Is this the most expensive headphone amplifier in the world?

There's no harm in aspiring to work with the very best equipment. And here we have what the manufacturer describes as "the most refined and feature rich headphone amp, DAC and compact monitor controller available".

Well at £1914 UK list price, it should be.

So you might want the M903 as a headphone amplifier. Clearly you will already be in possession of what you consider to be the best headphones in the world. I'm not going to say what I think are the best headphones because my favorite model isn't made any more and I'm still hoping to buy a spare pair on eBay. I don't want to push the price up!

Where you see a headphone socket on a piece of equipment, it is commonly put there as an afterthought. I have come across headphone sockets that didn't have enough voltage available to drive a pair of headphones to a reasonable level without distortion. I've seen headphone sockets that auto-destruct if you plug in a pair of low-impedance headphones.

So if listening on headphones is important to you, either for work or pleasure, then it makes sense to have a good headphone amplifier, and this is one area of electronics where you can often hear the difference.

But the Grace Designs M903 isn't just a headphone amplifier. It is a digital-to-analog converter and monitor controller as well.

So if you have any of the following signals to monitor, the M903 will handle them for you...

• S/PDIF
• AES3
• TOSlink
• Balanced XLR
• RCA
• USB

A rotary switch on the front panel selects the input and stepped rotary encoder controls the level. Outputs are 2 x headphone on the front, 2 x balanced jack + 2 x unbalanced RCA on the rear.

The M903 is what it is, and the designers have obviously intended it so. But in comparison with common requirements, there are things that you might consider the M903 lacks...

For example, although there are two headphone outputs, there is only one volume control. So for preference you should use two identical sets of headphones as otherwise they will almost certainly put out different levels. It does appear that the headphone, Line 1 and Line 2 output levels can be set independently.

Also although it is common to want to monitor from several different sources, this unit controls six different source formats. So if you had two sources that were balanced analog, for example, you would need to use an additional switch. This is not a criticism of the unit, just something that the potential purchaser needs to think about.

In summary, we approve of manufacturers who work at the very high end of audio. Even if the price tag is out of reach for many, this type of equipment serves as a useful reference point, and something perhaps to aspire to.