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hpupo 27th December 2011 06:47 PM

Power amp distortion for modern amps
Not sure if this is the right section for my question. If not, please someone move it...
Anyways, how much power amps in modern tube amps (aka, mesa dual rectifier, marshall JVM, ENGL, peavey 5150, etc) are allowed to distort?
I know most of the distortion for this type of amplifiers comes from the pre amp and that power amps run fairly clean, but what "fairly" in this case means? What id would like to know is if power amp distortion adds anything to the already very distorted signal from the pre amp...
Thanks a lot

GloBug 27th December 2011 07:04 PM

Very little, you would have to have it dimed to get any power tube distortion.

Now you could dial it clean and pin it, you might get a sound you like, but it won't be to practical for the most part.

Example, when I play out a 5150 while jamming, the post volume barely ever leaves "3", it's too loud. (playing through 8 x 12" Celestions) I could not imagine trying to get any real power tube distortion out of it.

You would be better off with a 30w to 50w might have better luck that route for good sounding power tube distortion.

Even better? run the shat out of a 5W amp and mike it.
You would be amazed at the amount of recording is done with these smaller "studio" boutique amps.

Much easier to work with.

bear 27th December 2011 07:24 PM

Yes, is the answer to your question.

They make a box that I think is called a "power soak" essentially a dummy load with a tap for the speakers that allows you to crank the power and keep the speakers at a reasonable SPL.

Distortion is additive, except where there happens to be some phase cancellations... but adding output stage distortion to input stage distortion will sound different.

Of course the best "distortion" is when the speakers are red hot (voice coils), right before they blow out! ;D


GloBug 27th December 2011 07:46 PM

Well that is cheating!

Most people find power brakes troublesome and end up getting rid of them.

1. It does not sound right, having a speaker is KEY for a guitar. The speaker IS the instrument you hear.

2.Reliability. I have heard more bad stories then good with them. In fact I have never come across single person who likes a brake. I have heard of many broken amps that have used them. Some amps just don't like to be run at "10" into a resistor, and fail.

At the end of the day, you end up going with a smaller watt amp that distorts the power tubes at an proper sound level.

It's like chaining a Corvette to a tree and running it full out. Not so good for the car. - poor analogy.
Just get the proper tool for the job.

Remember a guitar amp is for music Production, not Reproduction.
What's the point of running a 3K amp with a brake to make it sound bad? You can get a bad sounding amp for peanuts.
It's hard to explain the effect, but it sounds lifeless, generally crappy for lack of a better word.
Speaker cone breakup is just as important as tubes are to a genuine sound.

To each his own.

hpupo 28th December 2011 12:41 PM

Thansk a lot for all the feedback. Thats exactly the kind of answer i was looking for.
I have heard that before (use a smaller amp). I guess the key point in my question was how that distortion would add to the preamp distortion (assuming both brake and smaller amp). Thanks

GloBug 28th December 2011 01:23 PM

Power tube distortion is much more touch sensitive, can "bark" sounds "fat" or "chunky", it is more dynamic, the sounds can be cleaner when played softer. Good for chords and blues etc.

Preamp distortion has more "sustain", feels more "metal" think bee in a bottle. It is not "touch sensitive", therefore not very dynamic. Good for metal and soloing.

I like preamp distortion with a touch of power tube distortion, just to add a little "chunk" to the "buzzsaw." Gives a little bit more feel and dynamics to the sound then just preamp distortion.

I should add the rectifier influences the sound quit a bit.
I like to play heavier, faster stuff at times, like Lamb of God, Slayer and Metallica.

A tubed rectifier is just to "slow" for faster, heavier music. It sags too much, fast individual noted get blurred together and just sounds sloppy. A tubed rectifier is good for bluesy, semi distorted type sounds.

A solid state rectifier is much faster and tighter, you can play metal with these. The "ghuga, chuga" and palm mutes etc sound much better, tighter, individual as notes.
They do not "sag" therefore don't "feel" the same as a tubed rectifier.

This is why Mesa-Boogie has BOTH rectifiers in it, you can flip between the two with a switch.

Note: The "Dual Rectifier" and "Triple Rectifier" Mesa Boogie amps are called that due to the amount of channels they have, not the number of rectifiers. They both have two, a tube and SS.

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