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Warm Audio WA12

4.8 4.8 (4 Reviews)
Very versatile unit with lots of attitude
Warm Audio WA12

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Published by pacorro on 15th June 2012
User Review
Sound Quality
4 out of 5
Ease of use
5 out of 5
4 out of 5
Bang for buck
5 out of 5
Overall: 4.5 4.5
Warm Audio WA12

The WA12 pre is the first product from a new USA company: Warm Audio.
I invite to all of you to visit their web where you can see specifications and other news about the product: Warm Audio Microphone Pre-Amps

WA12 is based on the original design of legendary Api 312 at a low price. This is a mic or instrument mono channel preamp with external power supply and half rack format, there is an optional accesory to join two units to complete a 19” rack 1U.


Gain input 71 db
Gain button uses steps to give fine adjust.
Phantom +48V
Pad -20db
Impedance input selector (600 o 150 ohms)
Polarity invert
All discrete, no chips
Cinemag Trafos for all input and output signal
24 v external power supply
Hi Z frontal input for instrument
Power on button on frontal
Outputs on the back with XLR and ¼” TRS in parallel

When I received the unit WA12 the box remember me another unit I tested: the GAP 73 mic preamp, same external box, same internal protection, plastic bag, very similar at all.

Once unit is open I remember again same impression with Gold Age preamp: same layaout dimmensions, same power supply (Warm Audio recomends to use GAP73 power supply as alternative), similar buttons position. Frontal is orange colour.

From this point it is clear we are in front of another made in china unit, but Warm Audio uses exclusively good japanese and american quality electronic components: Cinemag trafos, and operational amplifier, these are more important pieces, and expensives.
So from the first impression WA12 is an api clone, if we compare both we can say GAP73 is a Neve topology and Warm Audio’s WA12 is an Api design, but from this point both units are totally differents only I feel a similitude comparing both units but this stops when we open the box.

Warm audio has decided to mount american components in China factory. Starting with all made in usa Cinemag transformers (same brand used by Universal Audio on his Solo610, for instance), and the operation amplifier is a clon made themselves by Warm Audio from a 1731 circuit (Api 312 original circuit).

Frontal offers main control, very basic at all:
One gain control
Switches for phanton, polarity, pad, HI Z input, impedance and power on
Jack input for HiZ DI

I agree specially to designer to provide a frontal power on switch. There are lot of units without this frontal button or put on the back!!!, so every time I can see one unit with a power on on the frontal layaout I really agree, it is really comfortable.

On the back side we find all input and output connectors in XLR and jack format. Ouputs are in parallel by one XLR and one ¼” jack, this is good point for the user, you can use both outputs for instance from xlr you can goes to an external processor (one compressor for instance ) and at same time you can connect your audio card by TRS jack and so you can record both signals, processed and clean. This is useful to backguard in some cases where we can use a bad compress signal, or simply to make a mix usign a parallel compression with clean signal. I check TRS output jack have a higher out signal, a couple of dB.

I personally prefer to see this preamp not as an Api clon except a new design inspired on this well known sound but using a personal touch. Even though at this moment I don’t have an Api on my rack to compare in A/B (doesn’t matter, wa12 goes to the classic Api 312 with 1731 operational and actual Api 512c uses a new 2520 circuit totally different at all ), I understand we must to value WA12 what it is and offers and not for this Api’s resemblance.
And as such, Warm Audio unit gives the size without problems.
This is a clean preamp, with low noise, solid, muscular, clear and detailed sound.
Have a good bottom bass, sweet highs, without loudness.
This preamp sound very well and give the size on every situation and instrument we can record.
I am not find the typical presence level of Api preamps, but really it is don’t needed here.

I don’t like one thing about the minimum gain level over 29 dB, a high value for a low gain. This implies in most situations we must to use Pad button, it is not a problem at all, but I think would be better a minimum level lower than actual, maybe 10 or 15 db less. When we put a mic in front a guitar amp or precussions it is necessary to use pad always if not input signal it is very high and we have some distortion and satured signal.
On the other hand we have a fluid gain potentiometer path (it must to cover less gain margin ) and uses steps of about 1/3 db value, so gives us fine adjusts and possibilty to note the value to remember the record situation in the future.

The main new point in front classic Api design is TONE button. This modify the impedance and change over tone. This button allow to adapt preamp impedance to microphone, and also could be used to get different tone on the same microhone signal since everybody knows same microphone offers different sound with different impedance on the preamp input (on this point I invite to check also The Magnetoaudiolabs VariOhm Microphone Impedance Converter ).

This option is propriety, but with a negative poing, when we push the Tone button general volume increase about 6 dB, what a nuisance! It is necessary to adjust everytime over gain control to check differences between different impedance value choiced, impossible to make A/B comparisons instantaneously.
But the truth is tone changes in an obvious way although subtle(fine) and this feature make this preamp more versatile, because give to us two different sounds but both really good at all.
In the normal mode (no tone pushed ) sound is clean, Look at graphics.

This is original pink noise as itself generated, still not passed thru any process or processor:

Now we can see same pink noise passed thru WA12.

As you can see the frequency response is flat, this point talks about this preamp don’t add any colour to sound spectrum, we can consider totally neutral.

Now we can see what happens with TONE pushed:

We can see there is a little drop on the highs and a little rise on the bass and meddium bass. This modifies the tone offering a more sweet on the highs. Sound becomes more thickset and consistent.
Personally I prefer how it sounds using TONE pushed and I used on this mode in a couple of studio recordings. In any case, it is good to choice the colour on the preamp sound to adapt better to every situation.

Now we will talk about clean/clear level., Wa12 es very very very clean, with a lower distortion level, for me fundamental on any preamp.
First I show image where you can see noise created by my digital audio converters DA and AD ( RME Multiface2):

Now we can see noise on preamp with gain at minimum:

Very low as you can see, we are moving between -105 and -115db, this is a very good value.
I must to explain last values on the top of gain, over 71 dB more, appears typical hiss when we get the end of the gain potentiometer, we can say this is normal on a medium class preamp. In a first level unit we note less noise hiss when we got high gain levels.
This is not a problem in any case, in WA12 until you reach over 55 dB pream is very clean and we don’t need any more, except in specific situations.
I check this point using a dynamic microphone, one ribbon and one LDC without any problem.

Now is turn for distortion levels:

Senoidal 1 kHz and gain at 14db:

For those who are not familiar with this type of graphics, the higher peak is a pure tone we are sending to the preamp circuits. When distortion appears we can see smaller peaks multiples of original signal.
You can see here there is not any signal, except over 2 kHz and 3 kHz (very little) as level is very low in reality this distortion is practically inaudible on ears.

Now we can see same at 5khz:

More or less we get the same answer, a little peak over 10kHz absolutely out of good clean sound.

And the last, now over bass 100hz:

On this point appears some more distortion but in low levels, practically without affecting original sound (-72 dB at 300 Hz).

As you can see we are in fron of a clean preamp, without practially any distortion on the original signal and without any colour in any frequency range, excepts when we push Tone button.
By the way, distortion level with Tone not vary from graphics showed and so I not put any graphic with this mode activated.

Pros and cons

Pros: I consider the following:

Very low level noise
Clean sound, well detailed, neutral but at same time with body and muscle.
Two balanced outputs simultaneously, good idea to get clean and processed recording signal.
TONE button offers two preamps on same box, Modifies sound is fantastic way (for me) and get a sound like a more expensive preamp unit.
Solid and robust construction
Best value price on this range


- I miss a high pass filter. Maybe could increase price, but they are very useful on all situations.
- When we push TONE button volume is increased, this point don’t let use a fast A/B test when we are looking for gain levels.
- An Output level control could be fine. I reach limit levels, when you are in high levels units starts to distortion but in sweet level, without an output level control there is no chance to play this option.
- Minimum gain is 29dB. From my point of view too high.
- Also a signal levelindicator (leds or vumeter), helps in more cases


WA12 it’s a medium class preamp but sounds as a high end unit. Difference price value with a high end unit will be justified depending where we use this preamp, obvious, but for those people with a home studio or project studio this is a very good budget, WA12 offers a great money value. For a user looking for quality in low price, WA12 is the option, maybe better in actual market. All circuits made in usa, well construction, and finished.
Talking about sound I personally prefers Warm Audio in front of others, like GAP73.
WA12 plays on same league than Chameleon Labs, GAP73, Focusrite Isa One, Dav electronics and little more, but offers a more competitive price and quality above most of them.
If I was thinking to invest on a preamp, WA12 would be one of the favourites.

Thanks to Marc from Makermid, spanish dealer.

Kadifornia Mastering
KADIFORNIA MASTERING | Estudio especializado en mastering de El Puerto de Santa Mar
By Category 5 on 7th April 2013
User review
Sound Quality
5 out of 5
Ease of use
5 out of 5
5 out of 5
Bang for buck
5 out of 5
Overall: 5 5
At double the price this is a great preamp. At $450 it is flat out steal!

Warm Electronics WA12 Microphone Preamp

With the significant increase in quality of on-board mic preamps in mid-range audio interfaces (thanks to a new breed of ultra clean mic preamp IC) there has been much discussion about more colored pres that might complement them for flavor. The usual suspects are of course the pedigree preamps that are commonly mentioned on gearslutz and similar boards, but that almost always comes with a price tag that’s out of reach for most hobbyists and small studios on a budget. Pres like the GAP73, which is based on the highly revered Neve 1272 circuit are a popular alternative, and lend themselves to several popular mods that can bring the sound quality in line with the big boys. When I heard about the WA12 from a new company called Warm, I naturally assumed this was the equivalent of the GAP, but based around the API 312 circuit instead. After getting my hands on a pair I am prepared to amend that notion.

At first glance, the WA12 looks exactly like I had imagined. A low cost alternative based on the API 312 design. There’s much more to it than that however. It’s clear that Warm is trying to tell us something, not just with the company name but with the bright orange faceplate the WA12 is sporting. This is a pre designed to warm your DAW tracks up. “straight wire” preamp designs like those found on boxes like the Ensemble, Apollo, and UFX are great for capturing the nuances of a great instrument and performance, but left alone they can end up sounding clinical, even un-exciting. Warming up your tracks is the precise reason you’d reach for an alternative like the WA12. As is my nature, I decided to pop the top of one of the WA12s and see what’s going on inside these boxes.

A few simple screws were all that separated my prying eyes from the inside of a very robust steel chassis, which yielded quite a bit of unused space inside. I am guessing that Warm saved a few bucks by going with an off-the-shelf chassis. No problem there. Inside I found three cleanly designed circuit boards, and a pair of Cinemag transformers quite neatly wired together. A main control circuit board contains the high-z input, the preamp’s mode selectors, and a gain pot. I would have preferred to see a gain switch here, but the stepped pot is smooth and makes repeating gain settings nearly as easy (another great cost saver). There are 6 selector buttons, each which has its own LED to make assessing the selected mode idiot proof (a nice touch). They control the input (mic or instrument), 48V phantom power, 20db pad, output polarity (nice to see in a budget box), tone selection, and the unit’s power. The layout is clean and ergonomic. The rear XLR mic input connects directly to this board, and is routed through the input transformer. Apparently the high-z input gets routed through the transformer too, so this makes the WA12 a great guitar or bass DI when you want to fatten things up a bit. The op-amp is based on the Melcor 1731, which is a vintage (pre 2520) gain block. That was my first hint that this pre might sound different than most other API-style pres on the market. It is laid out neatly on its own circuit board, and is not potted like the interchangeable gain blocks I’m used to seeing. No problem with that. Not only will this allow the transistors to keep cool, it also makes the gain block serviceable. The output transformer, and balanced output jacks (xlr and trs) are connected directly to the gain board and everything is securely mounted. Lastly, there is a neat power supply for converting the 24V AC input into +/- 18V for the gain section, and 48V phantom power for your active mics. I would have preferred to see Panasonic or Nichicon filter caps instead of the Chinese ones used here, but the ones Warm chose are rated to 105c, are of adequate size and (best of all) easily accessible should they fail and need to be replaced. That shouldn’t happen for a long time anyway.

The 312 mic pre design is popular because of its simplicity. It is essentially a high-quality discrete gain block coupled to an input and output transformer with a power supply. This means that what you hear is highly influenced by those components. That’s why I’m glad Warm chose to use Cinemag transformers, unlike many other companies who choose to have theirs wound by Chinese contractors. What you’ll be guaranteed of is both consistency and quality. Cinemag is one of the best audio transformer makers in business today, and it is certainly a surprise that the WA12 ships as equipped. This might make modders unhappy. There’s not a lot to upgrade here. While certainly compromises had to be made to hit the price point the WA12 ships at, it seems Warm have chosen them well and while you may notice a few you certainly won’t hear them. Attention to detail is excellent, and high-grade components have been used where they make a difference. Already the WA12 is looking like more than an API styled GAP (no offense to the GAP73, which is a great product at its price point).

I already have a 4-pack of API style pres, equipped with original transformers and a pair of both new and old genuine 2520 gain blocks. I was expecting the WA12 to sound very familiar, and somewhat redundant given that circumstance, if not quite as rich. After all, why do I need a budget 312 style mic amp when I have 4 high dollar ones that sound killer right here? This is where things get interesting. The WA12 shares its design heritage with those pres, but in use its sonic identity is as unique as its bright orange faceplate. While my high-dollar 312-style pres are very aggressive and tight, the WA12 is much creamier and smooth. I’d still categorize it as a mid forward pre, but its much less obnoxious about it. A quick email to Bryce, the preamp’s creator and owner of Warm, shed a bit of light on this. He deliberately decided not to have his transformers wound according to API’s original specifications. Both the input and output transformer are his custom design. He tells me he wanted the pre to be a little more colored that the rest of its 312 based cousins out there, and in fact Cinemag warned him that this would be at the expense of linearity. After all, the point of this box is for warming up tracks before they hit your DAW. Color is what the WA12 is all about. Well, mission accomplished Bryce. The WA12 is indeed very colored (in a glorious way) and gently imparts a very light rounding and subtle euphonic distortion of transients that’s instant music to my ears. There is certainly an overlap of sources that would sound good through both the WA12 and my other 312 pres, but there are quite a few instances where the WA12 would be my first choice and the others would not. I never liked my 312s for vocals, but the WA12 works great for this task. The sound almost feels like some compression has been added, without an appreciable reduction in dynamics. I would put its character somewhere between a traditional API style preamp, and a Neve 1272. It’s really quite polished and quite frankly is much better sounding than I expected it to be, especially at this price point. I don’t think I’ll be sending mine back! The WA12 wouldn’t be my choice for fast, transient sources like acoustic guitar or mandolin, but that’s a task for my interface pres. The WA12 sounds expensive.

There is a ton of gain on this pre so rest assured you can use your low output dynamic mics without fear, and while the design is quite vintage its noise floor is not. That should make your SM7 happy! There is a tone button on the front, which switches the wiring of the input transformer primaries from series to parallel. This gives you another 6 dB of gain from the increased voltage step-up while dropping the input impedance from 600 ohms to 150 ohms. This is likely to have a more profound difference on low output dynamic and ribbon mics, but essentially this works like a gentle high frequency roll-off in most cases. This is highly dependent on the mic used, and may not be a great match for ribbon mics that have a higher output impedance but in many cases it may be just the thing. Particularly harsh or shrill sources might find the lower impedance tames the highs more gracefully than EQ can. Plus, with the button engaged, there is a whopping 71 dB of gain from this box! You won’t be running out of gain here. Also, +/- 18V rails ensure you will likely be limited by the next device in the chain rather than the headroom of the WA12. There is more than enough usable headroom here.

There are a few things I wish the WA12 had, like built in metering, a high pass filter, and an output trim but it’s likely that these features would be redundant in a DAW environment and would have added to the cost more than they would have added to the usefulness of the pre. I was also bummed to see a wall-wart included, but coupled with the adequate power supply filtering and regulation it’s more of an ergonomics complaint than a performance one. A toroid would have added cost and complication to a well thought out design.

It turns out that this little box’s biggest secret isn’t what it is so much as what it isn’t. It is absolutely a high-quality transformer-coupled discrete mic pre that sells for the price of a budget IC based design. What it isn’t, however, is another API 312 clone in a sea of such mic pres, limited to the same specialized tasks the 312 design has become famous for. The WA12s will sit proudly along side Neves, APIs, Hardy’s, and more, and even in such fine company these little guys will get used. I have to commend Bryce and Warm for bringing such a great sounding pre to market for such a modest price. I have to wonder how they can make much doing it though, and suggest you pick up a pair before they realize they could easily sell these for more.

Shane Bushman (Category 5)
By johnpatrom on 18th April 2013
User review
Sound Quality
5 out of 5
Ease of use
5 out of 5
5 out of 5
Bang for buck
5 out of 5
Overall: 5 5
Warm audio wa-12

So... I recently purchased this little gem after doing three days worth of listening to online sound clips and reading reviews here on GS. Before going too further with the review a little background information.I am a hip-hop artist and self taught engineer so I'm not highly technical when it comes to the craft,more of a if it sounds good let's go for it type & mainly do vocals in my basement(by the way is treated just enough to record in for demos). Now back to our regularly scheduled programming.Getting this puppy was like Christmas although i thought the packaging was sub-par when i opened it and picked it up from out of the box i found the build quality more than what i could ask for at $400 US.This piece was a little heavy and felt like if it got dropped it would be like a pebble to a FA Tank.Using A xlr to xlr Mogami mic cable I placed it in my signal chain of TLM103 >Wa12 >Dbx166 comp/gate> Tascam 1641> Cubase 5 . This preamp was a replacement for my Art gold digital mp with stock tubes i currently still own. First vocal recording was a little awkward due to the fact it was a new piece. Immediately before processing i still noticed this baby was bright where it needed to be very silky highs EXTREMELY open mids and Brought out that Neumann creaminess i brought the mics for.When it came to the representation of the source vocals i felt it was spot on proximity effect and all.After mixing a few client sessions i found that this unit took to compression well and needed little to no Eq in many areas (with the tone button disengaged ).One thing that jumped out was how this baby mad the vocals cut through dense mixes with ease even before processing.My main fear was it was too good to be true so i took my mixes through the ringer from my pair of HS80's ,to my KRK rp5's, to my 02' Cadillac, to my gf's 02' Ford Focus,to my brother's 95 Lincoln town car,to my laptop, and to my mother's desktop speakers;and I must say it translated the same way in every speaker i put it to test on.Yes,some gave minor differences but the bulk of the sound was the same.Overall i would recommend this to anybody looking for an inexpensive preamp with world class pro sound.I wish i had cons for this pre's but the pro's of owning one far exceed anything i could think to say bad.Yes,there is no output knob on the pre but i don't think about that due to the compressor in my chain so it makes me have to dial in the sound i want. I can't say this is a con for a low level engineer more of an introduction to outboard gear. If you would like to hear this puppy in action check out https://soundcloud.com/johnpymgg/101-a-k-a-open-letter
thank you for reading
Last edited by johnpatrom; 18th April 2013 at 08:47 PM.. Reason: rating change grammar
By Bellico on 6th March 2014
User review
Sound Quality
5 out of 5
Ease of use
5 out of 5
4 out of 5
Bang for buck
5 out of 5
Overall: 4.75 4.75
Bang for buck is a 6 star

I totally agree with the former reviews.
Great pre!
Great sound!
Great color! as in the orange and the sound.

Features are as is but if you want/need more, go for the Tone Beast. Still great value with a few more options.

I just want to add that I did have a problem with my unit long into a week long session. Blew a resistor.

I contacted Bryce to find out the value so I could replace it and before I could ask he was ready to ship me a new PSU for it. I even said It's fine... I can buy the components and swap it myself, I just need to know the value of the resistor. He very casually stated that he would rather just send me a full new PSU.

A small company that stands that strongly behind their product in the audio world...

I gotta say that just made me want to buy more Warm Audio gear.

Personally I hope to see way more coming from Warm!!!!

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