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Blue Bottle Mic Locker

Valve Microphone & Capsule Set
By Hugh Robjohns

Blue’s classy — and enormous! — valve mic kit lets you swap between four different capsules for a range of modern and vintage sounds.

Blue Microphones have been around for long enough now that they probably need little by way of introduction from me, and I’m sure the company’s extensive range of aesthetically distinctive microphones will be familiar at some level to most readers. Suffice to say that the company have Latvian origins but the mics are built in the USA using parts sourced in both America and Latvia.

Unusually, the subject of this review is not an entirely new product, since the Blue Bottle microphone was in the company’s opening product portfolio. However, this flagship microphone has recently been relaunched in the form of the Bottle Mic Locker, a complete vocal mic set comprising a dedicated power supply, the Bottle microphone body, and four interchangeable capsules (drawn from a range of nine), and all neatly protected within an SKB hard-shell case.

The Bottle Mic Locker is intended to provide the ultimate hardware vocal mic, since the four tonally and technically distinct cardioid capsules can be swapped while the mic is powered, making it very quick and easy to find the capsule type that best suits any particular voice. The four capsules are based closely on classic designs to provide both vintage and modern sounds, without relying on any digital processing!

The aesthetic design of the Blue Bottle mic closely emulates Neumann’s very first commercial microphone, the CMV3 dating from 1928. This ground-breaking model quickly acquired the ‘bottle’ nickname due to its distinctive shape, and several modern manufacturers have produced notionally bottle-shaped mics that share the same vintage aesthetic, although most are physically smaller. A few manufacturers have also produced mics with interchangeable capsules that retain Neumann’s CMV3 M-series bayonet fixing arrangement, making their mic bodies fully compatible with the original vintage Neumann capsules, in addition to a selection of modern equivalents. The shortlist of compatible mics includes models from Violet Designs, the now-defunct Red Microphones, and, of course, Blue. Blue’s range has several compatible models including the smaller Bottle Rocket Stage 1 and Stage 2 microphones, as well as the original Bottle mic reviewed here.

Opening The Box

Opening the tough SKB case immediately reveals the no-expense-spared nature of this product, but it is the sheer size of the mic body that really grabs all the attention. This thing is huge, measuring around 270mm high by 90mm in diameter, and it weighs just over 1.6kg (without a capsule attached). The silk-finish, blue-anodised body features anodised aluminium caps top and bottom, the top one featuring a stubby spigot connector with a horizontal pin which locates the bayonet capsules, while the bottom one houses a 5/8-inch thread for direct attachment to a mic stand, and a seven-pin XLR socket for the included ‘Champagne’ mic cable to the power supply. The Blue company logo and a pearlescent power lamp indicate the front of the mic, while a metal label carrying the model type (9612a) and serial numbers is fixed to the rear. A shockmount is not supplied and, to be honest, this thing is so massive that I’m not sure a suitable model would be practical even if it existed!

The mic body houses the impedance-converter circuitry, which is based around an EF86 pentode valve wired as a triode in a common-cathode configuration. However, as you might expect in a flagship product, the valve is supplemented with a fair bit of additional solid-state circuitry and clever technology. For example, instead of the valve’s anode load being a simple resistor or the primary of the output transformer, it is actually a constant-current source built around a four-transistor Wilson current mirror. An active DC servo system is also employed to maintain the anode voltage at a constant 65V DC — an arrangement Blue claim to be unique in this application, and one which ensures a consistent performance and long valve life.

High-quality passive components are used throughout, as well, including metal film resistors and polypropylene coupling capacitors with very low dielectric absorption (DA) and ESR (equivalent series resistance), many of which are bypassed with polystyrene capacitors. The capsule connection receives its (adjustable) DC bias through a 400MΩ resistor, and the coupling into the valve grid is via a parallel pair of styroflex capacitors on Teflon mountings and another 400MΩ resistor.

Driving the audio output is a relatively large custom-made, hand-wound, 13:1 ratio transformer built in a symmetrical two-bobbin hum-bucking configuration with silver wire around nickel plates. It is protected from external magnetic fields within a permalloy metal casing and the transformer design has been optimised to provide both a high dynamic range and minimal LF distortion. The attention to detail throughout is very high — as you might expect in a product costing as much as this one does!

The same quality of design and components is evident in the chunky ‘Blue Power Stream’ power supply unit, which features a large control knob on the front panel. This is used to switch the capsule bias voltage between a nominal (and typical) 60V DC and any of eight alternative values from 30 to 95 V. Changing the bias voltage affects the sensitivity of the microphone capsule, with a range of -6 to +4 dB relative to the nominal value of 20mV/Pa. This not only makes it possible to accommodate particularly loud or quiet sources, but also to determine how hard the valve is driven, and thus how much saturation is incurred. The maximum SPL is 134dB (for 0.5 percent THD), and the self-noise is 7.5dBA. (All three specifications are those achieved with the standard B6 capsule, and there are no pre-attenuator or high-pass filter options either on the mic or the power supply).

At first sight it appears that only the centre of the large front-panel control rotates, but actually the entire disc moves (including, surprisingly, the recessed -, 0, and + markings), and the alternate switch positions are found purely by the tactile feel, as there are no labels. An interesting side note is that the same Power Stream power supply unit is employed with Blue’s Cactus microphone, but in that application the variable bias voltage is applied to the rearward half of its dual-diaphragm capsule, such that the switch alters the effective polar pattern in nine steps, instead of the overall sensitivity.

The rear of the Power Stream supply features an IEC inlet with an integral fuse-holder, along with an adjacent 110/220 V AC selector and on/off rocker switch. A seven-pin female Neutrik XLR accepts the cable from the mic, while a standard three-pin male XLR provides the audio output.

To avoid damaging the valve and shortening its lifespan, the power supply is designed to be very gentle and nurturing! When first switched on, only the valve heater circuitry is energised, and the circuitry ensures there can be no current surge through the cold heater filaments. Only after 80 seconds or so is the anode HT voltage slowly ramped up — a scheme designed to avoid any risk of a process known as ‘cathode stripping’, which can occur if the anode is allowed to operate at full voltage when the cathode is still cold, effectively ‘stripping’ electrons off the cathode before it is ready and potentially shortening the valve’s life or making it noisy. Sensibly, the audio outputs passed through the power unit remain muted for about three minutes after the initial switch-on to allow the system to fully stabilise before use.

B Happy

Included in the standard Mic Locker kit are four capsules, identified only with the model numbers B0, B6, B7, and B8. As shipped from the factory each capsule has three brass screws around the periphery which clamp the internal suspension for protection in transit. These must be removed before use and don’t need to be replaced for normal storage, although it’s a good idea to keep them safe in case the capsules need to be shipped anywhere in the future.

All four capsules are large-diaphragm designs with cardioid polar patterns — the de facto standard for vocal duties — but they have different mechanical designs and consequently deliver very different sound characters. The B6 capsule is Blue’s ‘standard’ or ‘reference’ design, and it is intended to emulate the sound of AKG’s classic vintage C12 capsule. It features an edge-terminated dual-backplate construction, and boasts a bright, crisp sound with plenty of low end thanks to a relatively strong proximity effect. Blue describe it as having classic warmth and a larger-than-life sound; which seems a fair description to me.

The B7 capsule is, in many ways, the perfect complement as it is essentially an homage to the K47 capsule employed in Neumann’s U47. This is a large-diaphragm, centre-terminated cardioid design with a single shared backplate and an unpolarised rear diaphragm. It delivers a very classy vintage sound which focuses more on the mid-range detail but still delivers a noticeably airy presence that really works in a mix.

Blue suggest the B8 capsule is the most versatile and flexible of the bunch, and arguably the most neutral-sounding but with a lot of detail and precision, while the B0 capsule delivers “the ultimate big vocal sound” with a bright, silky, and quite intimate character.

With such a diverse range of sound characters on offer here it’s hard to imagine one of these four capsules not working brilliantly on any particular voice. And since they can be hot-swapped in a matter of seconds it is very quick and easy to try out the alternatives with the advantage that the capsule is always in exactly the right place. Another handy benefit of interchangeable capsules is that the capsule can be swapped for double-tracked and harmony parts, lending each individual vocal pass with a slightly different tonal character, and that helps a lot in making the montage sit nicely in the mix.

Of course, the Bottle is not restricted only to vocal duties — although its imposing size is guaranteed to make any artist feel extremely special! It can be used on all manner of other sources too, provided you can place the mic body appropriately, and the five other capsule types offer some interesting options. For example, the B4 capsule is an omnidirectional capsule with a small diaphragm mounted to be flush with a Perspex sphere, à la the Neumann M50. The B5 is another omni, but this time with a large-diaphragm configuration, and the B2 is a vintage-style figure-of-eight design. Where the off-axis coloration inherent in large-diaphragm cardioid mics might prove unwelcome, the B1 and B3 capsules are small and mid-sized cardioid designs, respectively. So there are plenty of alternative capsule options to explore and which extend the versatility of the Blue Bottle microphone.


The Blue Bottle is quite an imposing mic — I can’t think of much that is a similar size, let alone bigger — and a big shiny microphone is always going to boost a vocalist’s confidence! Everything about the Bottle oozes class and quality, from the individual system elements to the sound itself, and the four capsules all offer clear tonal differences which can be selected to suit the particular voice and requirements. The ability to swap capsules without powering-down the microphone is extremely useful — although it’s important to remember to mute the mic channel or monitoring beforehand as there can be some pretty dramatic thumps and pops during the process!

All in all, the Blue Bottle Mic Locker is an impressive piece of kit, and a very traditional old-school alternative to the modern trend of employing sophisticated digital processing to ring the sonic changes associated with different capsule designs. However, while the high cost of the system is fairly justified given its quality and versatility, this is clearly a microphone system that will only appeal to those with deep pockets... and I certainly envy them!


Broadly similar equivalents are available in the Blue range (Rocket Stage 1 and 2), as well as from Violet Designs.


  • Superb build and sound quality.
  • Guaranteed to make every vocalist feel very special!
  • Adjustable capsule bias to change sensitivity and valve drive.
  • Supplied with four cardioid capsules to offer useful tonal variations.
  • A wide range of additional interchangeable capsules available.


  • Cost.


A huge and imposing valve microphone with no expense spared in its construction or electronic design. It is compatible with Neumann’s original M-series capsules, as well as Blue’s own extensive range, and capsules can be hot-swapped.


£4999.99 including VAT.

MusicPsych +44 (0)207 607 6005


Blue Microphones +1 818 879 5200

Published April 2017