This is a tube compressor.
"A lamp?? But I thought the lamps were used for amplification?" It is generally true, but not always. Lamps "rectifying" (such as diodes 5U4G example) are used to convert alternating current into direct current for powering the anode and cathode of power tubes. One can also use the lamps for one of their lesser-known feature is the case of the one used here by Vox compression. In fact, the lamps provide a warm natural compression and smooth. Unlike transistors whose compression will be cold and stiff, that's what finally claim the "pro" ... and marketing departments. Furthermore, the particular arrangement of lamps pre-amplification accentuates this effect. These are polarized to the cathode (bias self assembly) and not at the gate as the most power tubes. Without going into technical details (including association with a known ability bypass cap), it modifies the response of the lamp and increases its natural compression. In this regard, this assembly is conventionally used on the power tubes EL-84's Vox AC-30, and helps give it that warm and gentle compression that characterizes it.
The lamps require a fully regulated DC. Otherwise, it would change permanently the characteristics of the lamp. Therefore impossible a priori to be supplied from a 9V battery which power is too unstable, especially at the end of life. But Vox has managed this feat, including using a dual triode 12AU7 (ECC82 finally as the English say) instead of the classic 12AX7 (Queen lamps pre-amp, ECC83 for English). Personally I use my effects with a power supply, so I do not care. But it may concern nomads.

- Analog lamp: 1x12AU7
- Output volume
- Compression level
- Compression ratio changed: high or low
- = Attack rate of establishment of the compression
- Release = speed of decrease in compression
- = Compression treble emphasis: in practice, a tone on the treble
- Switch on / bypass mechanical true bypass
- Battery powered or 9V adapter (not supplied transformer)

Beautiful build quality and finish. Superb presentation.

UTILIZATION

Operation is simple. The advantage of this pedal is mainly to propose adjustments generally absent compressor pedal format: time to "release" and the compression ratio.
Some may miss the simplicity of the Dyna Comp pedal type fitted with a single knob. It is for everyone, right?
Each knob is sensitive, specific and progressive. It is possible with all available parameters to make a compressor map for rock, rockabilly, blues, funk, violing, metal, ...

For fans of compression.

SOUND QUALITY

The effect is clear (as it may be) while ensuring a good compression.
Personally I have no breath, even for high compression ratio and using a Telecaster, without noise gate to the exit.
It adapts to all styles, from vintage to modern.

OVERALL OPINION

This is an excellent compressor pedal, very versatile, well built, well finished, well presented.
A book still excited to compression because the many parameters available may annoy fans of simplicity.
A pedal that extends so interestingly range of compressors available. Add a value very attractive price.