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To round out introductions, the front switch turns the unit on when flicked up and confirms whether the battery is fit for operation when pushed down. A small red light confirms that the unit is powered up but it is very easy to forget to turn off the BPS afterwards. I guarantee that you will come back to your system more than once to find a dead battery - unless you are used to turning off all your gear when not in use. I am not.

The back panel has high-quality RCAs; a tiny ground post which wouldn’t accommodate the normal-sized fork on my Acoustic Solid tonearm cable; and a power input. What does a power input do on a battery-operated device? The primary recommended use is a compatible wall wart. Have the unit plugged in when not in use to keep the circuits charged without depleting the battery. With no appropriate transformer on hand, I did not test this. Neither did I try powering the Nagra with an external battery like a Red Wine Audio Black Lightning box to completely transcend 9V disposable battery inconvenience.

I would really like to see Nagra offer a rechargeable battery option in the future, either internal like Ray Samuels did in the fabulously easy-to-use F117; or even external in a matching enclosure. Who'd want to see a pedestrian black shoe-box battery pack sit next on a shelf to the slim silvery BPS?

Overall the Nagra is superbly built and despite diminutive dimensions offers all vital adjustment options to be bona fide high end. Ease of use could be improved a bit. Others have done it and no doubt Nagra can too. Their tape recorders are vaunted not only for sonics but also for how well thought-out their use is in the field. In the end, when it comes to high-end audio, sound remains the primary factor and rightly so. As hinted at already, the Nagra BPS performs at a level of musicality and quality that should make the brand proud. The BPS sound is firmly anchored in the house tradition – warm and rich yet excellently resolved and dynamic. I had concerns on dynamics from a single 9V battery power supply but should not have. The BPS delivers huge swings while preserving the bristling life of micro dynamics thanks to absolutely quiet operation and superb transparency.

When I speak of warmth, I really refer to two main aspects of sonic character. The first is a slightly emphasized upper bass and lower midrange; the second a propensity for slightly rounding over ransients. Warmth can also derive from foreshortened treble or distorted bass but not here. The BPS delivers a very large helping of tube impressions without their limitations of higher noise and distortion. As can be expected from Nagra, tonal intensity is simply exceptional and here fully supported by transparency which beautifully reveals texture and micro detail. String instruments have  richer wooden body, clarinets are more reed than wind, the blowing noise of flutes becomes more obvious – in short all the little details that make up the unique harmonic structure of an instrument are fully revealed. Because of the slightly softened leading edges, the Nagra is not as zippy on pinched strings of medieval guitars as an Esoteric E03 or  Ray Samuel F117 but neither of those reach the Nagra’s level of tonal complexity.

Speaking of comparisons, since I have reviewed quite a lineup of phono preamplifiers over the past year, how does the BPS stack up? Against the truly unique and twice-priced Esoteric E03, the Nagra is not as resolved. The E03 reveals small details at stage back that the Nagra misses. The E03 also goes deeper and tighter in the bass and transients are much faster and more explosive. On the other hand, the Nagra is more forgiving of poor records, making them enjoyable when the E03 only reveals their flaws (especially obvious on how different ticks and scratches appear through both machines). The BPS is also far quieter and goes further in showcasing instrumental tonal hues. The Nagra’s slightly enhanced upper bass is a double-edged sword, great with gear that could stand some enrichment in that range like the JAS Bravo 3.1 monoblocks and clearly overkill for gear which does not (the Genesis GR360 amplifier). That however was easily addressed with a leaner interconnect like the pure silver Slinkylinks. Those removed any hint of overweight when the Genesis was in the system. With both the Yamamoto A08s and FirstWatt F5 amplifiers, I liked the slight weight gain of the Nagra. It provided more musical gravity and better grounded the soundstage which was as wide as the E03’s but not quite as deep though close. The E03 being the best I've ever heard in that department, this is quite a compliment.

Compared to the ASR Mini-Basis Exclusive, I'll have to go from memory. I never had both in the system at the same time. My impression is that the ASR felt a lot drier and sharp and was tonally not nearly as developed while the Nagra is every bit as dynamic. To be blunt, the ASR failed to convey emotions while the Nagra never missed. Compared to the NAT Signature Phono, the Nagra offered similar textural and tonal transparency but added quite a bit of extra dynamics and bass weight which are the only relative weaknesses of the NAT. If size and weight matter, the Nagra delivers everything in a tiny fraction of the space the bulky NAT would occupy. The Signature Phono retains the edge on fluidity and openness thanks to its triodes but at less than half the price, the Nagra was otherwise a match and in some cases better.

I won't go through a detailed comparison with the Clearaudio Nano. Although both machines have similar sonic signatures—warm and easy to enjoy—the semblance stops there. The Clearaudio was bested by the much more expensive Nagra in every single aspect of dynamics, transparency and spatialization. That's just as it should have been. Nagra's warmth does not detract from the music unless it has very sharp transients whereas the Nano overlooked a lot of information passed on by the cartridges.