EI2401-1:2 Audio Isolation Transformer - 1:2 Step-Up, +6 dB Gain, 20 Hz-20 kHz, EI Silicon Steel Laminations, 3+3 DIP Through-Hole Pins, Passive Ground Loop Isolator

1. Product Name

EI2401-1:2 audio isolation transformer, 1:2 step-up, approximately +6 dB voltage gain, passive galvanic isolation, 20 Hz - 20 kHz, 3+3 through-hole DIP package.

Overview. The EI2401-1:2 is a passive 1:2 step-up audio isolation transformer designed to break ground loops and eliminate AC hum, buzz, and radio-frequency interference in professional audio signal chains. Its 1:2 turns ratio provides approximately +6 dB of voltage gain while galvanically isolating the source from the load, allowing devices referenced to different ground potentials to be connected safely without ground loop currents.

Because the device transfers signals purely through magnetic coupling, it requires no external power supply, no batteries, and no active circuitry. It simply passes audio cleanly and consistently from the primary winding to the secondary winding. The product is wound on an EI silicon steel laminated core, featuring an electrostatic shield winding and high-purity copper wire insulated with flame-retardant yellow polyester film tape, delivering excellent common-mode rejection across the 20 Hz - 20 kHz range. It is suitable for line-level studio interconnects, mixing console and preamplifier inputs, powered monitor feeds, and broadcast or public address distribution.

2. Key Features

1:2 step-up turns ratio. Approximately +6 dB voltage gain; the transformer boosts signal level while providing isolation.

Galvanic isolation. Breaks ground loops and eliminates associated AC hum and buzz.

Excellent common-mode rejection. Suppresses RF interference and AC hum induced on both signal lines, not just a single line.

20 Hz - 20 kHz response. Covers the full audio band and can be placed anywhere in a line-level chain.

EI silicon steel laminated core. Low core loss with stable performance across the entire frequency range.

Electrostatic shield winding. A shield layer between primary and secondary improves high-frequency noise rejection.

Flame-retardant polyester film insulation. Yellow polyester film tape wound over high-purity copper windings reduces heat and losses.

Fully passive design. No power supply, no batteries, no active circuits: zero power consumption and continuous noise-free operation.

3+3 through-hole DIP pins. Three primary pins and three secondary pins for standard PCB mounting, with center taps on each winding.

The electrostatic shield is the key detail that sets this product apart from ordinary audio transformers. It is a conductive layer placed between the primary and secondary that intercepts capacitive-coupled interference before it reaches the secondary—this is the path through which high-frequency stray signals from digital equipment would otherwise pass. The magnetic circuit is unaffected, so audio still couples at full bandwidth, while RF paths are shorted to the shield.

3. Technical Specifications

4. Pin Configuration (3+3 DIP)

Both windings are brought out with center taps, so the device can be used either as a standard 1:2 transformer connecting start to finish, or as two half-windings per side when the center pin is used. Whether the windings are connected in series or in parallel depends on how the three pins are wired on the circuit board; the transformer itself does not change. Pin 1 must be identified before assembly, as the phase of the secondary winding relative to the primary depends on which end is designated as the start.

5. Typical Applications

Professional audio interfaces. Provides signal isolation and balanced audio transmission for high-quality interfaces.

Studio mixing consoles and preamplifiers. Achieves isolation and noise suppression in consoles and microphone preamplifiers.

Powered studio monitors. Delivers clean, isolated audio for accurate and reliable studio monitoring.

Broadcast and public address systems. Provides balanced signal transmission and isolation for professional audio installations.

In rack equipment, a common fault occurs when two devices are connected to different mains circuits, each with its own protective earth. The cable shield connects the two grounds together, and the potential difference between them causes current to flow through the shield—this is the source of the hum. Inserting a transformer at this boundary breaks the closed loop while keeping the balanced or unbalanced connection intact. The step-up ratio is the second advantage this device offers: when consumer-level outputs need to drive professional-level inputs, the +6 dB of passive gain helps close part of the gap without adding active circuitry.

6. Quality & Compliance

Every unit is tested for audio signal isolation and inductance before leaving the factory, so non-isolating units are never shipped. The construction is robust and built to withstand elevated operating temperatures, with windings sealed in flame-retardant polyester film rather than left exposed.

This product is CE electrical safety certified, RoHS compliant, lead-free in construction, and manufactured under an ISO 9001:2015 quality management system.

7. Ordering Information

The EI2401-1:2 is supplied as a PCB through-hole component, suitable for OEM, studio, and audio project use. Custom turns ratios, center-tap configurations, and lead-free finishes are available upon request.

Please provide the target impedance, signal level, and application scenario so the most suitable model can be confirmed based on the design. For direct replacements, please provide the existing part number and the winding configuration used (start-to-finish connection or with center tap).