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AMAZING - CharterOak PEQ1 is one of those boxes that has the magic"
 
CharterOak ProAudio - Microphones, Signal Processors, Headphones
SPECIFICATIONS

FREQUENCY RESPONSE
20Hz-20kHz w/in 0.4dB -3dB down at 60 kHz
Harmonic Distortion
0.01% below +21dBu
Maximum Output
+23dBu
Signal to Noise Ratio
-85dB referenced to +4dBu
Maximum output
+23dBu
Input Impedance
600 Ohms balanced
Output Impedance
600 Ohms balanced
Dimensions
Standard 2RU / Length 19” Height 3.5”
RESOLUTION Mar 2012

PEQ1 Resolution Review: Mar2012

CharterOak PEQ1
It’s an EQ but not as we know it, Jim. Two channels, six bands and you’ll have to rely on your ears. GEORGE SHILLING struggles to find fault….


CharterOak surprised everyone with its unusual SCL1 compressor, which we took a look at a few years ago (Resolution V8.2). The PEQ1 is a stereo equalizer, and like the compressor this also uses some unusual principles. Following the styling of the SCL1, this is a 2U rackmounting box with a gorgeously shiny front panel. The compressor was almost the definition of ‘subtle’. And before we get onto the sonics, I’d cheekily suggest that the legending on this unit’s front panel perhaps also expounds on the philosophy: the laser-etched grey lettering on the almost mirror-like shiny black panel is so subtle it’s actually rather hard to read. On the rear are XLRs for left and right inputs and outputs, and an IEC socket, accompanied by voltage selector and fuse holder. Also on the rear is the power switch, no doubt located there for good performance-related reasons. All being well this will bring dim (subtle) green LED on at the front panel. Inspired by the Cello Palette (based on research by Richard Burwen) and operationally not unlike the excellent Gyraf GXIV, this is a stereo EQ with one set of dual-ganged pots that control both channels simultaneously. This is terrific if you are EQing stereo sources or a stereo mix, but rather precludes independent channel use, of course. However, there is a useful pair of separate Gain Trims for left and right channels at the far right of the front panel, with numbered knobs ranging for 0 to 10. These are not full range fader knobs and instead offer approximately -10dB to +6dB with unity at around 6.

The EQ comprises six bands, plus a Low Cut filter. Each band comprises a simple boost and cut knob, and a toggle to select between two or three frequencies. The lowest band features 20/60/40Hz, then 80/120, next is 400/800/630, then 1k/3k/2k, 5k/8k, and finally 15k/50k/20k. The knobs are gorgeously damped, feeling very smooth. Uncalibrated, there merely have a centre mark, with three dots spaced around each side.

At the far left is an EQ In/Out toggle along with the Low Cut toggle. The big surprise here is that the EQ boost and cut knobs have differeing ranges on the different bands. Outer bands have +/-12dB, the next two in have +/-8dB, with the centre two mixing at +/-4dB. This is the Burwen inspiration: our ears are more sensitive in the midrange, so therefore the mid frequency bands have smaller ranges than the outer ones – you are the more comfortable opening up the knobs to their full extent (if necessary) in all bands. This is also why there are merely dots on the panel, rather than numbers as this could influence engineers who might have the idea that adding 12dB at 50kHz is wrong. It inspires you to turn the knob to where it sounds good rather than worrying about how many dBs of boost there is. In fact, the ranges were reduced from the initial design, lessening the effect of full boost or cut in some brands. The bands are wide overlapping bell curves and unlike the Gyraf design this is a fully active unit. It uses high quality op-amps – these are Burr-Brown video chips, which give a very high bandwidth.

CharterOak found that when customers plugged in the original SCL1 compressor into, say, semi-pro gear, they found that there wasn’t enough gain on the input to achieve desired compression. So after the initial production run subsequent circuits were modified to enable compression at lower input levels. The PEQ1 has been more extensively beta-tested (which is why it has been a little long to market and review. Ed). This new unit is astonishingly quiet – with 600-Ohm termination and input and output transformers the headroom is an impressive 6 bolts RMS. The headroom means that the best performance is achieved with a hot signal, but even with a normal signal the noise floor is around -85dB.

I couldn’t resist having a peek inside. The power supply selection uses a toroidal transformer and its circuitry is housed in a separate compartment at the rear, away from the audio board. Chunky Cinemag output transformers are mounted on the front of the divider panel. The rest of the audio circuitry is on one large board. But the most striking feature is that, instead of running power along traces on the circuit board, two unusual looking 1cm high chunky metal bus bars are mounted across the board, comfortably delivering ample current, keeping impedance constant in any EQ situation. And rather than sourcing a single type and brand of capacitor, some experimentation was undertaken to find the most flattering type for each frequency.

For an initial test I plumbed the PEQ1 across an already smooth and sophisticated track of a jazzy female vocal and piano song, with bass guitar, cello, acoustic 12 string, percussion and backing vocals. The singer had a delicious chocolaty Rumer-esque warmth, and I thought the mix was already sounding organic. But quickly experimenting with the PEQ1, there was something appealing to do with each EQ band on the CharterOak. I added some high top; 50k (with Italian polystyrene capacitors) and 20k both incredibly sweet, yet perhaps a little too supersonic, but a dot of 15k was certainly enhancing. As was a dot of 8k, in fact a bit more than a dot’s worth on the latter, and a dot of 400 was removed. The Low Cut filter took away a little low end waffle from the bass guitar, tightening it up nicely without being too obvious. It starts at 40Hz (and is 6dB down at 20Hz) and this is often perfect for when you are mixing or mastering. Finally some bite was added to the vocal area with a bit of 3k boost. The track swiftly came to life, with a completeness and tightness that had been previously absent. Bypassing the unit made my mix sound shrouded in blankets (Albeit organic ones. Ed). I perhaps had overdone the EQ a touch – the PEQ1 is tempting that way – but it was all thoroughly natural sounding, the track presenting itself more like a completed record.

Although the PEQ1 can effortlessly do subtle, more radical settings will produce remarkably powerful tonal changes, with none of the unpleasantness that sometimes accompanies such brutality. Setting all the knobs to full boost- or cut – provides perfectly listenable results, but there’s more transformation going on than with, say, the very subtle Dangerous Bax. And the differing ranges described are soon forgotten. Like the fabled Rolls Royce Motors specification, all bands do indeed seem to have ample power. The 50k boost added astonishing delicate clairity to an apeggiated 12-string acoustic, and all manner of warming and tightening is possible with low frequency instruments using the various bands.

The PEQ1 is one of those devices that has the magic. Very soon after plugging in you will feel the glow that certain units just have. Ultra-clean, yet characterful and musical, there is always something delicious you can add with this. And this will surely become a favourite with mastering engineers – especially when they discover the mastering version, which uses Grayhill switches. Gorgeous.


PROS : supremely sweet, juicy and musical EQ; exceptionally good noise performance and headroom; six (ganged stereo) bands plus Low Filter.

CONS : hard to read legending.

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