Analog Mastering Chain: What Goes Where and Why

Analog Mastering Chain: What Goes Where and Why

  • 08.09.2026
  • Michael Krusch
  • Story
  • Basics
  • Mastering

The mix is done. It sounds right on your monitors, it survived the car test, the client is happy. And now somebody tells you it needs an analog mastering chain, and somebody else tells you a limiter plug-in will do. Both of them are sure, and neither of them explains what actually goes where, or why.

We build the units that end up in these chains: the Creme, a bus compressor with a passive mastering EQ in one box, the Vari Tube Compressor, the Classic Equalizer EQP-1 and the Schwerkraftmaschine. So this is the explanation from the inside: what an analog mastering chain is and is not, the order of the units and the one mechanism that decides it, how much compression and EQ a master actually gets, how to set the levels around your converters, how recall works when the settings live on a front panel, and three chains that exist in real studios, from one box to two, including the honest case for staying in the box.

In this article:

What an analog mastering chain is, and what it is not

Mastering is the last step before a recording becomes a product: the finished stereo mix is checked, corrected where it needs correcting, given its final tonal balance and its final loudness, and delivered in the formats the release needs. An analog mastering chain is the part of that job that happens outside the computer. The mix leaves the DAW through a D/A converter, runs through one or more pieces of analog hardware, comes back through an A/D converter, and is recorded as a new stereo file. Everything that has to be digital anyway, brick-wall limiting, sample-rate conversion, dithering, metering to a loudness target, happens afterwards, in the DAW, on that returned file.

That makes almost every analog mastering chain a hybrid chain. The hardware sits in the middle, digital on both sides. Nobody masters "fully analog" and then delivers a WAV; the question is only which stages you take out of the box and why.

What the chain is not: a repair shop. If the low end is boomy, the vocal is buried or the arrangement is crowded in the midrange, a compressor and an EQ on the stereo sum will make that mix slightly rounder, slightly louder, and still boomy, buried and crowded. We wrote about the relationship between mix and master in Mixing and Mastering with a Little Creme, and the point there still stands: the mix engineer can reach every track, the mastering engineer can reach two channels. A chain works on a mix that is already right.

And what it is for: a chosen piece of analog circuitry at the one point where the whole record passes through at full headroom. Tubes, transformers, a Vari-Mu gain cell or a VCA behave differently from arithmetic, and a mastering engineer picks them for exactly that behavior. Which brings us to the order.

The order: EQ first, then the compressor, and why

Every mastering chain contains the same four jobs: correct, compress, color, limit. The interesting question is where color sits relative to compression. Correction means removing what should not be there, a rumble below 30 Hz, a resonance the mix engineer missed. Compression means holding the dynamics together so the record feels like one piece. Color means the tonal balance you actually want: a little more air, a little more weight. Limiting means catching the last peaks so the file can be as loud as the release needs. The first three can live in hardware. The last one lives in the DAW, after the A/D converter. We do not build a limiter, and in a hybrid chain it belongs at the end of the digital side anyway.

The question everybody asks is where the EQ goes relative to the compressor, and the answer is a mechanism, not a taste. A compressor reacts to level. It measures the signal arriving at its detector, after any sidechain filter, and turns the gain down when that signal crosses the threshold. So whatever you do to the signal before the compressor changes how the compressor behaves. Whatever you do after the compressor changes only the sound, not the gain reduction. Sound On Sound's Mike Senior put it in one sentence in 2009: "pre‑compression EQ can alter the gain‑reduction action of the compressor, but post‑compression EQ won't."

Senior's own default, for a track in a mix, is EQ after the compressor, with EQ in front only when a frequency problem drives the detector. For a mastering chain with one EQ we land on the other side, and this is what Michael Krusch, who designed all four units, recommends: EQ first, then the compressor. The reason, in his words: the compressor should react to the signal you are going to hear, not to something else. If the EQ comes after the compressor, the compressor is regulating a tonal balance that no longer exists by the time the signal reaches the output. It might be leaning on a low-end bump you are about to remove, or ignoring a top end you are about to lift. With the EQ in front, what the compressor holds together is the record as it will be released.

There is a second reason that follows from the first. Correction before compression is the one point the sources agree on, because a resonance or a subsonic rumble that hits the detector makes the compressor work on the wrong thing; Bonedo's Peter Könemann summarized it in 2020 as "EQ cuts before the compressor minimize unwanted compression artifacts" (translated). His own conclusion is the sandwich: ideally one EQ before the compressor for the cuts and one after it for the boosts, and no rule set in stone. If your chain has one EQ, putting it first means correction and color happen in the same place, and the compressor sees the finished balance. Most people do not have two mastering EQs, and they do not need them.

The counter-view exists and we will not hide it. Dan Cooper of Production Expert runs the Creme in "Comp into EQ" mode on his master because, in his words, "the EQ section sounds more open after the compressor"; you can watch that chain in Production Expert: SKM, EQP-1 & Creme Mastering. Both orders are legitimate; they produce different records. The Creme has a switch for exactly this, so you can hear the difference on your own mix in five seconds instead of arguing about it. Our default position for that switch is EQ into compressor.

The compressor on the master: Vari-Mu for cohesion, VCA for control

Mastering compression is not mix-bus compression turned up. On a master the compressor works with small numbers: a low ratio, a slow attack that lets transients through, a release that follows the music, and a gain reduction in the low single digits: one to three dB is normal on a whole record, six is a decision, not an accident. Anyone who tells you their mastering compressor is "barely doing anything" is describing it correctly.

Which compressor you use decides what those few decibels do to the sound, and we build two families for the job.

Vari-Mu for cohesion. In a Vari-Mu compressor the tube itself is the gain element: the control voltage shifts the tube's bias and with it its amplification factor, so the compression is soft at the onset and gets firmer as the level rises. That is why a Vari-Mu on a master sounds like the mix was always one piece rather than like something is pushing it down. The Vari Tube Compressor is that principle in a 19-inch box: per channel three transformers and four triodes in the signal path, a high-pass filter in the sidechain so bass energy does not drive the gain reduction, and up to 6 dB of reduction on a full mix without audible pumping, which is headroom, not a target. Its Color/Comp switch lets you bypass the compression and keep only the tubes and transformers, which is a useful thing to have on a master that needs tone but no dynamics work. How the tube does the regulating is explained in Vari-Mu Compressor Explained.

The same principle with recall and M/S. The Schwerkraftmaschine keeps the all-tube signal path and computes the control signal digitally. On a master that buys you three things: servo-driven controls that return to any saved setting, a plug-in that stores the hardware settings inside the DAW session, and compression programs that a purely analog sidechain cannot do, including a Stereo Transformer mode that weights the compression between mid and side without an external M/S matrix. It also has a Vari Tube Compressor mode, so it can take that role in the chain described below, plus everything else.

VCA for control. The Creme is the other family: a VCA bus compressor in the tradition of the classic console bus compressors, with a passive Pultec-style EQ in the same box. Michael describes its compressor as the more analytical of the two, and that is the honest way to choose: the Creme holds a master together with less of its own sound, the VTC holds it together with tubes and transformers audibly in the path. The Creme's ratio goes down to 1.5:1 for leveling that stays transparent, the sidechain low-cut sits at 60 or 120 Hz, and every timing control is a stepped switch, which matters for the recall section below.

Starting points, not recipes. On the VTC: sidechain low-cut on, a medium attack, a long or automatic release, input raised until the meter shows one to three dB of reduction on the loudest passages, output to match. On the Creme: ratio 1.5:1 or 2:1, attack 10 or 30 ms, release Auto or Cream, sidechain low-cut 60 Hz, threshold until the LEDs show one to three dB on the choruses. If the drums lose their snap, the attack is too fast. If the mix breathes with the bass line, the release is too fast or the low-cut is off. Every one of these values is somewhere to begin, not somewhere to end; the record decides.

The EQ: broad strokes, not surgery

A mastering EQ works in whole decibels and wide curves. One dB of shelf above 10 kHz is audible on a full mix; three is a different record. The narrow, deep cuts of mix EQ are the exception here, because on a stereo sum every cut also removes something you wanted to keep. That is why the classic mastering EQs are program equalizers with broad shelves and gentle bells, and why the passive Pultec design from the 1950s is still on mastering desks today.

The Classic Equalizer EQP-1 is that design with tubes and transformers, two channels in two rack units. Bass boost and cut at 20, 30, 60 or 100 Hz, a high boost from 3 to 20 kHz with adjustable width, and a separate high cut at 5, 10 or 20 kHz. On a master it does two jobs. The first is weight: a small boost at 60 or 100 Hz, and if the boost brings mud with it, a little cut at the same frequency, which is the Pultec trick, explained in The Pultec Trick: Why Boost and Cut Don't Cancel. The second is air: one or two steps of boost at 10 or 12 kHz with the width set wide, which lifts the top of a mix without making it sound equalized. Michael's own description of the family is that the EQP-1 works in broad strokes and the MythEQ 500 is the surgical one; for a master, broad is what you want.

The Creme's EQ is the same passive principle without tubes and transformers, so it adds less of its own character: a low shelf from 20 to 200 Hz and a high shelf from 10 to 24 kHz, each in steps from 0 to 5 dB. Boost only, no cut. The high shelf reaching 24 kHz is the part people notice first, because it adds sheen above the range where an EQ usually sounds like an EQ. If the Creme is your only analog EQ and the mix needs a cut rather than a boost, that cut belongs in the DAW before the D/A converter, in front of the whole chain, where a digital EQ does surgery better than any analog unit.

Starting points: EQP-1 bass boost at 1 or 2 on the scale at 60 Hz, cut at 1 at the same frequency, high boost at 1 or 2 at 10 or 12 kHz, width wide, high cut off. Creme low boost 1 at 60 or 100 Hz, high boost 1 or 2 at 16 to 24 kHz. Then bypass and compare at equal level. If the bypassed version sounds thinner but the equalized version sounds worked on, you went one step too far.

Converters and levels: out once, back once

The analog chain costs one D/A conversion on the way out and one A/D conversion on the way back. Keep it at that. Every extra trip through a converter is a small loss, and in the Gearspace mastering forum the advice has been the same for years: analog processing happens in one pass, before the digital limiter, before sample-rate conversion, before dither.

Calibration. A common convention is to align the converters so that around −18 dBFS in the DAW corresponds to 0 VU, or +4 dBu, in the analog domain; −20 dBFS is just as common, and the interface manual tells you which applies. That alignment puts a normal mix in the range where the hardware was designed to work. The units we build accept +20 to +22 dBu at the input and deliver +22 to +24 dBu at the output, depending on the unit, so there is headroom above nominal, but the point of a mastering chain is to use the sweet spot, not the ceiling.

Sending. Do not limit the mix before it leaves the DAW. Send it with its peaks intact, peaking somewhere around −6 to −10 dBFS; with the alignment above that puts +12 to +16 dBu into the hardware, in the range it was designed for, and the compressor can react to real dynamics. A mix that arrives already flattened gives a Vari-Mu nothing to hold together.

Returning. The last unit in the chain sets the level the A/D converter sees. Leave the output a few dB under the converter's clipping point; the loudness comes later, from the limiter. Some mastering engineers deliberately drive their A/D converters into clipping instead of using a limiter, because clipping has no attack and release times and can be more transparent on short peaks. That is a practice, not a recommendation from us, and it needs converters that clip gracefully and ears that check every peak.

Comparing. Record the returned file, and before you decide anything, match its level to the untouched mix. A master that is half a dB louder almost always wins a comparison, and that half decibel is not what you paid for. Then switch blind. If you cannot hear the chain at equal loudness, the chain is not doing what you think it is doing.

If the mix comes in as stems rather than a stereo file, the chain starts one unit earlier, with a summing mixer that adds the stems in the analog domain and feeds the sum into the EQ and compressor; the Tube Summing Mixer does that with tubes and transformers and a stepped output switch, and Analog Summing: What It Does and When It Pays Off explains when that is worth it.

Recall: how analog settings survive until next week

The oldest argument against hardware in mastering is recall. The label wants a change to one song three weeks later, and the compressor's knobs are wherever the last session left them. Matt Houghton put it mildly in Sound On Sound in 2010: "recalling settings accurately can be a pain." In mastering it is not a pain, it is a disqualifier, because a revision has to match the original master exactly.

We answer that in three ways, and all four units use at least one of them.

Stepped switches instead of potentiometers. On the Creme every control except threshold and output is a rotary switch with fixed positions, and the two potentiometers are detented. On the EQP-1 the frequencies are switched and the boost and cut controls carry a 0 to 10 scale. The VTC has 42 detents on every control. A setting on any of these units can be written down as a handful of numbers and set again to the exact same values, and, just as important for a stereo master, the left and right channels can be set identically.

Digital recall sheets. Each of our units has a plug-in companion that does not process audio. You transfer the hardware settings into it, the settings are saved with the DAW session, and when you open the session again the plug-in shows you how the hardware has to be set. No photos, no paper sheets. The idea is described in Digital Recall Sheets.

Real total recall. On the Schwerkraftmaschine the plug-in is the control surface: the settings are stored in the session, and when the session loads, the servo-driven controls physically return to the saved positions. That is the one case where an analog tube compressor recalls like a plug-in, and it is the argument for the Schwerkraftmaschine in a room that lives on revisions.

Two more things about a stereo chain. Link the channels: the VTC has a link switch that runs both channels as a coupled pair, and the Schwerkraftmaschine can be split into dual mono from the plug-in when you actually want the sides regulated separately. And if the record needs the sides treated differently from the center, the Schwerkraftmaschine's Stereo Transformer mode does M/S-weighted compression without an extra matrix box in front of it and the wiring that comes with it.

Three chains that exist, and when none of them is the answer

Michael's answer to "which units, in which order" is three chains, from the least expensive to the most, and every one of them runs EQ first.

One box: the Creme. Passive EQ into VCA compressor, in one 19-inch unit, with the order switchable if you want to hear the other way. For a project studio that masters its own releases this is the entire analog side: weight and air from the EQ, cohesion from the compressor, everything on stepped switches. Not a mastering session, but the same argument for one box: on Robin Schulz's 2018 Brazil tour the full rack could not come along, so live engineer Dominik Piorr ran the master bus through a Creme and nothing else, "a decision that I have not regretted," in Robin Schulz on Tour with Only the Creme. If you would rather set the unit remotely than from the front panel, the Creme RC is the remote-controllable variant; it is a separate product with its own page.

Two boxes: EQP-1 into Vari Tube Compressor. The tube EQ shapes the balance, the Vari-Mu holds it together, and the transformers on both sides of both units do what transformers do to a full mix. This is the chain Nicholas D'Ombrain of Zeitgeist Mastering tested on video in Zeitgeist Mastering: VTC and EQP-1 Video Review, and it is the more colorful of the two-box options: everything the Creme does cleanly, this pair does with tubes.

Two boxes with recall: EQP-1 into Schwerkraftmaschine. Same order, same tube EQ, and in place of the VTC the compressor that stores itself in the session, adds M/S weighting and eleven compression programs. This is the chain for a mastering room that lives on revisions, and the most expensive of the three because the compressor does the most.

Variations exist. Iulian of 2probeats masters with the VTC and the Creme together, shown in Analogue Mastering with VTC and Creme. Dan Cooper runs Schwerkraftmaschine, EQP-1 and Creme all three, compressor first. Both work, because both engineers set the chain for their own records. The three chains above are where we would start.

When none of them is the answer. When the mix has problems: fix the mix, the chain will not. When you have a two-output interface: you have no converters to spare for a hardware loop, and the converters will have at least as much influence on the result as the units; budget the converters first. When you master one release a year: send it to a mastering engineer who does this every day, with a room built for it. And when your monitoring cannot show you one dB at 60 Hz: the chain will be set by guesswork, and plug-ins set by guesswork are cheaper. In Sound On Sound in 2024, Pontus Hagberg rebuilt a hardware mix in the box and concluded that with a target to aim for, level matching and oversampling, you can get there entirely with plug-ins; it is a fair result, and the reason we ask you to compare blind rather than take our word for it.

That is why every unit above can be tested for 14 days in your own room, on your own mixes, with your own converters. Build the chain, run a record through it, match the levels, switch blind. If it stays, it stays.

Want to hear an analog mastering chain on your own mixes for 14 days?
More about the Creme

Test the units individually: Classic Equalizer EQP-1 · Vari Tube Compressor · Schwerkraftmaschine

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