XDR2: Boutique Preamp Quality, At an Affordable Price
We spent a considerable number of research hours and a ton of money in R&D costs on the design of the original XDR mic preamp, which resulted in a preamp with sound quality similar to that of expensive esoteric outboard preamps. With the XDR2, we managed to improve our design even further, delivering more consistent frequency response across the entire gain range for superior sound.
While specifications are only one measure of how a microphone preamplifier sounds, XDR2 mic preamps match boutique outboard designs number for number. They offer incredibly low noise, with individual mic pre THD below 0.0007%, and overall mixer THD less than 0.005%. With 60dB of available gain per channel, the XDR2 preamp can handle inputs over a 130dB dynamic range, and can even handle hot line-level signals up to +22db, without any added coloration.
Four Criteria for Great-Performing Preamps
XDR2 Design is based around four critical criteria. While many high-end outboard mic preamps and conventional mixer preamps achieve only some of these goals, Mackie achieves them all. Here’s what they are:
Slow degradation (and eventual failure) of mic preamps resulting from hot patching is one of the mixing console manufacturing community’s dirty little secrets. If you route a phantom-powered mic through a patchbay, it’s roughly equivalent to shorting out a cable every time you patch it. The mic preamp's input transistors progressively break down (called zenering), while the mixer channel gets noisy and can eventually totally croak.
Mackie engineers weren’t interested in any “solution” that even slightly affected the preamp's sound. A lot of research and considerable, old-fashioned trial and error listening resulted in the addition of ultra-high-speed, large-geometry input diodes to the front end of our input circuit. This completely protects XDR2 mic preamplifiers from the consequences of hot-patching and direct short circuits in cables carrying phantom power. Yet it has no effect on sound quality.
The more capable of conveying fine sonic details and wide bandwidth a mic preamp is, the more prone it is to picking up the nearest trucker’s CB or All Sports Talk Radio station. Its rectification components can pick up radio frequency interference (RFI) from a variety of sources, including AM and FM stations, cell phones, and pager transmitters – even microwave ovens – and amplify them to audible levels.
We assaulted RFI on three fronts:
Bottom line for the non-technical: you can use our new XDR2 mic preamps at the end of extremely-long cheap mic cables in an RFI-saturated urban environment while talking on your cell phone and microwaving coffee... without hearing a trace of RFI.
A microphone’s frequency response (and thus how it sounds) is a function of the load presented to it. That load is the impedance characteristic of the mic preamp it’s connected to. If a mic preamp isn’t designed right, it will actually sound different depending on the impedance of the microphone and the cable load!
The XDR2 design incorporates a Controlled Interface Input Impedance system that’s able to accept an enormous range of impedances without compromising frequency response. At any load, frequency response is virtually unaffected down to just one tenth of a dB at 20Hz and 20kHz.
The “XDR” in XDR2 stands for Extended Dynamic Range. Why? Because the XDR2 has over 130dB of total dynamic range. That means the XDR2 mic preamps on our VLZ3 mixers can handle inputs from 24-bit, 192kHz sampling-rate digital audio workstations without added coloration. And it means you can generate 145dB sound pressure levels at the diaphragm of a suitable microphone and get a signal that doesn’t break up.
But wide dynamic range is valuable only if the noise floor stays low at normal gain levels. Our XDR2 preamps offer ultra-low noise at real-world gain settings. Equivalent Input Noise (E.I.N.) is a common mic preamp noise spec. But this oft-touted specification is traditionally measured at maximum gain levels. Normal operating levels are most often between +20 and +30dB of gain. Thus many mic preamps that brag about their -129dBm E.I.N. at +60dB generate far more noise at +30dB where you're going to end up using them much of the time. Our XDR2 design maintains lower noise levels in the critical +20 to +30 range than competitors. XDR2 mic preamps can handle input signals from a full +22dB line level (thanks to extended dynamic range) down to microvolts without a corresponding increase in noise.
All these features combined mean the XDR2 performs like a high-grade studio preamp in the real world, not just inside the controlled, pristine world of the studio, so you can expect great results regardless of whether you’re in the studio, in the field or on the road.
Hear XDR2 and decide for yourself.
When it comes to mic preamps, the proof is in the listening. Plug a really, really good condenser microphone into an XDR2 mic preamp and do some critical auditioning.
Notice the highly-focused high end. The superior ambience retrieval. The substantial, detailed lower bass octaves. Hear textural midrange details you never knew the microphone could reproduce.
Above all, hear this kind of mic preamplifier performance on truly pro, and truly affordable mic/line mixers: the VLZ3 Series.