What causes grainy sound

Status
This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.
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:
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)

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.
 
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.
 
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.
 
Grainy;-)
 

Attachments

  • 11serveimage.jpg
    11serveimage.jpg
    50 KB · Views: 693
Source must be close to grain free since with XA25 it sounds flawless. They’re all class A. The M22 is more grainy in the bass region and the F5 is more grainy in the vocal/treble/presence region. I’ll check idle current on M22 (all caps are upgraded and there are no electrolytics close to the audio path). There does seem to be a correlation to age and grain, with older sounding worse—but I hesitate to make an extrapolation from three data points.

My guess is, as was said, this gets into the proprietary knowledge domain that nobody has formalized in writing. I hope one day this changes. Maybe Nelson Pass will write up such insights in his memoirs.

Thanks guys.
 
Last edited:
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)

Your question is part of a much larger one. Which is, why do electronic components, that all feature objective measured performance supposedly well below the threshold of human detection, still seem to sound different from each other? We use terms such as grain, liquidity, sweetness, warmth, etc., to subjectively describe the differences some of us believe we hear. Yet, there seemingly remains a disconnect between the objective measurement and the subjective experience. The objectivist explanation for that seeming disconnect is that, we do not actually hear any difference, it's all psychological. Meaning, it's all self-delusion. There is undoubtedly truth to that notion in cases, but not all cases.

I often wonder how many true objectivists have purchased pre and power amplifiers that are more costly than an equivalent mass-market A/V receiver or integrated amplifier from Far East manufacture. To have purchased anything more pretentious does not seem logical for a true objectivist, because mass-market amplification routinely features objectively unimpeachable measured performance, as far as human perception is supposedly concerned. So do digital sources, for that matter. Objectively, we have indeed had 'perfect sound forever' since 1983. Subjectively....? Hmm :scratch2:
 
Last edited:
I don’t wish to unleash the subjectivist vs objectivist debate! I’m simply looking for tips on what to experiment with in my amps. :). My reason for mentioning the measurements was simply to prevent someone from guessing that it was merely odd order distortion or higher harmonics. PSU noise is on the list to fix anyway. I’ll see how that goes and report back if I find anything really interesting.
 
Status
This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.