Let's talk distortion

[misterwhizzy]

I read talk about preamp distortion, power amp distortion, and speaker breakup. How do I tell what I'm hearing in recorded music? I think I know, but I also think it's hard to find examples of just one of the three. I don't particularly think explanations like "modern metal is all preamp distortion" or "AC/DC is what power amp distortion sounds like" are particularly helpful. Can you go deeper?

 

[FuseG4]

Re: Let's talk distortion

It's hard to describe
Best thing to do is play
And most importantly crank to various volumes
Different amps

It helps I've been through a few tube amps and have had the pleasure of letting them rip with or without attenuators which helps give you the feel for how much the speaker colors as you turn up

Speaker breakup depends on the kind of speaker
Celestions sound different from old American types

Different power amps with different power tubes have pretty different breakup sounds

Some preamps are pretty good at getting a power-ampy tone without cranking things

It's really hard to say "that's what you're hearing" cuz there's a million variables and many of them lead to similar results

 

[FuseG4]

Re: Let's talk distortion

Generally though I'd say preamp is buzzier, thinner gain. Brighter as you add more of it
Power amp is smoother until you really crank it and the grind is more strong, thick sounding. El84s add brightness as you turn up, 6l6s are creamy and vocal, el34s sound mid-rangey and aggressive, 6v6 more balanced but somewhat wooly bass breaking up, pretty middler of the road

Old American speakers sound like a kazoo to me
Most new American speakers I don't get much breakup from that I can hear
Celestions have an additional layer of like a fuzz almost, and push things toward the mids

 

[PFDarkside]

Re: Let's talk distortion

Search for Johan Segeborn’s youtube channel. He plays a lot of old amps through old speakers at very loud volumes.

 

[eclecticsynergy]

Re: Let's talk distortion

As for hearing the various types in recorded music, there isn't any definitive way to say what's what. All you can do is try to learn approximately how each sounds and then decide for yourself, "This sounds kind of like that." Of course it's complicated by the fact that many players use pedals also. Many modern pedals are even designed for amplike behavior, mimicing the response of power amps and sometimes speakers.

Preamp distortion is easiest to experiment with because it's what you can get with the master volume turned low.

In tube amps it's not easy to separate the effects of power amp distortion from speaker breakup, especially since both normally occur in conjunction with the extra sustain that comes from playing loud. You can't tell how much of the sustain is power tube compression and how much is sheer volume. You can take speaker breakup out of the equation using an attenuator, but pushing the power stage hard also involves running the preamp hot so likely there will be some preamp tone involved and you won't really be hearing pure power tube distortion.

Today's high-powered solid state rigs may make it possible to audition speaker breakup more or less on its own though. In the old days, the only way was to use a big bass head through your guitar cabinet. We didn't do much of that because it was prone to blowing speakers. Some did this in search of atypical tones: I have it on good authority that the guitar solos for Reelin' In The Years were recorded using an Ampeg SVT running very loud. But even there, you can't say that all the distortion was from the eight 10" speakers - some will have been from the preamp and power tubes as well. Like any tube amp, even an SVT will start breaking up above 4 or 5.

 

[Mincer]

Re: Let's talk distortion

I can't tell in a well-recorded song. But if I was using an amp, I could certainly feel it. Power amp distortion is the touch-sensitive one, and the one that isn't as buzzy and compressed. It usually isn't enough gain for modern metal. It is also the thing we guitarists have been trying to achieve at a quiet volume for years.

 

[IMENATOR]

Re: Let's talk distortion

I am not a tube amp connoisseur but for what I have played a couple of times tube amps with real tube based power amp sections, it is more about the dynamics rather than the actual distortion tone. I think Mincer described it very well. But then even if it is just a 10% of the tone there are people that just need it, lucky me preamp distortion is enough for me so far.

Edit: About the speaker distortion it is really hard to tell for me but having a tube preamp into a SS power amp with lots of clean headroom I can say the same amount of preamp distortion sounds just ok in bedroom levels but then when I turn the volume up in rehearsal or a live gig it sounds a bit thicker, it may be the low end kicking but to me it sounds like turning distortion to 11.

 

[Ascension]

Re: Let's talk distortion

Run nothing but real tube amps owned about any thing you can name at some point and only very rarely run a drive pedal of any type so will chime in.
First off there are many variables and not all high gain tube amps run just tube gain some have clip diodes so essentially have a built in overdrive pedal.
Case in point on this would be the Marshall JCM 900 Dual Master volume amps of the early 90's. Had 2 gain controls Gain one was tube gain 2 the SS side so you could run one or the other or mix both. My 1991 Carvin X50B Hot Rod Mod head does the same thing. Has a gain control for the crunch side and a pull hot Rod Mod that engages the diodes for a set gain boost.
Pre amp crunch alone normally is thinner harder in feel and harsher than power tube distortion but not always it depends on the amp design.
Power amp distortion is looser and warmer and can be pretty sloppy on some amps.
Speaker breakup will depend on the speaker itself. Different speakers respond differently depending on design ad wattage.
This is an example of a miced up amp with really good pre amp crunch running at super low stage volume. My early 90's Mesa Boogie Subway Rocket at super low stage volume only effect is the verb in the loop as this one is a non reverb.

 

[Ascension]

Re: Let's talk distortion

Here is it's big brother my 50 watt 6L6 powered Mesa Boogie .50 caliber Plus from the same era unmiced out doors and running hard enough to get into some speaker and power distortion.

 

[Ascension]

Re: Let's talk distortion

Here is my little EL 84 powered 1/12 25 watt Zinky Blue Velvet combo running no effects un miced not dimed but pushing pretty hard and getting into both Pre and Power tube plus some speaker break up here.

 

[Ascension]

Re: Let's talk distortion

Here is another tottaly different set up. This is my 6L6 powered PRS MT 15 head running only a verb in the loop and have a cab miced up in the back in an iso booth so am cranking a little to get into both power tube and speaker break up.

 

[jeremy]

Re: Let's talk distortion

pi distortion is a big thing too and doesnt get talked about as much. i dont know if anyone has heard a guitar amp with pure power tube distortion. youd have to have a perfectly clean preamp with a ton of signal and a pi that could take it without folding and pass that huge signal to the big bottles and a speaker with a ton of power handling. the best "classic" distorted tones are usually a combination of a little preamp distortion, some pi distortion, a bit of power tube breakup and a speaker being pushed hard.

 

[misterwhizzy]

Re: Let's talk distortion

I was going to bring up PI distortion, because I think that was the source of most of the distortion in my Jet City JCA20H. Swapping that tube out for a 12AU7 did wonders for headroom and feel.

 

[Ascension]

Re: Let's talk distortion

I was going to bring up PI distortion, because I think that was the source of most of the distortion in my Jet City JCA20H. Swapping that tube out for a 12AU7 did wonders for headroom and feel.

Agreed on the PI having impact on many amps. Many say it is not a position that really affects tone but have seen otherwise. Does depend on the amp design how much but in many amps it can be substantial.

 

[LLL]

Re: Let's talk distortion

Phase inverter tube needs to work it to get the sweet spot... that's where all the juicy mojo resides.

 

[guitfiddle]

Re: Let's talk distortion

pi distortion is a big thing too and doesnt get talked about as much. i dont know if anyone has heard a guitar amp with pure power tube distortion. youd have to have a perfectly clean preamp with a ton of signal and a pi that could take it without folding and pass that huge signal to the big bottles and a speaker with a ton of power handling. the best "classic" distorted tones are usually a combination of a little preamp distortion, some pi distortion, a bit of power tube breakup and a speaker being pushed hard.

I watched an interview with Ade Emsley of Orange amps, and he gave the example of the clean channel on the Rocker 15 Terror, and the Brent Hinds Terror. He said that since they use only a single gain stage, you can't overdrive the preamp on those amps running into the clean channel, so any distortion you hear is going to come from the power amp. I don't know how much of that would be the PI tube and how much is the power tubes, but I thought it was interesting.

 

[jeremy]

Re: Let's talk distortion

just cause it only has one gain stage doesnt mean you cant overload that one stage with a really hot signal but it would be interesting to crank the clean channel up all the way and see how it sounds

 

[Rex_Rocker]

Re: Let's talk distortion

Do tubes "compress"? I thought they clipped, rather.

 

[jeremy]

Re: Let's talk distortion

clipping usually gives some compression?

 

[IMENATOR]

Re: Let's talk distortion

Do tubes "compress"? I thought they clipped, rather.

Tubes are just an imperfect amplifier, the imperfection is called "non linear". Those tube imperfection strart from very subtle when the input signal is very low and get more pronounced when the input signal goes higher, I guess a very preamp tubes may clip a signal when the input signal is super loud but all the sweet sounds from blues and classic rock are mostly in the in between. That is harder to achieve with transistors, transistors are also imperfect amplifiers but their "non linear" behavior comes in more abrupt, drastically. That is why tubes are so nice for low to moderate distortion sounds like blues and rock while transistors can do very super distorted sounds very well.

Edit: Compression is a natural consequence of distortion, it does not allow the signal peak to create a loud output sound, it rounds it a bit or even clip. I think there can be clean compression but cannot be distortion without compression really.