JZ Microphones JZ Track

For this classy device, mic makers JZ enlisted the design work of outboard aficionados SPL. Is this a match made in heaven?

Designed and built by SPL, the JZ Track is a 19–inch rackmount 1U mono channel strip, featuring a selectable mic, line and instrument preamplifier, a de–esser, a compressor/limiter, a three–band EQ, an output–level control and metering. The ‘JZ’ is in the name because it was created at the request of JZ Microphones, who asked that it be specified to match the impedance of their mics. While that will be reassuring for owners of JZ mics, pretty much any decent modern studio mic will give good results with this channel strip. I’ve long been a fan of SPL equipment and I recognise many of the elements that have been brought together from earlier proven designs. Don’t be fooled by the apparent simplicity of the controls — these are powerful tools.

Overview

A link function allows two JZ Tracks to be used in stereo, in which configuration the compressor side–chains are linked to avoid undesirable image shift. An optional 24-bit/96kHz A-D converter card with both ADAT and S/PDIF outputs is planned. This card features an A–D input jack, which allows a second JZ Track to output its signal via the converter’s otherwise unused channel. The A-D converter can be switched to any of the four common sampling rates (44.1, 48, 88.2 and 96 kHz) by means of 44.1/48 and x2 buttons, the latter doubling the sample rate selected by the former when engaged.

Our review model came without the digital expansion board fitted, making the layout of the rear panel fairly straightforward. The inputs and output are presented on both XLR and jack connectors; the input jack is unbalanced and the output jack balanced. Both the TRS jack and XLR output connectors are wired in parallel, so unbalancing one connector also unbalances the other. There’s a compressor–link jack with its master/slave button alongside, plus there’s a ground–lift button. Power comes in on a fused IEC connector with 115/240V switching via a recessed slide switch.

With a gain range of +8 to +63 dB, the mic input should have enough sensitivity for pretty much any application. As standard, the solid–state mic preamp is transformerless, but a version balanced by a Lundahl transformer is also available, and this provides 14dB more gain, which may be useful to those planning to plug in a passive ribbon mic. Line- and instrument-level signals have a gain range from –12dB to +22dB, and there’s also the expected 48V phantom–power button and 50Hz, second–order low–cut filter. The circuitry delivers a very wide audio bandwidth from 10Hz to 200kHz (+0/–3dB). Line/instrument switching on the front panel activates the rear–panel jack input, while a further button on the rear panel sets the impedance and sensitivity for line or instrument sources. The XLR input appears to remain live in this mode but is reduced in sensitivity when line level is selected.

Next up is the de–esser section, notable for its single ‘more or less’ control. The principle is based upon that of SPL’s stand-alone de–esser, in which the circuitry tracks the overall signal level to establish its own threshold, so that the de–essing can operate over a wide dynamic range without the need for a separate threshold control. Sibilant signals are separated out using filters and then added back to the dry signal in a polarity–inverted form so as to cancel out the offending part of the spectrum without affecting frequencies to either side. This makes the de–esser very transparent in operation and vastly reduces the lisping artifacts that less sophisticated de–essers tend to suffer from. A bypass switch takes the de–esser out of circuit when not required.

As well as the expected audio input and output, the JZ Track’s rear panel caters for stereo linking and for an optional A–D converter module.Also adjusted via a single control (or two if you count the make–up gain), the compressor has a ‘soft–knee’ characteristic in which the ratio increases with level to a maximum of 3:1 so as to maintain maximum transparency. Its attack and release times adjust automatically to adapt to the incoming signal. The circuitry is based around two VCAs, which work in a differential configuration, with a view to cancelling out any distortion products. A Limit switch puts the compressor into limiter mode, but this again has a fairly soft and benign character, and so it may not arrest fast transient peaks as effectively as a conventional peak limiter does — the manual recommends leaving around 4dB of headroom when feeding the resulting signal into an audio interface or other piece of equipment, so as to minimise the risk of transient clipping. Apparently, the rationale for the soft–limiting approach is that there are fewer audible side effects if the signal is pushed into limiting during recording. A bypass switch takes the compressor-limiter out of the signal path when it is not required.

Although not fully parametric, the EQ section is still surprisingly flexible for a general–purpose channel strip. The two lower bands adopt a bell characteristic, with between 10 and 14 dB of cut or boost range per band. Covering the 30 to 700 Hz range, the low band has a proportional-Q characteristic, meaning that the filter bandwidth changes depending on how much cut or boost is applied. Taking care of the mid–range, and with enough coverage to adjust the highs too, is a 680Hz to 15kHz stage, also with a proportional–Q response.

SPL describe their high–frequency filter as an ‘air band’ EQ. It uses an inductor/capacitor filter circuit, again with a bell characteristic, with the centre frequency set all the way up at 17.5kHz. As the name suggests, this band can be used to boost the highs, adding a smooth ‘airiness’ to the sound — but its single control may also be used to apply an HF cut where necessary. As with the other stages, the EQ section has its own bypass switch. There’s also an overall output–level control, and metering that registers the main output level and the compressor/limiter’s gain reduction.

Internally, the unit is powered from a toroidal transformer, with a true star–grounding circuit-board layout to minimise ground–loop issues. The noise performance varies according to which inputs are in use, but in all cases noise is very low. Importantly, it remains low at practical mic–amp settings, rather than giving good figures only when set to maximum gain. Likewise, the headroom varies depending on the input in use, with the line input accepting levels up to +28dBu and the instrument input levels of up to +12dBu.

Practicalities

Clearly, the JZ Track has been designed to be very easy to use without sacrificing sound quality, and largely it has succeeded in that. The one minor frustration for me was the placement of the instrument jack on the rear panel. I know panel space is hard to find when you only have 1U to play with, but groping around the back of a rack–mounted piece of kit to plug in a guitar cable is not my idea of fun.

That tiny whinge aside, though, the JZ Track is a real joy to use. I did my first round of tests using a JZ Black Hole microphone, which had been supplied with the review model. It performed just as nicely as I’d expected — but as I’d also suspected, the JZ Track performed perfectly well with any of the decent mics in my collection.

If I had to sum up the character of this channel strip in one word, it would be ‘transparent’, not only because of its clean preamp stage, but also because the compressor and de–esser barely intrude on the character of the source, even when they’re working overtime. Even with maximum de–essing, there was no sign of lisping as there is with some de–essers, and while testing the compressor I could get the gain–reduction meter hitting the end stops with the sound still feeling pretty natural. The same can be said for the EQ: it’s a broad–strokes, console–style EQ, except that what would normally be the mid control also covers the highs, leaving the air band free to control the very top of the audible spectrum. This arrangement works extremely well, and offers a smooth and natural character that hangs in there, even if you need to add more EQ than might normally be considered ideal. I love the SPL air-band character, where the use of an inductor coil adds a certain silky magic that allows the highs to be opened out, but without them becoming aggressive sounding.

SPL hardware is always designed with a meticulous eye to detail and the JZ Track is no exception. It may cost a little more than some ‘me too’ channels, but it gives a lot of more expensive — and supposedly exotic — devices a good run for their money too.

The JZ Track would make an ideal front end to an analogue recording system, as it enables you to head off trouble without compromising the sound. But it should be just as much at home in today’s digital world, used to add a touch of analogue polish to the signal before it hits the converters. Similarly, it can be used while mixing via its line input or, if fitted, the A–D converter card. This might not be your weapon of choice if you want to add ‘attitude’ to a sound, but if what you need is finesse and polish, it ticks all of the right boxes.