Warm Audio

New Gear/New Toys Reviews: Warm Audio WA-47 Tube Condenser Microphone

Warm Audio continues their success at offering careful renditions of classic professional audio gear at affordable prices with the new WA-47 Tube Condenser and WA-47jr FET studio microphones.

The WA-47 is a large-diaphragm tube condenser studio microphone that is a homage to the classic long-body Neumann U 47 considered to be one of the greatest microphones ever made and still widely used mostly as a vocal mic because of its mid-range "forward" yet warm sound.

The Warm Audio WA-47 is the result of listening to many vintage U 47 microphones to assess what people like about them and which components have the greatest influence over their intrinsic sound.

Not surprisingly the K-47-style dual-diaphragm capsule with a 6-micron thick NOS Mylar (PET film) diaphragm is the biggest contributing factor. Warm has contracted an Australian company to produce the 34-mm diameter WA-47-B-80V capsule with the same specifications, backplane hole pattern and frequency response as used in the classic German mic.

Next was the tube inside itself. The VF14 was a big part of the original's sound and since those steel tubes are long out of print, a modern replacement was needed. After auditioning several tubes, a Slovak Republic JJ 5751 was selected.

To complete the electronics, an American-made TAB-Funkenwerk (AM) transformer with large core laminations imported from Germany was chosen for the 200-ohm output. The transformer is mounted on a circuit board at the connector end (bottom) of the 254-mm long mic.

Looking inside of the WA-47 reveals a careful design with the tube mechanically held in place and everything else solidly built to last. Wima film capacitors and polystyrene coupling capacitors are used along with a large Solen capacitor for the output.

The WA-47 is connected to its power supply using a five-meter long Gotham Audio cable with 7-pin Neutrik XLR connectors at each end. The compact and rugged linear power supply supplies both the high voltage and filament power for the tube and runs on either 115/120 or 230/240 VAC--it's switchable. In addition to the power supply's (vintage-style) large on/off switch and jeweled pilot light, the power supply has a nine polar pattern rotary switch just like the original power supply. The WA-47 has three main patterns: cardioid, omnidirectional and figure-of-eight plus six interstitial patterns as well.

My Testing

Initially I set up the WA-47 in cardioid pattern here at my studio. I used a pair of Sunset Sound S1P Microphone Pre-amps and matched levels between it and my best (and much more expensive) condenser FET microphone. So I'm not comparing it to another tube mic (as I don't own one) but my A/B did remind me of the big differences between a transistorized mic and a tube mic like this.

Even similar at recording levels, the difference in the vocalist's "on mic presence" was remarkable! The WA-47 provided a thick, slightly saturated presence especially when my singer hit certain loud high notes. The sound of the WA-47 was warmer with a certain lower mid-range thickness that vocalists will just love. As compared to the transistorized microphone with its crisp, clean and transparent transient response, the WA-47 has a much more colorful syrup-like tone.

When double-tracking or stacking vocals you may notice a buildup of lower mid-range frequencies and this is typical and I would recommend changing either the singer's positioning around the mic slightly in the room and/or switch the polar pattern for each subsequent double. With the pattern switch back on the power supply you can have your singer do this for you out in the studio.

And switching patterns on the power supply did not produce noticeable or loud clicks while the mic was on. Since I record vocals all in the same room as my Pro Tools rig, it was easy for me to change the pattern right on the power supply sitting next to me. Depending on how much the singer energizes the acoustics of the space, you'll get varying amounts and different colors of room sound with each additional vocal overdub. This is especially a good idea when the same singer sings all the backing vocals and harmony tracks. Vocal tracks recorded with the WA-47 take EQ post recording just fine.

The WA-47 switched to on figure-of-eight pattern works great for two backing vocal singers. Instead of using the omni-directional pattern or two cardioid microphones (back-to-back) or recording these singers separately, have them face each other with the WA-47 in between. They will arrive at their own internal balance on the mic while we all would listen on the headphone cue. This maybe old school stuff but I liked the way two voices blended acoustically in the room and the WA-47 captured it all well. For each subsequent double-track, have them switch sides of the mic--the two sides of the WA-47 sound close to the same but the acoustic space is different on each side.

I found the mic's fig-8 side-lobes to reject the sound of the room very well so I had much less room tone in the recording than if I had used the omni-directional pattern. If possible, I would try to aim the fig-8 side-lobes towards the studio walls treated with absorption panels rather than the live and reflective surfaces.

When switching to the omni-directional polar pattern the microphone's output level drops a little and I picked up more room tone--maybe even a little outside street noise if I left the doors open! I found omni to be great for singing close in to the mic as there is no proximity effect and a little less P-popping. I used no windscreens for all my tests but I would always recommend using a windscreen. I use a Pete's Place Blast Filter.

The Warm Audio WA-47 Tube kit includes: a cushioned wooden box for the mic, the aforementioned power supply, a shock mount with a set of extra elastic bands, a 5-meter Gotham cable and the power supply's IEC AC cable.

The WA-47 Tube will make a fine addition to your recording studio's mic locker. I like it for its mellow yet big upfront "important" sound that's perfect for vocals, backing vocals or any instrument recording. It is super warm and round sounding with transients not too well represented--it is clear sounding but not clinical at all.

The Warm Audio WA-47 Tube Condenser Microphone sells for $899 MSRP.


Barry Rudolph is a recording engineer/mixer who has worked on over 30 gold and platinum records. He has recorded and/or mixed Lynyrd Skynyrd, Hall & Oates, Pat Benatar, Rod Stewart, the Corrs and more. Barry has his own futuristic music mixing facility and loves teaching audio engineering at Musician’s Institute, Hollywood, CA. He is a lifetime Grammy-voting member of NARAS and a contributing editor for Mix Magazine. barryrudolph.com