Distortion

[Jeff Matthews]

Tube distortion is stated to be of the "even" order and more pleasant than the "odd" order distortion of SS amps.

Is this "even"/"odd" order distortion in any way related to THD and IMD?

I have similarly heard IMD is more unpleasant than THD, and that when looking at specs, more focus should be placed on finding a lower IMD (i.e. that THD is much less of a worry).

[NOSValves]

You really need to get off this Spec craze!!

[Jeff Matthews]

You really need to get off this Spec craze!!

I was just wondering. It's not a craze. If it was, I'd have found the answer a long time ago. []

[PrestonTom]

Jeff, You are correct, it is not a craze. It is a reasonable question; however, it is also a difficult question.

IMHO, it should be certainly obvious that distortion is never a good thing and certainly should not be hoped for in an amp or speaker.

When the system is driven hard, distortion will occur. One non-linearity comes from clipping. This can have different origins (lack of transient levels of high current, etc). With tubes the result tends to be even harmonic (with a 1 kHz tone ---- distortion at 2k and less at 4k and even less at 6k etc). With SS the distortion tends to concentrate at the odd multiples. This later case is perceptually more aversive and probably more noticeable (there are qualifications on this statement of course). Unfortunately the degree of distortion will vary as function of overall level. Since not all of it is due to clipping (possibly coming from"crossover" distortion and other sources), different amps will behave differently. As one might expect, manufacturers can make these measures in the region where their equipment is most linear. This is compounded, since the measures are made with a dummy load having a uniform impedance. This is certainly not the case of a real speaker (along with its crossover). So the measure now becomes even more complicated if you include the speaker. Incidentally, it is the mechanical portion of the system (the speaker) is probably the biggest source of distortion.

THD is simply a sum of the distortion at all the harmonics without regard to whether it was even or odd.

One should not go to sleep at night with a happy smile because there amp is distorting at even harmonics. The goal is to get rid of as much distortion as possible. This is why high efficiency speakers are so attractive. It is also why they can be so revealing of bad components in your system.

IM distortion can be a real pain - it also sounds bad. These are a variety of combination & difference tones (distortions produced) when measured with a multi-tone input. The spec that is typically given only performs the measure for specific combination. An additional wrinkle is that, IM distortion can vary temporally. This is more difficult to measure and is referred to as Transient Inter Modulation distortion (TIM). Some (including PWK) thought this was a particularly nasty form of distortion.

The list is not complete, there are other kinds of non-linearities .........

To my knowledge, no one was actually done a systematic ranking on what levels of the different distortion components are most aversive. That would not be a simple measure since the domain is potentially quite large and probably interactive. To no ones surprise, you need to listen to the amp with your speakers and at your preferred levels etc.

I hope this gets people off the bandwagon that some distortions are "good" (add to the "musicality"). They are not to be sought after. Avoid them! The original recording had the real musicality of the musicians and their instruments. If it is not there, then get a better recording.

Good Luck,

-Tom

[Jeff Matthews]

Thanks, Tom. I see this is beyond serious investigation, and it is better to count on just a plain-listening analysis.

[NOSValves]

"Tube distortion is stated to be of the "even" order and more pleasant than the "odd" order distortion of SS amps." =========== It depends on the topology of either amplifier. The distortion signature of SET tube amps will be far different than PP tube amps. The distortion signature of CLass A will be different than Class AB, B, or C. And on ya go. In SS you have a wide array of topologies, classes, device types and bias schemes and again, all will affect the distortion signature. There are SOME generalizations (but given the current climate here on the forum I am loathe to make any of them) which might apply, but realistically why bother stating them? Get the amps. Give them a listen. Take notes. Then pondering the specifications will have more meaning. md

Chicken[]

[SCOOTERDOG]

I love distortion...But only when it comes via a fender strat and a marshall stack. makes the hair stand up on my back.

[steamer]

here are some distortions I never thought of

http://www.sasaudiolabs.com/theory9a.htm

Greg

[6foot8]

Thanks, Tom. I see this is beyond serious investigation, and it is better to count on just a plain-listening analysis.

Jeff..sorry about hammering so hard on the other thread. My point is use your own ears. Electonic measuring equipment is far more accurate than your ears. If you like tubes then enjoy them and forget about anyone else says, if you like SS then do the same.

You know there are those out there who don't think Klipsch sound good either...whoda figger'd that.

[DrWho]

Tube distortion is stated to be of the

"even" order and more pleasant than the "odd" order distortion of SS

amps.

The idea that tubes have even order distortion is an old wive's tale -

same with the odd order SS claim. Put em on a scope and you'll find

both kinds in both amps. There is an ongoing project on campus where

all sorts of audio related electronic equipment is being measured for

every possible spec in the world you could think of measuring. The prof

gave a seminar a while back where he presented a lot of the specs and

you cannot find one common trend in tube amps that you won't find in SS

amps. In other words, there is nothing inherant about either topology

that should make either better for any given application. (which is

sadly the opposite kinds of results the study was hoping to obtain).

They are conducting the same tests on all sorts of other equipment

too....everything from mics, guitar pickups, effects, mixing consoles,

all the way down to cables, speakers, amplifiers, etc etc...

Nevertheless, there is one common rule....distortion is bad. Just make

sure you're looking at ALL of the different kinds of distortions before

you decide a particular product has less distortion overall than

another product. But since distortions will always be there, it only

makes sense to pick a product with distortions that one finds pleasing

(which can be had with both tubes and ss actually). Sadly there really

is no way to quantify a distortion as "pleasing" - especially

considering people are more sensitive to different types of distortions.

[IB Slammin]

I love distortion...But only when it comes via a fender strat and a marshall stack. makes the hair stand up on my back.

Scoot,

agreed, but a stack of many J.B. Marshall's. The last time I saw Hendrix (about 90 days before his death) he used six stacks. Top and bottom.

You made chills run up my arms at the thought. (and some put down the thought of 100+ db play-back in our homes) Do you want live concert volumes, or don't you?

The way he did 'machine-gun" that night is burned into my mind forever.

Terry

[edwinr]

Thanks, Tom. I see this is beyond serious investigation, and it is better to count on just a plain-listening analysis.

Jeff..sorry about hammering so hard on the other thread. My point is use your own ears. Electonic measuring equipment is far more accurate than your ears. If you like tubes then enjoy them and forget about anyone else says, if you like SS then do the same.

You know there are those out there who don't think Klipsch sound good either...whoda figger'd that.

Hey, Big Man.

You are so right about those that believe Klipsch speakers suck. In a recent email conversation with a loudspeaker designer, who shall remain nameless, but sells his product in the USA, I was told the following...

The *********** or ************ are not comparable with the Klipschorn, but about 20 levels above them. I used to have a pair, as did 5 of my friends. All have ********** now. The Klipschorn is an amazing speaker and one of the items that I have enjoyed owning most, but they are a novelty, they are not a high fidelity speaker. They give a huge soundstage, but no imaging. Everything comes from everywhere. They also have no deep bass, being 10bd down at 35 Hz. To get 30 Hz out of a horn, it has to be 10 feet long, where the Klipsh is 4 1/2 feet.

I actually met Paul Klipsch when he was 92. He died at 106. A pair of my ********* easily outperforms the Klipschorn. Certainly not in loudness, but monstrously in musicality. The Klipsch can play with startling clarity at unbelievable volumes. I used to do high quality mobile disco and used 2 pairs of them in it in a custom made enclosure which opened out into a corner horn, and they were awesome for that. I actually had a pair here not too long ago and I was really surprised how the sound had dated. The Klipsch did have the ability to sound great with very average electronics, but did not show the improvements as equipment got better, where it is very obvious with the ********** and **********.

The Klipschorn was designed in the early 40s and has changed relatively little since. Back then it was a revelation. Time has moved on.

Now this guy may have met PWK, but some of his other facts are wrong. Maybe he IS right about the Klipschorn's sound though... []

[DrWho]

I love

distortion...But only when it comes via a fender strat and a marshall

stack. makes the hair stand up on my back.

Scoot,

agreed, but a stack of many J.B. Marshall's. The last time I saw Hendrix (about 90 days before his death) he used six stacks. Top and bottom.

You

made chills run up my arms at the thought. (and some put down the

thought of 100+ db play-back in our homes) Do you want

live concert volumes, or don't you?

The way he did 'machine-gun" that night is burned into my mind forever.

Terry

Just a little soundman secret...only one of the amps was actually

running. It is a little trick done quite often merely for the wow

factor. Nevertheless, that one amp was mic'ed and blasting through the

huge PA system - so I have no doubt that it was still incredibly loud

[H]