Warm Audio WA-412

Warm Audio is an American company that recreates legendary vintage audio equipment and brings it to market at an affordable price. The Texas brand has previously produced Pultec-style EQs , API compressor clones , and iconic microphone replicas . This is the case of the WA-47f which is a reproduction of the original U47 Fet microphone. On the preamplifier side, Warm Audio has launched the WA12-500 which is a faithful recreation of the classic API 312.

Later, the brand released an upgraded variant of the WA12-500 . This is the Warm Audio WA-412 which is on our test bench today. The WA-412's price is certainly affordable, but what about its sound quality? the API 312 really live up to its in terms of performance? Is it a good investment to get it? Find in this guide the presentation of the Warm Audio WA-412, and the results of the test that we carried out on this product.

Warm Audio WA-412: very simple design, but excellent build quality

According to Bruce Young, the designer of the Warm Audio WA-412, this preamplifier was created to allow professional audiophiles or home studio owners to benefit from high-end equipment at a low price .

There was a time when he himself could not afford high quality preamps due to his unstable financial situation at the time. This forced him to work on low-end preamplifiers which did not have the performance required for the realization of his projects. Creating and marketing the Warm Audio WA-412 is a way for him to return the accessor.

By way of overview, the WA-412 is an analog audio preamplifier featuring four microphone/instrument input channels. The electronic components are housed in an elegant 1U 19-inch case with a fairly simple design.

Our first impression is that in terms of exterior appearance, the look seems unappealing to us. This is probably because the Warm Audio WA-412 is more intended to impress with its sound qualities rather than its looks.

This is all the more true since in the studio, the performance of the equipment comes before aesthetic preferences. To offer this preamplifier at such a competitive price, production costs had to be reduced to a minimum, the aim being to prioritize sound quality .

Regardless, the Warm Audio WA-412's casing appears sturdy to us at first glance. We can see the high manufacturing quality of the equipment which already gives us an idea of ​​the performance of the equipment.

The very precise size of the case allows optimal storage of electronic components for a shorter signal path . The look and arrangement of the components also have a great similarity with that of the API 3124V . However, the Warm Audio WA-412 has many special features, including its silver lettering and front panel potentiometers.

Other test guide and review : Warm Audio WA-47F . A condenser microphone. Discover through the complete overview of this microphone, as well as its technical characteristics and our opinion on its sound quality.

Warm Audio WA-412 Microphone Preamplifier Overview

The Warm Audio WA-412 has 4 independent channels . Each of them is equipped with the following elements and controls which are located on the front of the preamplifier:

• HI-Z input : this is a Jack input directly connected to a “direct input” circuit of the buffer amp. The signal is collected there, then passes through the amplifier before being transferred to the rest of the circuit. In short, the signal passes through the input transformer and the discrete OP-amp before reaching the output transformer. The HI-Z input allows the connection of all kinds of microphones (dynamic, ribbon, etc.) and a wide variety of instruments, including acoustic guitar, electric guitar, bass guitar, synthesizers, samplers, etc.
• VU meter : This is an LED display indicating the signal output level. During recording, it is used to identify possible peaks requiring gain adjustment to prevent saturation or distortion harmful to sound quality.
• Gain potentiometer : it allows you to adjust the input level of the signal before it passes through the preamplifier circuit. On the Warm Audio WA-412, the gain range is +23 dB to +59 dB and +29 dB to +65 dB if the tone switch is on.
• +48 V phantom power supply : this is an essential feature for operating certain types of microphones.
• A tone switch or tone button (more details at the bottom)
• Polarity reversal button : allows you to reverse the polarity of the voltage at the balanced microphone inputs. This feature may be necessary during recording to allow for better sound capture depending on the location of the microphone: for example, reverse polarity may be necessary when the microphone is positioned behind or in front of a guitar speaker amplifier, or above or below the drum snare.
• -20 dB Attenuator : This feature provides -20 dB attenuation of the signal input level. It is very useful when you have to manage sources (microphones or instruments) at high output level. It is an effective device to prevent clipping, to have the lowest possible noise, and to have a greater margin of adjustment without saturating the signal at the output of the Warm Audio WA-412.
• Hi-Z button : allows you to switch from the XLR input (rear) to the Jack input (front).
• Output potentiometer : serving as a fader, it allows you to adjust the volume setting at the channel output. It is used in conjunction with the gain potentiometer to obtain the desired sound. For example, a high gain level combined with a low output level results in a sound with light saturation, but rich in harmonics. On the other hand, a low gain combined with a high output level gives a clearer, detailed and very clean sound.
• ON/OFF button : used to start or turn off the device.

On the rear panel of the Warm Audio WA-412, we find the following elements:

• An IEC mains socket to which the device's power cord can be connected
• A voltage selector : the user can choose between a maximum voltage of 115 V and 230 V depending on the mains voltage.
• XLR input for dynamic , ribbon or condenser studio microphone: you can connect all kinds of microphones or sources of the same level.
• Balanced TRS and XLR output on each channel: they directly collect the signals coming from the output transformer. It is recommended not to use both outputs simultaneously.

All of these features allow the Warm Audio WA-412 to effectively handle signals from loud sources to avoid saturation . Therefore, it can be very interesting to pass the sound of the drums through the circuits of this preamp before transferring it to the converter.

In this way, you obtain a slightly compressed sound by juggling the gain/output adjustment . Drummers and engineers looking for diverse sounds will be well served.

Note that the Warm Audio WA-412 is equipped with a six-pin operational amplifier: the X520 . The latter is designed on the basis of the very famous and popular API 2520 OP-amp , as well as on a discrete circuit including through-hole components.

The X520 is capable of , lively and colorful sound . It can effectively handle loud sources by rendering a low saturation that some artists, musicians and sound technicians greatly appreciate.

Even more interesting, the X520 can be easily replaced in the event of a malfunction or when one wishes to improve the performance of the preamp. It can be replaced with the API 2520 OP-amp , which will greatly improve the audio quality of the WA-412.

A tone switch to change input impedance

The particularity of the Warm Audio WA-412 is that each of its 4 channels has a tone switch also called tone button . This feature acts directly on the input transformer by increasing its rate from 1:5 to 1:10 .

It increases the influence of the transformer and the operational amplifier on the entire circuit. We then obtain a clear improvement in the quality of the signal which becomes more colorful. When the tone button is activated, the input impedance increases to 150 ohms . This is 600 ohms when the switch is off. Once the impedance is reduced to 150 ohms , the gain obtains +6 dB . We thus obtain a maximum gain of + 65 dB instead of + 59 dB .

Many microphones and musical instruments that are plugged into the mic or Hi-z input are sensitive to the action of this tone switch. This feature works great for ribbon microphones and anyone with a low output level . On the other hand, dynamic and condenser microphones work best with the impedance of 600 ohms .

For information, this button was called “tone” because of the more expressive, percussive and thick sound that we obtain thanks to its activation. Note that when it is deactivated, the sound is more natural , detailed , and less aggressive with a very low noise level.

Activating this button switches the entire signal to the old preamplifier which served as the model for the Warm Audio WA-412. So you get a vintage analog sound that instantly transports you back to the 70s. The quality rivals that of digital audio.

By the way, you can also check out our Presonus Revelator microphone review . This guide presents you with complete details of this USB microphone, its sound quality, its technical characteristics, as well as our opinion on this microphone.

Focus on the sound quality of the Warm Audio WA-412 microphone preamplifier

very high-end input and output transformers . They were designed by the American manufacturer ALTRAN Transformers .

This preamp is also equipped with operational amplifiers found in the most prestigious analog consoles used in the studio. These promote discreet sound reproduction whose quality has nothing to envy of those of higher priced preamplifiers.

Being a discrete microphone preamplifier , the Warm Audio WA-412 can be used to pre-amplify the signal coming from any type of condenser , ribbon or dynamic microphones. As ribbon and dynamic microphones have a low output level, they do not require an external power supply to operate.

On the other hand, condenser microphones whose particularity is to be extremely sensitive, it is essential to reinforce their power supply with a +48 Volt which is found in the Warm Audio WA-412. Furthermore, this preamplifier is suitable for all kinds of musical instruments , because it is equipped with an active direct box.

Obviously, the Warm Audio WA-412 can be used at home, for personal use. Simply amplify the signal it provides with a power amplifier . It can be a tube amp, a class A tuner amp, a transistor stereo amplifier, a mini-system or even a home cinema.

Aside from microphones and instruments, you can connect a CD player, record player, vinyl record player, FM tuner radio, etc. to the Warm Audio WA-412. To have satisfactory sound quality , you should choose a good speaker and a subwoofer that faithfully reproduces low frequency sounds.

When the Warm Audio WA-412 passes our test bench

It's time to take the test and see if Warm Audio's great promises about the WA-412 really hold up.

We carried out a first test with the battery . For this, we captured the sound of the bass drum with an Audix D6 wired microphone , the snare and hi-hat with an Audix i5 , the OH with an AKG 414 , and the whole thing (Room Mic) with a Rode microphone. NT1-A . For the adjustment levels of the potentiometers on the preamplifier, we referred to the positions of the hand indicating the time on a watch:

• Bass drum on channel 1: gain at 1 o'clock and output at 4 o'clock.
• Hi-hat and snare drum on channel 2: gain at 12 o'clock and output at 11 o'clock.
• OH on channel 3: gain at 12 o'clock and output at 5 o'clock. We activated the +48 V phantom.
• Room Mic on channel 4: gain at 11 o'clock and output at 1 o'clock.

We performed the test with the tone switch on. The result surprised us enormously. The sound quality is there . Overall, there is not the slightest saturation. You get a very expressive snare drum sound that sits well in relation to the sounds of the other drum elements. The frequency response on each microphone is satisfactory. Adding a high pass filter embellishes the sound even more.

On the bass drum side, the sound is also pure and punchy . Low frequencies are faithfully reproduced . We can hear the kick very well, and the sound is thick with a cutting attack which is extremely pleasing to the ear. Overall, the sound of each element is well nuanced. You get that robust, powerful sound with a half-punch character typical of the API .

For the second part of the test, a lyric singer and a Pop Music singer agreed to lend us their voice. For recording we used an AKG C414 XLII microphone. We set the gain to 4 hours and the output to 1 hour for the opera singer.

For the Pop Music singer, the gain was positioned at 10 o'clock and the output at 4 o'clock. For the latter, we activated the +48 volt phantom and the tone button. In both cases we didn't use a compressor and EQ.

We simply added a little reverb and DSP . This time again, the sound quality obtained surprised us. If some sound engineers favor the use of the Warm Audio WA-412 for more rock and funky music, we have confirmation that it is just as interesting to use it for recording vocal vocals .

Even if our singer went very high in the notes, her voice comes out with a very appreciable naturalness and . It is the same with the recorded voice of the Pop Music singer. It is rich in details, voluptuous, and brilliant.

For the last part of the test, it was around the bass guitar to pass. We used a regular bass guitar . Then, we connected it to direct input without subjecting the signal to compression or equalization. We chose this option even though we could run the instrument through a guitar amp. The gain was set at 9 o'clock and the output at 2 o'clock.

We activated the tone button and used the channel 1 input on the front panel. The test result was no surprise to us, as we expected exceptional sound quality after hearing the sounds obtained in the previous two tests.

Indeed, the bass guitar resonates with a serious and very precise sound . The characteristic high-pitched sounds of Slap are faithfully reproduced. Even though we increased the gain to get a more powerful signal , there was no saturation. We get a decent sound that most bass players are looking for.

Technical characteristics of the Warm Audio WA-412 microphone preamplifier

• Preamplifier type: Solid State
• Number of channels: 4
• Inputs: 4 XLR, 4 x Active Instrument 2 Mega-ohm Hi-z
• Outputs: XLR and TRS balanced by transformer
• Rack size: 19 inch 1U
• 4-channel microphone preamplifier + instrument DI
• Topology of fully discrete, transformer-coupled, through-hole electronic components.
• High quality input and output transformers, custom wound in Altran USA manufacturing facilities.
• X520 discrete operational amplifier in each channel, nested for convenience. Can be replaced with most 6-pin discrete op-amps for varying tones.
• Gain: +65 dB
• Tone button: If activated, switches the input impedance of 600 ohms to 150 ohms (acts by changing the tone of the mic and HI-Z inputs).
• Pad attenuator: -20 dB for DI and microphone inputs
• +48V phantom power supply
• LED meter and incentives on each of the 4 channels
• Output adjustment knob allows precise control of level and tone refinement.
• Internal power supply (3-pin IEC cord, grounded)

Our opinion on the Warm Audio WA-412 microphone preamplifier

The Warm Audio WA-412 is a fully-fledged studio equipment offered at an excellent quality ratio. Its four discrete gain preamps provide clean, detailed sound that can convince even the most demanding ears. The difference in sound quality is almost non-existent between the Warm Audio WA-412 and its muse the API 312. The design of the WA-412 is, admittedly, simplistic, when compared to that of certain preamplifiers, notably the Cambridge Audio Alva Duo which is a moving coil and moving magnet phono preamplifier.

However, the manufacturing quality and robustness are there. The existence of the output trim is one of the strong points of the Warm Audio WA-412. It allows full control of the signal before it is transferred to the next audio devices in the recording chain. It can be a mixer, a limiter, a mixing desk, an amplified speaker for monitoring, etc.

Consequently, saturation can be avoided and a clean, peak-free signal can be produced. This also allows for a suitable signal-to-noise ratio. During our test, the sound of the Warm Audio WA-412 really transported us back to the 70s. So, our conclusion is this: investing in this improved replica of the API 312 is a very good deal for any audiophile in quest for excellence in sound quality.

Warm Audio WA-412 Mic Preamplifier Demo

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