Warm Audio TB12 Tone Beast Microphone Preamp

Updated April 1, 2019 |  by Hollagully

The Warm Audio TB12 Tone Beast is widely considered the highest quality microphone preamplifier on the market in its price range. With a vast degree of versatility, flexibility and performance, the TB12 is a powerful product capable of shaping signals and entire mixes in a way that is highly desirable for both home based recordists and professional studios alike.


Warm Audio TB12 Tone Beast

  • 71db of gain.
  • Transformer selection provides both Steel and 50% Nickel CineMag output transformers for varying character.
  • Discrete Opamp selection allows for choosing between a 1731(vintage) and 918(cleaner) style opamp.  These are socketed/swappable with your choice of 2520 6 pin footprint opamps.
  • Impedance switch labeled TONE to switch between 150 and 600 ohms input impedance.
  • 2 Meg Ohm True HI-Z input on front panel sends instrument signal through entire circuit including both Cinemag Transformers and the discrete operational amplifier. Great for guitars, bass, keyboards and other instruments that have a 1/4″ output jack.
  • Capacitor selection between Tantalum and Electrolytic for different characters.
  • 80Hz hi pass filter.
  • Polarity Reverse.
  • +48V phantom power.
  • Output attenuation allowing for saturation flexibility of both the opamps and transformers.
  • ¼” insert for the use of inline compressors, eq’s etc.
  • Balanced XLR mic (front and back), balanced TRS line, and ¼” instrument inputs.
  • Balanced XLR and TRS outputs.
  • -20db Pad.
  • LED VU Meter.
  • 19″ rackmountable.
  • External line-lump 24V AC power transformer for low noise.

Based on the design of the API 312 preamp, the Tone Beast is Warm Audio’s upgrade to their previous WA12 mic pre, with a ton of extra flexibility.

First of all, you have your choice of a two discrete op-amp selections: the x731 which is based on the Melcor 1731, a predecessor to API’s famous 2520 op-amp revered for its big, warm and distinctly vintage character. The second option is the x18 which was modelled after Dean Jensen’s classic 918— a cleaner and more open-sounding op-amp that produces a fuller, more overall rounded sound.

A two-position output transformer dial gives the user the option of two selectable high-quality CineMag devices of different tone and make: a steel core transformer that has more of a vintage tone, or a 50% nickel core transformer that offers a much cleaner tone. Both are high-quality American-made components that can be switched out of circuit for a more transparent sound, though you will experience a -8dB reduction in signal level with these transformers bypassed.

Furthermore, a capacitor selector switch gives the user even more tonal shaping still with a choice between Electrolytic and Tantalum capacitors for varying warmth and character. These capacitors are very subtle but offer a lot of nuanced sonic flavours when used on different sound signals and alongside other parameters on the TB12 Tone Beast.

You’ll be able to get the very most out of every microphone in your collection with the Tone Beast’s push button Tone switch that determines the input impedance. With this switch disengaged you’re set to 600 ohms—standard for dynamic and condenser mics, while the engaged setting increases the gain of the unit by +6dB to a maximum of +71dB, at an input of 150 ohms. This is particularly useful when using Coles 4038 or any ribbon microphone. The unit’s line and Hi-Z DI inputs are also affected by the change in impedance, so it’s worth comparing the two options on all your audio signals.

The left half of the unit’s front panel is pretty much like the WA12’s, with the addition of a balanced XLR microphone input and a ¼” HI-Z instrument input which use the entire preamp circuit. Additionally, there are unique switches to control: the Line input on the back of the unit, +48V phantom power, -20dB pad, polarity reverse, and a 80Hz high-pass filter.

The right half of the front panel is where the Warm Audio TB12 Tone Beast becomes wildly addictive, so if you’re into tone-shaping, be sure not to burn up too much time here playing with the gain and output dials. These will allow you to control the amount of drive being added while attenuating the output, giving you ample headroom to drive the preamp. The level is indicated by a  6-LED meter which ranges from 0 at the bottom to a dainty skull-and-crossbones at top to indicate clipping.

Everyone could probably agree that the Tone Beast levels up ergonomically to it’s quality sound. It definitely feels like a sturdy 1U preamp with no cut corners on it’s build. All of the knobs, switches and inputs feel firm and secure—ready to be put to years of hard use. The mic and instrument inputs on the front make for easy access and the controls are all well-spaced apart for a clean visual.

The Warm Audio TB12 Tone Beast offers tons of character so if you’re looking for something that is more transparent, then look somewhere else. Here you’re going to find pure analog saturation in all its forms.

With so many options for tone-shaping, the Tone Beast lets you track audio with tons of inventiveness. It’s normal that after dialing in a preferred setting, you’ll find yourself needing much less compression and EQ down the road than you typically would without it. I found it extremely useful as a processor, adding incredible coloration to drum samples and other pieces of audio or applying it gently to my stereo bus while mixing.

When compared to other preamps costing several times the asking price, the Tone Beast absolutely shines in character and quality. Its sound is big, bold, and fully-professional. If you’re looking to add vibrancy and depth to your recordings and mixes and want to keep it under a grand, then the Warm Audio TB12 Tone Beast is for you.


Further Reading:

To help you out on your quest to find a great microphone preamp for your home studio, we’ve included links below to detailed reviews of a few models that make a good runner up to the Warm Audio TB 12.

We’ve put together The Ultimate Guide to Microphone Preamps that will teach you about all the components that give them character, and how to select the right one for what you’re after. Learn about a variety of affordable models that competently model some of the best sounding preamps of all time.


Focusrite ISA OneART Pro MPA 2 TubeGolden Age Project Pre-73Warm Audio WA12


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