R Comp Compressor

[Rolando Kumar]

Idid a bit of searching on this, but I couldn't find an answer. From what I understand, the Kinky Comp is based on the Xotic SP compressor. However, the controls for the Helix model are completely different than that of the SP compressor. Has anyone ever answered how the controls match up on the model compared to the real-life version?

The Helix model it is not a one to one emulation of the controls on the Xotic. The attack and release controls are presets via internal DIP switches on the Xotic whereas they are variable parameters on the Helix. Don't know what values Xotic uses for these. I would find something that works for you for these two settings. The Xotic also has DIP switches for an input pad and although it is not really the same thing the Helix has one of those in global settings so maybe they left it out. Same thing goes for the DIP switch hi-cut on the Xotic; can be found elsewhere on the Helix. Use the new gain reduction meters on the Helix to get the sensitivity dialed in right. Rough mapping of the respective controls is below. I did a general writeup on compression(before this pedal was added) you might or might not find helpful in getting ideas for settings.

I always run a simple "gain block' before the compressor which allows me to fine tune the signal level just before it hits the compressor. It's acts as a PAD (or boost) but is much more variable. My reasoning is that I find the stomp compressors on the Helix really aggressive (real models are as well) and squish notes much more than I like. Sure the blend is there, but that doesn't change the underlying effect.

Here is a document I have been working on but is not really ready for prime time yet. It is drawn from a variety of unquoted sources (my bad) and as I mentioned not yet fully edited but in the interests of giving you some general knowledge to work with I will post it up. There are probably other users on the forum who can provide more explicit settings for the compressors on the Helix and there are also user provided presets on CustomTone (good luck sorting through them) that serve as great examples. Anyway, here goes, a completely deranged and disorganized guide to compression that is designed to give you a working knowledge of compressor settings and operation rather than provide you with the settings but may nonetheless shed some light on the subject. There is a great link to suggested compressor settings for a variety of instruments as well as some other sample settings towards the end of this post. There is also a section further down on how to use the Helix 'LA Comp' compressor as well as a general section that applies to the Helix's 'Deluxe Comp'.

For those of us who use compressors in a preset, most of us probably have it on all the time (and that is ok), or perhaps have it setup to switch off when we want more dynamics, for instance when we kick in a distortion pedal or heavier sound on a solo via a snapshot or pedal assign. I think however that the compressor is a prime candidate for assigning parameters to snapshots so that you can change the values on the compressor to match your tempo, attack, or song part (intro, verse, chorus, solo, bridge, outro) instead of just switching it in and out or leaving it on all the time.

The HX line of devices added a gain reduction meter to the firmware at some point. You can use this by selecting any compressor block and look to see when the threshold you set is being crossed, and also how long it is being engaged until it is released. The gain reduction meter is extremely helpful for setting the threshold and release settings.

I have gathered a bunch of notes together over time from various websites regarding compression so this work is the result of others much more well versed on the subject. My apologies in advance for any inadvertent plagiarism. I would be happy to cite sources or remove text if anyone sees their text here. Some notes may be redundant as they came from a wide variety of sources. I hope this assists some folks in getting their heads wrapped around compression parameters and their usage in different scenarios with the guitar and bass but also with vocals, drums, etc..

Why use compression?:

First a brief description of common compression parameters (the 'Deluxe Comp' on the Helix has all these settings):

Note: On some simple, for example two knob compressors, two or more of these parameters' functions may be collapsed into one knob. For example, turning up the ratio may simultaneously turn down the threshold. (contributor: njglover)

So here goes, some general information and tips on using compression in no particular order:

Note: Sometimes 'pick attack' or 'string attack' is mentioned in this document and refers to how fast or hard the string is being plucked. This is not the same as the 'attack' setting on the compressor although 'pick attack' may influence your choice of the compressor's 'attack' setting.

Pumping, breathing, and distortion:

Attack time settings affect the sound quality in terms of overall perceived brightness or high-frequency content. If you use very fast attack time settings, the compressor will activate very quickly, reducing gain instantly at the waveform level of the sound. However, too fast an attack or release can cause distortion or unwanted artifacts like pumping or breathing, particularly on bass or low notes as the attack and release are actually faster than the cycle(hz) of the note being played. Since transient information at the front or attack portion conveys brightness character, especially with percussive sounds, immediately reducing it with the compressor will dull the sound. Selecting a slower attack time will allow the transient portion of the sound to pass through before the compressor starts clamping. However, if the attack time is too slow, ineffective and tardy compressor action may result.

Low frequencies (e.g. bass guitar, detuned or just low guitar strings) can be distorted by too fast a release time. Super fast release times, along with a fast attack time setting, will distort low-frequency sounds, as the compressor is capable of gain change within the period (the 360-degree cycle of the lowest fundamental frequency) of the sound's waveform. Likewise, over-long release time settings are another form of distortion, since gain reduction is "stuck" clamping the sound down for an unnaturally long time period. "Pumping" and "breathing" are engineer jargon words for obvious compressor artifacts or side effects with maximum compression. Sudden and usually unwanted deep gain reduction is called pumping, while a slower return (release) to operating level with a noticeable rise of the noise floor is called breathing.

For a more transparent sound you may prefer a release time that has the shortest possible time that does not produce a "pumping" effect, caused by cyclic activation and deactivation of compression. These cycles make the dominant signal (normally the bass drum and bass guitar) also modulate the noise floor, producing a "breathing" effect. For more sustain you may opt for a longer release time.

As previously mentioned, fast release/attack times may create distortion, since they modify the waveform of low frequencies, which are slower. For instance, one cycle at 100 Hz lasts 10 ms, so that a 1 ms attack time has the time to alter the waveform, thereby generating distortion.

Compression settings especially for guitar:

This is an interesting blurb regarding the Rockman compressor. The problem to solve, when you want to design a compressor for the guitar, is a double problem:

Act as a limiter during the first part of the note - a strong peak (think fast attack)

Act as a sustainor during the second part of the note - a slow decay (think slow release)"

Side-bussing compression:

You can side-buss the compressor with an EQ block to selectively compress frequencies or provide both a direct signal and a compressed signal to the mix.

Sidechaining compression:

You can sidechain the compressor such that for instance a kick drum hit will momentarily compress the bass guitar in such a way as to reduce the masking of the kick-drum by certain frequencies in the bass guitar. Sidechaining is essentially used to cause the trigger instrument to cause another target instrument to be momentarily compressed.

Ringing out microphones and feedback in a system:

A compressor can be used to aid setting up a system when it is being ringed out, i.e. its main feedback frequencies are being removed with an equalizer or a feedback elimination type unit. The compressor will have a low threshold level and infinity-to-1 ratio with hard knee characteristics. With no signal present, we will gradually increase the volume until the first feedback frequency rings. The compressor will catch it and keep it at a constant safe level, making adjusting the equalization an easier task. The process will typically be repeated until the third or fourth feedback frequency has been ringed out.

Sample Compression settings (source citations needed):

First a great link for compression settings for various instruments:

Note: You may want to try an attack setting of 20ms-25ms or more for electric guitar. This will allow more of the initial transient of the guitar note through and make for a more articulated sound with better attack and dynamics. The recommended value of 7ms in this chart for electric guitar is fairly low although good for fast picking or catching and suppressing loud sudden peaks/jumps.

An interesting article on how to set different compressors

Helix 'LA Studio Comp' Parameters And Usage Tips

Note: The 'Mix' control as on most compressors can help by adding back in the initial pick attack as well as potentially brightness or tone to the signal by providing some of the uncompressed signal in your path, particularly on higher 'PeakReduc' settings.

PeakReduc - This will set the 'amount' of compression and also adjust the threshold (how high the input level, or the often related, how aggressive the pick attack needs to be, to trigger compression). These two parameters(ratio, threshold) are collapsed into this single control on the 'LA 2A'. The ratio control being the ratio of dbs being reduced you are used to seeing e.g. 2:1, 4:1 and threshold referring to what input level is required to trigger compression. I don't know how or even if the attack and release are figured into the PeakReduc when it is adjusted. The original 'LA 2A' analog compressor the 'LA Studio Comp' is based on did not have attack and release controls (similar to a two knob compressor pedal) but instead used the "combination of an electro-luminescent panel and a photo-cell to determine the attack and release characteristics of the LA-2A". I am not sure how Line6 modeled that circuitry but that is what would set the attack and release in the original effect.

Gain - This is referring to the 'makeup' gain knob you see on most compressors. Generally the higher you set the compression (PeakReduc) the more the signal will be reduced and the higher the 'Gain' will need to be set. "This control does not affect the compression. The gain control should be set after the desired amount of compression is determined using the Peak Reduction control. Once the Peak Reduction control is set, adjust the Gain Control to achieve the desired output level."

Emphasis - Use this to have more or less compression on the sparkly high end of your guitar signal. "The LA-2A was designed for use in broadcast applications. The audio signal in FM broadcasting undergoes pre-emphasis and results in a 17 dB boost at 15 KHz. Due to this increase in signal level, transmitters are subject to over-modulation. The LA-2A provides a control (R37) which controls the amount of high-frequency compression. Increasing the resistance of this potentiometer on the original device by turning it counterclockwise will result in compression which is increasingly more sensitive to the higher frequencies." So, to put it another way, this large 17db bump at 15khz in the original LA-2A compressor meant that they built in an 'Emphasis' parameter that kept compression flat across the frequency spectrum but allowed you to apply additional compression to the high frequencies. I suppose in some respects similar to a two band "multi-compressor". I don't know exactly at which frequencies Line6 or the original effect applied that additional compression; on the original maybe around 15khz as that is where FM broadcasting signals were boosted. I am not sure of the answer to that question. It is worth noting that on the original device turning the 'Emphasis' control counter-clockwise (down) actually increased the amount of compression applied to the high frequencies.

Type - This parameter will adjust the ratio settings used in the 'PeakReduc' parameter to much higher values, generally you will set this to 'Compress' for guitar. Setting it to 'Limit' will change a 2:1 ratio into for example a 10:1 ratio more ideal for limiter use.

A few sample settings for different instruments:

If you want to use a little compression to bring the electric guitar forward and give it some punch or sustain, try these settings. You may have to experiment with the threshold setting in particular as various compressor models use threshold differently:

Threshold: 1dB

Ratio: 2:1 - 3:1

Attack: 25-30 ms

Release: About 200 ms

Gain: Adjust so that the output level matches the input level. You don't need much added gain.

To get a handle on the potential muddiness of the amplified bass guitar use a little compression. Compression can also help control uneven levels that result from overzealous or inexperienced bass players. Remember too fast an attack or release on bass because of the lower hz cycle can cause distortion as the compressor is cycling faster than the note. Try these settings for a start:

Threshold: 4dB

Ratio: 2.5:1 - 3:1

Attack: 40-50 ms

Release: About 180 ms

Gain: Adjust so that the output level matches the input level. You don't need much added gain.

These are good settings for strummed or picked acoustic instruments:

Threshold: 6dB

Ratio: 3:1 - 4:1

Attack: Around 150 ms

Release: About 400 ms

Gain: Adjust so that the output level matches the input level. You don't need much added gain.

The release is set very high because of the amount of sustain that acoustic instruments such as a guitar or dobro can have. If you play an instrument with less sustain, like a banjo mandolin, or even a ukulele, you may find that a shorter attack and release work just fine.

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