Tube Amp Compression

[wcriley]

No flats. Circle K rounds.
My technique is probably as poor as it gets.

[beans-on-toast]

Originally Posted by wcriley

Please excuse me for going off topic, but is this a problem many/most bass guitar players face?
Just asking because I've never had a problem with string to string levels being unbalanced.

Yes it happens. It depends on the instrument. You can have certain notes that are deader sounding than others as you move up the neck. Likewise on some instruments, a string can sound dead. This can sometimes be fixed with fret or bridge adjustments. Sometimes changing the gauge of the problem string can help. Sometimes a neck can have a dead spot.

A compressor can help even out the sound.

[wcriley]

Thanks.
I've heard of bass guitars with "dead spots" but, luckily, have never experienced it.

[kmon]

Originally Posted by wcriley

Please excuse me for going off topic, but is this a problem many/most bass guitar players face?
Just asking because I've never had a problem with string to string levels being unbalanced.

well what I find is that my E and A strings will pack a much larger sonic punch than D and G. I can deal with this by altering my dynamics a bit on E and A, or by using a compressor to tamp down E and A a bit. At least that's what I use the MXR for. There are times when I want the bigger punch, but I generally prefer that perceived levels be similar across the strings.

With a compressor I can have a higher overall volume level so that higher notes will be heard without kicking everyone in the nuts when I start hammering on lower notes, and I can play hard and fast when needed without worrying too much about altering dynamics(my brain has limited bandwidth). The MXR has a meter on it and is barely activated with higher notes, but definitely comes alive on lower notes. When I tune down to C# is when I get the most action on the compressor.

[beans-on-toast]

I should add that tube compression and a compressor device are two different things. They work in different ways. Sometimes the end result can be similar in terms of sound but most of the time they are not.

A compressor processes the signal at a low level and compresses or squishes it. An expander/compressor will boost lower level components and compress others. It does it in a fairly consistent way. Playing dynamics do affect it.

Tube compression is a type of distortion. Normally the output of an amp looks like the input, only it has a larger amplitude. The amplification is what is called linear with the output simply scaled up. With tube compression, the output doesn't look the input. Depending on how hard the amp is pushed, part of the signal can be squished or even lopped off (like what a device called a limiter does) or all of the signal can be squished. It is non-linear distortion. The output can look, and obviously sound, very different from the input. Tube amp compression can also come from changes that occur within the power supply as it is pushed. A sag in power occurs when the amp is pushed too hard. This results in a loss of headroom and it shifts the operating points of the tubes to a region where they are operating in a non-linear way. Tube amp compression is very dynamic, always changing. It depends on the signal from the instrument and how hard you are pushing the amp.

[chadds]

If you can watch your playing with a VU meter you may see it's your technique. This was an old teaching tool. Your ears should hear the differences between the strings. They are different gauges. Your fingers will then respond accordingly. You play a touch sensitive instrument. Put in the time. Use no crutches that delay your skill developing.

Play gently most of the time. Turn your amp up.

[Jim C]

Beans, I get your point in regards to some tube amps but don't think you mean to infer that all tube compressors add distortion (at least that's audible)
Certainly the LA2A audio compressors do not introduce audible distortion (at least to my ear)

[JimmyM]

Funny, but the very least compression I ever hear comes from my tube Ampegs and my REDDI. I so don't get the idea that compression is built into tube amps when my ears tell me the exact opposite. Yes, when you crank tubes, they compress, but at clean settings it's the least compressed sound I ever heard, and for that reason alone, it makes me love them.

[Jim C]

I think it's more of a touch / sensitivity thing with the SVT vs. something ultra dynamic like Trace Elliot or SWR SS amps. Having been able to A/B them in my living room (with an Ampeg switch box) the SVT isn't really compressed but all the notes are more fluid and have more equal girth.
(and yes I'm happy that no one wants to buy my dead mint, USA made SVT-CL for a lousy grand!)

[JimmyM]

That I could buy into, the fluid/girth thing. That's another thing I love about them. I hate playing high notes and having the bottom fall out, especially since playing oldies you use a lot of high notes.

[MAMMOTHvolume]

Originally Posted by JimmyM

Funny, but the very least compression I ever hear comes from my tube Ampegs and my REDDI. I so don't get the idea that compression is built into tube amps when my ears tell me the exact opposite. Yes, when you crank tubes, they compress, but at clean settings it's the least compressed sound I ever heard, and for that reason alone, it makes me love them.

i agree, SVT's have alot of gain on the front end though so it's easy to get them to squash up if you like and have one of the master ones

[Bassmec]

Originally Posted by Jim C

Beans, I get your point in regards to some tube amps but don't think you mean to infer that all tube compressors add distortion (at least that's audible)
Certainly the LA2A audio compressors do not introduce audible distortion (at least to my ear)

I think he is referring to tube amp compression and not varimu compression using 6386 tubes and the like.
I know he didn't make himself clear.

[beans-on-toast]

Originally Posted by Jim C

Beans, I get your point in regards to some tube amps but don't think you mean to infer that all tube compressors add distortion (at least that's audible)
Certainly the LA2A audio compressors do not introduce audible distortion (at least to my ear)

I think that it comes down to semantics. Tube compression is indeed a form of distortion. We just don't call it that. Audio designers do characterize it that way. From their perspective, there are many types of distortion, this is one of them.

It doesn't sound nasty and it is something that people look for in an amp, so they give it a name that characterizes what it does. It is a very useful thing when it comes to musical audio. The LA2A goes to great lengths to process the signal in a pleasing way, while at the same time, not adding nasty artifacts. Technically though, it is distorting the input signal. As I said, semantics.

[Bassmec]

Originally Posted by beans-on-toast

I think that it comes down to semantics. Tube compression is indeed a form of distortion. We just don't call it that. Audio designers do characterize it that way. From their perspective, there are many types of distortion, this is one of them.

It doesn't sound nasty and it is something that people look for in an amp, so they give it a name that characterizes what it does. It is a very useful thing when it comes to musical audio. The LA2A goes to great lengths to process the signal in a pleasing way, while at the same time, not adding nasty artifacts. Technically though, it is distorting the input signal. As I said, semantics.

Yes all signal processing is distortion of a sort but what you appear to be saying is that tube compressors like Fairchild 670's produce distortion whereas a Neve compressor does not because it does it entirely with semiconductors. Is that what you are saying?
A good quality audio compressor of any topology does not alter the waveform shape at all, it simply slightly reduces any differences in amplitude over time of the input wave form shape.

[beans-on-toast]

Originally Posted by Bassmec

Yes all signal processing is distortion of a sort but what you appear to be saying is that tube compressors like Fairchild 670's produce distortion whereas a Neve compressor does not because it does it entirely with semiconductors. Is that what you are saying?

No not at all. It doesn't matter if it is tube or solid state. The Fairchild and Neve compressors process the signal to achieve a controllable (this is really important), musical form of compression and expansion. Either type could also add noise, harmonic distortion, or dirt.

By definition, anything that modifies the signal that isn't pure amplification is adding distortion. Also by definition, compression is a form of distortion. That's all I was saying. Most people think of distortion only as adding grungy noise or harmonics. In a musical instrument amp, designers want it to compress the signal when the amp is pushed. The design limits the amount of compression as well as the amount of harmonic or nasty distortion.

Tube amps, when they are pushed compress the signal in a different way than an outboard processor does. For one thing amp compression is fairly limited relative to what an outboard compressor does. For instance, if you fed the amp a sign wave, under some circumstances only the negative part of the waveform might be compressed. Or part of the negative going peak could be cut off. This is going to give you a different sound than what you would get out of an outboard compressor. Outboard compressors go to great lengths to process the entire signal, positive and negative going waveforms, in a controllable way.

Bottom line is, don't throw out your outboard compressor because you bought a tube amp. Both compress, but the end result is very different.

[obimark]

To my ears (and as a hopeful future tube head owner) IMHO tube heads seem to compress nicely when you start slapping on them for instance, all on their own. Wouldn't see why anyone would need a compressor UNLESS, YOu JUST play too damn hard and don't have any dynamics to your playing. Maybe you just flail at your bass, in which case, a technique upgrade would do your more good than anything,.

It pays to play with a LIGHT touch...took me years to learn, Want to play a WHOLE lot faster, light touch. Then you can actually heavy up your touch/or pick for sections you want to have DYNAMICS.
We are tryign to work with our drummer on this, as having dynamics in your songs will actually go along way to making the whole band better.

[JHAz]

Originally Posted by Bassmec

Yes all signal processing is distortion of a sort but what you appear to be saying is that tube compressors like Fairchild 670's produce distortion whereas a Neve compressor does not because it does it entirely with semiconductors. Is that what you are saying?
A good quality audio compressor of any topology does not alter the waveform shape at all, it simply slightly reduces any differences in amplitude over time of the input wave form shape.

If a compressor did not alter the waveform, it would make no audible difference. For hyperobvious cases of compression changing the way the waveform looks, google "loudness wars."

Operated cleanly a compressor is not adding harmonics (ie it has inaudable THD) but it sure as heck is changing the shape of the wave. Listen to the piano on lady madonna. No piano in the real world sounds like that. AFAIK all the tonal manipulation occurs because they compressed the dickens out of the piano. In other words compression kind of becomes EQ once you're squishing hard enough. Normal EQ distorts the waveform too, or else it's inaudible. It's just natural for most of us to think of distortion = THD. But that's not the only distortion of a waveform that can occur.