New Gear Review: Heritage MCM20.4 Summing Mixer
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.
Features
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.
Having inserts on this mixer doesn’t just allow for some extra setup options, it allows you to insert analog outboard gear into your tracks without having to go in and out of your interface’s A/D and D/A converters, avoiding latency as well as extra stages of conversion.
So how does it sound?
I took a number of songs I had previously mixed in the box and re-routed them through the MCM20.4 via the 16 outputs my interface provides. In every case, the Heritage came through in a positive way. The differences with and without the MCM were not staggering, but were apparent enough that everyone I A/B’d the “before” and “after” examples for knew which version of the mix I was playing—and liked the Heritage-summed version better, every time. I think this is proof that the MCM20.4 does help sonically and is not just a hype.
Spreading the tracks out through the MCM20.4 resulted in a slightly wider, bigger, more alive and more three-dimensional-sounding mix. Flipping back and forth between the exact same mix done ITB vs with the Heritage, the Heritage version appears to breathe a little more, with a more defined stereo spread and a slightly more open tonal quality.
One would look at this unit and expect it to sound like a vintage Neve console, with lots of color, and while the Heritage does have some color, your ITB mix doesn’t change when re-routing it through it. This is a big plus, as it potentially allows you to mix in someone else’s studio, or with headphones on a laptop on a moving train, and then when your mixing is finished, you can open it in your studio, give it the Heritage MCM treatment and kick it up a notch without affecting the blend or tone you had. That is the whole point of a summing amp, and the MCM20.4 does it well.
If you were to do the same thing with an in-the-box mix and recall it through a vintage Neve console, your mix absolutely would change, and so in that situation, you’re likely to be best off mixing through the console for the duration of the mixing process. One might ask, “Why does a vintage Neve console sound different than a Heritage Summing Mixer? They look like they have the same parts (from the outside), right?”
That’s where potentially the biggest drawback of the MCM series lies: It has no input transformers—a crucial part of that Neve sound. Whether that is a good thing or a bad thing is up to you, but transformers tend to be a big color-additive, so leaving them off the design is notable.
I’m not a tech guru, but I’m pretty sure that most of the classic Neve consoles had input and output transformers on every channel, and probably a few more transformers along the way in the signal path. The MCM series has no transformers other than in the summing amp circuit. (If it did, it would likely be much bigger, way heavier and of course, pricier).
While the transformerless channels may result in a purer sound, it isn’t typical of a vintage console, which is surprising, as most of Heritage’s products are faithful clones of vintage circuits. If you think you are getting a vintage Neve console clone with the MCM, you are not. You are getting a small bit of Neve-type coloration, and a quality product that will likely add some excitement and width to your mixes, but this is not the same as turning all faders on a Neve 8014 up to 0 and using it as a summing amp.
The Sound
Here are some short audio samples of two different types of mixes so that you can do your own A/B comparison to really hear for yourself what the MCM20.4 does. (Click for full res versions, or stream below.)
The mixes done entirely in the box were printed by routing the mix bus in Pro Tools into a stereo track, rather than by “Bouncing to Disk”.
The mixes that were run through the Heritage Summing Mixer were spread out on the mixer and then printed back onto a stereo track, everything calibrated to the exact same levels as the ITB version.
To Be Critical
Although I preferred the Heritage-summed version in all cases, I felt the need to go a bit deeper. To be very critical and mathematical, I tested it more closely, and found that the frequency response of the MCM20.4 was not perfectly flat. While it did not wildly deviate anywhere, it seemed further from flat than one might expect from a summing mixer design.
In my own tests, I found that from 169Hz through 4.8kHz, what you put into the MCM20.4 is what comes out of it: It had a perfectly flat frequency response down to the tenth of a dB. At 7.5kHz, signal was down .2dB (theoretically noticeable, but barely), at 16kHz it was down a fairly significant .5dB, and at 18kHz it was down .6dB. On the low end, at 32Hz, I found a drop of .2dB, and -.4dB at 20Hz.
While these deviations aren’t huge, they aren’t what one might consider “mastering quality” either. Having a device that doesn’t precisely reproduce audible frequencies like 100Hz or 10kHz properly seems a little untrustworthy to me, but I must also admit—more importantly—that these roll-offs of the highs and lows may seem alarming on paper, but are essentially inaudible in practice, and may even arguably be considered part of the character or charm the box may add.
If you listen intensely close and do an A/B comparison of a mix going through the Heritage vs the same mix summed entirely in the box, you may notice a very minuscule loss of high frequencies at the extreme end of the spectrum, but you’d be listening really hard, and the loss is essentially insignificant in reality. And though these figures may seem odd or alarming in the digital domain, they are quite typical for analog consoles and processors.
As far as self-noise goes, as with any analog mixer, there is some—although not enough that it matters. When I put my recorder in input mode with only the cabling attached (but without the MCM20.4 hooked into it), I read a noise floor of -103dBFS. With the MCM20.4 hooked in, but with its master fader turned all the way down, my recorder’s noise floor read about -86dBFS. With 16 channels on the MCM turned all the way up to unity, the noise floor then read -80dBFS.
In other words, the MCM20.4 adds about 23dB to your noise floor in regular use. Noise at -80dBFS is generally inaudible though, on par with other analog consoles and nothing to be concerned with.
A feature—and drawback—of having a mixer and not just a summing amp is the introduction of faders and pan pots. (If you intend on using the MCM as a line mixer, then these variable components are features you’d likely want, but I have a feeling that most people considering buying these units intend on using them primarily as summing amps for DAW mixes.) Because of all these faders, pots and the additional circuitry they employ, there are slight discrepancies between channels, as well as more opportunities for switches and pots to get dirty and malfunction, or slide out of calibration.
In my tests, I found that generally, every channel ran pretty much uniformly, although some channels drove the mix bus as much as .2dB louder than others. This is not a huge difference, but I’d rest easier knowing every channel was hitting the mix bus at the exact same level—dead on—so that if I open a mix up and spread it out over the mixer set to unity, with nothing changing in my blends.
A look at the back panel of the MCM20.4, featuring eight balanced DB25 ports for easy connectivity, a Master Insert Send/Return, along with Main and Monitor outputs.
I also found that on a few channels’ pan pots, the center detent was not perfectly balanced and centered, being as much as .3dB off on either side. Though not huge, you definitely don’t want your kick drum, bass or lead vocal weighted .3dB to either side. This can be remedied by running test tones through your mono channels and manually finding the pan pot’s center point, although it would be nice to set it at the detent and forget it without having to run calibration tests. I’m not sure if the unit can be further calibrated internally, and it is possible that my test unit had a few channels that slipped out of calibration slightly due to movement and shipping.
I also found a small design flaw in that the pan circuits only boosted 2.8dB when panned hard left or right, where +3dB is really the target level for a pan pot to maintain mix balance when panned hard.
The truth is, though, all of these deviations mentioned aren’t massive, and plenty of engineers won’t bother calibrating anything when using the MCM to mix. Some sounds might end up the slightest bit left or right-heavy as a result, but generally, no one will actually notice. Some companies, notably Plugin Alliance with their TMT technology are now even modeling the kind of subtle analog randomness in their digital products as a feature.
True to the style of the old Neve EQ pots, there aren’t markings or detents on the channel faders, so if you don’t set your channels all the way up and instead get your blend with the console faders, good luck recalling. This may seem minor, but in 2017, recalls are not only common, they are the norm, so it’s a shame this mixer doesn’t have more markings or detents to make re-opening mixes simpler.
There are no power switches on the MCM mixers. Why? I don’t know. I like to turn my gear off when I’m not using it, especially if it’s something I don’t use all the time or if it uses a lot of power. That said, the absence of these switches is not a deal-breaker, after all sound quality is the important thing, but I don’t think implementing a small power switch would have hurt.
Unlike most line mixers, everything in the console operates at unity gain, and no higher. This is sort of a benefit as far as signal cleanliness, but not standard as far as mixing consoles go. There are no line trims on the inputs, and no additional boost on the faders, or anywhere else in the mixer. On most mixing consoles, the channel faders allow you to push +10dB above unity gain, and plenty of consoles have group and master faders with additional gain, allowing you to push the circuit with a higher output level than what was fed into it.
In a purist sense, faders that only attenuate and don’t include excess boosting circuitry seem like what you might want in a summing mixer. The only issue is, what if you want to hit your mix bus harder? The old SSL 4000 consoles responsible for so many hit mixes of the past 35 years generally like to have their mix buses hit hard, for example. The MCM doesn’t allow you to add any juice to your mix level. If your mix bus isn’t getting hit hard enough, your only option when using the MCM is to trim all of your channels up from inside the DAW. (The only problem is that this could potentially result in digital clipping on one or more of your D/A channels if you’re pushing things really hard.)
While I wouldn’t necessarily suggest that each channel fader on the MCM have additional circuitry to boost the individual channel levels above 0, it would make a lot of sense to put some more versatile gain options somewhere in the summing portion of the circuit, so that you can ease up or push harder on the mix bus with one easy control. A big part of analog summing is hitting the mix bus the right way. This unit doesn’t give you much flexibility in this department.
My last gripe—which is also half-compliment—concerns the setup of the stereo subgroups. In the MCM20.4, there are two stereo subgroups that then get fed to the master mix bus, and those stereo subgroups have inserts on them. (The MCM-32 has 4 stereo subgroups, also with inserts). This is an advanced feature for any small mixer, and very rare in outboard summing amps. It’s also a great benefit for a lot of engineers.
For example, if the vibe of the song calls for it, I’ll sometimes run all of the bass and drum tracks together through a bus compressor. This subgrouping feature on the MCM allows me to sum my drum and bass tracks together in the analog domain and then put an outboard compressor on the subgroup insert, keeping the bus compression in the analog domain.
The problem is in the way the subgrouping feature was implemented: Channels 1-8 always go to Subgroup 1-2, and Channels 9-16 always go to Subgroup 3-4. What if you want to route only channels 1 through 5 through Subgroup 1-2, and then run Channels 6 through 8 into Subgroup 3-4? You can’t. If you have tracks you want to put into Subgroup 3-4, then they have to be on Channels 9-16. If you have tracks running out to Channels 1 through 8 but you don’t want them going through Subgroup 1-2, tough. You’re going to have to process them with whatever else runs through Subgroup 1-2, or else re-route them to the other group of channels.
Heritage states that this fixed subgrouping was designed this way in order to keep costs down and save space. I’m not an expert on circuit design, but it would seem to me that they’d just have to replace each channel’s tiny on/off button with a “Subgroup 1-2” button and then add one new “Subgroup 3-4” routing button. Adding one of these very small switches requires a tiny amount of faceplate real estate, and I can’t imagine a two-switch routing matrix would have been too spacious or complicated to implement.
Summing it Up
To sum it up (pun intended), at a street price of $3,499 USD, both the MCM-32 and MCM20.4 are reasonably priced and flexible units delivering an added lift to any mix run through them, giving in-the-box DAW mixes a hint of that classic console and big-time album sound.
Whether the additional pan pots, channel faders and aux sends are a useful addition is really up to the engineer and the tasks they need the MCM Summing Mixers for.
While I can’t say for sure whether the MCM20.4 is the best sounding summing box on the market (the only way to know would be to compare them all over a variety of source material), I found no degradation of any of the variety of mixes I ran through it, and in the end, it only helped in all situations.
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