ZXY-DU18 Permalloy Audio Isolation Transformer, 1+1:1+1 and 1+1:3.5+3.5, 10 Hz to 100 kHz, DIP

1. Product Name

The ZXY-DU18 is a wideband audio isolation transformer packaged in a sealed permalloy case with DIP through-hole mounting. Eight pins are arranged in two rows of four with 5.0 mm pitch, measuring 38.5 mm × 24.5 mm with a height of 22.0 mm. Two winding ratios are available: 1+1:1+1 and 1+1:3.5+3.5, which differ in DC resistance and turns ratio while sharing all other parameters.

One case, two windings. Both ratio versions share the same external dimensions, so a single PCB layout can accommodate either variant by populating the desired one. The difference lies in the windings and copper wire: the 1+1:1+1 version has 56+73 Ω on the primary and 65+76 Ω on the secondary; the 1+1:3.5+3.5 version has 35+35 Ω and 360+360 Ω respectively.

2. Construction and Materials

Case. A sealed permalloy can, designated E1 (case) and E2 (core) in the datasheet. The permalloy can serves as both housing and magnetic shield: it closes the magnetic circuit against external field interference while protecting the internal windings from mechanical contact damage. Because the can is sealed rather than an open frame, the device appears as a solid metal block on the PCB and also shields neighboring components.

Pins. Eight through-hole pins in two rows of four at each end of the can, with 5.0 mm pitch. Through-hole rather than SMD mounting is chosen at this size for two reasons: a 22.0 mm tall can mounted on cable-side equipment imposes bending loads on the terminals that gull-wing pins cannot withstand, and the pin pitch is wide enough that through-hole layout requires no special pad design.

Windings. Each side has two winding segments, which is what the 1+1 designation means: the primary and secondary are each split in half and connected at pin pairs, so the resistance between pins 1-4 and pins 5-8 is specified as the sum of two segments. In the 1+1:1+1 version, the two primary half-windings are not equal at 56 Ω and 73 Ω, while the 1+1:3.5+3.5 version uses equal half-windings of 35 Ω and 360 Ω.

The chamfered edge visible on the can is the seam where the two case halves join and seal. The label indicates the winding ratio of the device, allowing quick identification of soldered units in a tray without measurement.

3. Features

Wide bandwidth, 10 Hz to 100 kHz. Response stays within ±0.5 dB across four decades, measured at 1 kHz −6 dB reference with 1% THD. A single device covers the audio band and extends into ultrasonic content.

Two winding ratios. The same case and core can be wound as 1+1:1+1 for direct isolation or 1+1:3.5+3.5 for signal step-up or impedance matching, giving two circuit applications from one PCB footprint.

+13 dBu at 50 Hz. The maximum 50 Hz input level is the headroom specification: this is the level the core can handle at the low end of the band before response begins to roll off, making the device suitable for line-level signals rather than microphone levels only.

Sealed permalloy case. The windings sit in a sealed can rather than an open frame, so the magnetic circuit is closed against external fields and the coil is protected from mechanical contact and the PCB environment.

DIP through-hole, 8 pins. Two rows of four pins with 5.0 mm pitch, and the through-hole layout fits without custom pads.

Isolation performance verified by test. Withstand voltage between windings is 1,250 V / 1 mA / 60 s, tested on every unit rather than stated as a type test only.

4. Advantages

Eliminates hum at the source. This transformer breaks the ground connection in the signal path rather than filtering the result. When a ground loop injects AC hum, removing the loop is the fundamental fix; attenuating the hum afterward is a compromise.

Protects front-end equipment. Because the two sides are galvanically isolated, a fault or DC offset on one side cannot conduct into the output stage of the other side's equipment, which is what the documentation means by "preventing front-end equipment from burning out."

Benefits both balanced and unbalanced. The sealed can reduces winding pickup of nearby magnetic fields, which matters especially for unbalanced transmission where there is no common-mode rejection as a fallback.

Flat where it counts. ±0.5 dB from 10 Hz to 100 kHz means this device will not be the factor limiting system bandwidth, leaving design margin for converters and amplifiers.

One package, two ratios. The 1+1:1+1 and 1+1:3.5+3.5 versions share the same outline, so a PCB can be laid out once and assembled with either version.

A through-hole package that survives rework. The sealed can with 5.0 mm pin pitch handles the mechanical stress of cable-side connections better than small SMD packages, which is why the line-level device uses DIP packaging.

5. Applications

Hi-Fi and audiophile systems. Used between source and preamplifier, or between preamplifier and power amplifier, where ground loops are heard as hum and the signal must cross the isolation barrier intact.

Home theater and multichannel systems. Each channel can be isolated independently, preventing a grounded source from coupling hum into other channels in the rack.

Automotive audio. Used between head unit and amplifier, which ground at different points on the chassis.

Mixing console outputs. Used on console isolation outputs so a stage interface box or recorder can be connected without tying its ground to the console's ground.

Multichannel isolated output circuits. Used where multiple outputs leave the same chassis and must remain isolated from one another.

6. Specifications

The following data is the specification of the ZXY-DU18, reproduced as declared.

6.1 Overview

6.2 Electrical Characteristics

6.3 DC Resistance by Version

6.4 Mechanical Parameters

6.5 Quality and Testing

7. Ordering Information

This product is ordered as model ZXY-DU18 with the winding specification stated. The case, core, pinout, and outline are common specifications; the turns ratio and copper wire configuration are not, so an order without the specification cannot be checked against a single acceptance table. Standard models are factory direct with in-stock delivery, and custom designs are available on request.

Brand/Manufacturer: ZXY, Shenzhen Zhi Xiang Yuan Electronics Co., Ltd. http://www.zxycoil.com