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Zelenka Music Press
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CompressionThis page is about "compression" as it applies to signal processing on a nylon-string guitar using piezo pickups.A compressor pedal is the tool to smooth out the sound of the piezo pickup and get a long, smooth sustain. This was a mystery to me years ago, when I thought that such a sound was some sort of technical wizardry way out of my reach. But all you have to do is buy a compressor pedal. Compressor pedals are a dime a dozen, and there are lots of opinions. Here are mine. First of all, a compressor should have "lots" of knobs, because a one-knob or two-knob compressor has all its functions chained together, and this is fine if you have an electric guitar and the compressor pedal makes the particular sound that you happen to want. But nylon strings have a different sound profile than an electric guitar does, and the relationship between the attack, sustain, and compression ratio is different, and for this, you need a compressor with as many separate functions as possible. So, rule of thumb: for nylon strings, get a compressor with "lots of knobs" and turn all the knobs all the way up and all the way down to see what they do, and find a sound you can live with. Compression is NOT the last stage of the signal chain - according to me, you need Reverb at the end of the signal chain, after the compression and the EQ. Compression is often compared to putting a pressure spigot on a garden hose: without it, the water dribbles out and falls down, and with it, you get a nice stream of water than shoots out for several yards. It's a fairly crude analogy. Compression cuts the volume of all signals over a certain level, and boosts the fading tail of the signal up to about that same level, and so you get a nice smooth sound that lasts a long time. When the sound is too compressed, it has no life, because the attack has been completely killed and there is no dynamic response, and no matter how hard you play the string, it gives the same volume. This is boring. So. We slow the attack down so that the compressor does not kill the attack quite so much, and then there is some life left in the notes. I'm not going to tell you how to do this - just play with the knobs until you find a sound you like. If you don't find a sound you like, buy a different compressor. I have only owned three compressors, and two of them I still use. The first one that I bought was a Nux Sculpture. It's cheap, it's small, and it works. But I found that it had some white noise, and it only has three knobs, and so I bought a Pigtronix Philosopher's Tone mini. This is a very nice compressor but it still doesn't have enough knobs - only four knobs - and I found that for me, on nylon strings, it cut the life out of the attack. It made a very smooth, long sustain, but the attack had no character. So I found another use for the Philosopher's Tone which I will explain in a minute. The third compressor I bought is a DemonFX Call76, and this has six knobs and gives me the sound I want. DemonFX is a Chinese company which specializes in direct knock-offs of pedals made in the USA or Europe that cost anywhere up to 400 dollars or Euros, and DemonFX sells theirs for 50 to 100 bucks. So far they appear to have good quality control, according to the reviews. The Call76 is supposedly a bass compressor - and I have more bass range than a normal guitar, and it works for me. The "bass" feature is that it has a high-pass filter so that it can leave the lowest bass register uncompressed. Then, it has a "dry" knob, separate knobs for input and output, and separate knobs for compression ratio and for attack/release (attack and release are chained together with the same knob). This compressor gives me a sound I like. I'm sure there are plenty of others I would like as well. So I shape my "clean" sound with the DemonFX compressor and the EQ. The DemonFX compressor comes second in the pedal chain, after the Broughton Buffer-Bandwidth-Filter , which contains the necessary impedance transformer for the piezo pickup. Then the compressed sound goes into the Mesa Rosette Acoustic Preamp (which has no impedance transformer, a design flaw!) where it gets EQ'd, because the Rosette is a great EQ, and then the signal goes to the effects loop where it gets reverb mixed in. My effects loop is complicated: I learned about multiple-path signal chains and had to try it. When the signal leaves the Rosette to go into the Rosette's effects loop, it has already been first filtered, compressed, and equalized. Then it goes into a signal splitter which I got from DPFX in Greece: this splits the main signal into three parts, all of which are buffered. As it turned out, I only use two of these channels. I had a cockamamie idea to put an octave pedal in the third channel, but I did not get the results I wanted, so I am not using the third channel. One of the two channels is not processed any further. The other channel goes first through the Pigtronix Philosopher's Tone compressor with the sustain and blend at 3 o'clock, the volume at 12 o'clock and the treble at 9 o'clock. After that it goes into a Keeley Omni reverb on the "Plate" setting with the knobs at 11:30. This gives the reverb a dark, smooth quality that is quite different from the clean sound. When a clean note stops, the reverb fills the space behind it, and I like this effect more than when the reverb is applied to the clean sound directly. Both channels then go into a little 3-channel line mixer from Saturnworks Pedals in Davis, CA, USA. Then the clean signal and the reverb signal, mixed together, go back into the effects return on the Rosette, and then out from any of three outputs which the Rosette has: XLR jacks for line and mic level signals, and a 1/4" TS jack for the one-mega-ohm output. Any of these I can send to a mixer with the appropriate inputs. |
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