Tuesday, July 25, 2023



Weight Tank WT-72 single channel preamplifier with minimalist features

The WT-72 is one sweet sounding tube mic preamp. It is designed and built in St. Louis, Missouri by Locomotive Audio.

The WA-273 is a two channel version of the WA-73. This solid state preamplifier was designed with the Neve 1073 as a guide for the appearance, controls and sonics. 

One channel of Warm Audio WA-73 preamplifier

In this review I'll be comparing the sound of a single channel of the WA-273 to the single channel Weight Tank 72-style tube preamp. Can the budget-reproduction of the classic Neve design keep up with the tubular bliss of the Weight Tank 72?    


Locomotive Audio is a small boutique builder of high quality studio gadgets which include direct boxes for reamping, exotic vari-mu compressors, tube mic preamps and tube mic processing gadgets. In this review we'll be looking at the WT-72 which gets its design heritage from the vintage German broadcasting, V-72 tube preamp.

The Weight Tank 72 uses the original German design as a starting point and then adds a second vacuum tube and some unique switching to yield 56 dB of total gain. The vintage German modules were only capable of 36 dB of gain. Locomotive Audio has pulled off a bit of a miracle to change this new incarnation into a very viable studio preamp even though it delivers way less gain than the typical Neve 1073 which clocks in with 80 dB of gain available. 


Warm Audio began making their 1073-style clones several years ago. High on Technology previously did a comprehensive review of the WA-73EQ vs the current Neve 1073spx and you can read it here (it's actually our most-viewed review-comparison). 

After many hours of listening tests we found the Neve EQ section sounded sweeter than the WA-73EQ but the actual preamp section of the Warm Audio hardware sounded VERY similar to the actual Neve hardware. With the EQ section turned off in both pieces it would be very difficult to hear any difference between the WA-73 and the Neve 1073. Armed with this information I jumped at a chance to get a great deal on a new WA-73 sans-EQ to add to my rack. 

The Warm Audio hardware is built somewhere overseas, they don't specifically reveal publicly the actual location or country of origin where their products are made. 

Warm Audio typically uses high quality components and builds in sufficiently large quantities which allows them to offer very low prices. 


Top = WT-72 over WT-Compressor

Locomotive Audio caught my eye with their "Weight Tank Compressor" which I saw advertised in an online forum. I checked out the company's web site and subsequently bought a Weight Tank compressor. It was built to order and arrived within the 2-week window I was quoted. Everything about the Weight Tank product is highest quality, even the shipping carton. I reviewed the Weight Tank compressor and you can read it here on High on Technology. The short version: it's awesome!

Round input transformer on lower left, output transformer top right

The WT-72 is the Weight Tank preamplifier. Inside the WT preamp hardware you'll find a pair of EF86 vacuum tubes and some clever switching which allows this vintage design to deliver modern performance and spectacular vintage tone. A shielded input transformer and a large core output transformer keep the WT-72 true to the original configuration and features. 

I plugged my Yamaha nylon string acoustic-electric into the WT-72 and had a blast playing blues licks. The WT-72 added a beautiful sheen to the tone of this instrument, complete with pinging harmonics; suddenly several hours of my life disappeared into a big beautiful jam. 


LOCOMOTIVE AUDIO WT-72 SPECIFICATIONS $899, Factory-Direct, built to order

  • Single channel, all tube microphone preamplifier, Made in USA
  • 19" (2) RU, steel enclosure
  • Vacuum Tube circuits (no semiconductors in the signal path)
  • Vacuum Tubes: (2) EF86 equivalent
  • XLR Input and Output 
  • Transformer-coupled input and output
  • Single knob "Gain Control"
  • Maximum Gain: 56 dB
  • Maximum Output Level: +24 dBu
  • THD +N: less than 1%
  • S/N: Greater than 70dB
  • Microphone or Line Level input selector switch
  • Polarity switch (sometimes referred to as "phase reverse")
  • Phantom Power On-Off Switch with LED "ON" indicator
  • (1) very sensitive LED indicates "Signal Present"


  • Single channel, solid state microphone preamplifier, Not made in USA
  • 19" (1) RU, steel enclosure
  • XLR and 1/4" TRS Balanced Input and Output 
  • Custom Carnhill Input and Output transformers
  • Rotary Gain Control Switch: 80dB of gain available
  • Four-position rotary Hi Pass filter switch (50-80-160-300 Hz)
  • Polarity Switch
  • Tone Button (changes input transformer circuit)
  • 48-volt phantom power switch
  • unbalanced insert(s), send-return 1/4" jacks
  • (5) LED Output Level Meter, Max = +20 (assuming dBu)



Warm Audio never fails to deliver a healthy list of great features which ultimately provide you with excellent options and professional performance. I compared the WA-73 preamp to the WT-72 preamp with various microphones and sources.

I like the 80 dB of gain available in the WA-73, I was recording a dobro with a ribbon microphone and used a lot of gain to capture the resonator tone. The higher gain positions on the WA-73 brought out more noise but they also delivered a relaxed character and greater intimacy to the tin-foil tone of the Gretsch resonator guitar ;-)

With a boutique U-47 style microphone on the input, the WA-73 delivers beautiful recorded tones that are sure to beat the preamps built into your DAW interface. Carnhill (in the UK) did a great job creating the clones of Marinair™ Neve transformers for the Warm Audio preamps. 

Once again Warm Audio goes very light on the actual performance specifications they publish. Instead they rely on you to buy the piece of hardware, see if you like it and return it if you don't. My industry insider contacts tell me there are very few returns. 


The WT-72 is made to be a studio workhorse. It promises and delivers spectacular vintage tube tone. It's the kind of simplified electronic configuration Johnny Cash or James Brown might have been singing through in the '50's or 60's. 

I've always loved the tone from the EF86 tube and Locomotive Audio knows how to extract every bit of goodness from it. The WT-72 sounds huge, warm and friendly. It takes whatever you feed in and adds delicious tube gain and harmonics. The output is brilliant, bright and clear, this is no box of fuzzy distortion, it's bold and solid sounding. 

Plugging a bass into the front panel instrument input on the WT-72 rewards you with unstoppable headroom, depth and tone. Tubes have unique distortion characteristics; unlike solid state designs that flip to a hard square wave (ugly sounding distortion) when their dynamic threshold is exceeded, tubes have a smooth progression towards higher levels of distortion. Solid state and even digital preamps can sound excellent unless that invisible line is crossed, in which case they sound VERY bad. The WT-72 never sounded bad, even floored out at max gain driven with humbucking guitar pickups on the instrument input. 

The WT-72 is the best answer for direct recording instruments, everything passing through it sounds gorgeous and it seems to never run out of headroom; push it and the WT-72 never gets gross, although it might overdrive the input on your DAW so look out!


If you want to capture classic tones you need classic gear, it really is that simple. We are lucky to be living in a time when innovators have been able to reverse-engineer the finest sounding classic designs and then do their best to bring similar sonics and the best capabilities to users around the world.

The Locomotive Audio, Weight Tank 72 preamp is not for everybody. It is for the person who appreciates huge tone. With a maximum output of +24 dBu the Weight Tank preamp has big potential to overdrive your DAW input if you don't keep a a close watchful eye on signal levels. 

The Weight Tank does not have any output level control on it, the designer intends for you to directly control the output with the one big gain knob in the middle. To set the level with this piece you need to find the position which does NOT overload your DAW. Hopefully the inputs on your DAW have level meters because the Weight Tank has NO output level indication other than the "signal present" LED located directly under the big Gain knob. 

Some of the gadgets that feed my DAW

I ran the Weight Tank into a Neve 8816 mixer which gave me additional level control with stereo metering. I fed this into my DAW and recorded it. The results were spectacular and will be featured on an upcoming album project. 

The Weight Tank preamp is a unique product; it's like an artists favorite paint brush, it delivers texture and dynamic control that connects with your ears and your soul. The Weight Tank is dynamic in an unusual organic way, your ears already know the sound, you just could not achieve it before. 

On another outing I played my Gibson BB King Lucille guitar through the Weight Tank preamp into the Weight Tank compressor into the Neve 8816 mixer; it was like the sweetest Twin Amp style tone I ever played through. I normally shy away from direct connected electric guitars but this tone was so fat, I've got to explore it more. 

My new WA273, it's two WA-73 in a single RU chassis

The Warm Audio 73' Style preamp is a high headroom Class-A design framed up with custom made input and output transformers from England. This package delivers honest boutique tone and a ton of features for an incredible price; used correctly, the WA-73 is indistinguishable from much higher priced clones and even the current offering from AMS-Neve. Playing guitar through the WA-73 into the Neve 8816 yields a rich and solid classic tone.

The Warm Audio price is only incredible if you're comparing it to other boutique gear prices. For an average guy, a $600 mono preamp is a big investment and he's NOT looking at $3200 clones of the same thing. Warm Audio brings a complete product to you for the price of a DIY kit. The WA-73 feels like, and sounds like, quality. 

The preamp stage is the first thing your instrument see's as it heads towards being recorded. The right choice in this shoot-out is BOTH! The WT-72's sound is huge and brilliant while the WA-73 is tight and focused; both sounds belong in your paint box when you can afford them.

With a Locomotive Audio tube preamp and a Neve style 73, you've got all your bases covered. 

Good Music To You! 

© July 2023 by Mark King

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