Likely culprit for harshness at higher volumes?

Hi all,

If anyone is still reading this, I was wondering if I might ask one closing question.

I've been reading up on jitter (who knew moving to digital wasn't going to be perfect?). I don't have a detailed understanding but I do have some questions about how it manifests itself:

1) when it happens, I assume it's not modulated by volume levels. I should observe equally at low and high volumes although it might be more obvious at higher volumes. Correct?

2) when it happens, does it happen just for a brief period (milliseconds? seconds?)? Or does it happen almost continuously? If it happens, does it just happen once and go away for awhile? Or will it happen frequently?

3) is coax and optical equally susceptible? or is one better than the other? In any case, it sounds like analog between the source and pre-amp is the way to go. So, this suggests I should focus on having a good DAC and electronics in the source and should not care what is inside the pre-amp / processor. Correct?

Thanks again to all for your help. My modest system is not perfect but it's much more enjoyable now than before.

@Csontos: Thanks for the explanation. I think I get the high level gist although I'll have to research more about the 3 attributes: fast, flat, linear. Not sure what the standard metrics are for these attributes, what range of values is considered acceptable, and make/model/costs associated with various ranges. I'll try to research my unit to form a baseline.

I measured, using an infrared meter, the top cover vents of the amp and left and right seem to be fairly close (91 degrees +- a couple degrees) while playing Monheit). I don't know what offset is and how to check / adjust it. Is that something available on all amps (nothing mentioned in my manual that I recall). Or only 'good' ones?

Almarg's suggestion about headphones may apply here. Anthem says the phone output is "in parallel with main path". I take this to mean it is the preamp circuit. Many components that offer phone output use a separate cheap circuit which would not reflect the sound you get from your speakers.

Saru - There are differing views on jitter, and digital in general, that go to the extremes on both end. This is just another example of an audio topic where you need to be open to the idea that very few of us are correct about everything and the truth is likely somewhere in between the extremes. Some will argue that digital comes down to a 0 and a 1 in the signal and quality only matters once it becomes an analog signal and others will spend thousands on digital components and such. Keep an open mind.

The guys at my local Hi Fi dealer were always telling me to ignor the specs and just listen. The owner gave me some specific examples of equipment that had specs that were the opposite of what you'd expect based on the sound. I'm an engineer so I like specs, but like all metrics they can be made to say whatever the manufacture thinks you want to see.

Check temp at idle, not while playing music since program material varies from one side to the other. Let it sit for an hour. DC offset is easy. You need a multi-meter. Preamp set on anything other than phono, volume at o, speakers disconnected from amp. Set your meter at 2v or preferably lower if possible, ie: 200mv, probes on speaker terminals, red on pos, black on neg. Ideally, it should read o. Anything up to 50mv is acceptable, however any decent amp should be in the 20mv or lower region on each side. It's okay if they vary within this range. A fast amp is going to have a rise time of at least 1.5u seconds(micro-seconds), and a slewing rate of at least 40volts per u second. Linearity has to do with timing of each frequency as it reaches your ears. Flat response is just that, equal amplitude of all frequencies. Not all amps' DC offset is adjustable. Some have potentiometers for this purpose in which case it is, some have DC servo circuits, and some have discreet components that control this, in which cases it is not. Without experience, I would not attempt to adjust, but simply check and double check. If it is suspect, and typically could very well be, you need to take it to a reputable tech and have it looked at. O DC offset results in a voice coil resting where it should, in it's mid position. The farther off it is, either + or -, the more distortion the speakers will produce. Most amps have potentiometers to adjust bias or in other words, quiescent current. This procedure is more involved except to say 150ma is optimum per ch.. TNT audio has a great article on this which I've read and followed. Just Google "adjust the bias of your amp". I currently have some Bedinis, Ampzillas, Leach Low Tim, and Meridian amps. They're all great amps, but the best of the lot are the Leach amps. Interestingly enough, they are the ones that have no vested interest to compete and they are the only amps I've heard that "disappear".