Late last year, I received an awesome email from Takeo Yamamoto, who had stumbled across Tape Op #4 when he was living in NYC ages ago. He now owns the pro audio sales/distributor and development firm, Umbrella Company, in Japan. One of their products is the Active Mic Cable, an interesting new idea for getting the most signal out of dynamic microphones – either moving coil or ribbon. By putting a high impedance Class A transistor-based, phantom-powered buffer circuit in the female XLR jack of a 16-foot mic cable, this device claims to achieve a wider dynamic range and "best impedance conversion and signal transmission."
My first experience with Active Mic Cable was in the middle of a busy tracking session. Years ago, while tracking at Tucker Martine's Flora Recording [Tape Op #29], my client requested a "less pristine" vocal sound. Seeing a shiny car hood ornament-looking thing in the mic locker, I pulled out an Electro-Voice Model 664 dynamic mic – it was exactly what we were looking for, with a tight midrange focus yet a very clear and interesting sound. I quickly bought my own 664. When I pulled it out during my busy session, I felt right away I wasn't getting enough signal or clarity out of the mic – it may have been the preamp I chose or something else, but I knew it had sounded better before. I remembered the Active Mic Cable, swapped it in, and went back to listen to the live vocal. It was much clearer to my ear, but I was baffled as to why I still had my mic pre set for 60 dB of gain. Since it was sounding better, we kept using it all day for live tracking, plus the final lead and doubled vocals.
Later, I looked at the info sheet included with the mic cable and realized my error; this is not a "booster" circuit, as I had assumed. I had been thinking it was similar to my Cloud and Royer boost boxes, but this cable only provides a load that the microphone sees and feeds into, thus sending down the cable a similar voltage level as the raw mic, but with the active electronics providing more clarity and dynamic range. Most microphone preamps have an input impedance of 1500 to 2000 ohms, but Active Mic Cable has a very high input impedance of 53,000 ohms, followed by the buffer circuit. It makes sense to me as a way to mitigate long cable run signal loss and high frequency loss due to the slight resistance and capacitance of longer wiring. Boost circuits for mics are a popular item these days, and they can be quite handy, especially with low-output ribbon mics and quiet sources feeding prosumer interfaces. But have you tried using one on a loud snare's close mic? That doesn't work. But what if you want the clarity and openness that a booster can bring on a channel like that? Here's Active Mic Cable.
In the following weeks, I tried the Active Mic Cable on snare drum. With two identical dynamic moving coil mics (we swapped mics around to make sure they were reacting the same), and two channels of the same preamp, I continually found the active mic to have a brighter tone and was slightly louder (+.63 dB). I also noticed a clearer low midrange transient shape, something that really helps snare tracks stay present in a mix. Next, with two ribbon mics on a guitar amp, I found that the active mic was actually a little bit quieter (-2.2 dB) but with a somewhat clearer high end and slightly less low (potentially muddy) mids than the other channel. In both these cases, I could see Active Mic Cable being helpful for achieving a more focused tone, and it did seem apparent that not only were frequencies affected, but that transient details (at low and high frequencies) came through in a slightly more distinct way. This part I found fascinating. Do I need 24 more of these Active Mic Cables? Hmmmm.
I understand why this product is made in cable form, and not as a little XLR adapter box or inline housing; this way the circuit inside the XLR jack can be as close as possible to the mic or it can be used as a handheld. But being that the Active Mic Cable looks just like any standard mic cable laying around my studio, I'm afraid it'll get accidentally used on the wrong mics or stored away on the spool with all the normal mic cables. Finding a place to hang it and making sure staff and freelance engineers understand what it is, when to use it, and what to expect only adds to the task of running a busy commercial studio. However, I guess I could say that about many of the studio innovations I've seen over the years.
Nonetheless, in the end I'd advise any studio or recordist to grab at least one Active Mic Cable for use in select situations, and I believe this is a useful new product to have on hand.