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July 25, 2019

Mixing with tube preamp | Fab Dupont




Did you know they used to make reverb units for home stereo systems? Fab kicks off this excerpt from the video "Inside The Mix: Fab Dupont Mixing 1234" by holding the preamp section of an old Fisher Space Expander, a tube-based spring reverb unit from the 1960s. He explains that people have been pulling out the preamps from these units to use as tube-saturation devices. He's going to show how it sounds to insert it on the master bus of a song he's mixing.


He says he's eager to hear how its tube circuitry will impact the overall tone. He says he'll check it out on both the verse and chorus sections. He points out that he'll hear more of the tube distortion on the choruses because they're louder and will hit the tubes harder.

A still from the video showing the Fisher Space Expander, which is the preamp section of a spring reverb originally designed for home stereo systems.

Fab starts with the verse, playing it through with and without the preamp. He suggests that you pay attention to the interaction between the vocal and the acoustic guitar, and how that changes when the preamp is on. He explains that it adds not only saturation but some compression that makes it sound denser. Yes, it sounds cleaner and more "hi-fi" with the tubes off, he says, but he's not looking for ultimate fidelity, he's looking to add a low-fi edge to it.

After making the comparison on a verse, he moves on to the chorus section, and the differences with the tubes on and off are not as drastic as you might expect. However, Fab says their effect, is nevertheless "pretty awesome for this purpose." By that, he means that they add subtle warming to the mix. He says that the tube preamp will be left on for the duration of the mixing process (Puremix Pro members can watch the full video) and the effect ended up on a number of the other songs on the record.


Although most of us don't have access to old tube preamps that we can run our mixes through, we can get a pretty good approximation of the effect using tube, and other saturation plug-ins.

When you're saturating an entire mix, as Fab did in the video, you typically want to dial in a pretty subtle amount. You don't want to make the mix sound like you routed it through a fuzz box.

If your distortion plug-in has a mix (wet/dry) control, one way to find a useful setting is first to dial in fairly heavy saturation, and then back the mix knob off until you're almost down to zero. As you're listening, turn the bypass control on and off so you can compare it with and without the effect. Try to listen to them both at the same volume, to avoid the "louder is better" effect. Saturation plug-ins can boost the volume, depending on how you set them, so if the effected sound is louder, back off its output control.

Soundtoys Radiator is modeled from an old tube-based mixer.

Besides adding the density that Fab described in the video, saturation plug-ins also soften transients, which is part of what adds to the perception of warmth. With the transients rounded off a little, it makes the source sound less strident. You can also get similar effects with tape saturation, which has a lot of the warming characteristics of tubes.

Example 1: You'll hear an excerpt from a mix repeat three times. The first time, there's no added saturation on the master bus. The second time, Soundtoys Radiator, a plug-in that models a tube mixer, is inserted on the master. Like what Fab experienced with the Fisher Space Expander preamp, the distortion that Radiator adds compresses the sound, adding density. The third repeat features the Waves J37 tape emulation plug-in. The effect is pretty similar to tubes in terms of how it affects transients. Focus on the snare drum to hear the difference between the versions.

Tape emulation plug-ins, like Waves J37, emulate the sound of soft clipping that you get when you overload a tape track.


In addition to their obvious uses on guitars and basses, saturation plug-ins also work well on other individual tracks and can be useful when you don't want to saturate the entire mix. Many instruments and even vocals can benefit from a little bit of warming. Here are some examples:

Example 2: First, you hear a drum kit for four bars without any saturation. It's a little dull sounding. Then, Soundtoys Devil Loc Deluxe, which models an old podium-mic limiter and can get some trashy sounding distortion, is added. The distortion is kept relatively low, so it just gives the drums a little bit of warmth and compression.

Soundtoys Devil Loc Deluxe is a saturation plug-in based on an old hardware limiter that was used in mic podiums and it's capable of serious distortion when set high.

Example 3: A sax is another instrument that, especially in a rock context, can benefit from subtle saturation. Here, a UAD Neve 1073 preamp plug-in adds transformer-type saturation to the sax starting on the third repeat of the riff (bar 5), fattening and warming it up.

Depending on the context, saturation can be useful on virtually any source. If you're looking to make a digital track or mix less sterile, or add some warmth and excitement to it, saturation effects are worth experimenting with.