels are used SPECIFICATIONS Model A121 A251 S121 S251 Power supply Switchable 110 240Vac 50 60Hz IEC Output RMS 4Ω 120W 250W 120W 250W Mic input front MIC1 combo connector XLR jack N A N A Mic inputs rear MIC1 MIC2 6 3mm jacks N A N A Line input front AUX stereo mini jack 3 5mm N A N A Line inputs rear LINE1 LINE2 RCA pairs N A N A Mic controls MIC1 MIC2 L...

Page 7: ... file types standard compressed digital audio files required Check memory device works on a PC or Mac for standard playback Output is very loud or LIMIT LED is on constantly Check level of input signal is not too high Reduce channel volume and EQ settings Reduce MASTER level until LIMIT light stops flashing Ensure Hi Z line level input s not connected via MIC1 or MIC2 Output is working but at very...

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