Lack of air and volume as an indicator of crossover distortions - diyAudio
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Old 7th November 2006, 04:58 PM   #1
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Default Split from Bob Cordell Interview:

Quote:
Originally posted by PMA


Nonsense. I made a comparison of 2 true class A amplifiers, both with very low distortions and with almost unmeasurable distortion at low level. My experience is different - distortion brings excessive "air" and "space".
This noncence again may be explained in technical terms. Distortions of tube amps create "effect of compression", so while loud sounds sound subjectively louder because of distortions they are in reality have less power. It means, subjective dynamic range is wide, objective dynamic range is narrower, that's why you hear reverberation better, it's power against direct sounds is more. And it sounds natural, because class A tube amplifiers add coloration on high power, that sounds natural.

Distortions which level increases on low power and spector widens on low power level (so called crossover distortions) kill the "air", distortions which level increases with power add the "air".

I don't argue, I explain. When I need "air and space" on concerts I use reverberator.

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Old 7th November 2006, 05:04 PM   #2
anatech is offline anatech  Canada
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I don't think you can blame compression for the lack of "air" in a reproduction.

I have both tube and solid state amplifiers that I enjoy listening to and neither one suffers from compression within their power ratings. Often, single ended tube amps are said to have an "airy" quality to them. This would seem to contradict Wavebourn's preceding statement.

-Chris
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Old 7th November 2006, 05:30 PM   #3
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Quote:
Originally posted by anatech
I don't think you can blame compression for the lack of "air" in a reproduction.

I have both tube and solid state amplifiers that I enjoy listening to and neither one suffers from compression within their power ratings. Often, single ended tube amps are said to have an "airy" quality to them. This would seem to contradict Wavebourn's preceding statement.

-Chris
Chris,

you did not understand me.

Crossover distortions are distortions that "cut off" very small portions of signal when it "goes through the null". As the result, fading signals fade faster, less proportionally than in the nature, and in process of attenuation level of distortions becomes higher, their spectrum extends. It is what kills "air and space" distorting reverberation, this is what kills fading sounds of piano strings when you listen to Beethoven.

Crossover distortions are generated by common transistor amplifiers with abused emitter followers. They may be generated by transformer cores of push-pull tube amps, also under-biased push-pull tube amps generate such distortions.

Well biased class A tube amp, especially single - ended one - do not generate crossover distortions. It generates different type of distortions that indeed highlight reverberation, i.e. "air and space", what I explained in my previous post.
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Old 7th November 2006, 05:40 PM   #4
anatech is offline anatech  Canada
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Hi Wavebourn,
In this day and age, I think most amplifiers would be free from crossover distortion, older Exposure excepted. The lack or presence of "air" is still discussed in the absense of crossover distortion. I won't even consider that case.

I was responding to your earlier statement .......
Quote:
Distortions of tube amps create "effect of compression", so while loud sounds sound subjectively louder because of distortions they are in reality have less power. It means, subjective dynamic range is wide, objective dynamic range is narrower, that's why you hear reverberation better, it's power against direct sounds is more. And it sounds natural, because class A tube amplifiers add coloration on high power, that sounds natural.
-Chris
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Old 7th November 2006, 06:03 PM   #5
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Chris,

the problem is, they present but are greatly underestimated. And as I see from this discussion, are underundestanded.


Quote:
Originally posted by anatech
Hi Wavebourn,
In this day and age, I think most amplifiers would be free from crossover distortion, older Exposure excepted. The lack or presence of "air" is still discussed in the absense of crossover distortion. I won't even consider that case.

I was responding to your earlier statement .......


-Chris
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Old 7th November 2006, 06:20 PM   #6
MikeB is offline MikeB  Germany
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I guess we all know how evil crossover distortion is, it makes the sound harsh/bright/unpleasant. It will never do any good to sound.
A proper designed ClassAB does not rise distortion with attenuated signals.

Mike
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Old 7th November 2006, 06:36 PM   #7
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Quote:
Originally posted by PMA
When this "Ayry" amplifier tries to play complex classical music, the result is often poor resolution and great mismatch.
Come in captain "Hansen Solo"..

Anyhow, to ya all,

let's take a word from Papa and then lets move on, the distortion and harmonics stuff has been covered quite well in the past here on diyaudio.

Cheers Michael
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Old 7th November 2006, 06:53 PM   #8
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Quote:
Originally posted by MikeB
I guess we all know how evil crossover distortion is, it makes the sound harsh/bright/unpleasant. It will never do any good to sound.
A proper designed ClassAB does not rise distortion with attenuated signals.

Mike
Presence of "lack of air and volume" is a well audible indicator of how well is it designed.

Sometimes power amplifiers are innocent, when crossover distortions are created by mixers, microphones, even... contacts!

Mixers contain operational amplifiers. For example, currently TOA RX-216 mixer is on my surgery table. It contains a lot of BA4558 chips, much more than needed. All of them contain differential inputs and symmetrical emitter follower output, both are sources of small crossover distortions. It may be Ok if you use one such opamp in signal path, but if you use more, and some of them in non-invertion connection, resulting crossover distortions kill "the air and volume".
My main console Yamaha MX400-24 has OpAmps too, but they are different, used mostly in inverting connection, and much less number of them in signal path. As the result, Yamahe sounds more "airly".

One more example is modern Marshal MXL 770 condencer microphone, on the same surgeon table. It has couple of emitter followers that working on cable capacitors generate "broken glass" distortions, they are different from crossover distortions, but anyway are unnatoral. Another the same mic I already modified contains output transformer and no emitter followers. As predicted, it sounds very clean.

In my life I played a lot not only with amps trying to squeeze less distortions from some standard topology, but generated distortions developing analog synthesizers and guitar pedals. You know, when you have experience in creating effects you better understand how to avoid them when you hear similar to what you already heard many times experimenting.

So, if you hear "lack of space and air", always look for crossover distortions. Probably, even hysteresys loops may present on very low powers. The less them you have, the finest will be the effect, but anyway it will sound innatural. Especially, when their level is higher on top end of audible spectrum.
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Old 7th November 2006, 07:43 PM   #9
anatech is offline anatech  Canada
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Hi Michael,
Quote:
let's take a word from Papa and then lets move on, the distortion and harmonics stuff has been covered quite well in the past here on diyaudio.
Yes!!, and thank you!

So let's get on with the subject, "Bob Cordell Interview".

Wavebourn,
If you are going to get into details of your own work, please start a thread of your own.

Back to our regularly scheduled program ..............

-Chris
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Old 7th November 2006, 07:51 PM   #10
moamps is offline moamps  Croatia
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Yes, mortuary table stories of fifty-dollar mikes and 30-year-old consoles are indeed a step in the right direction.
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