Thermionic Culture Rooster and Earlybird Microphone Preamplifiers

If we take a close look at both the Earlybird 2.2 and Rooster from Thermionic Culture, we see a long list of design and operational similarities, followed by significant differences that guide each to a different set of ideal applications.

The earlybird 2.2

Earlybird 2.2

The Earlybird 2.2 is a two-channel, Class A custom Sowter transformer-loaded tube-based mic amp with three bands of active “lift only” EQ, high-pass filters and a function switch that allows either mic, padded mic, line or Pullet inputs. [According to Thermionic Culture, the Pullet is Thermionic’s two-channel passive EQ that requires significant make-up gain. The Earlybird’s inputs accommodate with ideal gain and impedance—Ed. The EQ circuit utilizes “vari-slope” curves for the bass and top lift controls and a broad, low-Q curve for the mid boost (at either 800 Hz or 2.8 kHz). This EQ is placed in the feedback portion of the Earlybird’s circuitry and therefore does not introduce a new gain stage to the circuit; Thermionic reports that it allows EQ adjustments with- out fear of losing the original tone.

High-pass filters are available at 40, 100 and 800 Hz, with a -12 dB/octave slope at 40 and 100 Hz plus a broad slope at 800, designed to interface with the bass lift band in that “resonant filter/response dip before boost/simultaneous bass boost and cut” method well known to Pultec EQ users.

Although the Earlybird has two different input impedance settings—300 and 1200 ohms, helpful in fine tuning EQ and transient response—there’s no DI or instrument input. Gain is at either 36, 44, 52 or 60 dB, with the pad applicable to any gain setting. There are output level trims, polarity flip and a 48 VDC phantom power switch.

The Rooster

The Rooster will accept mic and line inputs, but also front panel DIs that bypass the input transformers, sending signal directly to the unit’s ECC81 double-triode input tube.

The EQ section offers bass lift (varies lope at 60 Hz); bass cut (five different frequencies at a variety of slopes); a mid/high lift (either 2.5 or 4 kHz or varies lope at 12 kHz); a mid-cut (700 Hz bell) and a LPF, which may just be useful when using the Attitude section.

Attitude provides control over the amount and type of distortion created by a 5725 valve (as found in Thermionic’s popular Culture Vulture distortion processor). This circuitry starts with a minimal 0.01% distortion in the 1st position and increases dirt with either Triode (2nd order) or Pentode (3rd order) as one dials Attitude towards a maximum of six. The Rooster’s continuously variable out- put via PCF 80 tube and Sowter transformer has a three-segment LED display.

The ‘Bird Vs. The Rooster

Both the Rooster and Earlybird are overall clean, clear and full bandwidth, but slightly colored in a subtle way; percussive signals and bold tones are musically tamed. With sustaining sources, their low-mids seem to be accentuated and compressed; high end is crisp and present but not irritating or “on the edge.”

These subtleties are just that subtleties until the user approaches saturation of the circuits. Hitting the Rooster’s or Earlybird 2.2’s front end with too much signal create light distortion in a non-obtrusive, mostly low-mid woofiness that’s only a little ugly, but not Splatty; I dove for the input gain a moment too late with a jumpy alto.

Audio System

On drum overheads, the Earlybird had enough speed to catch lively snare, enough fullness to translate toms and a smooth musicality that mitigated the harshest cymbals. Snare top via SM57 yielded nice, woody mids and a little extra top end EQ crafted a nice “crack.” Acoustic guitar shined with the ’Bird, while broad-stroke EQ work is enough to make room/instrument corrections well within your purview. Vocals of all varieties sound great via Earlybird, although input gain riding isn’t possible, but at least output is.

Although the Rooster does “clean” just fine, I found it to be geared towards dirtiness. The Rooster is designed rather similarly to Thermionic’s flagship distortion processor, the Culture Vulture, and sounds quite similar, though with far less control variation, less gain available, but wider bandwidth (much like the Culture Vulture Mastering model).

The Rooster can add serious attitude to DI bass tracks with creative EQing, filtering and adding its Attitude control. Drum tracks can receive that edgy triode distortion from Attitude, dangerously adding character to rock or retro-style productions.

Whole mixes can be goosed up with the Attitude #2 Triode setting, but I found few mixes benefited by Attitude #3 triode or higher (it goes to 6). Attitude is likely more useful on subgroups of synths, drums, vocals, etc. with Triode for subtlety and Pentode for wild fuzziness.

Acoustic guitar shined with the ’Bird, while broad-stroke EQ work is enough to make room/instrument corrections well within your purview

Summary

I found myself enjoying these two Thermionic Culture units with no qualms concerning build quality, design or features. The Earlybird and the Rooster have enough EQ power to shape and mold sources not in need of surgery; both are gentle and forgiving with hot inputs, and neither is a big fuzz pedal (except when crushing the Rooster’s Attitude in Pentode).

These designs and high-class sonics come priced in the thousands, thus not for the audio production hobbyist. If you place high importance on nebulous variables like musicality, transient shaping and tunable saturation, you may find these two cultured Brits to be necessary members of your audio flock.