Music First Audio Transformer Isolation Box Review

Posted on 12th December, 2022

Music First Audio Transformer Isolation Box Review

This little box of audiophile tricks beguiles James Michael Hughes…

Music First Audio

Transformer Isolation Box


Music First Audio Transformer Isolation Box Review

Cards on the table time – I have a serious long-term addiction to line transformers. Indeed, for over thirty years, I have used a Marantz DLT-1 (Digital Line Transformer) with various CD players. It acts as a barrier to harmful high-frequency noise thanks to a 'floating' ground. While this noise lies outside the audio band, it can still adversely affect the sound. A transformer also allows the audio output to be balanced, which significantly reduces the risk of picking up induced noise such as hum, radio-frequency, or electrical interference – especially with long runs of cable.

Music First Audio Transformer Isolation Box Review

With this in mind, I've been following the work of Music First Audio with interest. It has made a reputation for itself largely due to its excellent transformer-based passive preamps but makes a range of interesting products. One such example is this, a passive transformer isolation device, designed to work in the analogue domain at line level.

Balanced (XLR) and unbalanced (RCA) inputs and outputs are offered and, being a 1:1 transformer, there is no change in gain. It's intended for use with CD players, streamers, outboard phono stages, or any other source with a line-level analogue output between 2V and 4V. It can even be used between preamps and power amplifiers. The housing is made from brushed aluminium and measures 225x140x100mm. Inside it, you'll find two large hand-wound transformers – one for each channel – connected via point-to-point wiring. Two rear-mounted switches select between balanced and unbalanced inputs and grounding arrangements.

Music First Audio Transformer Isolation Box Review

The Transformer Isolation Box offers unity gain and has an extremely flat claimed frequency response from 20Hz to 20kHz. Deviations are less than 0.15dB, so it's a very natural/neutral device – and unlike my DLT-1, it does not alter the tonal balance at all. Less than 0.008% distortion is quoted at +9dB (2.8V). Transformers can suffer saturation if fed with too high a signal, and the DLT-1 was prone if pushed very hard. However, the Transformer Isolation Box is said to accept a maximum of +18dB (7.94V), so hopefully, no worries on that score!


In my system, this little box of tricks increased its clarity and definition. Subjectively, a good transformer has the effect of making individual instruments and voices seem that bit cleaner and better separated, and that's what happened here. Along with an enhanced sense of space and depth, music sounded more solid and focused and less diffuse. There was more body and greater substance, while backing vocals and accompanying instruments became easier to follow and less inclined to sound vague and out of focus.

Music First Audio Transformer Isolation Box Review

I found its sound to be more articulate and subtly nuanced, with a greater sense of texture and richer tonality. There was less high-frequency edge too. My best albums sounded better than before, but so did albums that previously seemed disappointing.

While results improve with balanced connections, the benefits are there with unbalanced too. I mostly used my old DLT-1 unbalanced, but were the subjective impressions of increased clarity and focus down to the Transformer Isolation Box adding a magic sauce of its own? I'd say not.

Music First Audio Transformer Isolation Box Review

Such qualities are already there in the recording, albeit masked by hash and high-frequency noise. The transformer simply allows you to hear more fine detail. As a result, all kinds of music, and any recording, whether old or new, seem to benefit.

You know that lovely unforced clarity and dimensionality you hear from the best jazz recordings of the late nineteen fifties and early sixties? At best, it's a bit like that. Back then, the mixing consoles in recording studios were full of tubes and fully balanced with transformer coupling at every stage.

Music First Audio Transformer Isolation Box Review

I tried After Hours - a 1989 jazz CD on Telarc featuring Andre Previn on piano, with guitarist Joe Pass and bassist Ray Brown. The digital recording is smooth and clean but tonally a wee bit thick and suffused. The sound is natural and truthful but slightly lacking in sparkle. Using a Shanling T300 CD player via its unbalanced outputs directly into the amp, Ray Brown's bass was weighty but a tad boomy and unclear. The overall balance was dark and lacking in brilliance and transparency. If my amp had a treble control, I'd have added some lift.

Music First Audio Transformer Isolation Box Review

Using the T300's balanced XLR outputs into the Transformer Isolation Box and clarity and separation improved noticeably between the three instruments. The bottom end was full but less muddy. The extra focus made everything clearer and easier to follow. Overall, I heard a marked improvement in clarity and coherence with no adverse effects elsewhere. After a while, one ceases to notice the transformer altogether, but disconnect it, and the sound will lose some of its solidity and effortless clarity.


An interesting little box of tricks this, one that may have great appeal for some audiophiles. It's a hand-made item of the highest quality and good value, considering the sonic improvements it can bring. And if you don't want balanced, Music First has a smaller, more affordable unbalanced version to tempt you.

Visit Music First Audio for more information


    James Michael Hughes's avatar

    James Michael Hughes

    An avid audiophile for many decades, Jimmy has been writing about hi-fi since 1980 in a host of British magazines, from What Hi-Fi to Hi-Fi Choice. Based in London, England, he’s one of the UK’s most prolific record and CD collectors – no streaming service can yet match his amazing music collection!

    Posted in:Hi-Fi Accessories Isolation
    Tags: music first audio  g point audio 


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