IsoSmart 1 Channel Transformer Audio Isolator – Balanced to Unbalanced with Ground Lift

IsoSmart 1 Channel Transformer Audio Isolator – Balanced/Unbalanced with Ground Lift

The IsoSmart is a passive, single-channel audio isolator built around the Neutrik NTE1 1:1 transformer. It provides electrical isolation between the input and output signal paths and a switchable ground lift to help resolve ground-loop hum.

Hand wired in the UK with Neutrik connectors and Van Damme internal wiring, it supports balanced connections and can convert a suitable unbalanced source to an isolated balanced output.

This is an audio isolator, not a conventional instrument DI. It does not deliberately reduce instrument or line signals to microphone level and is not designed to provide a high-impedance input for passive guitar or bass pickups.

Connections and Wiring

The input-side XLR and jack connections are wired in parallel. The output-side XLR and jack connections are also wired in parallel, with the Neutrik NTE1 transformer separating the two sides.

• XLR pin 2 / jack tip: hot.

• XLR pin 3 / jack ring: cold.

• XLR pin 1 / jack sleeve: screen/ground.

• Ground lift switch: disconnects the ground connection between input and output.

• Metal enclosure: bonded to output XLR pin 1.

• Fully passive operation: no battery or external power required.

With a suitable low-impedance source connected to the input-side combo socket, the separate input jack can provide a direct parallel thru connection. This thru is not buffered or isolated; the connected equipment contributes to the load seen by the source.

Why the Neutrik NTE1?

The NTE1 is a compact, professional audio transformer intended for general-purpose audio isolation, splitting and XLR inline applications.

Its 1:1 turns ratio transfers the signal without deliberate voltage step-down. Actual level and frequency response depend on the source impedance, destination impedance and signal level.

Typical Applications

• Helping resolve ground-loop hum between compatible audio devices.

• Providing an isolated balanced output from a suitable unbalanced source.

• Isolating low-impedance audio signals within the transformer’s operating limits.

• Providing a parallel connection alongside an isolated output.

Signal Level and Compatibility

The NTE1 has limited low-frequency headroom. Neutrik specifies a maximum input level of −3 dBu at 50 Hz for 1% total harmonic distortion, under its stated source/load test conditions.

Strong signals, particularly those containing substantial bass, may cause transformer saturation and audible distortion. This unit should therefore not be treated as a high-headroom professional line-level isolator.

For direct connection from a passive guitar or bass to a front-of-house microphone input, use a dedicated instrument DI with a suitable input impedance, mic-level output and amp thru connection.

Technical Specifications

The source/load figures above describe transformer operating conditions. They do not mean the unit has a fixed 200 Ω input resistance.

Frequently Asked Questions

Is this a DI box?
It provides transformer isolation and can balance a suitable unbalanced signal, but it is not a conventional instrument DI. It does not provide deliberate step-down to mic level or a dedicated high-impedance instrument input.

Can I connect a passive guitar or bass directly?
This is not its intended application. The transformer and destination input can load passive pickups, affecting level and tone. Use a dedicated instrument DI for this purpose.

Can I connect an amp and an isolated output simultaneously?
The parallel input connections allow a direct thru alongside the isolated output. Suitability depends on the source’s ability to drive the combined load. The thru connection is not isolated.

Will it remove all noise?
It can help with hum caused by ground loops. It will not remove noise already present in the audio signal, such as hiss, distortion or pickup interference.

Does it require power?
No. It operates passively without batteries or an external power supply.