Grove Hill Audio introduces the LIVERPOOL, a hand assembled, all-tube feedback compressor.
Tube compressors were first introduced in the early 1930's, and became widely used in the USA and England in the 60's. An American Mu tube compressor found its way to England were it was improved with several modifications; these units are still in use today. These rare iterations have never been commercially available. For years there’s been much curiosity surrounding the actual modifications made to these famous compressors. To differentiate the modified units, the original green front panels were painted gray and a new model number was assigned.
In the spirit of the elder engineers, we respectfully took liberties and made subtle circuit and control modifications that make this compressor very special. We listened carefully and tweaked it over and over to capture the vintage tone and vibe that make it unique. We then twisted knobs and pushed the tube circuitry, exposing additional creative capabilities.
Then we did a little hot rodding to the Liverpool - you can push it harder on the front end and the back end creating a useful creative tool. This is why the product is unique and NOT a clone. It is a hybrid of both the American compressor and the British modified compressor with modern enhancements, carefully thought out in the spirit of the original Mu tube compressor, but new to the market with additional design enhancements.
The LIVERPOOL compressor took well over a year to recreate the sonic character relative to the units still in use at world famous recording studios. Custom wound Cinemag input and output transformers (Made in the USA), critical component choices and circuit layout were all carefully considered in developing a reliable creative tool for a wide variety of instruments, vocals and program sources.
Technically, the LIVERPOOL uses a medium Mu, semi-remote cutoff twin triode tube as the gain reduction element. This tube is re-biased by the 6AL5 vacuum tube rectified side-chain control voltage which causes the Mu tube to smoothly change its mutual conductance, providing the change in gain.
The faithfully recreated Liverpool power supply provides low noise and stability even at 30dB of gain reduction.
Our passion is to share this wonderful compressor, at an accessible price, with the creative recording arts community. Because tubes for this compressor are in short supply, we are building the compressor in limited quantities.
- Type: Tube compressor
- Frequency Response: +/- 1.5dB, 10 Hz to 40,000Hz
- Frequency Response (Altec): +/- 1.5dB, 30 Hz to 15,000Hz
- Power Output: +20 dBu
- Total Harmonic Distortion: 0.08% at 1 KHz with output at 0dB
- Noise Level: 82 dBu below rated output
- Source Impedance: Any up to 15,000 Ohms
- Load Impedance: 600 Ohms
- Attenuation: 30 dB in 5 dB steps – Constant impedance.
- Maximum Compression: 30dB
- Attack Times (msec): 3*, 19*, 48*, 77*, 109*, 138*.
- Recovery Times (*msec): 127*, 447*, 917*, 1.9 sec., 3.4 sec., 6 sec.
- Threshold: 0dBm to +16dBm Output
- Compression Ratios: 2:1 at 0dBm Threshold, 4:1 at +16dBm Threshold
- Tube Complement: 6BC8/6BZ8, 6CG7, 6AL5
- Circuit Design: Variable transconductance compression circuit utilizing a medium Mu, semi-remote cutoff twin triode tube.
What We Think
It has that classic sound, it has that classic control, I don't know what's not to love! If character is what you seek first of all, look no further as driving the input of this old school style tube comp will bring that drive and "hair" reminiscent of 60's recordings we all know and love. You can easily turn the output down to allow for more push, too. The compressor circuit, if you've ever used a vari-mu style before, is exactly what you expect. It can perform gentle compression to obvious limiting / clipping style of control. The choices of attack and release times are very easy to get used to, I mostly enjoyed setting both in the medium/fast position and rockin' out. You can bypass the compression circuit in between attack time settings, handy to A/B or if you just want to use this box as a tube saturator. There is a "hold" position between each release time also, a very unusual feature but one that back in the day was used with lathe cutting, and you could creatively use it to hold reduction after a long passage, and then re-engage once the performance begins again. From drums to bass to vocals, the Liverpool just oozes old school class and character. If you're after a sound no plug-in can touch, this is it.