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Nagra PL-L Tube Preamplifier Review

The $8,995 Nagra PL-L Class A tube preamplifier: Swiss engineering as experienced by Constantine Soo

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Nagra PL L tube preamplifier

Nagra Audio of Switzerland drafts its space-age engineering prowess from its parent company, the Kudelski Group, a 650-million-dollar, publicly-traded European conglomerate founded by Stefan Kudelski in 1951.

Today, the company continues to be run by the founding family, and another of the Kudelski Group’s divisions, Nagravision, develops and owns the exclusive encryption technology used by Echo Star Dish Network for its satellite broadcasts. This technology is also adopted by a majority of European satellite receivers, in addition to significant portions of Asian satellite receivers.

Nagra’s business diversity owes its origination in the early 1990s to a renewed vision from the 2nd Kudelski generation, whose strive for the industry leadership position in high-quality, high-tech media content management infused not only Nagra’s renowned professional audio section with new energy, but also created the company’s consumer high-end audio section.

Nagra Audio’s high-end division exemplifies the engineering brilliance of products from its professional origin, which currently includes Nagra’s distinguished SNST-R, a special-edition precision miniature analog stereo tape recorder designed specifically for music recording. The SNST-R’s esteemed historic predecessor, the SN “Série Noire”, was discovered and adopted by the U.S. Government, and was ordered by President J.F. Kennedy for the Secret Service. Moreover, the Nagra SN was also used by the astronauts on an Apollo lunar landing.

Today, the company’s high-end division offers, in addition to the SNST-R:

1. the DAC ($11,995), a solid-state up-sampling DAC developed from the Nagra D and Nagra V professional broadcast-grade DACs;
2. the PL-P ($11,495), a battery-operated tube preamplifier with phono;
3. the PL-L ($8,495), a remote-controlled tube linestage;
4. the VPA ($19,295/pair), an 845-based tube push-pull monoblock amplifier;
5. the PMA ($10,995/pair), a solid-state monoblock amplifier;
6. the PSA ($6,595), a stereo power amplifier.

The subject of this review is an $8,995, remote-controlled tube linestage, the PL-L, equipped with the optional, $500 balanced output transformer. According to John R. Quick of Tempo Sales & Marketing, Nagra’s U.S. Sales and Marketing Manager, the PL-L is a 2nd generation Nagra product, with the PL-P, VPA and MPA being of the 1st generation. Per John:

“PL-L was introduced in 2002, and in many ways similar to PL-P without phono and with a simplified circuit layout. Whereas PL-P is powered from a battery pack, which in turn drives a switching power supply, the PL-L uses an outboard precision switching power suplly, and is derived from a high-performance low-noise microphone preamplifier for the professional market. Nagra has done a lot of work in minimizing noise in a portable configuration, and battery power is a theoretical optimum for low noise. The PL-P essentially has twice the components of PL-L with input and output level control, and 6 tubes in total.”

As there is no more space in the PL-P for adding the remote control convenience without compromising its compactness and performance, the PL-L linestage was conceived to incorporate the remote control functionality, at the same time also demonstrating Nagra’s professional heritage. One of the reasons John Quick brings Nagra’s professional recorders with him to Shows all the time is to let audiophiles experience the professional side of Nagra, and the extend to which Nagra is carrying on its professional heritage:

“Since it is a Nagra machine, part of its charm is its industrial design. For the front-end products, especially. In addition, the PL-P is a very sophisticated products, more complicated to use than the PL-L, like volume trims, etc. So, they simplified things quite a bit in the PL-L. The PL-L was to allow for remote control, balanced in/out, etc. They removed the battery supply to give more room, and designed a very good outboard switching power supply for the PL-L.”

The PL-L linestage has only one gain stage going through 3 tubes with one potentiometer. John feels that while the line-level input of the battery-powered PL-P phono to be a little sweeter and quieter on the top-end than the PL-L linestage, the two machines have comparable signal-to-noise ratio and soundstaging prowess, with the PL-L sounding a little more dynamic. Per John:

“Hence, if you need a phono stage and doesn’t mind the battery operation, then the PL-P is the best choice. Differences between the two can be very subtle.”

Dubbed by Nagra as “designed to provide the highest quality of audio performance in an ultra high-resolution audio system”, the PL-L is designed and hand-built in Switzerland by Nagra engineers. Its external power supply, the ACPS, isolates the main unit from AC irregularities, and connects to the main unit via a Lemo-fitted umbilical.

Nagra claims that the high-grade vacuum tubes, namely two ECC83 and one ECC81, operates fully in pure class A biasing, and are subjected to 400 measurements before computer matching on Nagra’s custom platform with a 12-hour burn-in process. An internal Nagra vacuum tube usage timer tracks the operating hours of the tubes, and Nagra recommends 5,000 hours of maximum tube operation for guaranteed performance, after which time tube replacement is recommended via a $250 tube replacement kit. The kit includes all new Nagra-tested tubes and a new tube usage timer.

The PL-L’s main circuit board is mounted on elastomer dampers to minimize vibrations to the tubes, hereby controlling the microphonic noise. The chassis is CNC-machined in “hardened, anodized aluminum” to shield the delicate circuitry from electromagnetic interference.

Whereas the PL-L can be fitted with a set of Nagra’s custom transformers for a truly floating XLR output, the RCA outputs are already capable of driving a 600Ω load with only 1dB drop in signal level. More importantly, the RCAs bypass the transformer and are directly coupled to the output tubes. Finally, internal switches are provided to customize PL-L’s output to any amplifier.

The PL-L offers 1 pair of XLR and 3 pairs of RCA inputs on its left side panel, while outputting in either the 2 pairs of RCA or the 1 pair of XLR on the right side panel. The front panel features a large dial on the left that controls OFF, and A, B, C, D & R input selection. Two smaller dials near the center control VOLUME and BALANCE. Occupying the right of the faceplate is the MODULOMETER, a tool derived from its professional counterpart for monitoring and matching output levels.

Three small toggle switches are placed near the bottom of the front panel, namely STEREO/MONO, a brightness and power check on the modulometer, and LINE OUTPUT (1, mute, 2).

The Nagra RCU remote control unit commands up to 6 designated Nagra products via buttons 1 through 6, while the A-D buttons activates the four corresponding inputs. In addition to balance and volume control, the Nagra RCU also provides the ON, MUTE and OFF functionalities.

Finally, the aforementioned “R” position on the left, large dial relegates power on/off functionality to the remote control. When at the OFF position, only the Nagra PL-L’s audio circuitry is turned off. Also, should the front panel dial be at the OFF position, a muted 15-second soft-start is engaged to protect output stages from voltage surge.

System Set-Up & Auditioning

The Nagra PL-L was auditioned with various digital front-ends, such as the Oracle CD 2500 CD player/transport that Ed Momkus reviewed in September, as well as Audio Note’s $7,500 CDT-Three CD transport, Wadia’s $9,995 27ix v3.0 Decoding Computer, 47 Lab’s $26,800 PiTracer CD transport, Audio Note’s $29,995 DAC5 Special and the $59,995 DAC5 Signature. An $11,185 Roksan record system, including the $4,795 Roksan Xerxes.20 turntable system complete with the XPS5 Speed Control Board & DSU Power Supply, a $1,400 ArtaXerxes Phono Pre Amp module & DS1.5 Power Supply module fitted with DX2, a $2,495 Artemis tonearm and a $2,495 Shiraz cartridge also partook the Nagra audition.

In amplification, Nagra’s own PMA Pyramid Monoblock Amplifier joined Linn’s $8,995 Klimax Chakra 500 Twin and Combak’s $24,995 Harmonix Reimyo PAT-777 SET in rotation with the Nagra PL-L, driving the 100dB/8Ω MaxxHorn Immersion horn speaker ($12,500), the discontinued 95dB/8Ω Tannoy Churchill Wideband ($19,000), the 95dB/8Ω 2003 Audio Note AN-E SEC Silver ($19,995) and Austrian piano-maker Bösendorfer’s 91dB/4Ω VC 7 ($26,000) respectively.

Two pairs of Combak’s $2,250, Harmonix 2-meter HS101GP Golden Performance interconnects, one $2,665, 2-meter single-wired pair of the Harmonix HS101-SLC “Sophisticated Listener’s Choice” speaker cable and a $1,210, 1.5-meter Harmonix HS-102RCADG “Harmonic-Strings” RCA digital cable constituted system cabling. Bestowed with the same professional heritage as Nagra’s professional products, the PL-L’s compactness strikes fancies in anyone coming into contact with it. As it did me. Its design for mobility was symbolized by the 4 rubber pads of tiny proportions adhered to the bottom chassis of the PL-L. For a measure in isolation, I put an $865 set of 4 Combak Harmonix TU-66ZX “BeauTone” tuning feet underneath the PL-L.

The PL-L’s performance was largely inert to applications of most specialty power cords, a disposition probably attributable to the use of its ACPS external power supply. The only exception being in the form of Isoclean’s $3,800 Supreme Focus power cable, which elevated the PL-L’s performance colossally. For the benefit of this review, Isoclean’s $1,000 2-meter Focus power cable was used.

Location of the inputs and outputs on the Nagra PL-L’s opposite side panels is a revelation in operability ease, as changing cables via the sides of an equipment is so much easier. In addition, the fact that a MUTE toggle switch is provided on the front panel also allowed me to walk up to the preamplifier and mute the output when changing records, all the way to the moment when the Roksan Shiraz was tracking the groove again, when I would flip the toggle back up to 1 and let the music play as I return unhurriedly to my seat.

Pianist Evengy Kissin’s reading of the Chopin 24 Preludes 20-Bit RCA Victor recordings provided testimonial on the Nagra’s potentials. Large record labels such as Deutsche Grammophon and RCA possess the necessary financial and marketing muscles for the recruitment of top artists like Kissin, and yet it is often the small, independent labels like First Impression Music, Mobile Fidelity Sound Lab and the XRCD division of JVC that push the sonic envelope of recorded music. Hence, the fact that recordings from major labels such as RCA are beginning to be of such demonstration class is a much belated but welcome development to our long prayers.

The Nagra’s reenactment of the performance from this Redbook CD via the front-end of PiTracer/DAC5 Special and the PAT-777-driven Bösendorfer loudspeaker, complimented the pristine sound of the CD most auspiciously in the spotless rendition of Kissin’s incisive and yet subtle keystrokes. The captured resonances of the piano carried a richness so comparable to those from machines costing much more that I continue to have difficulty putting this aspect of the $9k Nagra’s performance into proper perspective.

The Nagra’s ability to convey the piano’s energy equitably also accorded a most surreal experience of piano playing notably in the 15th Prelude “Raindrops”, in which the preamplifier’s sustenance of the celebrated section of powerful outpour was no less exhilarating than the majestically provocative contrasts it revealed in Kissin’s transitional handling of delicate subtlety versus breathtaking high-notes. It was the first time I’d heard such dynamic contrast clarity from a sub-$10k preamplifier, let alone a compact and unassuming-looking one that is the PL-L.

Audio Note’s (20003) AN-E SEC Silver loudspeaker, though less expensive than the Bösendorfer, also reaffirmed the Austrian loudspeaker’s conclusion of the Nagra magic with a level of resolution all of its own, churning out roomful of top-end airiness and delicacies that never come around enough in our lifetime.

Complex tonalities as presented by the piano did not recede in scale when replaced by large-scale orchestral ruptures, as the PL-L was able to raise its dynamic envelope in attendance of taxing demands of passages while simultaneously tracking all instruments of varying forces with displays of powerful and sophisticated tonal differentiating.

The Redbook CD layer of the Mobile Fidelity Sound Lab’s Ultradisc UHR hybrid SACD/CD reissue of Mussorgsky’s Pictures at an Exhibition with the St. Louis Symphony contains a level of dynamics and spatiality that belies its original vintage of 1975, sounding utterly distinct and powerful via the Nagra PL-L throughout, that not only the tuba and timpani were endowed with a lifelike dynamic substance and tone, there even was a rare, glowing solidity to that of the triangle which made it sound more dimensional.

Exchanges of brasses and woodwinds in the MFSL reissue were also depicted by the Nagra tube preamplifier with an unexpected but finely delineated dynamic variances, as trumpets were rendered with an evocative, excitable edge that imparted the sound with an zealous energy, when their presence were quickly superseded by the expeditious flutes and piccolo with a superbly defined transient that I had only encountered in top solid-state designs.

In this particular case, the Nagra PL-L was the most dynamic and yet sublime sub-$10,000 tube amplifier I’ve encountered.

Perhaps just as equally transcending as Combak’s Harmonix Reimyo PAT-777 is in its ability to drive the 91dB/4Ω Bösendorfer, the compact Nagra PL-L’s interaction with all aforementioned amplifications resulted in consistent influences over both solid-state and tube power amplifiers. For instance, Nagra’s own PMA Pyramid Monoblock Amplifiers and Linn’s Klimax Chakra 500 Twin both exhibited degrees of tonal sophistication and fluidity over program material selected, affirming the PL-L’s compatibility with quality amplifications to my ears, as well as its intrinsic finesse.

Finally, the $12,500, 100dB/8Ω MaxxHorn Immersion loudspeaker system has always been a most revealing tool on idling noises generated by amplifications by virtue of its sensitivity, and we all know how unsettling the noises from a 12 o’clock volume position on any tube preamplifiers can sound like with such sensitive horns. In this regard, the same 12 o’clock volume position on Nagra PL-L generated the lowest level of noise among tube amplifiers from the MaxxHorn.

In retrospect, the Nagra PL-L was also highly sensitive to output levels from sources upstream. While a 9:30 volume position on the DAC5 Signature-coupled PL-L was mightily sufficient to generate a sound pressure in excess of 90dB through the Combak/Bosendorfer combination, the 11 o’clock volume position became necessary to attain the same level with the Roksan ArtaXerxes Phono Pre Amp. I do concede at this point that I usually listen to vinyl at the 10 or 10:30 lower position to avoid the occasional but disconcerting clicks and pops of surface noise as picked up by the delicate Shiraz cartridge. Laurence A. Borden lectured me to no end on the necessity of “getting past” the vinyl format’s noise characteristics were I to appreciate the format, and I hear his voice every time I frown at the noises.

Conclusion

Though a tube preamplifier, the Nagra PL-L disclosed a sonic disposition that sets it apart from a majority of solid-state and tube preamplifiers I’ve heard. Its rendition of acoustic instruments exhibited no trace of transient obscurity, and its prowess in spatial definition was of equal precision.

Though costing $9k, the Swiss preamplifier was endowed with such comprehensive and definitive faculty that even systems costing over ten times its price benefited from its demonstration-class tonal clarity and dynamic punctuality. Most important of all, the Nagra PL-L produced a precious liquidity that was simply priceless and decidedly class-transcending.

The Nagra PL-L is an engineering marvel, compact in size but powerful in action, its operability is ingeniously conceived and masterfully implemented. The Nagra PL-L: Another crowning achievement in engineering from the land of precision instruments.

Manufacturer’s Comment:

On behalf of Nagra, I would like to thank Constantine for his thoughtful, thorough evaluation of our PL-L line stage. We feel he has accurately captured the most important elements of what make the PL-L special, from its sonic attributes to its ties to Nagra’s professional heritage. The goal of all Nagra high-end products has always been to try to recreate what our precision recorders have captured over the past 55 years of service: to be as true to the live event as possible.

We would like to address a number of minor points:

First, sadly, the SN-series of miniature tape recorders has been discontinued after 40 years of continuous production. Less than a handful of the final version, the aforementioned SNST-R, are still available. Just as icons in other businesses, such Leica with their new M-series cameras, have begun to switch from analog to digital mediums, Nagra has been making the transition with their recorders for some time. The current Ares-M, Nagra V, and the upcoming Nagra VI are perfect examples; each uses a hard drive and/or flash memory to store recorded data.

Second, the Nagra D and Nagra V are actually professional digital recorders, and it is true that some of the technology we developed for these machines can be found in the Nagra DAC; the same applies to the new range of CD players we will launch soon, which owe a portion of their ability to a digital circuit designed for the new Nagra VI.

Third, with regard to maximum tube life in the PL-L, we have had experience with units having closer to 10,000 hours of use whose tubes still measured perfectly! As with all tube designs, although the PL-L runs fairly cool, proper ventilation is a must. Due to the new ROHS regulations that call for an elimination of certain materials in all electronic devices, such as lead in solder, the tube usage timers are no longer available.

Last, for those who play vinyl and are interested in the PL-L, Nagra will have a solution in 2007… please stay tuned!

Best wishes for continued growth and success,

John Quick
U.S. Sales & Marketing Manager

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