on test

Phoenix Audio N‑8 the cable screen and the chassis earth to Active DI & Line Amp be broken to mitigate loops. In contrast, the Monitor O/P socket Crammed with discrete electronics and provides secondary outputs that are 8dB boasting huge headroom, this box has rather lower in level than the main ones, the idea being that connected monitoring more to offer than the average DI... equipment won’t be overloaded if the main outputs are driven hard. Hugh Robjohns features, including ground lift, polarity Although the Owner’s Manual claims invert and input pad facilities. At its these monitor outputs are balanced, hoenix Audio’s products have core, the input stage is transformerless it doesn’t make clear whether they appeared a few times in the and presents an unusually high 10MΩ are ‑isolated feeds, or P pages of Sound On Sound, and input impedance, while the output whether they are affected by the I first came across them over 15 years stage features the well‑proven DSOP‑2 ground‑lift buttons. However, it turns out ago when I reviewed a two‑channel amp, with its custom‑wound DB694 that these monitor outputs are actually mic preamp with integrated active DI, output transformer. derived from a centre‑tap on the primary called the DRS2 (SOS February 2003: The N‑8’s circuitry is housed in a black, http://sosm.ag/phoenix-audio-drs2). You 1U, rackmounting steel chassis, which can find out more about the company’s is 1.2mm thick and extends around Phoenix Audio N‑8 history in the ‘About Phoenix’ box. 210mm behind the rack ears. Given the £1476 The device under the microscope requirement for eight output , p r o s here is their eight‑channel rackmounting it’s not surprising that it weighs almost • Lovely, full‑bodied sound, with attractive active DI. Called the N‑8, it borrows from 5kg, with a good deal of the weight musically appropriate overdrive behaviour. the company’s long‑established Nice DI, towards the rear — some support at • Though billed as a DI, it doubles up as a two‑channel device which employs the the back of the unit might be a sensible a characterful eight-channel line amp. active Class‑A DI stage first introduced precaution, especially if you plan on • Uses Phoenix’s highly regarded DSOP‑2 in Phoenix’s DRS‑series products. The installing it in a touring flightcase. output stages. • Ground‑lift switches on main transformer overriding ethos for this bespoke DI The rear panel is very simple, being outputs, and ground‑free monitor outputs. design was to maintain musicality and equipped with just two AES59 (Tascam • Locking power connector. character for instrument sources, using 25‑pin D‑sub) connectors, one labelled as c o n s elegant, discrete circuitry with a wide ‘Outputs 1‑8’, and the other as ‘Monitor • Although not a safety issue, the chassis bandwidth and excellent handling of O/P 1‑8’. The main Outputs socket is not grounded. transients and micro‑dynamics. provides transformer‑isolated, floating and balanced line‑level outputs, which are s u m m a r y Overview intended to serve as the main recording This eight‑channel DI and line amp is Though the N-8’s circuit design is very or FOH feeds. Eight illuminated (red) inspired by classic Neve Class‑A discrete circuitry and offers the musical coloration similar to the Nice DI, it’s not entirely buttons on the rear panel allow, on an that this would lead you to expect. the same and includes several new individual basis, the connections between

50 October 2018 / www.soundonsound.com side of the output transformer (which the right channel would be absent achieve the very high input impedance, accounts for the reduced output level). and balanced sources would lose the since this is what most discrete DI designs So they’re actually direct outputs, rather cold‑side signal contribution.) do. However, although FETs were tried than transformer isolated. Technically, Each channel’s controls feature two for this role early on in the development they’re also unbalanced, but the wiring at illuminated buttons, the first (which is of the Nice DI, they didn’t deliver the the D‑sub connector adopts a common blue) selecting a ‑15dB pad, and the desired musical colour and depth. While approach in which the output signal is second (green) a polarity inversion. An Phoenix Audio are naturally a little presented on the hot output terminal and unusually slim and tall red-winged knob, reluctant to disclose all of the design the audio ground on the cold terminal. lending a Neve‑esque air to the N‑8, details, I can report that the instrument To help avoid ground loops, there is no adjusts the gain of the output stage, but input stage uses a pair of bipolar cable screen connection at the N‑8’s there are no level meters of any kind. transistors in a configuration Phoenix connector. This configuration is common Audio have dubbed a ‘Manx‑tailed practice and generally works perfectly Inside pair’. Students of electronics will be well with both balanced and unbalanced As I mentioned above, the internal able to relate that term to the classic equipment, and I have no issue with it construction is a bit of a squeeze, but it ‘long‑tailed pair’ topology and know in principle. That said, there are specific is done very neatly. The DSOP‑2 output that ‘bootstrapping’ techniques are situations where it won’t work, and as electronics and transformers for the often used to raise the input impedance the Owner’s Manual in bipolar transistor is rather light on gain stages — and information in this “When the guitarist really dug in I imagine a variation respect it could lead on that idea is to bewilderment and and deliberately pushed the input stage being employed here. a lot of head scratching into overdrive he liked the result — and In my discussions in such situations. with Phoenix Audio If Phoenix were to I’m sure others will like it too.” product designer update the manual Shaun Leveque about to include a detailed the circuit design, I also description — or better still a detailed eight channels are mounted on a single learned that, unlike many other ‘musically block diagram — it would remove the motherboard which stretches across the flavoured’ DI devices, the N‑8 doesn’t rely potential for confusion. full width of the chassis, with two short on saturating the output transformer for Moving to the front panel, each ribbon cables at the back to carry the its sound character. Instead, this comes channel is provided with two quarter‑inch, outputs to the two D‑sub connectors. entirely from the output‑stage circuitry parallel‑connected, input and link sockets At the front, the input circuitry for and the specific way in which it is loaded labelled ‘DI Input’ and ‘Through’. The each channel is mounted on a pair and biased via the output transformer. Owner’s Manual states that these are of vertical daughter cards, with one This is important: with the transformer TRS sockets that can “accept both mono carrying the channel’s buttons and level only providing isolation and not tonal and stereo jack plugs”, and they can, control, and the other hosting the two colour, the monitor outputs sound exactly physically. However, the ring contacts sockets and the discrete input buffer the same as the main outputs (albeit 8dB of both sockets are grounded along electronics. These cards plug into sockets quieter), despite the former being derived with the sleeves so, in all practical on the main PCB, so servicing should from the primary winding and the latter senses, these are standard unbalanced be fairly straightforward. from the secondary! If the tonal character TS instrument connections. (If you I was expecting the instrument input came from transformer saturation effects were to try connecting a stereo source, circuitry to use a FET at the front end to that wouldn’t be the case, and the

www.soundonsound.com / October 2018 51 on test Phoenix Audio N‑8

Both the main and monitor outputs are delivered via D‑subs. Although each output is tapped from a different side of the same transformer, the design means that they always sound identical, differing only in level. recorded sound would be significantly line‑lump class‑1 (earthed) PSU. I approve between the appropriate motherboard different from the monitoring outputs. of that, as the connection is so much terminals — although I could find no more secure and reassuring than the mention of this option in the manual. Power ubiquitous coaxial plugs. Of course, While there’s a valid technical Like the classic Neve hardware that an external PSU also reduces the heat argument for the absence of chassis inspired the underlying circuit design, inside the case and minimises the grounding (it avoids creating a secondary the N‑8 runs on a single‑sided +24V DC risk of mains hum being induced into ground loop through the rack, which power rail but, unlike the two‑channel the transformers. All in all, it seems to me can be a real problem with some elderly Nice DI, this product is powered from an to be a sensible compromise. There is no hardware), it is unusual and I’d have external line‑lump universal PSU which power switch, so the N‑8 is powered up preferred, at the very least, to see accepts mains supply voltages of 100‑240 whenever the line‑lump is the user manual explain the situation V AC. Regular readers will know that I’m receiving . clearly, and to spell out the options for not generally the world’s biggest fan of grounding the chassis if required. such external supplies, but in this case I Bench Tests think it’s sensible — lifting the lid on the As I always do for hardware reviews, Tech Specs case, I could immediately see that, due to I put the N-8 on my test bench and Running through a range of bench the profusion of transformers and DSOP‑2 performed a standard PAT test before tests using an Audio Precision system, modules, there simply isn’t enough space starting to use it, and I was surprised to I found the output level control provided for an internal power supply; and were the see the PAT tester indicate that the case a maximum gain of +30.5dB with the case to be made deeper to accommodate metalwork wasn’t earthed back to the control fully clockwise. With the knob at an internal supply, the unit’s weight (and mains plug. To be completely clear, there 12 o’clock the boost was around +15dB, thus leverage exerted on the front panel is no safety issue at all here — technically, and at the fully counter‑clockwise position when racked, as intended) would be since the N-8 has an internationally it attenuated the signal by around ‑50dB problematic. certified external low-voltage PSU, the — effectively turning it off. This control A nice, screw‑locking, three‑pin chassis doesn’t actually need a mains has a detented action and the second Amphenol‑Tuchel chassis plug accepts safety earth connection. click gave around 40dB of attenuation, the 24V DC power from the supplied Initially I presumed this was a the third about 16dB, while the fourth deliberate design feature for mitigation achieved roughly unity gain. About Phoenix of ground loops, but I subsequently With an input signal at ‑20dBu discovered that the mains safety earth (nominal instrument level), and the output Originally set up in the UK in the mid connection is actually extended onto level adjusted for a nominal +4dBu line ’90s by former Neve engineers, Phoenix the unit’s motherboard as the negative level, I measured the total harmonic Audio started out servicing classic Neve side of the DC power supply. This (THD) figure at a respectable mixing consoles and associated equipment, then becomes the audio signal ground 0.05 percent, and the floor was but it wasn’t long before the company reference, and so it’s carried through ‑83dBu. So with a maximum output level launched a retrofitable output stage upgrade for classic Neve gear (originally to all the front-panel instrument socket capability of +26dBu the unit has an called the TF‑1, but now evolved into the sleeve terminals and main output cable admirable dynamic range potential of DSOP‑2). Next came a Class‑A active screen connections. This means that 110dB. As the input level is increased the DI stage, and the company subsequently all the audio socket grounds link back distortion level builds progressively to started designing and building their own directly to the mains safety earth, while around 0.1 percent before tipping into products using more modern, but still the unit’s metal case doesn’t — though, asymmetrical clipping. discrete, Class‑A circuitry, inspired by the illustrious early Neve consoles. In 2009 of course, in most practical installations The input stage clips when the Phoenix Audio relocated to California the chassis metalwork will become unbalanced input exceeds about +9dBu, — home to a significant chunk of their grounded when mounted in a rack. but selecting the input pad allows levels market — and they have continued to For stand-alone operation, it is also of at least +20dBu to be accommodated build both their reputation and product possible, fairly easily, to extend the without clipping (this being the test limit portfolio, under the direction of company mains earth to the chassis to ensure for the unbalanced output of my Audio president Robin Ashley. effective screening by installing a wire link Precision system). I should state that this

52 October 2018 / www.soundonsound.com on test Phoenix Audio N‑8

With all the Class‑A circuitry and output transformers, there really is no room to spare for a built-in power supply! overload behaviour is notably different to pad) should provide more than enough input impedance will inherently tame earlier incarnations of the N‑8 (the review headroom for most standard instruments, the output transformer’s resonance. model had serial number #3484), and the even active basses and very hot guitar input cards had several wire links added pickups, but the pad is available if more Conclusion which were absent from earlier models. headroom is required. I didn’t experience Overall, the N-8’s concept is a great The first review model (#3053) had the pad any problems playing a conventional one — classic discrete Class‑A circuitry circuit located after the active input stage passive bass through the N‑8, or when throughout, a custom output transformer rather than before, and with a high headroom so the pad switch did not margin, and eight increase the input headroom “Unlike many other ‘musically channels in a well‑built at all (the earlier design also flavoured’ DI devices, the N‑8 rackmounting unit. clipped at +3dBu). Instruments captured When I raised these doesn’t rely on saturating the output through the N‑8 sound issues with Phoenix they very good indeed, and requested the opportunity transformer for its sound character.” its unusually high input to rework the design, impedance really does help and I’m very pleased to report that the recording a friend playing an electric electro‑acoustic instruments to sing, with modifications exhibited in this second guitar. When the guitarist really dug in detailed transients, plenty of character, review unit are most welcome and very and deliberately pushed the input stage and smooth sustains. effective. As a direct result, not only into overdrive he liked the result — and On top of that, the N‑8 is very is there considerably more headroom I’m sure others will like it too. versatile, as it can be used not only as for instrument inputs, but the N‑8 can Taking a response a DI but also to apply a little ‘polish’ to also be used to introduce some subtle measurement showed a low‑frequency line‑level sources by introducing some Neve‑ish coloration to line‑level signals roll‑off of ‑3dB at 18Hz, and the high end high‑headroom, Class‑A character, — something that greatly expands its was flat to well beyond 50kHz, so the with some iron in the signal path. This versatility and cost‑effectiveness. N‑8 certainly ticks the ‘wide‑bandwidth’ extends the N‑8’s role far beyond Clipping at +9dBu (without the box. I measured a gentle rise in the simple instrument tracking into mixing response above 30kHz due to the and post‑production, which for many Alternatives output transformer’s resonance, but prospective users will help to justify its this was when effectively unterminated purchase price considerably. There’s nothing directly comparable with the Phoenix Audio N‑8, though if your (the AP Analyzer presents a very high needs would be met by two channels you 200kΩ input impedance by default), ££ £1476 including VAT. might consider Phoenix’s Nice DI. For more and the actual HF response in typical TT Studiocare +44 (0)151 236 7800 conventional DI applications, Radial offer E applications will be substantially flat (or E [email protected] the ProD8, which is a very clean and capable WW www.studiocare.com gently falling) in this ultrasonic region, eight‑channel rackmount transformer DI. WW http://phoenixaudio.net as a more conventional destination’s

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This article was originally published in Sound On Sound magazine, October 2018 edition

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