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Likely culprit for harshness at higher volumes?

Hi,

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.
saru
meiwan
399 posts
 
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.
shadorne's avatar
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shadorne
7,477 posts
 
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.
saru OP
30 posts
 

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.
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