Naim ‘DR’ power amps and upgrades

In the wake of the ambitious NAC S1 and NAP S1 Statement project, Naim Audio has recently revised its ‘classic’ amplifier line up to incorporate some of the more significant advances resulting from the exhaustive research and development for that flagship product.

In the second half of 2015, the NAP200, 250 and 300 all acquired the DR suffix; the NAP500DR has taken a little longer due to the more complex nature of its circuitry. To coincide with it’s release the company hosted an event to present some of the technical background behind the new amps and have the opportunity to compare new against old through the range.

Recently appointed CEO Trevor Wilson opened the day with brief introduction outlining Naim’s current status, with updates on Spotify and Tidal compatibility in hand for streamers, and confirming a continuing commitment to the traditional hi-fi separates market in which they are doing particularly well. It was then over to Steve Sells, chief designer behind the Statement electronics and subsequent DR engineering to explain some of the electronic theory behind the upgrades, supported by imaginative demonstrations to show its effectiveness in practice. This was followed by listening tests to compare the original NAP250, 300 and 500 against their updated DR counterparts driving Focal Scala V2 Utopia loudspeakers.

Introduced in 2012, the initial DR designated upgrade consists of replacing the long-standing LM317 integrated circuit used to provide power for low-level circuitry such as preamps and active crossovers with a new board of made up of discrete components. As such, it is applicable to the standalone power supplies and smaller power amps that incorporated circuitry to similar effect. The improvement has been well documented, and firmly substantiates the company’s long held belief in the importance of power supplies in the system.

DR – short for discrete regulation – is something of a misnomer when applied to the new power amplifiers. The regulation involved here is capable of delivering tens of amps when necessary, and always been made up of discrete components, with not a single integrated circuit in sight. However, research carried out for the requirements of the massive Statement amplifier led to a redesign of this circuit, resulting in far lower noise floor and superior current delivery. The regulation circuit now utilises a complementary pair of power transistors to supply current to the amplifier section, where the older topology used NPN-type devices for both the +VE and –VE rails. The actual output stage retains the quasi-complementary configuration, where identical NPN-type devices are used, and remains unchanged.

Rather like using a stethoscope, a demonstration allowed us to hear ‘inside’ a 250 amplifier and monitor the noise on the power supply while music was playing. The effectiveness of a regulated supply in cleaning up this crucial part of the circuit was immediately obvious, but more impressive was just how much better the new DR regulator was than the original circuit, audibly substantiating the claim that it is thirty times quieter.

The other highly significant factor in the DR makeover is the use of the NA009 power transistors, commissioned for the exacting demands of the Statement. This is a direct off-shoot of Naim’s close collaboration with semiconductor manufacturer Semilab over many years, and has enabled Naim to control design and fabrication to an unparalleled degree.

These unique devices are numbered and parameterised during manufacture, a process that allows precise matching from adjacent positions in the die from which they are fabricated. The benefits of close matching transistors are not only measurable in terms of lower distortion, but have a significant impact on performance, and that is borne out by controlled listening tests. Close examination of other factors – such as mechanical and magnetic properties – have resulted in the total elimination of ferrous materials in the construction of these transistors, while thermal considerations led to the development of aluminium oxide ceramics to couple the transistors to the heatsink. This is claimed to deliver more efficient thermal transfer and reduced bias modulation, while at the same time lowering the stray capacitance between the device and the metalwork, again minimising noise at a crucial part of the circuit.

Naim has also recently announced an upgrade program commencing at the beginning of 2016 that will be available to many existing owners of Naim’s NAP200, 250, 300, and 500 models, but unfortunately older versions (pre 21^st Century models of the ‘olive’ or ‘chrome bumper’ vintage) are not compatible with the new electronics. The NAP200DR is by far the most straightforward upgrade, as it does not incorporate regulated rails for the power amplifiers nor does it demand the extra current capacity of the 09 transistors, requiring instead only the substitution of the on-board preamp supply for a DR board. By contrast, the NAP500 requires the replacement of no less than twenty supplies due in part to its bridged configuration, and together with the 250 and 300, redesigned circuit boards and heatsink assemblies necessitate replacement of virtually all of the electronics. There will be a further option to have the power supply serviced, replacing all the reservoir capacitors in the process.

The demonstration of the NAP250, 300 and NAP500 against their new DR counterparts was handled expertly by Jason Gould, and was both enlightening and informative. While the hierarchy of the range was strongly evident, the improvement in each case was beyond question. The DR amplifiers exhibited a lower noise floor that allowed more detail, greater articulation and presence, together with a far more expansive range of dynamic expression portrayed with a wider bandwidth.

With their predecessors sounding drab and lacklustre by comparison, the technology handed down from the Statement electronics and the way in which it has been incorporated into the new DR amplifiers would have to be judged as a brilliant and unqualified success. This is arguably one of the most significant enduring legacies of the Statement project, as the lessons learned in producing this cost-no-object amplifier are directly filtering down to more attainable amplifiers in the Naim Audio range. That one of those ‘lessons’ involves the production of a transistor specifically for Naim Audio shows the levels of commitment the company is willing to make to get the job done properly.

The prices of the new Naim DR amplifiers and upgrades as follows:

                          RRP Price                DR Upgrade                        DR Upgrade and service 

NAP250 DR    £3,495                      £995   (£500)                       £1,295

NAP300 DR    £7,295                      £1,495 (£750)                      £1,850

NAP500 DR    £19,500                    £4,200 (£2,940)                  £4,900

All prices include VAT. The figures in brackets indicate the upgrade price if the unit was purchased within three months prior to launch.