Likely culprit for harshness at higher volumes?


I'm a newbie to higher end audio. I have a very modest system:
1) Pre-amp: Anthem AVM2
2) Amp: Adcom GFA-5400
3) Source: Sony CDP-X111ES CD player
4) Speakers: KEF C75
5) Toslink between source and pre-amp; cheap RCA cables from pre-amp to amp; 16 or 18 gauge speaker wire (Radio Shack?)

Room setup (10-ish feet x 20-ish feet rectangle):
1) 2 foot deep cabinets along one wall (20-ish foot)
2) Components stacked on top of small end table against rear wall (10 foot); centered between cabinets and opposite wall.
3) Speakers slightly in front of end table and about 2 feet from side walls and 4 feet from rear wall

Sounds good at about -45 to -25db; but higher frequencies get harsh at higher than -25db.

Appreciate your thoughts.
You are either overdriving your speakers or your amp is clipping. Usually an amp issue, but I'd think the Adcom has lots of power - What is the Kef speaker power handling rating?

Or, your room needs treating for high frequencies - at higher volumes you be noticing harshness in your system that you don't at lower volumes (even though it's there).

You might look to upgrade your wires (speaker and interconnect), although I doubt that is the specific problem.
It could be the CD. Many modern CD's are mastered so that they sound harsh. Some genres like rock, pop and heavy metal are badly affected and virtually all recent material (as well as recent remasters of old material) can sound harsh.

You may be over-driving the speakers - the KEF75's are not known for their power handling (and can sound harsh if pushed).

Finally, it may be jitter - I doubt the AVM2 is particularly good at jitter rejection and digital interfaces very often add jitter. Try the analog output of your CD player to test this possibility.

Thanks guys.

The KEF C75 (4ohm) is rated for at least 150W I think. I think the Adcom GFA-5400 is rated for 150W/ch for 8ohm, 200W/ch for 4ohm.

I'm waiting for Monster MC 200I-2M interconnect cables (for pre-amp to amp) to arrive; hope these are okay. :) I didn't plan to change the Toslink yet. I am also planning to get some (better?) 16 gauge speaker wire from Radio Shack (I was thinking about Monster XPMS but it's 3x the price and not sure if it's any better).

The typical CD's include Jane Monheit "Never Never Land", Joe Pass "Virtuoso" and various Diane Krall; also some Burrell, Coltrane -- usual vocal/jazz stuff I guess.

I was wondering if it was the KEF's since the AVM2 and GFA-5400 seems to have good reviews. I only have KEF Q10's to try but I can see what happens. I'll also try using analog from CD to pre-amp. I was only using the digital connection because I was assuming that the AVM2 DAC's are better than the Sony's.

2 easy things to try and I'll report back later. Thanks for the help. Open for any other thoughts as well.

It is obviously not your choice of music. I doubt it is the amp or preamp.

Therefore that leaves speakers or a jittery digital input.

One further possibility is your room, if you have tile on the floor and fairly reflective surfaces then this could be the issue - an issue that gets worse as you increase the volume.
I'm going to go out on a limb and say that it's probably your speakers or the room. The cables you describe should work just fine. I recently compared a set of $2,000 Nordost cables to a $7 pair of hardware store cables and certainly couldn't tell $1,993 worth of difference, at least for my system that I have about $5,000 in for the main stereo components. Cables make small difference and what you're describing sound like they are more significant in scale. Keep in mind that there are many members on the forum that have systems where cables might make a significant sound difference, but I don't think it applies to you and me. I'd suggest going with something like Blue Jean cables if you want something that's respected and affordable.
I would try decent (not necessarily expensive) analog cables instead of the Toslink first.
It's your speakers.

From a review: "The overall sound can get a little grainy if pushed too hard"
perhaps clipping.
Source music is awful, as has been noted by Shad, above.......look up 'loudness wars' if your want more info.

Also, Since speakers so not have watts, I'd simply ignore that rating. Good, loud, dynamic music demands a lot of an amp. Maybe it's just not passing muster.
Hi guys,

Thanks for the good info. I connected the CD player to the pre-amp using non-brand but what seems like otherwise decent, gold plated RCA cables using the analog output/inputs. To my surprise, while the harness is still there at higher volumes, since I was listening somewhat critically, the analog actually sounded a noticeable crisper and brighter than using the toslink. The toslink sounded slightly muffled in comparison. I'll get better cables next week to connect the pre-amp to the amp; maybe the combination of using CD analog outs and better pre-amp/amp cables will help.

Anyway, the harshness is still there regardless of toslink or analog.

So, based on the comments so far, that leads to speakers and/or the room (ignoring the cables for now). I'll try using the Q10's I have and see if that makes any difference. Will report back again later.

The room is fully carpeted but the drywall walls are bare and the cabinets are either dense wood or glass so reflections are probably possible.
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Using the KEF Q10's didn't seem to make much difference; noticeable less bass but the harshness is still there, especially when a singer hits loud, high notes. Perhaps the KEF Q10's are too similar to the C75's?

I hope the Monster MC 200I-2M I'm getting next week to connect the pre-amp to the amp will make a difference.

I'll need to research what ferrite claps are -- I've never heard the term before. But sounds easy enough. I can try it w/ the current interconnects and when the Monster MC 200I-2M arrive.

Thanks for all the comments. Still open to any suggestions until the issue is solved. :)

I'll try the ferrite claps and report back later.
Its difficult to know anything by the volume references you have included. Typically, you want to report loudness in decibels (ie. 80-90-100, whatever) via the use of an SPL meter to better report how loud you are talking about. Since you like the Shack, they have them in there for pretty reasonable prices. If at some point you are going to address room issues, having even a moderately good SPL meter is very handy.

Your speakers may or may not be the cause, remember the speaker is conveying all the problems from the source on through to it. Lots of areas to pick things up and be exposed by the speakers at higher volumes.

Do a simple clap test in your room, without music on and listen for the slap echo, etc. . . a lively room will really accentuate such problems. I would do this and then address some reflectivity with items around the house for experimentation (blankets, pillows, speaker location, etc. . .

Good luck and don't start replacing too much until you at least look into the room to some degree, it could save you a fortune and lots of headaches.
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Add a subwoofer for better foundation.
You are probably boosting the volume to get more bass
and this is overdriving the other frequencies.
This used to happen to me.

I am turning up the volume a bit; not necessarily to get more bass but to hear some of the other instruments that may be in the background and/or a little quieter.

I found that on some CDs, at background listening levels, sound seemed to come mostly from one side or the other. When turning up the volume a bit, I'd then notice additional instruments coming from the other side (mostly some sort of percussive instrument). Since then, I've gotten used to playing CDs at a certain volume levels.

So, the 'desired' listening levels may be a little loud but I don't think they are overly so -- I'm not concerned about damaging my hearing at these levels (but perhaps my ears are already bad :)).

But if certain frequencies are being overdriven, what's the solution? Get different speakers? If so, any specific speaker attributes I should be considering? Larger tweeter / mids? Bi-wire capable? Capable of higher power inputs?

Or is this an amp issue? Need a more powerful amp?
Sounds like (excuse the pun), it's an issue with the amplifier. Your Anthem is a pretty good pre, but Adcom power amps are not that great (having owned one). Seems like at low volume the adcom lacks detail and dynamics - you need to crank it up to get anything out of it. It may be having trouble driving the 4 ohm Kefs. You may not necessarily need more power, just a better quality power amp.
Best idea would be to borrow or try another/better power amp and see what happens. A good power amp will have lots of detail/dynamics at lower volume levels.
hat on some CDs, at background listening levels, sound seemed to come mostly from one side or the other. When turning up the volume a bit, I'd then notice additional instruments coming from the other side (mostly some sort of percussive instrument). Since then, I've gotten used to playing CDs at a certain volume levels.

You may have a burnt voice coil that is rubbing - possibly one or both speakers are damaged. What you describe is definitely NOT normal.
It's possible that your speakers have a distortion which is present but below the detection threashold at lower levels, and then as you go up to high levels, the distortion becomes louder than the decection threshold. In other words, your ears may have a non-linear perception of what is fundamentally a linear distortion.

It is also possible that your speakers have a distortion or coloration that is level-dependent, or non-linear. For example, if the voice coil of your midwoofer is heating up faster than the voice coil of your tweeter, then your midwoofer will compress more at higher levels. So you could end up with a brighter tonal balance at high levels.

My instinct is that the first situation is the case, this based on my work with horns. In effect a Uni-Q driver horn-loads the tweeter, but much about that "horn" is not optimum from a distortion-minimization standpoint. We see this in prosound with a sub-optimal horn: It sounds fine at low levels, but crank it up and it sounds harsh. The distortion was there all along, but we don't hear it at low levels.

Imo, ime, ymmv, etc.


Hi folks, thanks for the continued comments.

So, if I summarize correctly, the primary suspects include:
1) speakers (distortion)
2) amplifier (insufficient to drive the KEF 4ohm load)
3) RF noise entering the lines (will get the ferrite clamps to check this out)
4) room dynamics (reflections); I walked around the room quickly and clapped in various locations. It was interesting -- even though the room is fully carpeted, I could hear reflections and a kind of pinging after each clap (I don't really know how to describe it -- a kind of reverb echo).

Oh, yea I know that the volume level reference I made above is a little abstract but I assumed that you experts would have an order of magnitude sense given the components I'm using. :) Not extremely loud but louder than conversation levels.

I'm going to try some of the easy suggestions next (this weekend):
1) using the KEF Q10's again; do a larger sample to see if perhaps my C75's are blown (but by nature, the KEFs may be subject to the distortion I'm observing in which case I may hear no difference; in this case, may need to borrow some speakers)
2) use some blankets to minimize reflectivity
3) use the ferrite clamps
4) Not sure what I can do to check if for amp insufficiency; I can try using my Nakamichi AV8 receiver but I'm assuming that the Adcom is a better amp.

Anyway, I'll start w/ #1,2,3 and go from there. I'll report back later.

Quick question on the ferrite clamps -- do I need two per channel (one at each end of the cable, so 4 altogether for a left / right pair)?

Or do I just need two for each cable pair (one at each end that wraps around both channels)?

Or do I just need one for each cable pair (one that wraps around both channels, placed either near the source or near the sink)?

I'm not sure how to use these clamps..... Thanks.
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Tsk, tsk, tsk. Twenty one posts to this thread and no one has suggested upgraded power cables? :O
Seriously though, sounds to me like speakers or room reflections are the most likely cause of your problem. You are on the right track with your 4-step program. Although I would move number 4 up to 2 and scrap number 3. Good luck and keep us informed.
Saru, why don't you at least post the city or vicinity you are located. I am sure others may be willing to stop by and listen, diagnose, and even help you ID the problem with bringing some stuff (equip, cables, deflectors, etc. . . ) over.

Any component can create congestion, HF glare, etc. . . as part of a combination with other components (or alone).

I once owned an amp (Theta Dreadnaught II) that was literally unlistenable for me. Nora Jones sounded like the worst singer in the world with that amp, any time her voice reached up it sound like she had a horrible scratchy, distorted voice. This sound only revealed itself when the amp was installed. I replaced the amp and everything went away. I once had the same issue with a DAC and another time with a CDP (but with the CDP it was only at higher volumes where it became apparent - and much less so than with the Dreadnaught).

Your steps seems to be in good order, but try to find people in your area before you start replacing components on a guessing basis. You may replace half your components before you find the real culprit if it really is even component related???
Its probably a combined effect of everything together more than due to any one thing.

I'd get some decent ICs as an easy and cheap thing to try as a first step.

I'd recommend a used pair of MIT Terminator 2 or 4 ICs for < $50 used as a first step to help tame things down a bit and get more out of what you have before changing anything else.

Next I'd look at some decent but not expensive speaker wires also for an upgrade. DNM Reson would be my first choice.

From there, perhaps a tube DAC upgrade to use with the CD player or a tube pre-amp if the harshness exists in multiple sources, not just digital.

For a tube DAC to help tame things further, I'd recommend an mhdt Paradisea or even better a mhdt Havana if you can squeeze it.
Is there any adjustments on the pre-amp or amp that might be turned up too much. Isn't it possible to have the inputs too sensitive?

Hi folks,

Again, thanks for the continued expertise and help. BTW, I should mention I'm on a pretty tight budget which explains my rather dated and very modest system as well. :)

Started the experimentation this morning with room dynamics while waiting for Radio Shack to open.

I'm still testing but it seems that room dynamics is having a strong first order effect.

I changed the configuration of the room such that the listening direction is across the narrow of the rectangular room. So, the listening distance may be slightly shorter (not by much -- maybe a few feet at the most) but it allowed wider separation of the speakers. I also put up some fabric to try to minimize reflections.

This change allowed me to increase volume levels from about -20db (when I would start to hear harshness) to about -5db (where it starts to get uncomfortably loud); at this point, I hear a little harshness but it's not nearly as much as before. The harshness is almost (but not quite) acceptable.

Wow!! Just a little grunt work and things seem to be improving. Either that or I need coffee and my ears haven't woken up yet.

I'm still working my way through the 4 steps but so far things seem promising. I'm hoping to make what I have work -- basically have a zero sum budget. If I buy something, I need to sell something else. :)

BTW, a lot of terms, brands, parts (ie - HF glare, congestion, ferrite clamps, etc) you folks mention are new to me. I've been spending a lot of time looking things up on the internet. Thanks -- I'm learning a lot. This has been a good experience -- you've all been very helpful.
Good to always max out the configuration of what you have first via tweaking with placement and room acoustics first before changing anything.

If you can squeeze it somehow, an inexpensive IC upgrade might still do some nice things.

Good luck!
@Mceljo: I set the Front Speakers as Large. I don't have center, surround or subwoofer (probably meaningless, but I set the sub x-over frequency at 160Hz from 80Hz; I feel my speakers put too much weight on bass). Other than that, I set the effects to Stereo (no processing) and have bypassed Tone controls.

Using analog inputs now --- I have them going into the Direct Analog inputs which is supposed to bypass everything except volume and tone (which I've set to bypassed).

Other than that, I'm not sure what to check. Is there something else I should look at in the config that I've missed? Nothing else seems to be mentioned in the manual (that I recall).
@Mapman: I have Monster MC 200I-1M being delivered next week for the pre-amp to amp connection. While picking up the ferrite clamps from Radio Shack when they open, I was thinking about picking up their AUVIO® 3-Ft. Stereo Audio RCA Cable for the CD to pre-amp connection.

Is this better than the non-branded red/white RCA cables (that might come with cheap consumer electronics)? Or are you thinking about something even better? I'm not really sure what to look for in a IC cable.
You say "hardness", can you be more specific? It's hard to determine if you have electronic or an acoustics problem. Throw some blankets up and listen. If that helps you can experiment with different approaches. Sometimes you can put big plants, bookshelves, or other objects to disperse instead of absorb the sound. This can be an alternative if damping makes the room too dull.
Hi again,

It's hard to describe some of the things I'm hearing since I don't share the audio vocabulary (yet) that you folks have. Not quite accurate, but the closest description is that the harshness is somewhat like humming and then patting your chest -- what should be a smooth sound is disrupted by unnatural vibrations.

I bought the Auvio RCA cable and the ferrite clamps that I installed, 2 per channel, on the CD-pre-amp and pre-amp to amp interconnects. I installed the new Auvio cable between the pre-amp and amp. The remaining non-brand RCA cable seems to be pretty good as generic goes (a little thicker than normal and w/ gold plated leads).

Again, re-configuring the room layout and adding some fabric to minimize reflections (still get some echo from clapping but not as bad as before), seemed to have a dramatic impact. I could turn up the volume louder before the harshness kicked in.

I also moved everything into a larger room (temporarily) that is asymmetrically shaped (no/minimal echoes from clapping). The sound really opened up then and harshness was moved to even louder volumes.

I'm guessing that:
1) room dynamics is having a large first order effect
2) the better(?) cables and the ferrite cores may be helping but not sure; hard to tell after changing the room config
3) the harshness also depends on what I'm listening too (Monheit singing louder and at higher frequencies can result in harshness; acoustics like Joe Pass seems less susceptible). Perhaps room dynamics affect certain frequencies more than others; or maybe just the selective sensitivity of my ears.
4) at some loud (uncomfortable but not painful) volume level, I think I'm approaching the limits of either the amp and/or the speakers (starts at about -5db) -- harshness that is maybe distinct from the symptoms I hear with Monheit at lower volumes.

I think now I can listen to things like Monheit at volumes I desire (around -15db to -20db) w/ acceptable levels of harshness (perceptible but perhaps not enough to drive changes to components with their associated costs) whereas before the harshness was unbearable and tiring.

I'll continue to experiment with room dynamics and look into getting a better (24/192?) CD player (my 20 year old Sony has had a good run). But the sound is much more enjoyable than 24 hours ago. :)

Thanks much to all for the help and suggestions!
Saru - I read through the manual for your pre-amp and didn't see anything like what I was referring to. On my truck subwoofer amp and also some of the amps in the audio system at my church have adjustments for the input sensitivity that can really change the way things sound. I think some seperates have this type of adjustments, but not all. I was thinking that you might have things oversensitive and amplifying something in the digital recordings.

You might actually try allowing your pre-amp to do some processing rather than bypassinge everything. On my Integra 50.1 receiver I generally listen in direct mode when I'm in audiophile mode, but for some recordings it simply sounds better in stereo mode where the signal gets processed a bit. It may be similar for your system but for different reasons.

I highly doubt that you'll hear much if any difference from any cable swaps you make unless you are currently using a damaged cable currently or you're getting a lot of interference in an unshielded cable.
1) CDs. Some are mastered horribly bright
2) Room. Too much reverberation at high frequencies
3) Speakers.
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Given that your preamp has a headphone jack, my suggestion is that before going much further you invest in a pair of headphones. Considering the number of variables and possibilities that have been cited, I think that comparing results between headphones and speakers would be very useful in distinguishing between source material or front-end issues, and room/speaker/amplifier issues (despite the fact that headphone listening is a fundamentally different experience than listening via speakers).

A good fairly low priced choice would be the $84 Sony MDR-7506, which is widely respected within its price range. I have a pair that I use for non-critical purposes, primarily for monitoring while doing amateur videography and voice recording, and I've been pleased with it, especially considering the price. I haven't tried it in my main system, though.
04-22-11: Meiwan
At higher volumes you may be noticing harshness in your system that you don't at lower volumes (even though it's there).
This is an important point to keep in mind. As volume increases, the sensitivity of our ears to high and low frequencies increases, relative to their sensitivity to mid-frequencies. That is known as the Fletcher-Munson Effect.

-- Al
My best guess is it is the CD player and maybe amp. I doubt it is the speakers or room. Higher order harmonics are not genrrated by the room. You can take steps to improve room acoustics, but that is more like icing on the cake and no way to fix bad equipment. When i first started with CD, my first impresion on 90% of CDs was things were way too harsh at even moderate volume levels . I found the only real way to improve things was to get CD players with way better digital filters and analog stages. I made the natural progerssion with better players and noticed a big improvement with each step. I went from Pioneer BPC, to Theta, to Krell, to Wadia, and back to Krell. :)
you might look for any reviews on your amp to see how it does higher order harmonic distortion. I know Adcom only really made one amp that was even close to "high end", that being the model designed by Nelson Pass. The rest of Adcom amps are strongly mid-fi and not much more than BPC. (sorry to say)

Hi -- thanks for continuing to check in on this topic and offering your suggestions. I am continuing to experiment, mostly with fabric (types and locations) for reflections, speaker location (separation and proximity), analog vs digital interconnections and various types of music (classical, jazz, vocal; low (ie - bass, sax), mid (vocals / guitar) and high (some vocal and violin) pitch sounds across various volume ranges.

I've been spending a lot of time listening, moving stuff around (including using a different room and moving components between rooms) and characterizing. :) This seems really more of an art than a science.

I've tried a lot of things and I think I'm reaching the limit of room dynamics and my components without buying stuff (dampeners, drapes, different components, etc).

While it's not perfect and some harshness is still there, it's definitely better than a few days ago and I'm actually able to turn up the volume quite a bit more before the harshness becomes unbearable. Again, before, I would get unbearable harshness before the sound was uncomfortably loud. Now, I can get the sound to be uncomfortably loud before the harshness is really unsettling (and perhaps I'm also now reaching the limits of my speakers and/or amp). The clapping / pinging test is much better now, especially in corners where it was the worst.

I appreciate the suggestions and understand the reasoning for a power conditioner and the headphones (actually, I really want to buy some nice headphones and using them for additional testing here is an additional reason). And I keep learning new things: I had to look up the Fletcher-Munson Effect (never heard of it before). BTW, what is BPC (as in, my Adcom amp are not much more than BPC)? Not that I disagree but just not sure what it stands for. :) I think my GFA-5400 is rev 1 of 2 versions (I have the rev made in Japan, not China).

But, given my budget, I can almost buy a used CD player that may help improve a weak link in my system (access to additional bits and higher sampling rates); I think my current DACs (in both my AVM2 and X111ES are 8 or 16 bit and 48 or 96 KHz). Perhaps getting something like a used Cambridge Audio CD player in the $200 price range would be the best use of any budget I might have.

Or maybe I should just be happy with what I have. It doesn't actually sound too bad now after trying some of the inexpensive suggestions received; it's not perfect but better. But I can see how a budget could very quickly spin wildly out of control here. :)
Your Adcom is having difficulty with transients. The poorer the recording, the more apparent this becomes. Try a really good one like say, Lyle lovett's "Natural Forces" or Jimmy Roger's "Allstars", or Ray Charles' "Genius Loves Company". A really good amp won't be limited by the recording in that it will simply reproduce what's there accurately. So if the information is diminished, it won't attenuate that upper mid-range already attenuated in the poor recording we're all familiar with as "harshness". The recording will simply be apparently "lacking". If a great recording eliminates the issue, you need to consider the perfomance of your amp. All KEFs are great speakers regardless of there particular shortcomings. If it hurts or is bothering you that much, it's the amp.

@Csontos: Thanks for the suggestion. I want to make sure I understand the methodology. The presumption is that a well recorded CD (ie - something that is well mastered using larger word sizes (24bit?) and higher sampling rates (ie - 96 or 192KHz?) and well done (ie - good recording studio, good equipment, etc) should play well on any system (up to the limits of said system).

The assumption here is that the pre-amp and speakers are not the weak link at the volumes I'm using. And even a source that is 8 or 16 bit at 48 or 96 KHz should be sufficient for a good recording to highlight deficiencies in an amp.

So, by playing a known good recording (like ones suggested), I can determine if the amp is limiting if there is harshness detected.

Whereas, if harshness isn't detected, then it's just poor recordings I'm listening to (in addition to other things like room acoustics)?

Actually, I've been wondering if there is a way to challenge each component in some way. But I've just learned that this way of thinking may not be useful -- that components play off each others strengths and weaknesses so you need to measure the system as whole in the room you are targeting. Must drive audio component retailers crazy - a component that sounds good in the store may sound lacking at home :)

So, if I learn that the Adcom is lacking, I guess that's what the amp forum is for. :)
That's just it. It's not the good one that reveals the amp's true potential nearly as much as the poor one. The amp is the heart of the system. Once you've gotten used to the attributes of your other gear, you then begin listening to, guess what?... your amp, "again". The component you get used to the quickest is believe it or not actually the weakest link, your speakers. What you will never get used to are the shortcomings of your amp because they are constantly being revealed and so become your focus. For the amp to "disappear", it needs 3 attributes relative to your ears; it has to be "fast", it has to have a truly flat frequency response- one that is not can seriously contribute to the harshness you're talking about, and it must be very linear. Whatever other attributes it has are a bonus A truly high-end amp is probably the one that leaves you scratching your head wondering what makes it a high-end amp because it's so "flat and dry". Everyone out there building amps is applying their own brand of "voo-doo" in order to compete with each other. What I mean by that is it's easy to show a flat response on a 6 inch tape. Stretch it out 3 feet and you'll see just how flat it really is! It's not possible to add without subtracting, and they're all doing it fooling you into thinking you're getting a superior product. It's usually located in the bottom end and/or upper mid-range- it being the most bothersome since it thickens transients in the vocal range which can be fatiguing or downright ear-piercing. At first it's an up front in your face soundstage but then begins to take it's toll on your ears with lots of missing depth. Poor recordings should simply sound as they should.."lacking". They should not be ear-piercing or irritating at all! Remember, the entire system is nothing but a playback device. If the components are of sufficient quality and functioning properly, "revealing" poorly embedded information should sound as smooth and clear in terms of what's there, as the opposite. It doesn't "improve" it, but just plays it back.DC offset problems and bias issues can definitely cause the problem you are experiencing. Are both channels the same temperature within a couple of degrees? Have you checked the offset? These factors can ruin the sound of an otherwise great amp.
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".

Left: 7.2mV; Right 13.2mV. Same reading with volume at -95db (minimum) and 0db (wasn't sure what you meant by 'volume at 0'). So, I'm assuming that the DC offset on my amp is acceptable, even though left and right are a little different?

I don't really have any idea how to measure fast and linear but I assume that's not something adjustable (w/out changing internal components?) so I have what I have. I'm not even sure how to adjust for DC offset so it's a good thing it's within the range you suggested. :)

Planning to order the Sony headphones recommended by almarg when I get the money.....
Volume at minimum. Yes, very acceptable. Without bench equipment you cannot get specs for speed, linearity or frequency response but the best way to check those aspects is with your ears. It's really those characteristics we're dealing with when we judge and come to a conclusion on how an amp sounds, hence my original suspicion your amp is having difficulty with transient performance, referring to it's "speed". The poorer the recording, the more difficult it is for an amp to reproduce especially vocal transients ie: s, z, ch, j, v. Probably because one of the main ways to describe a poor recording is compression when the transients become very fine and close together. This can result in some pretty harsh sounds when the amp can't deal with them effectively.
Try hooking up an iPod or other mp3 player via a mini plug to RCA cable and see how that sounds. It shouldn't sound a clean as your CD player, but might help to determine if the CD player is part of the issue. You could even rip some music in WAV format so that it's not compressed for a slightly better comparison.
Saru - I'm not familiar with your gear, but I am familiar with "humming and then patting your chest -- what should be a smooth sound is disrupted by unnatural vibrations"
In my case it was the simple fact that I was overdriving the room. I was putting too much sound (volume) in there, and the bass interferred with the midrange, mainly vocals.
I fixed it by changing speakers and putting acoustic treatments in the room. That distortion is a distant memory.
Since you have a $0 budget, I suggest that you put some bulk in the room to help diagnose the problem: Blankets, pillows, boxes of stuff, even an extra piece of furniture (cloth). If this helps or eliminates then you know what the problem is. Then you might look for more permanent solutions that look good.
The fact that you rearranged the room and added blankets and got improvement leads me to believe this is your problem.
But do remember that there are limits with any system. You won't be able to play as loud as you want.
Saru - One other thought that is quick and easy.
If your room has a door, try playing loud to where the distortion occurs and then open the door. If you are overdriving the room then opening the door may relieve some pressure. If the distortion is decreased then this may give an idea if this is your problem.
My room is 12' x 13' and opening the door has this effect.