SP-2SX 2-Chan speaker to line level converter

The Iso-Max SP-2SX is a two channel speaker to line level converter that lets you convert the high power signal from an audio amplifier output to a +4 dB (nominal) balanced line level for further processing or signal distribution.

  • Converts any speaker or amplifier output to line level
  • Delivers exceptionally low distortion down to 20 Hz
  • Ruler flat frequency response from 5 Hz to 20 kHz
  • Plug and play easy to use, no power required

The design begins with a rugged flanged enclosure that comes standard with gold plated XLRs and a removable screw-down barrier strip for easy installation in NEMA enclosures and 19” racks. Plug and play easy to use, this passive interface does not require any power to work. Inside are two Jensen high performance transformers that isolate the output to eliminate hum and buzz caused by ground loops while they eliminate issues with ‘bridged’ and ‘class D‘ power amp outputs. A series of input pad DIP switches let you select the range to suit various power amps for at 25 W, 75 W, 250 W, or 750 W max in to 8 Ω. All types of amplifiers may be used including 25 V and 70 V line driver types.

Once connected, the SP-2SX is able to withstand signal levels to +19 dBu at 20 Hz without introducing distortion, phase shift or artifact of any kind. This opens the door to expand existing systems without having to run additional line level signals throughout a facility.

Other versions available are the SC-2NR speaker level to consumer audio level and the SS-2NR speaker level to subwoofer audio level.

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Applications

Using two amps in series

Some installations require expanding the audio system with more power to feed additional speakers to an adjacent room that may already be wired up. Use the SP-2SX to tap the signal from an existing amplifier to feed a second system.

Add powered monitors on stage

The SP-2SX lets you take the speaker output from a wedge monitor and feed it to a set of powered monitors for the drummer or side fills. Simply connect into the SP-2SX, set the power level and it will deliver a distortion-free line level signal.

Specifications

+19 dBu on plots = max rated input voltage, Source = <100 Ω, Load = 22 kΩ unless noted

PARAMETER CONDITIONS MINIMUM TYPICAL MAXIMUM
Input impedance, Zi 1 kHz, 10 V, varies with power selection 1.1 kΩ   2.3 kΩ
Voltage gain 1 kHz, input voltage = rated maximum ( see below ) 17.5 dBu +18 dBu +18.5 dBu
Magnitude response, ref 1 kHz 20 Hz, 10 V -0.15 dB -0.03 dB ±0.0 dB
Magnitude response, ref 1 kHz 20 kHz, 10 V -0.35 dB -0.20 dB ±0.0 dB
Deviation from linear phase (DLP) 20 Hz to 20 kHz, 10 V   +1.4/-0° ±2.0°
Distortion (THD) 1 kHz, 15 db below rated input voltage   <0.001%  
Distortion (THD) 20 Hz, 15 db below rated input voltage   0.04% 0.10%
Distortion (THD) 20 Hz, maximum rated input voltage   0.8% 1.5%
Common-mode rejection ratio (CMRR) 60 Hz   115 dB  
Common-mode rejection ratio (CMRR) 3 kHz 80 dB 90 dB  
Output impedance, Zo 1 kHz   5.3 kΩ  
8 Ω Amplifier power rating / rated maximum input votlage S1 off, S2 off, S3 off     25 W, 14 V
8 Ω Amplifier power rating / rated maximum input votlage S1 on, S2 off, S3 off     75 W, 25 V
8 Ω Amplifier power rating / rated maximum input votlage S1 on, S2 on, S3 off     250 W, 44 V
8 Ω Amplifier power rating / rated maximum input votlage S1 on, S2 on, S3 on     750 W, 77V
8 Ω Amplifier power rating / rated maximum input votlage Any switch settings, without damage     77 V
Optimal cable length input      
Optimal cable length output      
Temperature range operation or storage 0°C   70°C
Breakdown voltage* speaker input to line output ground or chassis, 60 Hz, 1 minute test duration 250 V RMS    

Graphs

Phase Distortion
Frequency Response
THD vs Level at Low Frequencies
THD vs Frequency at Various Levels

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