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What causes grainy sound
What causes grainy sound
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Old 19th September 2019, 02:22 AM   #1
skem is offline skem  United States
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Default What causes grainy sound

I’m wondering what causes some solid-state amps to be more grainy in presentation than others.

I’m not referring to a defective amp sound. Rather, think vocals and how silky smooth vs. grainy they sound.

I ask because I have 3 good amps, two by Nelson and one vintage Pioneer M22, and they all have different levels of graininess. They all measure with incredibly low distortion <0.005% THD. The worst of the three has third harmonic at -118dB and higher harmonics are buried in the noise floor. It doesn’t seem to be harmonic distortion.

Could grainy sound be some character or degradation of transistors? capacitors? resistors? (rather than topology)

Some important notes
1. This is quest to understand the cause of a subjective phenomenon. Please do not turn this thread into an objective measurements vs. subjective observations debate, which can be had elsewhere.
2. Program material, etc. are not (notionally) at issue, since this is a comparison between amplifiers using the same program. Unless you think there is a specific interaction between amps and program material.
3. If you don't know what grainy sound is, just pass on this thread. Yes, it's difficult to define in precise terms (EDIT: Post #148 makes a good effort), but there's no utility in pointing out that it's hard to define.

update: this thread got hijacked by people wanting to argue. The only substantive theory was that it might be caused by certain kinds of noise or noise-related IMD that increase with volume and are thus not part of the noise floor, maybe from resistors. Nobody really knows.

Last edited by skem; 6th October 2019 at 04:12 AM.
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Old 19th September 2019, 04:38 AM   #2
El Reino is offline El Reino  Finland
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What causes grainy sound
Try Pass M2 super smooth sound
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Old 19th September 2019, 06:17 AM   #3
johnego is online now johnego  Indonesia
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Quote:
Originally Posted by skem View Post
Could grainy sound be some character or degradation of transistors? capacitors? resistors? (rather than topology)
The 3 you mentioned has their shares for graininess. Still, i can't make a class B amp that has every strengths usually found in class A amps, unless the amp is highly bias into AB (200mA in my case).
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Old 19th September 2019, 06:33 AM   #4
Fast Eddie D is offline Fast Eddie D  United States
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Quote:
Originally Posted by skem View Post
Iím wondering what causes some solid-state amps to be more grainy in presentation than others.

Iím not referring to a defective amp sound. Rather, think vocals and how silky smooth vs. grainy they sound.

I ask because I have 3 good amps, two by Nelson and one vintage Pioneer M22, and they all have different levels of graininess. They all measure with incredibly low distortion <0.005% THD. The worst of the three has third harmonic at -118dB and higher harmonics are buried in the noise floor. It doesnít seem to be harmonic distortion.

Could grainy sound be some character or degradation of transistors? capacitors? resistors? (rather than topology)
Did they sound less grainy when they were new?

If they work but need servicing, there's a couple quick things to look at. If it has low output offset voltage, that's a good sign. Below 20 mV is excellent. Above 60 mV and something isn't right. Above around 2 volts and something is very wrong.

Next check idle current against specification. Low idle current can cause "graininess" at low power levels. Be careful turning it up! Let it warm up after adjusting and double check.

I've replaced electrolytic capacitors in vintage units that sounded terrible. Newer capacitors are way better than old fashioned units. Look at replacing power supply capacitors, any capacitors in the audio chain, and any bypass electrolytic capacitors on the audio boards. I did this to an old Pioneer receiver that worked but sounded terrible and the results were astounding. I also added extra bypass capacitors to the amplifier board, which I squeezed onto the bottom of the board, right to the power supply connections to the output transistors. I pulled it out of the dumpster years ago and it still works.

And finally, some older designs aren't that good, partly because they were constrained by the parts (especially transistors) available at the time.
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Old 19th September 2019, 06:37 AM   #5
VladimirK is offline VladimirK  Uzbekistan
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IMHO, first step to get out from graininess, is to use class A amps. Next contributors are electrolytic capacitors, one should carefully place them and shunt them by film caps. Next is transistors ships quality (absence of impurities, purity of manufacturing process), and quality of resistors. Next is quality of volume control potentiometer. Next is wires quality, RCA and speakers connectors. All these factors do not contribute to usually measurable THD. If one would measure THD at uV with 200dB resolution, then these factors would contribute. But they do listenable.
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Old 19th September 2019, 06:40 AM   #6
analog_sa is online now analog_sa  Europe
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What causes grainy sound
Do these 3 amps share the same type of passive components and connectors? The same PS transformers and diodes? The same transistor types?

Afraid our current understanding of cause and effect in audio is just not good enough to answer your question. At very best we understand how the distortion spectrum and phase affect timbre and perhaps perceived depth but that is all that is known. The designers of some of the world's greatest amps are likely to have a lot more empiric knowledge which they obviously prefer keeping to themselves.

As for getting more than answers based on empirical observations...perhaps early next century.
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Old 19th September 2019, 06:44 AM   #7
analog_sa is online now analog_sa  Europe
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What causes grainy sound
Wow. Have been writing while Vladimir posted.
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Old 19th September 2019, 06:50 AM   #8
VladimirK is offline VladimirK  Uzbekistan
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Even some SE tube amps can easily reveal grainy sound, if one simply uses electrolytics and low quality resistors. That is what I heard myself.
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Old 19th September 2019, 07:24 AM   #9
cumbb is offline cumbb
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Quote:
...two by Nelson and one vintage Pioneer M22..
Is the M22 the most grainy amp;-?
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different/relative,-)
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Old 19th September 2019, 07:31 AM   #10
analog_sa is online now analog_sa  Europe
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What causes grainy sound
Please don't ask uncomfortable questions
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