About ProCo Products Support Where to Buy? Contact Us


IT4A      4 Channel Isolation Transformer Unit


  • True Floating Transformer Isolation for Unbalanced Line-Level Outputs
  • 4 Channels in Single Rack Space
  • Input, Output and Loop-Thru XLR and 1/4" (6.3mm) Phone Jack Connectors
  • Ideal for Portable and Permanent Sound Systems
  • All Connectors Accessible From Front
  • High Quality Transformer-Isolated Output
  • Rugged ProCo Uni-Box Construction Provides Protection and EMI/RMI Shielding


The ProCo TradeTools IT4A Isolation Transformer Unit provides four high-quality 1:1 line-level output transformers for applications requiring the high degree of electrical isolation only transformers can provide. The primary applications for the IT4A are in sound reinforcement systems where it may be necessary to break ground loops between pieces of equipment connected with unbalanced lines. For instance, the IT4A can be used to float the unbalanced outputs of an active crossover unit that must drive long cables connected to power amplifier inputs. Transformer isolation in such situations minimizes interference from SCR lighting dimmers, radio transmitters and 60 Hz AC power wiring. Furthermore, the common-mode voltage range of a transformer makes it far more forgiving of improper connections or fault conditions than any  electronically balanced or “differential” transformerless circuit. This makes transformer-floated outputs essential for safeguarding portable sound reinforcement systems and installations.

The IT4A is fitted with standard 3-pin XLR-type connectors and 3-conductor 1/4” (6.3mm) phone jacks for LINE IN and ISO OUT, so hookup typically requires only standard cables. The use of the ProCo LOT-P transformer allows the IT4A to provide floating, low-impedance outputs with wide, flat frequency response, ultra-low distortion, and no ringing or overshoot to degrade transient response. 

The IT4A’s rugged 16–gauge steel and aluminum “Uni–box” construction enclosure is finished in a durable black texture powder coat finish with black anodized aluminum side channels. Easy–to–read control graphics are incorporated into the Lexan® front and back panel overlays. Inside, the specially designed transformers combine superb audio quality with unsurpassed noise rejection.

The IT4A can be mounted in any standard 19” (482.6mm) rack. Top quality connectors and switches provide trouble-free service even in abusive situations such as remote broadcast and recording operations. The rack-mounting design allows the user to assemble a conveniently packaged expandable isolation system that combines top quality audio performance with an economical price.



All measurements made with 0 Ω source feeding LINE IN/OUT and 600 Ω load on ISO OUT  to simulate typical "real world" source and load. LOT-P transformer configured for 1:1 operation.
0 dBv ref. = .775 volts.

Phase response and rise time measurements are essentially those of the driving amplifier used rather than those of the LOT-P transformer.

Frequency Repsonse:

20 Hz - 20 kHz, ± 0.5 dB @ 0 dBv output.
-3 dB @ approximately 85 kHz.

Total Harmonic Distortion:
<.25% 20 Hz - 20 kHz @ 0 dBv output.
<0.5% 30 Hz - 20 kHz @ +18 dBv output.
<1.0% 20 Hz - 20 kHz @ +18 dBv output.

Phase Response:
<-3 degrees @ 20 kHz (ref. 1.0 kHz).

Rise Time:
<4.5 microseconds (2.0 kHz square wave, 10%-90%).

Voltage Loss:

<2. dB @ 1.0 kHz.

Input Impedance:
>680 Ω @ 1.0 kHz.
>680 Ω @ 10kHz.
Nominal source impedance is 0 Ω.

Output Impedance:
<120 Ω @ 1.0 KHZ.
<120 Ω @ 10 kHz.
Nominal output impedance is 600 Ω.

Maximum Input Level for 1% THD:
+20 dBv @ 20 Hz.
+24 dBv @ 30 Hz.
+30 dBv @ 50 Hz.