The Phoenix is a tube compressor made entirely by hand. In the midst of the digital whirlwind, in which manufacturers mass-produce their products and in whose specifications terms like resolution, sample rate or transfer speed are commonplace, the people at Thermionic Culture (makers of the Phoenix) continue to base their circuits on vacuum tubes and build their products by hand, one by one.
However, this doesn't mean this gear fails to meet today's quality standards. With more than 50 years of experience in the world of tubes, the company's founder and designer, Vic Keary, knows how to get the best out of these devices while adapting his gear to deliver the distortion and noise levels expected of a modern product.
With these credentials comes the Phoenix stereo compressor. An exceptional processor, one of those that bring analog warmth to the digital world.
Free from Solid State additives
The term Solid State was coined to distinguish transistor-based circuits from those that worked with tubes. As the use of the former gradually displaced the latter, the expression Solid State indicated that the circuit used transistor-based active elements instead of tubes.
The name comes from how the devices work internally. In tubes (also known as valves), electrons are forced to cross a space in which a vacuum has been created, while in transistors they pass through solid semiconductor materials, hence the name Solid State.
Although transistors are much cheaper and more durable than tubes (and modern electronics would be unthinkable without them), the truth is that tubes give the audio signal a special "color" that has won them many die-hard fans, who believe they sound more real and natural.
Sharing this opinion 100%, the makers of the Phoenix compressor pride themselves on the fact that the audio signal doesn't pass through solid-state components in any of their products. All processing and amplification is based on tubes, with solid-state components relegated to the power supplies, where "they do a good job."
The Phoenix compressor, the Early Bird 2 mic preamp, the Culture Vulture distortion unit... they all use vacuum devices to process the signal. Even the company's name, "Thermionic Culture," comes from these components, since, although they are popularly known as tubes or valves, the full name is thermionic valve, due to the process by which electrons are forced to flow between cathode and anode.
Variable-mu
Among all types of compression, using a tube as the gain control element places the Phoenix in the Variable-mu class, the first type of compressor ever built.
With attack and release times somewhat faster than optical compressors (but slower than FET- and VCA-based ones), compressors of this kind have the particularity of not having a ratio control.
Instead, the ratio varies automatically according to how far the signal exceeds the threshold. The more the threshold is exceeded, the higher the ratio, and the closer you are to it, the gentler the compression. On the Phoenix the ratio ranges from 1.2:1 at minimum compression up to 5:1 when 15 dB of reduction is applied.
So the input gain and threshold controls are what determine the type of compression applied.
Description
The Phoenix compressor takes up three 19" rack units (3U). Although its design is retro, it also conveys a sense of modernity that gives the impression of being in front of a state-of-the-art device.
The controls are generously sized, letting you check the compressor's settings and operation even from some distance. From left to right are the input gain, attack, release and threshold knobs, all marked with numbers from 1 to 11.
The input gain increases along this scale. The manufacturer suggests positions between 3 and 5 for natural compression on line-level signals.
Attack time can range from 4 ms to 120 ms, and release offers values from 60 ms to 2.2 seconds, both increasing clockwise. On both controls the suggested starting position is 3, although excessively fast release values can cause distortion in the lowest frequencies.
Although it's marked the same way as the previous controls, the threshold works the other way around: at position 11 no compression is applied, and turning the knob counterclockwise lowers the threshold, thereby increasing compression.
Two switches labeled Bypass let you turn each channel on or off respectively, and between them is another switch, Link, which allows stereo use of the compressor by linking the two channels. When the processor is used in this mode, each channel's controls remain active, so it's advisable to set them to similar values.
Unfortunately, the Phoenix has no sidechain inputs, so both channels must be used if you want this type of processing. In these cases, the signal to be processed is fed into channel 1 and the control signal into channel 2. By setting the first channel's threshold to the no-compression position and engaging the link switch, the first channel is compressed according to the signal fed into the second.
The rest of the front panel is taken up by two large VU-style meters showing the amount of compression, the output gain controls and the power lamp and switch.
The meter scale ranges from 0 to 20 dB of compression, although the manufacturer warns that it should be taken as a reference, since the exact amount of compression varies depending on the tubes. It also notes that the VU meters are slower than the compressor itself and may therefore not reflect the processor's exact behavior when there are rapid changes in compression.
The output gain knobs are again marked from 1 to 11, with position 2 suited to use at -10 dBV line levels and 7 for +4 dBV levels.
The metal chassis has large ventilation holes through which you can see the six tubes (three per channel), as well as four internal trim pots for adjusting the unit. Two of them are used for biasing, should a tube need replacing, and the other two set the zero position of the VU meters.
On the back we find the input and output connectors (balanced XLR), the voltage selector and the power socket.
Every unit comes with a hand-completed report specifying the compressor's frequency response, distortion and tube types.
In action
Testing began with a vocal track. The first step was to connect the compressor with the threshold set to no compression, to hear how the processor itself "sounded." Using a signal generator, the input and output gains were calibrated to make sure the signal level didn't change when passing through the Phoenix.
Then the vocal signal was fed in, and the first results couldn't have been more encouraging. Without any compression at all, the voice gained body, sounding warmer and more pleasant. It had picked up some "color."
Light compression (1-2 dB) was enough to even out the performance. The body and warmth were still there, but the voice had gained solidity and strength, the result of completely transparent compression. The highs (somewhat cold in the original track) were smoothed out very pleasantly, making the harshness typical of some condenser mics disappear completely.
Heavier compression added urgency to the voice, making it more intimate and present, but even with reductions of more than 4-5 dB the compression remained discreet.
In applications requiring more aggressive compression, the processor also did an excellent job. With a somewhat faster attack time, 3-4 dB of reduction was applied to a kick drum track, nicely accentuating the beater's impact on the head. The result was a kick that cut through the mix better, with well-defined, controlled lows.
Considering the character of the effect achieved, the reduction may actually have been greater, with the meters' latency not showing the effective compression.
By slightly varying the release and attack times, the compressor managed to give body to a somewhat thin snare, adding character to the instrument. On the bass track, the processor was able to even out somewhat inconsistent dynamics, achieving a round bass with body and punch.
As a stereo compressor
If up to this point the Phoenix stood out for its ability to work flawlessly in different settings, in the field of stereo compression the processor sealed the tests.
The result was exceptional. With a moderate attack time and a not excessively long release, input gain and threshold were set to achieve maximum compression of 1-2 dB.
The mix gained body and liveliness, with controlled, powerful lows that added strength and punch. Again, the highs were smoothed very pleasantly, eliminating any trace of harshness and adding a subtlety in the details that wasn't there before.
However, it's easy to "overdo it." As soon as slightly higher doses of compression are applied, freshness is lost, and attack and release times must be adjusted carefully so as not to ruin the mix.
Conclusions
The Phoenix is one of those pieces of gear that can be considered a musical instrument in its own right. Apart from the possibilities compression provides, any signal passing through this processor takes on a special character.
When used to even out dynamics, the work is exceptional: transparent compression that delivers solid performances while adding warmth and smoothing the shrillest highs. Ideal for giving character and strength to "thin" instruments lacking body, especially vocals.
When it comes to more aggressive compression, the processor is also perfectly valid, arming us with an effective tool for shaping the signal's dynamics, with more than enough output gain.
Its work as a stereo compressor is also outstanding, and it wouldn't be surprising if the Phoenix became one of those processors you use on all your projects to give them a special touch.
However, as is often the case with high-quality pro gear, the price is high. That said, if you consider the vast knowledge behind the processor's design and, above all, that it gives us a reliable tool for adding warmth to tracks that lack it, we may well come to see the Phoenix as a great investment rather than a cost.
