DNM PA3 S Power Amp

hfnvintageDoes enormous power always make musical sense? Martin Colloms hears a new stereo power amp from a designer who begs to differ

DNM's long-awaited update to the PA3 power amplifier has finally arrived. Fully regulated, the PA3 S reflects the uncompromising approach of its designer Denis Morecroft. Offering just 23W per channel but costing £3750, this stereo power amp has undergone a long gestation, the reasons for which Morecroft outlines in our interview boxout.

He would be the first to accept that the PA3 S forms part of DNM's pre/power architecture, which includes the long-running and oft-upgraded 3B preamp, plug-in cards for which were recently revised to take into account the anticipated leap forward in performance of the PA3 S power amplifier.


For the purposes of this review, DNM supplied the entire 3B/PA3 S system including integral, factory standard, DNM single-strand cabling. On request, DNM also supplied a 'one-off' PA3 S, standard in all respects except for the provision of phono input sockets and speaker cable binding posts to enable more precise comparisons within the context of a standard review system.

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DNM operates a trade-in upgrade policy whereby older and more junior members of the range may be returned in exchange for a full allowance on a new model, minus a £50 handling charge. So, for example, DNM's previous PA1 (£1650) may be exchanged for the unregulated 45W-per-channel DNM PA3 (£2500) or the PA3 S. The returned models are remanufactured to factory condition, and then resold with a full three-year guarantee.


DNM founder Denis Morecroft caught on camera in the early '90s at the Hi-Fi News show held at the Penta/Renaissance hotel at Heathrow

The 'S' version of the PA3 is said to be half as powerful as its unregulated predecessor, Denis Morecroft asserting that the cleaner, more dynamic delivery makes these two power amps equally loud, subjectively at least. In theory, the 3dB difference corresponds to just one volume control notch – or so I keep telling myself!

What you receive is a compact acrylic-cased power amp linked umbilically to a separate transformer box, the latter equipped with a power switch and a detachable IEC plug cable. Inputs are on 5-pin DINs; dealer-set outputs, as required, are for single, double or triple pairs of speaker connections, via buried 2mm gold-plated sockets.

Discrete components are used throughout the PA3 S, which operates in push-pull, direct-coupled, Class A/B mode. Single FET output devices are sufficient at this power level. Stable, rail-to-rail differential circuitry avoids current mirrors, and while this amplifier uses substantial negative feedback, great care has been taken to make the current paths as pure as possible to help maximise ultrasonic stability and allow feedback to be optimally effective, unconstrained by stray inductance and higher order modulation effects.

With its near-zero metal content, signal paths aided by 'super short' surface mount technology, and idealised 3D topology, the perfected amplifier kernel is fed from stable, clean and dynamic regulated power supplies, these push-pull circuits essentially as refined as the audio amps themselves. While the unregulated version of the amp uses 'Slit Foil' reservoir capacitors, the 'S' version employs the latest 'T' network 10,000pF types, which have been patented by the designer.

sqnote Diminutive Dynamo
Several visiting products enlivened matters here, including the revived JBL 4312-II, a three-way standmount speaker with a rated sensitivity of 93dB/W. Other models included the Wilson WITT Series II, the Quad ESL63, Spendor SP2-2 and the Electa Amator II from Sonus faber. Reference amplification was the Krell KPB 600, Cary 572 SE triode, Conrad-Johnson Premier 11a and the Naim NAP 250. Control was in-built with sources such as the Krell KPS20i/1 and DAX Decade, these supplemented by the Conrad--Johnson ART and the XTC PRE and, of course, the matching DNM preamplifier, the DNM 3C.


An amp that proves less is more? Original pages from the June '98 issue of HFN in which Martin Colloms tested the PA3 S from DNM

The set of triple-paralleled DNM speaker cables supplied with the PA3 S were terminated in 4mm plugs. For the 'one off' power amp, Transparent, Siltech and van den Hul speaker cables were used. The interconnect to the power amp and links to the 3C were as defined by DNM Design, and DNM's single-stranded mains cables were fitted.

If, for any reason, you have to turn off the PA3 S, you'll find its subsequent rapid warm-up remarkable. From the very first track, the sound unfolds and 'opens out'. Instead of waiting 20 minutes for the mists to clear, they disappear in practically no time at all.

I was surprised to find myself completely at home with this amplifier system. It may be small scale, but the quality was such that I didn't feel short-changed. This diminutive dynamo really did succeed in conveying dynamics and expression, achieving the same degree of satisfaction that had hitherto required substantially higher listening levels.