Presonus: RC 500 channel strip

The RC 500 is a 1RU-height, rackmount, solid-state channel strip, with a mic/line/instrument preamp that routes to a FET VCA-based compressor followed by a three-band semi-parametric EQ. The EQ and compressor utilize the same circuitry as in the PreSonus ADL 700 [Tape Op #93]. It's an all-metal rugged unit with a small VU meter in the middle. Initially, I couldn't tell if the knobs are metal or plastic, but the knobs and pots feel good. (I later learned from PreSonus that they are metal.) The white lettering on the black chassis is easy to read, though small. The preamp has switches for polarity reverse, 48V phantom power, 80 Hz high-pass filter, and 20 dB pad. The compressor and EQ can be fully bypassed with separate toggles. The 1/4'' instrument input is on the front, and there are XLR line and XLR mic inputs on the back, as well as send and return 1/4'' TRS jacks for insert processing. There's a toggle to switch between mic/instrument and line inputs, and plugging into the instrument input disables the mic and line inputs; all this means that you can leave both the mic and line inputs plugged in. The power switch is on the back. The processing chain order is fixed - preamp, insert, compressor, EQ. A master output level rounds out the front.

The first thing I did was plug in a guitar with single-coil passive pickups. I had the preamp level set too high, and I was greeted with a pretty decent overdrive sound. With the compressor and EQ engaged, I found I was able to get great clean and dirty direct tones. There's enough gain in the preamp to drive it into instability with a wild and glorious squelching sound, even with my not- that-hot pickups. If any boutique guitar pedal makers are reading, you should figure out how they did this. I got so lost with guitar tones, I ended up playing for an hour. This would make a very nice front end to a high-end instrument recording rig. The onset of distortion is farty though, so applications where you want soft saturation would probably not work.

The balanced send/return insert deserves special mention, especially for DAW-based recordists. It can be used as a direct-out, while the main output, which is post-compressor and EQ, is still active. I have owned a few channel strips, and I sold them because I found that I was not wanting to commit the channel strip's EQ and compressor on the tracks I was recording. I have excellent plug-ins that are better than what I can afford in the analog domain, and I do not even use analog high-pass filters, because I'd prefer to tune those exactly with a nice plug-in rather than use fixed- frequency/slope resistor-capacitor circuits. The huge downside to this approach is that when the recording musicians are monitoring in headphones, they are stuck with a lesser tone while they are playing. Plug-ins on a lot of DAW systems, including mine, often introduce unacceptable latency for live monitoring, with the exception of reverb, where the latency sounds like pre-delay. The RC 500 offers the best of both worlds by allowing you to record the unprocessed signal from the preamp, while monitoring (and also recording if you choose to do so) the compressed and EQ'ed signal. You can also insert an outboard EQ or anything else prior to the compression stage. There are some neat tricks one can do by externally processing the send prior to hitting the compressor and EQ, and mixing that with the direct-out preamp signal, but there's no side-chain function.

The preamp played well with all my mics, including and especially my beloved Bang & Olufsen '60s ribbons, the lowest-output mics I know of. There was plenty of gain available from the preamp, without having to resort to maximizing the master output level, and the RC 500 was able to resolve high-frequency transients from these mics better than any of the preamps I own (much to my depression, actually) such that the mics sounded brighter, but retained their signature smoothness. At one point, I had to double-check that the EQ was bypassed. The RC 500 could handle anything I threw at it with ease - you name it, from bass to ukulele. The RC 500 is clearly in a quality range where performance can't really be questioned; it's down to a matter of taste and what features you need.

Frequency response measurements at 192 kHz sampling-rate revealed that the published specifications are conservative. PreSonus claims 10 Hz-25 kHz, ±1 dB, but I measured the high end as flat well beyond 25 kHz. In fact, the measured frequency response of the RC 500 matched the performance of my interface by itself, which means the measurements were limited by the measurement device. I also did a practical noise test between all of my preamps, by setting levels with a test tone and placing a covered mic in a quiet room, and the RC 500 (with compressor and EQ bypassed) was the quietest thing in my studio, with the exception of the preamps on my RME interface, which had the distinct advantage of being internal to the interface that was doing the measuring. The impulse response was practically the same as the pass-through response of the interface.

The compressor is described as FET-VCA, a voltage-controlled amplifier where the amplifier is a FET. This is not the same as an 1176, for example, where the FET is a voltage divider; and the results are much cleaner. It was hard to make it sound bad - other than being able to completely squash the attack of anything or release so quickly that a clipping-like sound can occur. The ratio is fixed at 3:1, but I found I could get a wide variety of feels by adjusting the balance between preamp level, threshold, attack, and release. I was able to make a drum kit bloom, for example, but the compressor is way too clean to add sizzle. It would make an excellent bus or mastering compressor, in my opinion, but stereo linking with another unit is not offered. While doing noise measurements, I noted that the compressor adds significant noise relative to the rest of the unit, but only enough to bring it on par with other, standalone preamps I own. There's no makeup gain in the compressor section, so when A/B'ing compressed/uncompressed signals, I had to quickly turn the master volume. This was annoying but not a deal breaker. The same is true in the EQ section. The EQ does not add significant noise (unless of course you're boosting), and I found it to be smooth and sweet with any given source. There's plenty of boost and cut if you choose to radically change a tone. When I measured a few settings, I could see that the low and high shelves had gradual, broad curves leading up to resonant humps at their corner frequencies, followed by their plateaus. The low and high bands can be switched to peak/notch with a fixed-Q, which yielded broad, symmetrical-looking peaks and valleys. (My setup is not precise enough to comment on perfect symmetry.) These matched the fixed-Q mid band. Note that the frequency ranges of each band overlap. This is a tone-sculpting EQ, not a high-Q surgical tool. The only anomaly I noticed is that the settings on the cut/boost knobs matched my measurements in all but the case of the bass boost. The measured bass boost was a few dB less than labeled.

I had some issues with the VU meter. It has no calibration screw, and there's no mention of calibrating it in the manual, and of course, it did not match the levels reported by my RME interface. The bezel on the meter is thick compared to the small size of the meter, obscuring the meter itself. With my head only 18'' above and 2 ft away from the unit, the meter is partially obscured by the overhang of the bezel.

While the unit is 100% professional, the manual is written for a new recordist, and it's a good launching point even if you've never used a compressor or EQ before. I spotted some other channel strips in this price range that I'd recommend checking out before committing to this one, but none of them made mention of a preamp direct-out, which in my case would eliminate them from consideration.

Spending time with the review unit made me want to own it. Although it sits squarely in the high-fidelity category, you can overdrive it - and you can also get creative with it. It has the feel of a boutique piece that I'd rather only tell close friends about, but it's too late now, because I'm writing this review. While it is not entirely made of discrete electronics hand-soldered by somebody wearing lederhosen (it's probably too hot in Louisiana to consider lederhosen anyway), its performance makes it feel like that, and it is relatively inexpensive given its features and sound. I would love a rack full of these. ($799.95 street; www.presonus.com)