Plugin Alliance is a company that doesn't need a big introduction. We are talking about one of the largest professional plugin producers. He recently released the software version of the well-known Vari-MU (tube) compressor SPL IRON: one of the most talked about plugins of the moment.
To take care of the realization of this was brainworx, a well-known brand that has developed many other plugins, which also works for Universal Audio.
SPL IRON it is labeled a "mastering compressor", however I will test it thoroughly before giving a full judgment.
The interface
This compressor in the real world it works at 120 V DC, which guarantees a high headroom, an important dynamic range and an optimal signal / noise ratio.
As you can see in the second image, it uses parallel dual-tube circuit technology in addition to the fact that there are transformers.
It also shows the flow of the audio signal and how the various controls interact with each other, from the point of view of voltages.
Now let's take the first image as a reference to try to understand them better.
By adjusting theINPUT , THRESHOLD I determine how much audio material must be involved in the compression.
Please note that this compressor does not have a ratio control, and this basic one is not fixed. This shouldn't be too surprising when it comes to Vari-MU compressors (spelledμ ).
By acting on the two controls just mentioned, I can influence the ratio. In short: the higher the input, the lower the threshold and the more the compression will be decided.
With the OUTPUT control I can make any volume compensation, as well as adjust the overall level. Also note that the input and output knobs work in jerks; +/- 2 dB to be precise.
For ATTACK and RELEASE there is not much to say, especially if I consider them individually. But I can tell you that these are influenced by other controls; so let's continue to explore the interface to better understand everything.
Through a switch a 3 positions I can adjust the TUBE BIAS. Let's take the second image for a moment as a reference: the bias of the tube is the voltage present on the grid, which affects the flow of audio signal from the cathode to the anode.
The higher this voltage is, the weaker this signal flow is; an increasingly decisive compression ensues.
To produce the voltage to control the valves connected in parallel, the device uses a rectifier circuit (RECTIFY).
To be more specific, we have available 6 rectifier circuits which use different technologies (led, silicon, germanium) as well as the capacities of the capacitors; the latter are measured in farads (F).
Each rectifier circuit, according to its own characteristics, is able to modify the values of ATTACK e RELEASE; it can therefore alter the behavior of the compressor in an evident way.
In the manual you will find a table with all the attack and release values in game, although it is good to experiment with your ears rather than referring to the numbers.
For the more “brave”, as well as for those who chew a little electronics, I will leave a link about the rectifier circuits.
We have 4 types of internal side chain available (SIDE CHAIN EQS) quite particular, plus the possibility of also using an external side chain.
Each of these causes the compressor to react more clearly to some frequencies than to others.
The behavior of the device is strongly influenced by all these controls. We cannot (and must not) rely solely on the attack and release knobs.
There is also a meter that can be used to display the gain reduction (GR) or as a classic VU METER.
Post compressor, through a switch, it is possible to equalize the audio signal quickly, using 2 preset equalization: AIRBASS e TAPE ROLL OFF.
The first emphasizes the two extremes of the band, while the second performs the classic roll off on the highs and very lows, typical of tape recorders. To do these interventions the device uses two passive filters.
It must be said that, bypassing these two presets, the compressor however does not have a perfectly “flat” frequency response from 20Hz a 20KHz. In fact, I found a slight roll off on the very highs and very lows, after doing the classic test with white noise.
This should not be too surprising, as we are analyzing an “analog in the box” compressor.
Also in the manual of the original machine there is an answer of this type; after all, the plugin manual is mostly a copy of the hardware manual.
SPL IRON: frequency response and equalization preset
The switch SC LINK, when set down, it allows us to make the device work in dual mono mode. The two compressors you see in the first image will work separately, so the left-right or mid-side channels are processed independently. This mode allows you to preserve the stereo image as much as possible or even expand it, especially when working in mid-side (M / S) mode, as there is the possibility to work with the parameters of the two compressors in an unlinked way. (PARAMETER LINK off) by setting them independently. Among other things, I can comfortably solo the mid or the side, going to the top right.
Instead, by adjusting the switch upwards, the device works in the classic stereo mode, in which you have to imagine that you are referring to a single compressor (physically the channels are always 2). In fact, the parameter link button in this case makes no difference: the parameters of the two compressors are always linked. This setting can be useful if you intend to potentially preserve the mono compatibility of the audio track, as the two channels affect each other from the point of view of compression, not to mention the fact that the sound is different than in the previous case. However, you can quickly compare the two results and decide.
Curious functionality
It is possible to activate an AUTO BYPASS function via the switch located in the center of the interface.
Using the knob INTERVAL it is possible to establish after how many seconds the device must deactivate / reactivate (it will do it cyclically).
Instead of using the seconds, we can synchronize with the BPM of the session by placing the switch on HOST SYNC. In this case we will have to take the session grid as a reference.
This function can be useful for those who want to focus on the sound and then make the appropriate comparisons at regular intervals automatically, avoiding activating and bypassing the plugin continuously manually, or to do a sort of "blind test" without knowing for sure whether the plugin is active or not.
"Even the eye wants its part"
You can change the graphics by going to UI menu top right, choosing one of the three available interfaces; this is also reflected in reality.
Tools
The plugin offers the ability to store quickly 4 preset, which is very useful considering that the controls in game are certainly not few, in addition to the fact that decisions can be made very quickly, passing from one preset to another. The internal Undo / Redo commands are also very comfortable.
Additional controls by Brainworx: the bottom interface
Other controls are offered that enrich this plugin: a HIGH PASS-SIDE CHAIN FILTER that can improve the sound in some cases, excluding a certain range of low frequencies from the compressor detection.
There is the possibility to manipulate the stereo image very quickly, by acting on the controls SINGLE MAKER e STEREO WIDTH, which you can also find on other Brainworx plugins.
We can also work in parallel by acting on the control PARALLEL MIX, and, as previously mentioned, there is also the M / S mode.
A check that should not be underestimated is HEADROOM: it is able to significantly change the behavior of the device.
Working with a very low headroom the compressor can saturate / clip very easily, even before starting to work concretely (low gain reduction). The levels in the game also contribute and in any case this is not a bad thing, a lot depends on the source we are dealing with and if we want to add color or not to the sound. Maybe it could work on a single track when mixing or working in parallel.
With a high headroom the compressor works in a more elegant way, you can therefore lower the threshold and / or raise the input to obtain a clean compression, which could be useful perhaps in the mastering phase or when a certain "transparency" is required.
By giving higher "priority" to the input or the threshold you can obtain different colors, especially with low headroom. All the other controls also play their part, in terms of harmonics.
Pay attention to the overall volume when you overdo the input: the clicks of +2dB are not to be underestimated. In that case the output knob can be your "friend".
TMT (Tolerance Modeling Technology)
Brainworx owns a technology that allows us to appreciate the tolerances of the electronic components that make up analog devices in the digital world. This is also present in other plugins from the same manufacturer.
The electronic components have tolerances that you find noted in the technical data sheets. Two resistors from 2K Ohm, apparently the same, in reality, due to the tolerances, they could have different resistance values; for example one could be 1,8K Ohm and the other 1,9K Ohm.
So two devices, apparently the same on paper, will most likely sound different, even if not blatantly.
Brainworx makes available 19 o 20 different channels depending on whether we use the mono version or if we use the two-channel version, working in STEREO MODE D (digital).
In REAPER I only have this last version available which I can however adapt to mono sources.
If we work instead in STEREO MODE A (analog) we can choose two adjacent channels, starting from 1 to 20, perhaps doing it in a RANDOM way and then stop when the sound fully satisfies us.
If I work in analog stereo mode, taking a mono track as a reference, I can very easily appreciate the difference between the two adjacent channels chosen, in terms of frequency response, dynamics and so on.
In practice, buying this plugin is like buying more than one virtual analog in the box model of the same compressor.
Latency and CPU consumption
This plugin falls under the category of plugins a low CPU consumption and it is absolutely 0 latency. We can load dozens of instances without any problem (I worked on 44/48 khz with an average buffer size).
Conclusions
The product costs dollars 329 (Excluding VAT), certainly an important figure, but keep in mind that Plugin Alliance often launches flash offers on specific products with discounts that can go up to 90% (for registered users).
Plus the original hardware costs 5000 €, for which "the arduous sentence to posterity". Below, I summarize some salient aspects:
- We are talking about a compressor with a musical and convincing sound.
- It is not immediate to set, which should not worry and should not be seen as a defect, but as a synonym of versatility.
- We can give the sound density or a snap / punch character, choosing the right rectifier circuit, the right side chain and adjusting the attack and release accordingly according to the sound you have in mind, without neglecting the other controls.
- We can saturate or destroy the sound if we want, perhaps working with low headroom and fast attack.
- We can get more transparent compressions by working with a high headroom, taking care not to ruin the transients, which is welcome in mastering, or we can try to contain the strongest peaks and perhaps gain perceived volume. However, a lot also depends on the audio track, as well as its envelope and spectral content.
- Having two side chain controls allows you to further increase versatility and find the right setting based on the track being considered.
- The additional controls of the lower interface as well as the 2 equalization presets are very welcome.
- I can say that it finds fertile ground in both mix and mastering.
- The only thing I didn't really like was the jerky handling of + -2dB, as far as the input and output knobs are concerned, because it didn't allow me to do a perfect gain matching.
In practice, it is good to start with a tube bias low or medium, to then experiment (it costs nothing, as always) with all the other parameters that certainly make a significant contribution to the sound.
We must not underestimate the levels involved and, above all, we must not compress with the eyes but with the ears, especially when working with this compressor. Watching the gain reduction every moment, without trusting your listening, leaves the time it finds, in addition to the fact that it is quite counterproductive, especially if the compressor is set without knowledge of the facts and without having the slightest idea where you want to get from the point. of sound view.
In any case, the product is definitely recommended and I gladly add it to my collection of compressors.
I will soon publish the results of the audio test, with all the relevant considerations; in the meantime I leave you some useful links.
That's all for today, see you next time.
Links
https://www.plugin-alliance.com/en/products/spl_iron.html
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