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Thermionic Culture Phoenix HG15 High Gain Valve Compressor  From Thermionic

Stereo High Gain Valve Compressor

Thermionic Culture


"Experience the Difference"

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Manufacturer's Description from Thermionic

The Phoenix HG 15 is a single channel version of our classic Phoenix Stereo Compressor, having the same gentle “variable mu” type compression curve, though it becomes near to a limiter at high compression levels.

The gain has been boosted to suit mic inputs, particularly valve and FET condenser types, but many moving coil types, such as Shure, Audio Technica, etc. are fine to use if the sound source is quite loud or close-miked.

With the Threshold switch set to Comp Out it’s a clean mic/line amp, now add a little Active Eq, “Presence” and/or “Air” to brighten the sound, then switch in some compression and achieve that gentle “super-natural” effect that only Thermionic Culture can give you.

The Output Level control acts as a reverse linear attenuator after the electronics, and can be used simply to reduce level if feeding a low level input, or to add “Attitude” by reducing the output and increasing the input.  If you’re working from line level, it’s OK to switch the input from “Line” to “Pad” but ensure the +48v switch is OFF!

2 HG15s can be linked together for stereo use by a phono-phono lead from the Link socket at the rear.   There’s a Side Chain Bass Cut switch, which can also be useful in mono operation.

To sum up, The Phoenix HG15 is ideal as just a mic amp for vocals, violins, horns, guitars…… especially when using a high output mic like the U87.  Then having the ability to add compression and a bit of eq.


A very versatile tool with a super-natural sound.  About the nearest we’ll ever get to a conventional “channel strip”



 ♦ High Gain Mic Amp/Compressor/EQ with super-natural valve sound;

 ♦ Based on Phoenix design with 52 dB gain available;

 ♦ Fully Balanced circuit with XLR in/out connectors;

 ♦ +48v Phantom power available;

 ♦ Threshold control has 7 way switch with Compressor Out position;

 ♦ Time Constant switch has 6 combinations of Attack & Release;

 ♦ Side Chain Bass Cut;

 ♦ Presence and Air switches to boost mid and high top with In/Out switch;

 ♦ Bass Cut to roll off low bass;

 ♦ 2 valves, 6AQ8EH input and 12AT7/ECC81 output;

 ♦ Solid State side chain! ;

 ♦ Link socket to connect 2 HGs for stereo buss operation, etc. ;

 ♦ Made in England.


Thermionic Culture

About Manufacturer

Thermionic Culture is focused on producing the very best all valve design audio products. In this day and age of mass-produced solid-state audio equipment it's a refreshing change for a company to constantly strive for the ultimate all valve signal path.

The owners/key people involved at Thermionic Culture are totally dedicated to valve audio equipment, all having many years experience in recording and working with valves. Company founder and designer Vic Keary built his first studio in the late 50's and went onto building Maximum Sound Studios which was later bought by Manfred Mann and renamed The Workhouse, Chalk Farm Studios, and the all valve based studio Chiswick Reach.

Jon Bailes, Thermionic Culture's co-founder is responsible for the mechanical design & visual appearance. Jon has a wealth of experience as a Chief Designer in the electronic manufacturing industry .

Nick Terry engineers on many current albums and singles working recently with artists such as McAlmont & Butler, The Libertines. All this 'real world' experience is an invaluable aid to creating all valve equipment that other artists will no doubt appreciate.

Audio amplification, compression, mixing and equalisation took a backward step when solid-state technology was introduced. Valves are much more real and natural when amplifying and processing audio. We use no transistors or ICs in the signal path. Solid state is relegated to where it works best - in power supplies, although we do use a valve voltage regulator in The Culture Vulture's HT supply.

Some of our circuits take ideas from the 1940s to '60s and refine and update them to produce the low noise and distortion which are expected now. Other circuits are really original! To achieve high standards we use modern components such as 1% metal oxide resistors and polypropylene capacitors where their use is a positive advantage, but we avoid Hi-Fi type gimmicks such as gold plated XLR connectors. We take pride in the construction and reliability of our equipment. To date it is all hand wired using the best quality components. We give a 2-year guarantee against manufacturing defects, though we can only guarantee valves for 1 year. Many valves we use, are Military/Industrial grade. Also, we select and match (where necessary) all of the valves that we supply so a far longer life span can be expected


Input impedance MIC: 1kΩ


 LINE: 10kΩ

Output Impedance: 600Ω

Max gain MIC: 52 dB

 PAD: 38 dB

 LINE: 25 dB

THD (30kHz filter) 1kHz: 0.12%

 100Hz: 0.22%

N.B. Distortion may increase with compression, especially

with faster settings and 12 dB + compression.

Frequency response +0/-1dB 16 Hz to 50 kHz

Max O/P level (MOL): + 25.5 dBu, 10kΩ load

Signal to Noise: 96 dB

Power Consumption: 19W

Indicator Lamp: 12V / 3W

Net Weight: 4kg 

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