Let's talk about NATURAL compression...

[cacibi]

Thought I might start a thread about all the NATURALLY occurring compression in a rig's signal chain, NOT related to a compressor pedal.

In other words - what compression contributors are pre-existing in an average rig before a player even turns on a compressor pedal?

How and why do the following contribute to compression?

Pickups
Other (non compressor) pedals (OD's are an obvious starting point)
Preamp stage
Power stage
Transformers? (does the OT provide any compression?)
Rectifier
Speaker

[getbent]

I think playing with your fingers is the single biggest difference you can make.

[scooteraz]

Originally Posted by getbent

I think playing with your fingers is the single biggest difference you can make.

To compress? Just looking for an explanation, because I am not sure I have seen a compression effect from playing with fingers. Perhaps I am not using compression in the correct sense.

I had thought compression was when you took a, say for example, signal where the minimum volume was 60 dB and the maximum was 100 dB (40 dB difference) and say amplified it to a signal that had a minimum of 90 dB with a maximum of 120 dB (30 dB difference). The signal was louder, but the difference between loud and soft was "compressed" by 10 dB.

Does playing with fingers actually add to this? Or am I looking at compression in way too technical a way (certainly I have my artistic challanges).

To answer the OP, all of the above. Each component does not quite exactly reproduce the wave as originally generated, there are losses. As we amplify, the maximum sound pressure level and the the minimum sound pressure level of the music content get closer together due to the non-linearity in amplification. Tubes begin clipping by rounding off the top of a sine wave (so called soft clipping) as each tube just begins to clip, the loudest signals have more loss than the softest. Therefore they get closer together. Turning the volume up so that the peaks are at a given level affects more signals. Therefore more compression.

Transformers also have magnetic limits. When those limits are reached, they too will begin to "under amplify" the loudest signals, creating more compression. Pickups are like transformers in that they rely on electromagnetic processes. As they recieve too much excitation from a string, they will exhibit some of this same behaviour.

Rectifiers add to the mix by affecting the power supply. If they cannot provide enough current, the power supply voltage drops (sag) and the tubes all have less headroom to deal with.

Again, speakes have mechanical and electro-magnetic limits, same rules apply. This all gets pretty technical pretty fast from here as to amount and exact phenomena causing compression, but it is the result of increasing entropy due to imperfect energy transfer.

[Old Cane]

Compression is more like, using your example, you push from the top (squish). So instead of going from 60-100db you go from 60-70db. So, now you need make-up gain (turn it up!). At that extreme in your example there is going to limiting going on as well. Limiting is usually considered compression at 10:1 or greater I think. It's been a long time for me remembering this stuff.

To me, natural compression is either the 4 walls in the room blocking the sound from getting out (neighborhood compression), my tubes running out of juice from being cranked (yes, heavy distortion is sort of a compression) or my wife finally yelling at me to TURN THAT THING OFF! This is know as life compression, having to fit what you want to do around what she wants you to do.

[alanfc]

To my ears, a low gain tube in the phase inverter gives me a compression of sorts. I change back to a regular 12ax7 every once in awhile but I always go back. The low gain P.I. tube flattens and combs out the detail in my chords.
I also use a position 1 preamp tube that I specifically chose for its "early breakup", smoothness and fatness.
I use no pedals upfront.

[getbent]

Originally Posted by scooteraz

To compress? Just looking for an explanation, because I am not sure I have seen a compression effect from playing with fingers. Perhaps I am not using compression in the correct sense.

imho, yes. Try with your acoustic guitar when you really snap and pop, I think you'll hear it... not just a pima folky thing... more of a jerry reed thing or even with chord melody travis stuff those guys were playing hard and getting good natural compression. Even the John Hurt stuff has that kind of natural compression.... Doc W. does on his travis style stuff.

[chabby]

I don't know much about the electromechanics of compression, but I do know that I get more natural compression out of my Lil Dawg 5E3 than any amp I've ever owned. I never use pedals with it. When I first got it I did use a compression pedal. But then I started almost by accident (forgot pedal) playing without one. Now, I really don't miss any pedal with this amp. Certainly never need an OD pedal. And while if I was gonna use any pedal with it, it probably would be a compression pedal, I haven't been compelled to.

[mudbean]

A good example of how much your amp compresses your guitar's signal is this, if you have the necessary toys: Record your guitar directly by plugging into a recorder and not your amp. Here how each attack and inflection is right in your face? Badly so, even. Now, play through your amp and record the sound with a mic in front of the amp - you'll hear how much the amp smooths out your sound. That's natural compression.

mud

[Tele-evangelist]

I agree that components like OT's, tube rectifiers and speakers can all affect the signal by compressing. But when regarding 'Natural compression', lets not forget mic placement. I like to place a Shure SM57 off axis to the amps speaker for natural compression. So instead of pointing the mic right at the speaker, I rotate the mic so that the waves from the speaker are travelling across the diaphram and not hitting it head on. Carefull rotation during setup allows me to dial in how ever much compression I like, and with an open backed cabinet, I like to mic the back on axis and then flip the polarity during mixdown bringing both signals in phase. This way I can blend the two to mono or spread out the signal for a wider sound, and if I want to thin the sound out, I just flip one of the signals out of phase for cancellation. So many possiblilties. Sorry if I got off topic there.
Tim

[mudbean]

Sorry to take issue with this, Tim, but I've never heard compression from a mic - tonal variation due to placement, yes.

mud

[Tele-evangelist]

Originally Posted by mudbean

Sorry to take issue with this, Tim, but I've never heard compression from a mic - tonal variation due to placement, yes.

mud

Dear Mudbean.
Compression from mic placement isn't something I made up, as it's been around for longer than I have. It does stand to reason that if you place the diaphram 90 degrees off axis to the sound source, it won't move back and forth as much as it would if it were placed pointing directly at the source. If you make up the gain you have lost with a high quality preamp and then record and compare both mic placement samples, you should find that you do have a lower dynanic range with the off axis recording. I certainly do. This is actually a very old trick, but the fine art of micing has been slipping away as we rely on DSP more and more.

Tim

[scooteraz]

Originally Posted by getbent

imho, yes. Try with your acoustic guitar when you really snap and pop, I think you'll hear it... not just a pima folky thing... more of a jerry reed thing or even with chord melody travis stuff those guys were playing hard and getting good natural compression. Even the John Hurt stuff has that kind of natural compression.... Doc W. does on his travis style stuff.

Thanks. Guess I never thought of that sound as compressed, per se. Need to think about it. I know a compressor helps with "pop" when chicken picking, but I thought that was just a bringing up of the overall sound floor. Of course, I am not so good at the chicken picking, so, experiments in this area are a bit difficult for me personally. Better stop posting and get to practice!

Old Cane, actually we are talking the same thing, just in your example, your overall gain is -30dB. From and engineering point of view, the compression is the "squeezing" of X amount of dynamic signal into "Y" amount of space where X>Y. After that squeezing, whatever we do with overall gain is sort of immaterial from the engineering equation space. However, from our psychoacoustic experience, it may have quite a bit of difference.

[octatonic]

Compression isn't something that is necessarily desirable from a musical point of view.
All compression does is lower the dynamic range and overall level of an audio signal.
This is not always what is required especially if you want to play into a crescendo.

A compressor (either pedal, rackmount or plugin) can smooth the playing levels out, useful to a degree but not a be all and end all.
For instance, solid state amps at high gain have an awful lot of compression going on but most guitarists dislike that tone.

Getbent is 100% correct- the fingers have more control over the volume of the signal than any other component.
A great player can control the level of the guitar signal in an interesting and musical way- a compressor pedal can't do it to the same degree- but that doesn't mean a compressor pedal doesn't have its place.

The amp and its individual components has an impact of course- but it is mostly the player.