Wednesday, May 11, 2022


The internet has provided an alternative path for smaller boutique gear manufacturers to deliver their wares directly to the discriminating buyer, years ago we called this “Factory Direct”. 

I was totally unfamiliar with “Locomotive Audio” who manufactures the “Weight Tank” vari-mu tube compressor, but a fortuitous click on a banner ad took me to the Locomotive web site where I started reading about this unique processor. Everything I read about the WT-COMP made me want it, finally I could stand it no more, I ordered it. Was it worth the wait?


The Weight Tank compressor is a two rack-space piece of hardware. Three large two-position toggle switches are provided for ON-OFF, Bypass and Tone selection (Round or Drive). Inside a pair of vacuum tubes do the heavy lifting. Gain reduction is caused by using variable-mu tube technology (no VCA, no optical). The tube circuits are accompanied by three audio transformers and other high quality components. A beautiful lighted gain-reduction meter on the front panel shows you what’s going on with your signal. On the rear of the heavy duty steel metalwork you’ll find XLR input and output jacks plus a removable AC power cord.

The Weight Tank compressor has a fixed ratio of 3.5:1. You adjust the amount of compression by turning up the INPUT knob, then use the OUTPUT knob to adjust the signal back to equal the input. It’s similar to the way you adjust an LA-2a or 1176 style compressor. From input to output there are NO solid state semiconductor components in the audio path. 

There are separate knobs for ATTACK and DECAY times, these are very active and need to be tweaked to find the best settings depending on the material you’re processing. 

A hardwire BYPASS switch lets you compare your source to the compressed output.

Another switch selects between “Round” and “Drive” tonal options. I was confused about this switch until I bought the unit and experienced the results in each of the possible positions. Let me say right now, this switch does not change the WT-COMP into a fuzz box (which I was very glad to hear). Setting this switch to the DRIVE position, combined with a lot of compression produces a unique thick sounding tone that my ears love. 


Great! To play with it is to love it. I do a lot of direct recording, both guitar and bass. I am very excited about using the WT-COMP on some upcoming recording projects. 

The soft knee compression effect created by the Weight Tank Compressor has a unique sound. I hate describing audio with words because they are so easily misunderstood. The WT-Comp sound has a soft character that belies what’s actually happening. It’s this soft character that attracts my ears. Where other compressors can come off stiff and fast, the WT-Comp sounds natural and smooth. 

The adjustable Attack and Release time controls really allow the WT-Comp to be dialed in for the song you’re using it in. The designer chose to give engineers these extra variables over more simple “fixed” settings or “auto” mode. Adjusting the Release Time control really helped shape my guitar recordings. 


For some of my initial testing and experimenting I split my guitar signal and recorded it on two DAW channels, one channel was direct and the second channel was with heavy WT-COMP processing. When mixing these two tracks, blending between them provides the best, fattest sounding parallel compression I’ve ever experienced. This also works for bass guitar and sounds huge. The WT-COMP could easily replace my old LA2a which pretty much has lived on the bass guitar mixer-channel for the last five years. 


Reasonable, factory direct price $899

Shipped in seven days from order, just as the web site said it would

Heavy duty metal work

Solid feeling switches and knob/pots

Awesome vintage styled meter, super useful

Vari Mu sound quality


It smells like burning paint when it warms up

Two rack spaces is a lot of space for a mono processor

Needs a third rack space above it for cooling


I will return to add more about my experiences with the WT-COMP after I’ve had more time to use it in different situations. Like many other folks who’ve experienced the WT-Comp, I already want another one. :-) 

While $899 is not chump change it’s also not $1899 or $2899 like several other single channel vari-mu compressors on the market. 

The Weight Tank Compressor is capable of juicy tube processing and whether you need that is up to you. The good folks at Locomotive Audio are located in St Louis, Missouri. The company offers several other products besides the WT-Comp. 

The WT-COMP gets my very rare “HIGHLY RATED” award because it provides such delicious sounding tube tones.

Thanks for reading High on Technology, Good Music To You!

©May 2022 by Mark King. It’s not ok to copy or quote without permission.

Neither High on Technology nor the author received any compensation or consideration in this review. We bought our unit just like everyone else.