Sunday, April 16, 2017



Review by Mark King for


Microphone preamplifiers are definitely in the top five things audio engineers bicker about. Don't they all basically sound the same? Don't they all basically do the same thing? If your mixer or interface already has a microphone preamp in it why wouldn't you just use that?

These are all valid questions with equally valid answers depending on how well developed your ears are, whether you think the end is justified by the expense and perhaps most importantly whether you can afford it.

When I purchased my 3124+ I was looking for something to take my sound to a higher level. Over the last 50 years I've owned dozens of preamps (not counting all the mixer channels). I'm usually a bottom feeder when it comes to equipment prices but I decided I needed to know if the 3124+ could improve my drum recordings and other tracks.


API mixing consoles have been used since the 60's to mix some of the biggest albums ever created.

The original API consoles used a sort of universal preamplifier on a plug-in circuit card called the model "312". The 312 card featured a transformer coupled input stage, a discrete op amp stage with adjustable gain and a large transformer output stage. As old API consoles fell out of use the 312 cards were harvested and repurposed as 500 style microphone pre-amplfiers, Brent Averill (now known as BAE) modified a lot for 312 cards into 500 style pre-amplifiers.

When the modern day API company created the 500 series format they gave birth to a new version of the classic 312 and renamed it 512. The 3124+ pays homage to the original 312 name, it's basically four complete channels of 512 style preamp in a single space rack mount enclosure.


On the front panel of the 3124+ there are four identical channels with the same functional controls you'd get on a full size API recording console.



SOUND QUALITY: This preamp sounds amazing. It adds weight and fullness to anything you pass through it. Nothing is exaggerated or emphasized, but everything sounds more full and authoritative than lesser preamplifier designs. 

OUTPUT LEVEL METER: Every preamp needs this, I'm surprised how many big name expensive preamps don't have an output meter, are we supposed to just guess? Good for API to go to the trouble to put this extremely important feature right on the front of the box.

VARIABLE GAIN KNOB: The knob design is patented, the potentiometer inside is smooth as butter. The combination of the gain knob and level meter make adjusting this preamp quick and easy. 

POLARITY: This push button switch inverts the polarity of the signal which in some situations may reduce or minimize phase interference between microphones. Yellow LED indicator light when polarity is inverted. 

PHANTOM POWER: Pushbutton switch to activate 48-volt DC phantom power, red LED indicator light when phantom is ON. 

INPUT PAD: This -20 dB pad is before the input transformer so the transformer won't be overloaded. Many people think this pad changes the sound quality dramatically. If the signal is too hot this button will knock it down by 20 dB, pretty handy when you need it.

MIC ON-OFF: This button mutes microphone output when engaged. It also selects the Hi-Z IN on the front panel.

HI-Z IN: This is a 1/4" input suitable for a musical instrument to be plugged into directly. A Fender P-bass sounds really nice through this input. The "natural weight" the API preamp adds to the bass tone has been heard on countless albums. This is like having a very high quality direct box built right into the preamp. 

ON-OFF: So many pieces of professional equipment don't provide a front panel ON-OFF switch, thankfully the API 3214+ has a power button conveniently located on the front and a power LED to indicate when the unit is powered on. 

INPUTS AND OUTUTS: Around back the 3124+ has an XLR female input jack and male output jack for each channel. 



The 3124+ feels like a good quality piece of equipment. The outer case is heavy gauge steel, the aluminum front face plate is a nice thick solid piece of metal. All the buttons and switches feel good.

The 3124+ has fantastic headroom, even when the upper +18 dB peak red led lights there is still another 10 dB of clean reproduction available before this beast begins to clip or sound crunchy. Many people don't think an API preamp sounds good until you push it into the crunch zone. 

Here in the Proworkshop studio our favorite application for the 3124+ is vocals. We feed it into a Warm Audio EQP tube equalizer, then into an 1176 compressor and finally into the DAW. Depending on the material we're working on we like to add a little compression at each step of the recording process. Having the 3124+ right after the microphone yields a full sound we really like. 

Whether it is used on guitar, bass, vocals, percussion, drums, synthesizers or drum machines, the 3124+ from API lends a unique character to any recording. 

API has released a new model of the 3124+ which is called the API 3124V. The V on the end of the model name means "variable" as in variable output level. This new version adds an extra op amp stage and provides an optional 3:1 transformer ratio. The original 3124+ that I'm reviewing only has one op amp stage per channel and the output transformer is fixed at 2:1. 

The 3124V is shown for $3130.00 US on Sweetwater today, that's $782+ per microphone preamp.

When I acquired the 3124+ we use in the Proworkshop studio it was $500 per channel. Today it's selling used on for $625 per channel. I feel good about investing in high-end equipment when it holds its resale value or better yet, goes up in value, that's a win-win in my book. 

It really comes down to whether you can afford it or not. The API 3124+ won't fix bad pitch or lack of soul in a vocalist but it will help take a really good vocalist up to the next level. 

Did the API 3124+ take our recordings up to the next level? Yes would be my answer. It's not what I use on everything but for our critical vocals and electric guitar recordings the 3124+ is an integral part of the music we create. It adds body and heft like no other preamp in the house.

Good music to all!