Speaker Hiss with Krell Amp

audiolabyrinth, 

I have gone through the whole excercise to isolate the 'hiss' last year.  I had the same experience when I owned Krell Showcase series, and now Evolution series. 

Going by the test sequence, with everything else being off and disconnected I started with powering up amp first, heard faint hiss. Then powered processor, the hiss noise was further enhanced. I reversed the sequence by powering processor and nothing.  Keep in mind, I am hearing this hiss only when I draw my ear close to tweeter.  

My speakers sensitivity is rated at 90dB.

The hiss doesn't bother me cause I don't listen to my music standing next to my speakers :-)

dsper,

Have you tried just running the amp with no input (or shorting plugs)?
With no signal applied, does the volume setting on your preamp change the results?

It might be a grounding issue.

Roger

Hi lalitx, interesting,  mmm, do you have shielded and RFI/EMI  interconnect's such as taralab's cable's? , my interconnect's have an out board station that has it's own ground to  component's or connect to whatever earth ground, I hear no hiss ever.

Dsper
I also know that there are not connectors between the XLR pins so Almarg could have this right.
The hiss is audible about three feet away.

Hi Dsper - this is from Krell.

On krell amps the shorting pins usually get installed into pins 1 and 3. If these shorting pins are installed between pins “2 and 3” this will result in no output from the channel in question. It’s 50/50 as to whether or not a system being operated in single ended mode (RCA) will have noise present without the shorting pins installed.

FYI: When we initially began shipping amplifiers with actual balanced (XLR) inputs in maybe March or April of 1988, we did not use shorting pins. It was not until a few months later after we swapped out or replaced a few new amplifiers for “noise problems” that we learned of this. Hence the appearance of shorting pins in the balanced (XLR) inputs on all Krell amplifiers that had balanced inputs, beginning about mid way through 1988. The only balanced amplifiers we did not install shorting pins on are the FPB “cx” series because that had only CAST and XLR inputs, no RCA inputs.

So I would get some shorting pins first before you continue with the audition. Makes one wonder how many other Krells are being run with RCA’s and no shorting pins.

IME - Krell is a challenge to get setup with RCA’s. You need to be anal with your grounding and cables placement. Krell is very sensitive to hum. It is using really high current even on idle, which translates to more hum if there is some kind of ground imbalance existing. Different manufacturers use different grounding schemes. This contributes to the problem. That’s why removing a chassis ground on some equipment fixes ground loops. A temporary fix.

Unsound
IME, most Krells seem to work best when used in balanced configuration, though I can’t really comment on Krell’s CAST usage.

Unsound, IME True for reasons stated above. Most audiophiles/music lovers I know in general, are lazy - including moi. Even if one is very careful with grounding and cables placement initially; all it takes is an errant placement of an interconnect later, going unnoticed, to maybe cause a problem. You need to be remain anal about grounding and cables placement to run a high current Krell Single Ended.

dsper - very interested to hear about how this plays out, if you choose to get the shorting pins and continue your audition.

Cheers

Guys, I like my Prima Luna Dialogue Premium preamp which is unbalanced and I really do not want to mess with this problem as the Krell has not reached out and grabbed me to say this is the one.

Thanks for the input!

For the money I guess I need to try a McCormack or Coda unseen and unheard.