DPA Bruel & Kjaer 4040 Limited Edition Gold Tube/FET Microphone mid-90s - Used

DPA (Bruel and Kjaer) 4040 Limited Edition Gold Tube/FET Microphone. Handcrafted in Denmark.

In the late 1990s, the Danish acoustics firm Brüel & Kjær released the 4040 — a hundred handcrafted microphones built around the same Type 4006 capsule that had won them their measurement-grade reputation. The 4040 was their answer to a question they were not, strictly, in the business of asking: what does a measurement microphone sound like, in a room, on a voice.

The Brüel & Kjær 4040 is a special edition microphone (only 100 were made! One was kept by the designer). The microphone has a large diaphragm and separate preamplifier outputs offering both tube and transistor stages.

Every component placed by hand. The 4040's outer tube is left transparent on purpose. You can see the discrete electronics, the hand-soldered joints, the tuning capacitors — the actual labour behind it.

The Type 4006 head. The thing that makes it what it is. The brass capsule head sits proud of the body, ringed with the same radial vent pattern Brüel & Kjær use on their reference measurement microphones. It's the same hardware that calibrates concert halls and aircraft engines — pointed, in this room, at a singer.

One diaphragm. Two amplifier stages. The matched preamp splits the signal into two parallel channels — tube and FET — both fed by the same single membrane. Because the source is one, there is no phase offset between the two outputs, and no comb filter. The engineer gets both signals on separate channels and blends them in the studio in any ratio.

Tube warmth and FET accuracy, aligned by design.

For vocal recordings, the microphone feeds a minimum-phase preamp with as close to no character as anyone has ever managed. From diaphragm to digital, the signal passes nearly untouched. What you hear on the record is what was in the room.

The 4006 capsule design has had a longer trajectory than most. Brüel & Kjær's pro-audio team spun off as DPA in 1992; the same capsule lineage now sits on NASA's Perseverance rover, recording the surface of Mars. The mic in this room, and the mic on Mars, are siblings.

The microphone arrived from Denmark in a Samsonite Style 2000 briefcase — brass-plated Brüel & Kjær, with foam machined to the mic, its dedicated preamp, the matched shockmount, and the cable. Two decades on, the case still does what it was made to do.

A matched preamp, hand-built for this one microphone.

The black panel inside the case is labeled “Microphone Preamplifier for Brüel & Kjær Type 4040.” Dedicated input, three-step pad at −20 / −10 / 0 dB, single power LED. Not a generic preamp — the mate for this microphone.

It is very interesting and unusual. And it is B&K’s flagship microphone.

This one is serial number #35

All were sold prior to manufacture to artists and engineers. They rarely come onto the market.

A rare opportunity for any serious recordist or collector. The value will only go one way.

Includes case, power supply, cables.

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