Advanced Audio: CM-28 small-diaphragm tube mic

I love this mic. There - I did it. I didn't bury the lead under my normal lengthy preamble. In fact, I'm going to do the review backwards. The Advanced Audio CM-28 is an amazing deal. It provides wonderful versatility, great balance and detail, and is one of the few SDC tube mics that comes with a pile of interchangeable capsules. I'm going to add a pair of these to my arsenal, because I've used them on almost every session since getting them for review. At $545, it is a ridiculous deal.

Okay, now that the conclusion in out of the way, what am I talking about? The Advanced Audio CM-28 is a front-address, small-diaphragm tube condenser mic with an output transformer. I've used Advanced Audio's mics before. Their CM-47 (Tape Op

#71) and CM-12 are two of my favorite mics. Dave Thomas told me about the upcoming CM-28, so I bugged him about getting a demo pair. As I mentioned before, the CM-28 comes with interchangeable capsules. The prototypes I used had cardioid, omni, hyper-cardioid, and wide-cardioid capsules. The tube is a subminiature 6J1b, which is a Russian version of the EF 732. The mic body has a built-in 15 dB pad, as well as a switchable high- pass filter. The mic connects to the external power supply with a 7-pin cable. The mic, power supply, included capsules, cables, and shockmount all come in a custom aluminum case with foam compartments.

I tried a CM-28 pair first as drum overheads on a jazz session coming in. I decided to also use an SDC pair that I was more familiar with, the Josephson C42 (Tape Op #34). I tracked both for the purpose of comparing later. Now, I think the C42 is a good mic, but in this application, the CM-28 was far better. The thing I keep realizing when using Advanced Audio's mics, is that they are really well balanced. I never find any sonic anomalies in the response. This is again true with the CM-28. The overall balance of the cymbals was really smooth, much more so than with the C42, which exhibits a much "peakier" sound in comparison. The CM-28 pair ended up getting used for the mix.

I then had a session that required solo piano for a television underscore. Although I had other mics set up closer on the grand piano, I set up a CM-28 stereo pair with omni capsules about 15 ft back from the piano. I was amazed at the immediacy and depth from the sound even with these mics fairly far back. There was a good deal of body and presence - much more than I expected. Later, I mic'ed the piano with the CM-28s closer up. I achieved a much better overall sound than with the ribbon or LDC setups I usually use. The CM-28 is my new favorite for piano.

Okay, so enough with the nice, acoustic instruments. Let's see what it can take. Just to be cruel, I jammed it right up to the grille of a Fender '59 Bassman, alongside of a Royer R-121 (Tape Op #19). I switched on the 15 dB pad, but didn't switch on the high-pass. We were tracking electric guitar with a variety of tones, from clean to fairly crunchy. I was shocked. This thing never gave a hint of crapping out, and it sounded marvelous. It provided a great complement to the Royer. I often double-mic guitar cabinets and record to separate tracks so I can have some tonal variety on the mix. The CM-28 gave me great detail and shimmer without ever being grainy or spitty. I haven't found many SDC mics that can do that.

I also used the CM-28 on acoustic guitar, again with great results. As with the other applications, the result was very balanced, natural, and detailed. The same was true when tracking a horn section. Although I didn't close-mic any horns with it, I did once again set up a stereo pair in front of the section. I mixed the CM-28 room mics in with the close mics to add some "glue".

It worked really well. Again, the "reach" of the mics and the perfect balance to the response made the difference between "okay" horn tracks and the feeling of a coherent section.

Okay - I admit it. I haven't used a ton of SDC omnis, but these mics have made me a convert. I'm really seeing the difference between the proximity effect that is indicative of cardioid capsules, and the character of body with the omnis. They both have their application, but the naturalness of the omni's lower midrange was really refreshing. Being able to quickly choose which you wanted by changing capsules was really great. I found that the omni capsule had just a touch more body to it (when used for distance mic'ing) than the cardioids, but they both display similar character and detail other than that.

So next I compared the CM-28 to a similar, but more expensive mic, the Telefunken Ela M 260. The Telefunken uses a different version of the same type of tube and a similar approach to the electronics. The Ela M 260 does not have a built-in pad and high-pass filter, however. I tried the mics side-by-side on various sources. They were not as similar as I was expecting. First let me say that most of the tests involved only the cardioid capsules, as the M 260s I was using only had the cardioid capsules supplied.

First I compared the two on acoustic guitar. There was much more noticeable proximity effect on the CM-28, as compared to the M 260. The M 260 had more sheen to the sound, and less body. Although this initially seemed to make the M 260 jump out as being more present, I realized that the midrange didn't articulate as clearly on the M 260 as compared to the CM-28. Also, there wasn't as much high-end presence to the CM-28 as there was on the M 260. However, while experimenting with EQ, I found I could easily bring forward the high end in the CM-28 without harshness. I got similar results when mic'ing mandolin and piano. The M 260 has a pretty major dip in its frequency response at about 2 kHz, with a slight slope up to about 10 kHz, where it then begins to roll off, and its low end starts to fall off at 200 Hz. Unlike the M 260, the CM-28 just plain has a flatter response with a great low-end extension, and it doesn't exhibit the same types of peaks and valleys. On an electric guitar amp, the CM-28's behavior at the critical 1 kHz range worked a little better than the M 260.

Furthermore, the CM-28 does not display any of the "cheaper condenser zing" that can get so quickly tiring. It also doesn't have quite as much top end as some SDCs that I've tried, but that is not to say that it is at all dull or lifeless. Now, I've heard some people comment that ribbon mics can "take EQ" really well. I'd make the same comment about the CM-28. If you need more brightness, it can be easily EQ'ed in without the mic sounding harsh, and I often found I needed to do just that. But even with EQ, the response was a combination of smoothness and detail. The added ability to alter the proximity effect by switching capsules gives the CM-28 wonderful versatility as well.

After a few months of use, I found myself reaching for the pair of CM-28s in almost every session. I used them in situations that I would normally not think an SDC would be the right choice, finding them extremely versatile for tons of applications. Sure, there are times when the somewhat exaggerated sheen of an AKG C 451 is the right choice. So if you're looking for an SDC that will add loads of shimmering high end without EQ, this may not be your favorite mic. But I've been finding lately that I'm really appreciating a mic that can deliver a balanced perspective of the source, without too much hype.

The build quality is consistent with Advanced Audio's other mics, which I find to be excellent. It shares a similar type of brushed-metal mic body as the CM-47 and CM-12. As with any tube mic, care must be used when seating the 7-pin cable into the mic or power supply, as the pins are fairly thin. But overall, the construction of the mic and power supply is excellent.

So now I refer back to line #1 of this review - "I love this mic." It is a great deal at $545. It has become a mainstay of my studio. I refused to send the pair back to Dave. I just sent him a check. ($545 direct; www.aamicrophones.com)