Black Lion AM/CHA1

Does a 'boutique' approach to building outboard have to mean inflated prices? Not according to this manufacturer...

Black Lion are a Chicago‑based company that started out developing and providing upgrades for other manufacturers' equipment — generally addressing the technical corners often cut in trying to bring a product to market at a budget price. The company's approach is that great‑sounding equipment doesn't necessarily have to be expensive, it just needs to be designed properly — and they are right about that, in my view.

After developing a good reputation and loyal following for their numerous product upgrades, Black Lion started to branch out and develop their own boutique products from scratch, with the declared aim of producing "excellent products at exceptional prices.” They're not mass producers, either: everything is done in house, and mostly by hand.

One of the company's latest in‑house designs is a two‑channel, transformer‑coupled and inductor‑based passive equaliser (but with active gain‑makeup stages), called (rather mysteriously) the AM/CHA1.

Overview

This 2U-high, rackmounting unit, which extends roughly 145mm behind the rack ears, is all very old‑school in concept and technology, but thoroughly modernised in construction with the use of surface‑mount, integrated-circuit gain stages and supporting circuitry.

Of course, plenty of manufacturers have inductor‑based equalisers in their catalogues, from the classic Pultec and Neve designs (and their numerous clones), through to more modern API and Massenburg products — and many more besides, with most being very expensive, too. However, the Black Lion AM/CHA1 was designed from the outset to be an original design, rather than a clone of something else, and to be more cost‑effective than is, perhaps, the norm for inductor‑based semi‑passive units. However, before you rush off to smash the piggy bank and count the penny pieces, this is still an expensive device in real terms — but it does represent good value for money for a product of this kind.

The AM/CHA1's circuitry is actually based on a standard state‑variable filter topology, but uses carefully optimised, custom‑wound Cinemag inductors in the filter circuits, and Edcor PC‑mounting steel‑cored transformers for both the input and output stages. These low‑loss coupling transformers use grain‑oriented iron‑silicon alloy laminations, with a 10k/10kΩ-impedance type handling the input and a 600/600Ω impedance for the output. Amorphous‑core Lundahl transformers are available as a cost option, if preferred. With this amount of iron in the signal path, it will come as no surprise to learn that the AM/CHA1 has something of a vintage sound character, with distinct warmth and sheen properties! That character is largely maintained even when the EQ is bypassed, which is useful if you want to add a bit of flavour to a mix.

The rear panel of the AM/CHA1 includes inputs and outputs on balanced TRS jacks.The rear panel carries the IEC power socket with an integral fuse holder and voltage selector, while four quarter‑inch TRS sockets handle the audio in and out. The front panel is divided into four equaliser-band sections, each with a rotary switch to select the filter frequency, and continuously variable Q (bandwidth) and gain controls (the latter without a centre detent). A miniature toggle switch is used to power the unit, and two push-buttons provide independent channel bypasses to complete the facilities. The review unit had a hole where the power LED was supposed to be (it had fallen back inside because it is only held in place by the goodwill of its connecting wires!), but there are no other lamps or illuminated buttons to indicate when the unit is working or bypassed (and the push-button status isn't at all obvious).

The frequency ranges are switched rather than continuously variable, because of the need to insert different inductors to adjust the filter tuning, of course, but the four bands do overlap quite generously, to maximise usability. The top three bands all have four frequency options, while the lowest band has just three — giving 15 frequency options altogether. For those with a passion for the numbers, they are: Low band, 65Hz, 115Hz and 290Hz; Low‑mid band, 205Hz, 500Hz, 840Hz and 1.76kHz; High‑mid band, 560Hz, 1.2kHz, 3.1kHz and 6.1kHz; and High band, 2.4kHz, 3.7kHz, 8.2kHz and 15.6kHz. The top and bottom bands can also be switched from shelving to a peaking response, via small front-panel push-buttons. The variable Q of the two lower bands can be adjusted over a range of 0.2 (nearly five octaves) and 1.5 (just under one octave), while the upper mid spans 0.3 (nearly four octaves) to 2.6 (half an octave), and the top band 0.3 to 3 (just under half an octave).

The review unit arrived configured for 110V mains power and was not marked to confirm its CE compliance. Although the voltage selector integrated into the IEC power socket made changing the supply voltage easy enough, I decided to perform a quick PAT safety inspection before powering the unit up (I've been burned — once, quite literally — by uncertified equipment before!). Unfortunately, a safety earth continuity check revealed that the earth terminal of the mains inlet socket was not connected to the chassis metalwork at all, despite this being a fundamental requirement for a Class 1 device. An internal inspection revealed that the mains earth went to the audio circuitry ground, but nowhere else! Consequently, all my further testing of the unit was carried out while it was powered from a mains isolation transformer, to ensure my safety. This interesting approach to mains-power safety does need attention before the unit can gain CE certification and be deemed acceptable for use in Europe, so I raised this directly with the manufacturer and was told: "When we were testing the unit, for some reason we kept on finding that it was quieter [when grounded] that way, and the grounding was still reliable in the case of a short or over-voltage, so we didn't pay it too much attention. The difference, however was not enough for us to keep it that way, so in the end we have actually decided to go back to grounding directly to the case, because as we see it (and I'm sure you agree), quieter or not, it's just a more reliable grounding point.” So presumably future retail models will have properly grounded casework, but this might be worth checking before purchase.

Getting Technical

Opening up the AM/CHA1 reveals neat construction, with most components mounted on a single PCB.

Running through a standard set of test measurements, the overall technical performance was very good, although it became clear that the gain through the unit is affected by the loading impedance — as is common with transformer‑coupled devices. With a 600Ω termination on the output, the overall gain was about 3dB, but that rose to 5.5dB when feeding a high-impedance destination. This is not of huge practical significance, perhaps, but worth bearing in mind when optimising a system's gain structure. It was also apparent that the dominant third‑harmonic distortion on the unit's output was attributable to the I/O transformers, and remained even when the EQ was bypassed.

The variety and flexibility of the AM/CHA1's equalisation curves is comprehensive. As is fairly common with this kind of equaliser, substantially higher levels of boost and cut are available when lower Q settings (narrower bandwidth are employed. Roughly ±16dB of gain range was available for the lowest Q‑value settings, rising to a ±26dB swing with the highest Q setting. The unit has a headroom margin of +22dBu (rising to +24dBu in bypass), so great care is needed when using high boost levels on hot input signals with high Q settings. This wide variation in maximum gain is because of the 'constant energy' nature of the passive filter arrangement used here — you can see exactly the same kind of thing in a Pultec EQ, for example. Since the total energy within the filter band is always the same, if the bandwidth is reduced the amplitude increases, and vice versa. Most modern active equalisers — such as those in most consoles — don't tend to use constant‑energy filter designs, so this effect is not that common. Given that this equaliser is best suited to subtle tonal sculpting, the gain range, even in low-Q modes, does seem excessive, and perhaps a reduced range would provide more resolution and control. I rarely found the need to dial in more than about 6‑8dB of gain or cut during my trials, for example.

One oddity that emerged from my Audio Precision testing was a strange frequency‑response distortion effect only apparent in the upper‑mid band. I suspect that this was due to inductive cross‑coupling between channels, and it only occurred when one channel was on maximum boost and the other on maximum cut — so it's very unlikely to be a problem in practice, and no other bands were affected in the same way.

Again, I raised this minor issue with Black Lion and they said: "Small quirks like that can often times be the result... of the varying tolerances of inductors [and it] appears that it's not actually cross‑coupling with another band, but a sudden jump in the filter's reactance. Luckily that's not an issue that would cause the filter to actually become unstable. Thanks for the heads‑up on that point. Definitely gonna take care of that.” I find that a most reassuring response from the manufacturer.

In Practice

The absence of centre detents on the filter‑band gain controls makes zeroing the EQ more difficult than it should be, but the controls are nicely weighted, feel solid, and are arranged in a nice, spacious panel layout. Despite the absence of any manual (in the box or on the web site), the device is perfectly intuitive to understand and use. I found the way the gain changes quite dramatically when altering the Q control to be a little frustrating occasionally, as it made EQ optimising a rather iterative process, but the AM/CHA1 is not alone in this operational quirk.

The frequency options available in each band are well chosen and seem musically appropriate, and the unit works very well when it comes to gentle, creative tonal shaping. This isn't a surgical tool for removing specific unwanted signals, but does work well to pull out the best, or to recess any irritating aspects of a mix or source's tonality. For this reason, a more moderate gain range for each section would allow the EQ to be applied with a little more finesse and control, but perhaps this is nitpicking.

Verdict

The AM/CHA1 definitely brings its own distinct sonic character to the party, with a musically benign but noticeable warmth and thickening of the bottom end, and a smooth, almost creamy high end. Good analogue equalisers like this are a joy to use, with minimal settings often delivering sublime enhancement. The top 15kHz filter setting in peak mode with just a hint of gain is great for adding air and sparkle, for example, and overall the AM/CHA1 is a delightful-sounding equaliser. A mastering version with switched and matched controls throughout would be a big hit, I'm sure.