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Jensen Transformers SP-2SX Stereo Speaker to Line Audio Converter


Made in the USA
Jensen Transformers SP-2SX ISO-MAX Stereo Speaker to Line converter

Jensen Transformers SP-2SX ISO-MAX Stereo Speaker to Line Audio converter

Jensen Transformers
SP-2SX Stereo Speaker to Line Audio converter is a unique product that provides an elegant way to convert speaker-level audio to line-level audio.

Handy DIP switches make it easy to select input power ranges from 25 watts to 750 watts, making the SP-2SX compatible with a wide range of audio amplifiers.

This two channel "speaker" level to unbalanced "pro" level converter and ground isolator is designed to accept, in four switch selectable ranges, speaker drive voltages of 14 Vrms, 25 Vrms, 44 Vrms, or 77 Vrms. These voltages will be developed at full output of power amplifiers rated at 24 W, 75 W, 240 W, or 750 W, respectively, into 8 Ω loads or rated at 48 W, 150 W, 480 W, or 1,500 W respectively into 4 Ω loads. Input ranges also include 25 V and 70 V lines used in commercial sound systems covering large areas.

Since the speaker inputs are ungrounded, they are especially useful with power amplifiers where both outputs are actively driven and cannot be grounded (these are often referred to as "bridge-mode" or "floating" outputs). The speaker inputs represent a trivial additional load for the driving power amplifiers - maximum input power is 0.08 W, 0.4 W, 1.5 W, and 5.4 W respectively in the four input ranges. In addition, all models provide inherent low-pass filtering to remove ultra-sonic switching artifacts from the outputs of "digital" or "class D" power amplifiers. These artifacts can cause subtle distortions in downstream amplifiers [Deane Jensen and Gary Sokolich, "Spectral Contamination Measurement," AES 85th Convention Preprint 2725,1988}.

The standard versions have dual, or "stereo," outputs that correspond independently to each of the speaker input signals. The SP-2SX output signals will reach 6.9 Vrms (+19 dBu), a level that represents 15 dB of "headroom" in professional audio systems where the nominal or "reference level" signal is standardized at +4 dBu or 1.23 Vrms. "Mono" output versions, denoted by a " - M " suffix in the model number, have a single output that represents the sum of the two speaker input signals. These would be used, for example, when the inputs are Left and Right channels and the output, L + R, drives a single sub-woofer.

 This audiophile-grade Stereo Speaker to Line converter is a completely passive device, so there is no chance of raising the noise floor of your audio system as might be the case with an active device.  The configuration pictured here has Neutrik SpeakON inputs and XLR outputs, although terminal strips and RCA connectors are also available as SC-2NR.  Also available in a single-channel mono version as SP-1SX below.  When built this way, and there will be only one transformer inside.  The outside appearance is identical except that one of the channels will have blank covers instead of jacks.

The SP-2SX is an ideal solution for deriving sub-woofer inputs in pure stereo audio systems that do not normally provide subwoofer outputs.  Channel-summing (mono output) models are available as well, opening a whole new range of possibilities.

The SP-2SXis housed in a sturdy metal enclosure, measuring 7.0" W x 3.5" D x 1.6" H., including the flanges.  The flanges have mounting holes, which are handy for permanent installations.

At this point we typically like to remind customers not to confuse the SP-2SX with similar (but inferior) products from other manufacturers, but in this case, we know of no similar products, so even more than usual, the SP-2SX really is in a class of its own.

With inferior products coming from all over the world, we think it is a genuine treasure to find a company like Jensen Transformers, actually designing and manufacturing some of the finest products in the world, right here in the USA, and we are proud to be able to offer their products.  The SP-2SX is made in the USA, is backed by the manufacturer's comprehensive one-year warranty, and has a remarkable 20-year warranty on the transformer device itself.

Please check out our Jensen Transformers Application Guide for information on the other members of the ISO-MAX family.

Jensen Transformers' Description


2-Chan [stereo] 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.


  • Flat response from 5 Hz to 20 kHz and low phase distortion for improved transients and imaging
  • Transformer-isolated design eliminates issues with "Bridged" and "Class D" power amp outputs
  • DIP-switch selected ranges for power amps rated at 25 W, 75 W, 250 W, or 750 W into 8 Q
  • Input ranges include 25 V and 70 V line applications
  • Entirely passive - requires no power supply
  • Available as shown here with professional (XLR) output model SP-2SX with Neutrik SpeakON® input connections, or as consumer (RCA) output model SC-2NR with screw-strip input connections.
  • Channel-summing (mono output) versions of both available [available by special order only] - ideal for derived sub-woofer input
Jensen Transformers SP-2SX ISO-MAX Stereo Speaker to Line converter, front-right view

Another angle.

Jensen Transformers SP-2SX ISO-MAX Stereo Speaker to Line converter Connection Exampleshowing two amps in series

This connection example illustrates how the SP-2SX might be used to connect two amplifiers in series.  The audio system can be expanded to feed extra power to additional to 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.

Jensen Transformers SP-2SX ISO-MAX Stereo Speaker to Line Converter Connection Example showing powered monitors

As shown in this illustration, 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.

Jensen Transformers SP-2SX ISO-MAX Stereo Speaker to Line converter Data Sheet, PDF

SP-2SX Data Sheet and Specifications.  PDF format.

Jensen Transformers SP-2SX ISO-MAX Stereo Speaker to Line converter Manual, PDF

This is the User Manual, in PDF format.

Purchase Information
Product Description SKU MSRP Your Price Quantity
ISO-MAX Stereo Speaker to Line Converter
(as shown on this page)
SP-2SX $494.99 $449.99
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Special Order Configurations and Pricing
ISO-MAX Product Description SKU MSRP Your Price Quantity
ISO-MAX Mono Speaker to Line Converter, Single-Channel Version
(Special Order)
SP-1SX $384.99 $349.99
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