Dynamics with oversized amplifiers

[tvrgeek]

Well that's just it. The differences in signal level are heard on a logarithmic scale, so a drooping supply rail makes no literal sense to me. But it does make sense in terms of distortion, especially if a complex music signal seems to selectively raise the noise floor during the peaks.

I also have my pet theories about speakers interacting with amplifiers, and depending on what the designer intended, there can be great variability in the end result.

Yes, changing noise floor our ears/brain does not like. Even worse if the distribution changes.
Yes, the load can make a huge difference. Easy enough to model in Spice the effect on the amplifier, harder to understand the result acoustically.

40 years off and on building speakers and amps, rail droop is a significant factor. Verified it on the bench and by ear.

Anything that does not reflect the input signal plus gain is distortion. Don't limit yourself to harmonic, but we also have linear, liner with respect to power, time, phase, noise modulation, and how how the load effects these.

 

[tvrgeek]

My understanding of IM thd is when two signals combine to create new signals. Above and below the frequencies of orinal two.
Not sure how lack of this is dynamics.

To me dynamics is simply a difference between low and high signal level. Without any compression. Small speakers with small membrane surface area simply can not reploduce both low signal and full fortissimo of the orchestra, because of the limits in peaks.
That would be my understanding of the dynamics. Not sure how IM thd comes in.
But i may be wrong.
With complete lack of any data from thread starter, this thread is meaningless.

Your definition of dynamics is a pure sense is correct. It is often confused with the audiophool term which is a subjective understanding.

Lower IM, just like lower HD will sound less dynamic as what your brain hears in the distortion it assumes is higher level as the average is higher. Your brain says it is a higher peak. This is why some very clean speakers and electronics are often criticized as boring. I believe you can re-train your perception to recognize the correct. Do you find it amazing some talk about the wonderful dynamics of an LP when they are limited to about 65 dB and a lot of pop music was compressed in the "loudness wars" to more like 50? If you analyze your CD's, you may find a lot less dynamic range than you assumed.

Maybe if someone is really looking for a more "dynamic sound" they should find an old DBX, MXR, Phase Linear or Pioneer peak unlimiter. It will for sure add back al the HD you are missing. 😈

Small differences in EQ will effect the perception of dynamics. A bit too hot may sound dynamic to some. Broad mid boost will move the image forward and make the vocals seem more dynamic. All they are is just louder.

If the system is not capable of producing the required output, then of course, it won't.

 

[tvrgeek]

Well that's just it. The differences in signal level are heard on a logarithmic scale, so a drooping supply rail makes no literal sense to me. But it does make sense in terms of distortion, especially if a complex music signal seems to selectively raise the noise floor during the peaks.

I also have my pet theories about speakers interacting with amplifiers, and depending on what the designer intended, there can be great variability in the end result.

You are not considering the effect on the IPS and VAS current sources or if the driver stage is capable. You are not considering at what lower voltage the VAS clips. Sometimes considerably lower than you may expect. Some think moderate clipping is more dynamic due to the spray of harmonics. In many amplifier designs, in a steady state, the VAS clips before the outputs, but with isolated rails ( RC filter) the outputs may clip first in a transient.

The engineers are in a catch-22. Independent windings for the input are too expensive. If they just boost the rails, then marketing will want to up the rated power spec even if the engineer knows the thermal management and output devices can't take it. A well designed amp might have 3 dB overhead, but marketing will scream to call it a 100W amp instead of a good 50. A practical solution is far more coulombs of storage.

It's complicated. A bigger amp, all things equal and they never are, can only hurt the pocket book, but a well designed smaller amp can do the same job. Take your pick.

 

[wiseoldtech]

Slew rate does not effect "dynamics". It does effect the distortion.
Clipping is of course the wrong amplifier for the load and level required.
Insufficient current reserve will cause the rails to droop, which causes "dynamic compression" as you approach clipping.
Correct negative feedback should account for Beta droop in a BJT output, but my ears tell me MOSFETS linearity are still my preference.
A lot of "dynamic" sound is nothing but distortion. Like it, don't like it is everyone's choice. You may find a very clean amplifier sounds less "dynamic" than what you are accustomed to. I have heard this criticism about the newest very clean class D as well as the Benchmark. Basically, lack of distortion.
Take a good look at the speakers before you blame the amp.

Along with that, consider the warnings usually included with such things as headphones, and audio equipment as well, when using CD players...
The "clean-ness/distortion-free" of the audio signal of those devices makes people turn up the volume levels more, and SPL increases can lead to hearing damage.

 

[tvrgeek]

Quite true. But restoring the "dynamics" is only a dB or so. Ear buds have killed the hearing of a generation.

 

[tiefbassuebertr]

I've been going crazy for years with the power of amplifiers, my cabinets are active I have a 120 db coaxial compression driver, a 101 db mid-bass and a 94 db sub.
With a low power amp the compression driver is supposed to sound like a deafening dynamic single watt, but if I plug in 20w or 10 amps it sounds really loud but the sound lacks impact, everything changes when I plug 1000w amps into above. Right now I have 5000w for the sub 5000w for the midbass 3000 for the midhigh and 3000 for the treble the sound has much more dynamics and impact at any volume and the amps don't even turn on the signal lights.. .but if I reduce the power to something more logical, the dynamics, the physics and the impact of the sound disappear.

Can someone explain to me why the power in abundance is noticeable even at medium or low volumes?

One of the most important measurements on power amplifiers to show this effect is the compression character (the extent of compression) on 16-8-4-2 and 1 ohms load impedance.
To make this, tone bursts (vibration packets with several waves) of sinus curves in the measurement signal are necessary. Without load the difference in magnitude between start and end (last wave) of a packet isn't present and with a 1 ohm load this difference is very large - even with very oversized power transformer and oversized electrolytic caps.

The extent of the difference in this measurement defines the extent of this unwanted audible effect.

Unfortunately this measurement usually wasn't make although it represents a very important criterion for sound character of an amplifier for audio.
The only magazine I know was the German issue of "Production Partner" (magazine for studio equipment and public address).

I remember an amplifier test from the 90s testing a Stage Accompany power amp that showed these diagrams.
Maybe one of the members have this magazine and can upload this review.