Advanced Audio: CM-47 large-diaphragm tube mic

It used to be that you couldn't get a large-diaphragm condenser mic for under two grand, and there weren't that many choices anyway. Then some less expensive mics started appearing, and it seemed like every day, the price for an LDC dropped some more. Unfortunately, many of these less expensive mics had an initially seductive brightness that quickly became fatiguing. Now, there are some great mics being made today that don't cost a fortune, but you have to sift through the dozens that only appear to be good to find the ones that actually are good. One day, while lurking on a recording forum, I ran across posts referencing a line of mics I had never heard of before-Advanced Audio. I noticed that the designer of the mics was responding to these posts and really seemed to know what he was talking about. Pretty soon I found myself on the phone with him, and we spoke at length about the history of mics in general. He makes quite a few models patterned after various classic mics. The one in this review is the CM-47. There seems to be almost a frantic fascination these days with the classic Neumann U 47 mic and the character of sound it delivers. There are endless threads on the Internet with people asking which "clone" is the best, while the prices for vintage examples just keep climbing. Well, the CM-47 mic isn't a clone, but it is designed to be in a similar sonic direction as a U 47. It is a large-diaphragm condenser tube mic with nine selectable patterns on the power supply, ranging from omni to figure-8. The mic deviates from the original by not employing the "getting impossible to find" Telefunken VF 14 M metal-bodied tube. It instead uses a much more available 6072A tube, like the one used, for instance, in a Telefunken Ela M 251E as well as many other mics. Dave Thomas (the company owner and designer) explains that the 6072A doesn't roll off the high frequencies as fast as a VF 14, nor is it inclined to be as microphonic. He also points out that he is not configuring the 6072A tube circuit in quite the same way as some would. Instead of using the tube as a single-stage plate output, he's configured it as a two-stage with the output stage being a cathode-follower line-driver. This drives the output transformer at a lower impedance and is supposed to provide a bit more punch to the sound. The transformer is claimed to be wound to the original specifications and perform within 1 dB of the original. As for the capsule, you actually have a choice there. You can use the stock 6 micron capsule, or you can order this mic with a Peluso PK-47 capsule, which are both center-fed designs. The difference is a slightly better tolerance on the frequency response from mic to mic with the Peluso capsule. Also, the PK-47 has a bit more authority in the lower mids and the proximity is a bit wider. Dave points out that one detail that is overlooked in some less-expensive tube mics is the polarization voltage of the capsule. If this voltage is not correct, it can result in an edgy frequency response. Needless to say, he makes sure this mistake is not made, and it does contribute to the sound being more in the direction of a vintage U 47, which employed a different voltage than some other deigns. Okay, I'm going to rant for just a minute. I have seen endless comments regarding various pieces of gear, especially microphones, that loudly proclaim, "If it's Chinese, it's garbage." I've seen idiots who proudly state that they won't even try something if it's made in China. Enough!!! Yes, there is ultra-low-cost, poorly-designed gear that is made in China which doesn't sound good. But guess what? Some Chinese gear is fabulous. Quality varies no matter what country the production line is in. Many companies try and squeeze out every dime of profit margin by requesting that the manufacturing plants cut every corner they can in parts quality and in lack of quality checks throughout production. Many people don't realize that there are very well known, very high end American companies that use Chinese manufacturing, and their products are fabulous. The difference is in how well the products are designed, the quality of parts specified, and the level of QC along the way. That being said, Advanced Audio says that they have really paid attention to the circuit design, parts selection, and quality check procedures throughout production. Inside and out, the build quality is fantastic. The mic body is beyond solid. The heavy, brushed-metal body reminds me of the construction of Brauner mics. Opening up the mic, the internal construction is fabulous. There's just no hint of cutting corners anywhere. The shockmount is better than most of the examples included with most sub-$1000 mics. It is not just a pressure fit; the mic securely threads into the shockmount. It all comes in an aluminum case with foam compartments. Okay-enough blather. How does it sound? I first tried it on a session with one female and one male vocalist. Recording her in the past had been somewhat challenging due to sibilance that was a bit harder to control. I had set up some other mics as well, including a Telefunken R-T-F M16 MkII. The CM-47 performed very well. It didn't exhibit the same top end as the Telefunken, which was not a surprise. The CM-47 had a more mid-forward sound without the same type of top extension as the Telefunken. The CM-47 provided an articulate sound while not exaggerating the sibilance. This is in part due to the capsule and electronics, but also due to the physical orientation of the capsule. As with a vintage U 47, the capsule is mounted higher in the basket so that the ring around the top of the grill slightly bisects the acoustic path to the capsule. This can result in a change to the frequency response, and I'm told that this is partially why it handles sibilance a little better. There is a tendency towards brighter LDC mics these days, and many are used as if the "brighter is better" approach is the "correct" way things should sound. But I must say, it is so refreshing to hear a mic that has a more balanced sound without defaulting to a large HF rise. Don't get me wrong, there are times when the type of vocalist requires that sort of sizzle, but it's great to have the option of another approach. In this case, the Telefunken put a sort of high frequency "zing" on the voice that sounded great on the solo vocal, but might turn into an issue when stacking some voices on multiple parts. On male vocal, the results were similar. The CM-47 was more natural and balanced overall, while the Telefunken seemed a bit more hyped on both ends of the spectrum. We listened to several mics to make a choice for an upcoming project that will feature many stacked vocals. We chose the CM-47, feeling that the overall balance in the sound was more desirable, and a touch of HF EQ could be added later if needed. One thing I must mention-this mic is difficult to overload. Really difficult. The way Dave Thomas has designed the circuit has resulted in a good deal of headroom overall. I tracked a female R&B singer who is notorious for getting very loud and fairly shrill. The CM-47 took it and never crapped out. The characteristics of the mic also helped keep the tone from getting overly edgy. I had earlier tried various mics with this singer, and the CM-47 was the winner. I also tried the mic while tracking an electric guitar through a Vox AC15 amp. I often use more than one mic in this application, and in this case, I coupled the CM-47 with a Royer R-121. Being able to adjust the balance between two mics gives me more control in tone-shaping than just EQ. The articulation of the CM-47 was wonderful, no matter if the tone was clean or crunchy. The high end was defined, but not strident, and there was just the right amount of body to the tone. I now did a comparison that wasn't completely fair. I compared the CM-47 to a $6500 Wunder Audio CM7. This is their top model with the EF 14 M metal tube and the M 7 capsule. We even chose the best sounding example from a pair of CM7s. On vocals, the Advanced Audio CM-47 held its own very well with the Wunder CM7. Now, the Wunder is a fabulous microphone, and there's no doubt that it performs with a certain magic and sparkle. In this test, both mics sounded very similar in overall tonal shape, but the Wunder had a bit more extension on the top and bottom. I was surprised, however, at how close I could get the mics to sound with the slightest touch of EQ. I will say that I could probably punch in a lead vocal (with some care) using the Advanced Audio mic on a track that had been originally recorded with the Wunder. The Wunder exhibited a bit fuller low end when worked close, but again, this could be compensated for with minimal EQ. The Wunder retained its tonal characteristics slightly better when worked from a distance. It had a bit more "reach" than the Advanced Audio, but only by a very small amount. Although I didn't have one for comparison, I'm told that the CM-47SE with the Peluso PK-47 will have the tighter low end and will hold the tonal quality with a bit more reach because of the construction being more similar to the original K 47. On piano, they were again quite similar in character and in off-axis response. They both sounded very natural without any peakiness in the upper midrange. I then mic'ed a Bassman amp from about a foot and a half away, recording a clean guitar tone from a Strat. Here, the Advanced Audio CM-47 actually was preferred in this application due to having a more focused midrange than the Wunder. With the previous tests, the CM-47 could be made to very closely resemble the Wunder with slight EQ changes, but in this case, I couldn't get the Wunder to sound like the CM-47. The CM-47 just plain won that test. The CM-47 was actually harder to overload than the Wunder. Not by much, but it did seem to have a bit more headroom. The only area in which I could knock the CM-47 (in these tests) was in its self noise, being only slightly more apparent than the Wunder's. Its noise floor was nothing that I had noticed previously, and it's not something that I would think would be an issue. It wasn't until I had it side-by-side with the Wunder that I noticed it at all. After speaking with Dave Thomas, he expressed an interest in hearing the clips to evaluate the results to see if he could improve the performance, which he seemed confident he could do. Whereas the Wunder is designed to emulate what a U 47 would sound like in brand-new condition, the Advanced Audio CM-47 is attempting to go after the sound of a vintage U 47 today, after some aging. The high frequencies aren't as pronounced, for example. Dave Thomas says that through playing with tube selection and voltage settings, as well as choosing which of the available capsules to use, the mic could be made to sound "newer" or "more modern" in its response. This type of flexibility is great. This is what I love about boutique manufacturers who make gear because they love to; they respond to users and try and improve their products immediately. Again, the Wunder is an amazing mic; I'm just thrilled that the CM-47 can deliver such a competitive level of performance for those who can't afford a $6000 mic. There are those out there who are critical of mics that deviate from classic designs. I firmly believe that there is real value in the merits of vintage equipment, but I also firmly believe that there can be exceptional value in modern adaptations of those designs. There are many manufacturers that make equipment that is inspired by classic products, while employing differences in approach. Advanced Audio is in that category. No one is claiming that the CM-47 is a U 47, but it is designed to have similar characteristics. I feel that this mic fulfills the type of role for which one would want a U 47. It is amazingly well built and delivers unbelievable performance for the price. At $735, it is quite a deal. Partially this is due to the fact that Dave Thomas doesn't have to support a 5000 sq ft factory or a staff of twenty. He works by himself. He's been an audio engineer and tech for thirty years and is now applying his knowledge to the area of great mics for a decent price. I can't wait to audition some of his other offerings. He makes a very popular CM-12, which is more along the lines of (you guessed it) an AKG C 12. Also in the lineup are CM-67, CM-47 fet, CM-87, CM-414, and CM-54, with more models in the works. These are definitely worth checking out. I'm adding several to my mic collection. ($735 direct; www.aamicrophones.com)