New Gear Review: Heritage MCM20.4 Summing Mixer

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Heritage Audio provides a feature-packed solution for analog summing with the MCM20.4.

Although founded in 2011 and still a fairly new company, Heritage Audio of Madrid, Spain is quickly becoming a household name in the pro audio industry.

Known mostly for their handmade, accurate reproductions of classic vintage Neve modules, the company has just added some new designs to their range of products, notably the new MCM20.4 analog summing mixer and it’s brother, the MCM-32.

First, what are summing mixers? To put it simply, they are hardware boxes designed to hook up to the individual outputs of a digital interface to simulate the sound of mixing on a big analog console, while still allowing the vast majority of the mixing to happen “in the box.”

Before this current phenomenon of outboard hardware summing amps, the term “summing amp” referred to the circuit found within the mix bus of an analog mixing console. It’s the summing amp that handles all channels of audio running through your big bad SSL console and combines all that electrical energy into one stereo output—this circuit is a big part of what gives an analog console its sound during mixdown.

Your DAW and its digital mixer need to sum your tracks as well, so every DAW has its own digital summing algorithm for mixing in the box. Unfortunately, the quality of that summing algorithm may vary depending on the software, and generally tends to sound smaller and flatter than tracks summed together in the analog realm.

Some theorize that the more tracks you sum digitally, the worse it sums and the smaller it sounds. Others argue that a well-designed algorithm should be perfectly transparent if implemented properly, and that analog summing can only enhance signal by essential distorting it in a, subtle, pleasing and familiar way.

For a few years now, plenty of engineers have been mixing in the box—using plugins for compressors, EQs and effects, and automating their levels using their DAW’s automation—but will also spread subgroups of tracks out on an analog console to get more of that big, classic console sound. While this hybrid method is not quite the same as doing a mix entirely on an analog console (with an old computer reading SMPTE to control moving analog faders, and analog EQs and compressors on every channel), it is a step closer towards that sound while requiring almost none of the associated efforts or costs.

In recent years, a number of hardware manufacturers have taken just the summing amp portion of these big consoles and implemented them into a small hardware unit, enabling that big console sound but without all of the unnecessary features, bulkiness, power consumption and price. A true summing amplifier by definition has no faders or pan pots, and just sums mono analog channels into a stereo bus.

The Heritage MCM units, however, are not referred to as “Summing Amplifiers” nor “Line Mixers,” but instead “Summing Mixers,” and do a lot more than just sum—they have faders and pan pots, subgroups, switchable inserts on every channel and subgroup, and even aux sends (in the MCM20.4). This qualifies the MCM as more of a line mixer than an outboard summing amp.

Whether or not these additional features are necessary is up to you, but I think it’s cool that Heritage gives you purchase options as far as one model (the MCM20.4) being more of a mixer with less channels and more features, and the other model (the MCM-32) acting more like a basic summing amp, incorporating more channels but less features. Let’s take a look at some of the capabilities the MCM20.4 Summing Mixer has that most outboard summing amps do not.


Both the MCM20.4 and the MCM-32 require four rack spaces, share the same price tag, and both are hybrids of line mixers and summing amps based on vintage Neve console designs. (Loosely based…more on that later).

The difference between the units is that the MCM-32 has 32 inputs and 4 stereo subgroups while the MCM20.4 has only 16 main channel inputs and only two stereo subgroups—yet it includes two mono or one separate stereo aux send, as well as two more stereo inputs, for a total of twenty inputs. For this review, I was given the MCM20.4 to test, however, much of what you’ll read in this review should apply to the MCM-32 as well.

First, every channel on the MCM20.4 has a rotary level fader (looking and feeling like the EQ gain pots on a Neve 1073 module), a Neve-esque concentric pan pot around the level fader with a detent in the center, a channel on/off switch and insert return on/off switch.

Below that, we have another set of concentric pots—the ones used to control our aux sends. A “Pre” button is included just below the pots to engage pre-fader sending, and a “3ST” switch, which lets you choose whether you want to use Sends 1 and 2, or just Stereo Send 3 (you can’t use all at the same time). There is no gain on any of these faders, only attenuation. At full-up, or clockwise, we have unity gain, making things potentially easy to set up and recall.

It also has master faders for each of the sends and master faders for Stereo Subgroup 1 & 2 and 3 & 4. These subgroups are fed by the fixed set of Channels 1 through 8 and 9 through 16 respectively, summed via a modern active design—unlike the original vintage Neve consoles. However, these two stereo subgroups are then summed passively and boosted with 1073-type mic preamplifiers to bring them back to a proper level at the master fader—the method vintage Neve consoles employed for mix bus summing.

There are advantages and disadvantages to both styles of summing, and the designers at Heritage have utilized both methods in order to achieve the benefits of both worlds and produce, as their manual states, “massive headroom and lower noise without making any compromises to its vintage characteristic sound.” Two bright, old-school Neve-style VU meters located at the top right corner of the unit let us see how hard we are hitting the Heritage MCM mix bus and remind us that we are now mixing in the analog domain.

As far as connections, most everything is hooked up in the back via 8 channel balanced DB25 connectors. This includes inputs, insert sends and returns for every channel, insert sends and returns on the subgroups and insert sends and returns on the master fader. The main outputs and monitor outputs are +4dBu balanced male XLR connections. Whether or not you want to use a patchbay and wire up all of its inputs, outputs, inserts and sends is up to you, but either way, setup is fairly easy.

In Use

I set my test unit up in a very simple manner and ran all 16 outputs of my interface directly into all 16 inputs of the Heritage via two short DB25 cables, and then ran the left and right main outs of the Heritage mixer into a stereo pair of inputs on my interface for printing the final mix back into Pro Tools.

I also ran the MCM’s channel insert sends to my patchbay (to the same patch points that had previously been fed from my interface’s outputs). The insert sends on the MCM are always functional, even when the unit is off.

This simple setup allowed me to continue running my interface’s outputs to my patchbay while leaving the MCM powered off when not needed for mixing. This method also enabled me to maintain all the same patch point access I previously had while implementing an entire mixing console into the setup without needing to add any additional patch points.

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