Quantum Electric Q24 Studio Condenser

Review Valve/Tube Microphone

Handmade studio microphone with innovative thinking

A while ago I had a listen to the first microphone from a new Swedish manufacturer, the Q47 from Quantum Electric. I was incredibly impressed with the performance of that mic, but the price tag could be perceived as a bit of a deterrent for anything but truly professional recording or broadcast contexts. My colleague who tested this mic emphasized that the Q47 was not expensive per se, but it might still not be suitable for anyone with a smaller wallet. Now this manufacturer has presented a microphone that remedies this. Let’s have a look at the Quantum Q24.

Quantum Electric – a star is born

The company which bears the name Quantum Electric is the life’s work of Vladimir Carrasco Castillo. Not that he’s been downright idle before; he’s worked as a Grammy-nominated music producer, songwriter, screen writer, and much more. But it was only when he decided to design really good and good-sounding microphones that everything seemed to fall into place. Vladimir’s first creation in this field, the Q47, which was in a way a tribute to a vintage predecessor with the same numbering, was released a couple of years ago, but when it was time for a successor with a more manageable price tag, the manufacturer chose to give it the number from the year development took off; thus the Quantum Q24 was born.

Construction

The Q24 is assembled by hand in Sweden and it comes in rather an unassuming – but impact-resistant – plastic case. But the case is a deliberate choice. Instead, Quantum Electric has chosen to focus on the things that really have an impact on the sound.

The mic comes with a very robust shock-mount, a power supply with a rugged metal enclosure (230/115 volts), equipped with Binder och XLR Neutrik connectors. Also included is a 5 meter Sommer multicable with Binder and Neutrik connectors respectively. A Swiwelmount with Sommer multicable plus Binder connectors is optional.

A lot of effort and many hours have been put into creating a microphone with a natural and pleasing sound, a mic that can compete with the best of them performance-wise. Components have been chosen with great care, and the entire microphone emanates top quality. A specially designed M7-type capsule forms the very heart of the construction, and even the transformer used has been custom made.

Already there, all measures and steps have been taken so that the conditions for recreating the vintage sound of the microphones Vladimir has as sources of inspiration in his work (i.e. Neumann M49, the Church, and the like) can be met.

The Q24 is based around a recreation of the classic Neumann M-7 centre-terminated capsule.

However, Vladidmir has taken a few more stides in his pursuit of the perfect sound. This may seem an impossible task in itself, but Quantum Electric has its goal clear. If no one else can make circuit boards that meet their requirements, they manufacture them themselves, the components that are intended to populate that board are chosen with the greatest care. To the greatest extent possible Vladimir tries to track down NOS components – such as the RFT-manufactured capacitors – these have been prioritized. Many other parts have, as mentioned, been custom-made.

Another part that shows Vladimirs attention to detail is the basket surrounding the microphone. Here, the manufacturer is using two layers of different thicknesses of stainless steel wire mesh, to give the microphone a better chance of surviving a fall to the studio floor; something that a couple of users have already expressed their deep gratitude for. One might argue that the shielding properties with stainless, are not as good, compared to brass or copper, and three layers of these meshes (as in old Neumann mics) would probably have provided better protection against involuntary plosives, but as we all know, there are special appliances for such issues…

History has also shown other manufacturers who have used steel for its better impact resistance, such as AKG with its C12, C28 and D12. As a manufacturer, you have to weigh all the pros and cons.

The included power supply has also been constructed with the greatest care. I had the opportunity to have a look inside it, and it was an incredibly neat build, with, among other things, really substantial decoupling capacitors. But of course appearance is not all important in the audio world, because in the PSU as well, all the components included have been selected and dimensioned for the best possible performance for many years to come.

Nuvistor

The manufacturer has also put a lot of effort into tracking down another important component in the context. A military-grade Nuvistor replaces the traditional valve as the impedance converter in the input circuit. The first Nuvistor was introduced by RCA in 1959, and its design and manufacturing process were radically different from the traditional glass or steel tubes. The Nuvistor was manufactured by means of a simple remote control inside a vacuum chamber. The metal casing was then sealed with a ceramic bottom plate. The power-efficient Novistor could be as small as only a couple of cm high and about half as wide, and its miniscule size meant that it could fit in contexts where the significantly larger glass tubes had difficulty asserting themselves.

Today, Nuvistors are mainly used in highly advanced hi-fi amplifiers, but in the early 1960s there were many applications. They were used in tv-sets, radio receivers and -transmitters, and for various military purposes. They were also used in the Ampex MR-70, a one-inch four-track studio tape recorder from the mid-60s.

Quantum Electric is not the first company to use Nuvistors in their microphones though. As early as 1962, a 7586 Nuvistor was used in the AKG C12A and later in the C12B. Both of these microphones were manufactured right up until 1976, and well-maintained specimens of these are highly sought after on the used studio equipment market today.

There was actually for a time in Neumann’s history a conversion kit to replace the VF14 tube in their U47 with a Nuvistor, the 13CW4. This was at a time when people were beginning to suspect that the era of traditional steel tubes would not last forever.

Today, in the Q24, Quantum Electric has utilized the Nuvistor for all its good properties, such as mechanical resistance, low microphonics, excellent noise figures and an extremely compact format.

Noise is not what we’re looking for…

I was very impressed when I heard recordings made with the Quantum Electric Q47, and I was therefore naturally very curious as to how the manufacturer would succeed in producing a microphone with the same type of sound image, but at a significantly lower price.

Admittedly, the Q24 has been freed from a lot of bells and whistles such as switchable attenuator, LF filter and user-selectable polar patterns, but the fact remains, there is a lot that has to fall into place for the Q24 to approach the Q47’s performance.

I wasn’t disappointed, though. To begin with, I found the Q24 to be just as free from self-generated noise and hum as its big brother, the Q47. Both the meticulously constructed power supply – in terms of low hum – and the Nuvistor with its peripheral components, have probably contributed to the extremely low noise. But of course, it doesn’t stop there.

It was also evident that the Q24 had a higher sensitivity than my reference microphone. I had to increase the gain of my Peluso by 4-5 dB to approach the same level as the Q24, and then of course I would have also raised the noise to the same degree.

I’ve compared the Q24 to microphones from several other manufacturers that attempt to recreate the sound of the golden era when valve microphones were more or less the only thing offered for recording purposes. None of the others can offer anything close to the qualities inherent in the Quantum Electric Q24.

Above all, this applies to the noise level, but also the qualities that we sometimes carelessly call warmth or valve sound are inherent in the Q24 to a much higher degreel. We are now talking about microphones in roughly the same price range, i.e. around SEK 25.000 (approx. £

Vintage Design – Vintage Sound?

In terms of use, the manufacturer recommends the Quantum Electric Q24 for recording voices and all forms of acoustic instruments. When it comes to voices, I see the Q24 as an excellent microphone for both voice-over and for other post-production or broadcast contexts. Partly for the low noise figures, but also for its warm, yet neutral, sound character.

According to the manufacturer, components have been chosen so that the microphone can handle transients in a fairly typical way for vintage valve microphones. This means that the Q24 adds a small amount of tube compression without sacrificing dynamics. They have also chosen to create an amplifier section with few components and to keep all signal paths as short as possible – all in order to keep the self-generated noise at the lowest possible level.

I tested the Q24 with a few different mic pre-amps. First the ones built into my audio interface, but I also used a pre from TK Audio, A Summit Audio 2BA-221, and finally a VMS ONE from Slate Digital, a mic stage built to be ultra-linear and have a neutral and uncolored sound character. Funnily enough, I found the combination of the Q24 and TK’s M81D mk2 to be the combo that worked the best. Is it a coincidence that TK chose to call the company Vintage Design in the very beginning?

Recording; a song but no dance

I used the Q24 to record a number of different acoustic instruments: guitar, mandoline, harmonica, flute, recorder and a shaker. I also tried miking up two different valve-ampliers, a Fender Blues Junior and a Tweed Deluxe that I built myself, both of these used to amplify the typical Fender and Gibson guitars.

I also took the somewhat drastic step of recording my own voice – both in spoken form and with a certain (barely discernible) tendency towards singing. And when it comes to the recordings, this was probably the area where I was most pleasantly surprised. I have never really liked my own voice – who does? Q24, however, managed to showcase a side of my voice that I had previously only dreamed of.

Instead of the somewhat thin, slightly nasal voice that I had previously experienced in most of my recordings, the Q24 showed me a significantly warmer, fuller and almost enjoyable baritone voice. Well, let’s not exaggerate, obviously the Q24 cannot perform miracles. However there were parts in the mid-range area where it felt like the Q24 lifted the warmer parts, while managing to hold back the somewhat more disturbing parts. Is it magic?

Above all, the Q24 had an ability to make everything I placed in front of it sound unreservedly good – that is, both full, transparent and airy at the same time; all great characteristics that we normally associate with a well-maintained vintage microphone.

The Q24 also had characteristics that made it easy to discern different signal sources. I could hear a very distinct difference when I tried small changes in mic placement in front of the acoustic guitar. It also felt like the Q24 amplified (sorry) the difference in sound quality between my Blues Junior and my Tweed Deluxe. Suddenly the Blues Junior sounded very gappy and flat. (I’ll definitely have to think about selling it.)

The Tweed Deluxe sounds so much better. The Q24 made this very obvious.

The Q24 also performed well in terms of off-axis frequency response. That is, it sounded good throughout the entire range even when you ended up on the edge of the microphone’s primary pickup area.

This also applies to the proximity effect. It is of course also here, but I experienced it as fairly mild. You can stay really close to the microphone, and the voice still doesn’t feel overly wooly, you just get a very intimate feeling. And neither do you lose too much in the lower register when you move away from the microphone.

Figures confirmed

Later obtained measurement data confirm many of my experiences during the tests. The frequency range of 20 Hz to 20,000 kHz feels completely relevant. The curve is fairly straight but does have a slight “bump” around 50 Hz, but on the other hand it has none of the unnatural lift around 10 kHz that we often find in pickups built in Asia and which often make sthe mic sound a bit harsh. Instead, it slowly falls off after 15 kHz. This, too, is reminiscent of the mikes Vladimir had as a role model. The same applies to both sensitivity and inherent noise, where the measured value is 8 dB (A). Impressive for a valve mic! The output impedance is stated as 600 Ohms.

This is probably one of the best-sounding microphones I’ve tested in my 30 years as a tech writer. You probably can’t express it in any other way than that the Quantum Electric Q24 more or less wipes the floor with the other microphones in the starting field; then we’re talking about microphones that were designed here in the West and where the manufacturing was transferred to a country in East Asia, and which have a price tag of between SEK 20 and 30,000. In that starting field we find many microphones with a fairly good reputation. But … we have a clear winner in this race.

p.s. While preparing for this review, I spoke with Charles Storm, a young and successful Swedish sound engineer/producer, who actually bought two of these Quantum Electric microphones early on. I asked him what he used them for. He replied with a big smile: Pretty much everything!

I can definitely see his point there. d.s.

Pros