The Sound engineer's Guide to the Galaxy

I started writing this article in the midst of a lockdown, a moment of reflection and nostalgia, 12,000 km away from home, just a stone's throw from the South Pole, immersed in the South American magical realism, amidst a pandemic, empanadas, and revolutions.

In the past 3 years, I took a break from the metropolis and moved to Chile, working for Stam Audio as the Director of Engineering, involved in the development of highly complex projects geared towards intercontinental distribution. It has been an incredibly enriching experience, both personally and professionally, allowing me to tackle pro-audio design at an advanced level.

I have just returned to Italy, ready to reopen the doors of Braingasm Lab in Rome and rev up the engines at full throttle, armed with a new wealth of experience and the desire to rediscover the personal relationship with my clients.

SERVICING NEUMANN U67

RIPARAZIONE U67

RESTAURO U87 - TEATRO DELL’OPERA DI ROMA

RESTAURO U87 - TEATRO DELL’OPERA DI ROMA

Mass production is an opportunity in terms of product distribution and processing times, but 2 years after the introduction of Magnitube, Ferro, and Multi-Deluxe, which performed very well in the international market, I felt the desire to return to custom shop and repair work. This is the activity with which I started and it transformed Braingasm Lab from a desk and soldering iron in the home workshop into a recognized and appreciated brand.

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CUSTOM M49’S

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CUSTOM U47’S

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POINT TO POINT ACTION

I have created an illustrated guide to large-diaphragm condenser microphones, inspired by the classics, differentiating designs based on the main components that characterize a microphone's sound, listed in order of importance.

This "Sound engineer's Guide to the Galaxy" started as a divertissement (in the true sense of Blaise Pascal), a frivolous distraction in a moment of existential crisis. However, I decided to continue it as a tribute to my visceral passion for microphones and as a critique of the incurable heaviness of our French neighbors.

To design the guide, I chose to start with what I believe is the most defining element in a microphone's sound, identifying the 4 most well-known large-diaphragm condenser capsule models (M7, K47, K67/87, and CK12) and continuing the analysis of subsequent stages.

my beloved 1960 u47

my beloved 1960 u47

my favourite vocals recordng setup

drums recording with my neumann u47

drums recording with my neumann u47

  • Capsule: The beating heart of a microphone, the electroacoustic transducer, a bridge between two worlds (acoustic and electric), largely responsible for frequency response, detail, and definition. It would take an entire blog to talk about capsules and describe all the ones I've tried, disassembled, broken, and repaired, up to designing and producing (with the help of specific machines and specialized engineers) a Braingasm signature line that I use both in my models and as an alternative to the originals in major repairs.

  • Amplifier: With few exceptions, there are two choices: tube or J-FET, sometimes configured as unity gain active elements (simple impedance converters), other times as true amplifiers (gain stages). The most significant differences concern headroom, transient response, and harmonic content. The debate of 'one is better than the other' is inconclusive, just like the intuitive misconception that a tube distorts and a transistor doesn't, or that the tube is more 'colored.' Nonsense. It depends. Always. Don't be fooled.

  • Output Stage: Again, there are two options here, solid-state driver or transformer. The interaction of these elements with the amplifier on one side and the external world on the other influences frequency response and the S/N ratio, determining also the microphone's output impedance. With few exceptions, a tube microphone always requires an output transformer configured as step-down. As a general rule, the higher the tube gain (technically its transconductance), the higher the required transformation ratio, necessitating a higher-quality transformer in terms of inductance and core material. The risk in this case is a loss in low-frequency response, ringing or resonances, and worsening of the S/N ratio. The choice of the amplifier circuit and output stage becomes crucial not to nullify the work of a good capsule. In my 'MAGNITUBE,' for example, I chose a tube highly valued in the hi-fi world, not microphonic, and with low output impedance, rarely used in a microphone but very similar in curves to a VF14, which I know well from owning a Neumann U47 (S.N. 4805 from 1960). This (somewhat unexplored) choice offers significant advantages because it allows the use of a low-ratio transformer (in my case, a Sowter 9145, used as an input transformer in the 1073, in my case wired in reverse), ensuring a full spectrum response and huge headroom.

In the case of a J-FET amplifier, on the other hand, a high-ratio output transformer is always necessary (generally between 7:1 and 10:1), as in classic designs like U87 or KM84, which inspired my 'FERRO.'

Finally, in the case of a transistor output stage, we find 2 BJT connected in transconductance, the classic 'Schoeps CMC-style' amplifier, ultra-linear, quiet, and low-consumption, which inspired my 'MULTIDELUXE.'

magnitube power supply

magnitube power supply

drums recording with braingasm microphones

drums recording with braingasm microphones

bg7 capsule

bg7 capsule

CONCLUSIONS

Fortunately, there are none. I will never speak about which microphone is better or worse than another.

Use your ears, unleash your passion for sounds, experiment, and have fun, in defiance of Blaise Pascal!

Session Test Microfoni a Condensatore

Braingasm Neumann U 47


Holidays? Pokémon? Pornography?

Much better. A total session where we roll out the entire Braingasm catalog alongside the finest microphones in circulation.

The goal of this test isn't to determine who's better or worse, but simply to listen, evaluate, and discuss nuances, tones, spatiality, and attitude, setting an upper limit and understanding 'how far we can go' in designing a good studio microphone.

We spent a very nerdy day at Avalon Studio in Montefiascone, in the company of Luca Gentili and Alfio Scoparo, listening to all the Braingasm condenser microphones on vocals, guitar, and drums, comparing them with the best from Neumann, Schoeps, and AKG.


This is the list of microphones we tested:

Neumann U 47 - 1960

Neumann U 67

Neumann U 87 Ai

AKG 414 ULS

Schoeps CMC 5

 

comparing with our Tube 47 and Soviet 67 , plus the J-FET’s Deluxe 12, Deluxe 36Deluxe 47


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Braingasm Microfoni da studio test review comparazioni

We can't wait to share all the news for the upcoming year, including a new lab, collaborations with the best artisans in Rome, and projects in the pipeline such as studio outboard gear and preamps...

Meanwhile, enjoy your holidays. It's been a year full of achievements, all thanks to you incurable enthusiasts.

See you in September,

Rock 'n roll

Teo.

 

Neumann large diaphragm condenser microphone capsules.

While sending some condenser capsules to my trusted workshop for restoration, I realized I had in my hands the history of studio microphones:

An original M7 and various editions of the K87 and K67, all genuine Neumann/Gefell specimens, the reference sound of music production from the '50s to today.

Fascinating, inimitable, beautiful even just to look at. These capsules are the result of meticulous and distinctive research by German engineers, and if they have had no rivals for over 60 years, the reason is simple: they sound damn good.


Each capsule characterizes a condenser microphone according to its distinctive tone, and although the design of the amplifier circuit continues to change (tubes, transistors, back to tubes, with and without transformers, etc.), our favorite large-diaphragm capsules survive this constant evolution. It's now more a son of marketing than real technical needs.


This is an M7 capsule, a large-diaphragm condenser from Neumann/Gefell dating back to around 1957.

The design is the work of engineer Georg Neumann himself, who, perhaps somewhat unwittingly, revolutionized the way we record and listen to music with this project.

The double membrane is made of PVC (Poly-Vinyl-Chloride), a liquid polymer plastic deposited on a glass support to create an extremely thin membrane, approximately 8 - 10 micrometers thick.

Unlike modern Polyethylene membranes (such as Mylar and Hostaphan), which also come in thicknesses of 3 or 6 microns, PVC is much more challenging to work with and is more prone to degradation over time. For this reason, it's very difficult to find an original M7 capsule that has retained its characteristic tone.


In the 1960’s a new capsule was introduced, called the K67, the beating heart of the new Neumann condenser microphone, the U67.

As Telefunken ceased production of the VF14 tube (Neumann was the sole buyer, and the costs for the factory were no longer sustainable), engineers set to work to launch a new condenser microphone model, the U67, which quickly became the reference microphone in recording studios worldwide.

The transition to Mylar had already occurred between the M7 and the K47, as well as the membrane mounting system (screwed instead of glued). Additionally, unlike the K47, which shares the same drilling pattern with the M7, the new backplate has an innovative design. These features give the microphone a sound very different from its predecessors. The K67/K870 is the same capsule found in modern U87 Ai studio microphones.



At the end of the 1960s, with the advent of transistor technology, a new studio condenser microphone, the famous U87, was introduced.

For various design improvements, a new capsule called K87 was introduced. It shares the same drilling pattern as the K67, but this time divided into 2 electrically isolated backplates. In fact, it's the only capsule with 4 contacts instead of 3 (2 membranes and two fixed electrodes). In essence, the K87 is exactly a K67 with the two backplates isolated (this means that if the two electrodes of an 87 are electrically contacted, a 67 is obtained, but the reverse is not achievable).

Missing from the lineup are the K47 and K89, mounted respectively on U47/M49 and U89.


The capsule is the beating heart of a microphone, being largely responsible for its tonality and often the component that determines its final cost, at least for the handmade condenser microphones we design and produce at the Braingasm laboratory. For more refined tastes, we choose M7 capsules (Thiersch Red Line in Mylar or original Microtech Gefell PVC) for projects in the style of the U47, or Tim Campbell for projects in the style of Elam or C12.

Some of these K67 and K87 capsules that will be restored are part of an ambitious project in collaboration with a highly talented sound engineer with whom we are designing custom signature models. Stay tuned!
 

Tube 47 - Braingasm Custom

My Neumann U47 needed functional restoration, and once it returned back, shining like the sun, it gave us an idea: a Braingasm-branded valve U47.

Aware that we were stepping onto the field for the Champions League final, we got to work for many months, studying the original schematics and various "clone" projects, testing the Neumann in all its aspects to discover its versatility, and soldering away. Finally, we are ready to present it.

Like other handmade microphones born in the lab, this is not just another U47 clone or replica in circulation. We aim to create something innovative, inspired by the genius of our predecessors. Always keeping in mind that the Braingasm Lab’s mission is to offer high-quality sound at an affordable price for everyone. We seek to move forward, not sideways.

Before diving into the usual technical details, we are publishing the beta test of the finished microphone, compared to the original Neumann and a Braingasm Deluxe with a Gefell M7 capsule, the flagship model of our transistor series. The microphones are positioned as close as possible to each other, about 3 meters from the drum kit. The preamp used is a Tubetech. Check out the sound:

We have a long testing session planned where we aim to be as comprehensive and precise as possible, appreciating the performance of our new tube microphone on vocals, electric, and acoustic instruments. For now, we'll settle for these three tracks. Follow us to hear the rest.

After treating your ears with some snare and kick, let's finally move on to our beloved technical details:


Let's start with the body, made in Europe with CNC machines. Like the original model, the grille has three levels of mesh, the basket is made of copper, and the body is anodized aluminum. We experimented with other models, shapes, colors, and materials, but the nuclear torpedo has always been the hands-down winner.

Braingasm Tube 47 - Long Body

Braingasm - Laboratorio Microfoni Artigianali - U47 Custom

Neumann U47 Short Body (1960)

1960 Neumann U47

We've maintained the original layout and point-to-point wiring on the sides of the transformer, ensuring that the high-impedance area is as close as possible to the capsule and valve. Our electronic design differs from the original in many aspects, including the capsule biasing circuit and the tube’s power supply voltages. Among various options, we've chosen a Telefunken EF800, powered according to specifications.

NOS Telefunken EF800 tube, AMI BV8 transformer, MKP film capacitors

Braingasm - Custom Studio Micorphones - U47 Custom

VF14 M tube, BV8 original transformer

Neumann U47 inside tube VF14 BV8 transformer Bosh capacitors

Finally, the capsule is a Thiersch STW7 transducer (M7 Red Line). Soon, we'll also test fitting a vintage M7 Gefell. The original Neumann U47 mounts a KK47.

Thiersch M7 Red Line capsule

Neumann K47 capsule

Neumann U47 KK47 capsule

Decca Tree 47

Three identical microphones in cardioid/omni versions for Decca Tree recordings. With this matched trio of 47s, we've raised the bar even higher, implementing a subminiature switch on the circuit for polar pattern selection.

The directivity and slight emphasis on high frequencies (typical of pressure gradients in omni configuration) nod to the behavior of the M50s, absolute protagonists of the traditional Decca Tree setup.

Another special feature is the very strict matching (the capsules were selected from a stock of 20 transducers).