Speaker Hiss with Krell Amp

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.

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

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,

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

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 :-)

The problem of hiss is NOT your krell amp,  but rather your front end,  I  had the same issue once with an ayon cd2s player,  none before or after every heard a hiss from my krell 700cx,  and I always run directly to amplification. 

Do you hear the hiss with only the Krell amp in the chain? If not the cables it could be a pre or source. To me if the hiss is common in an amp of that caliber I would pass on it especially if a super low noise floor is what you're after. With either an Octave V70se/V100 I had absolutely no noise unlike my Bryston (low hum). Now I have an Aavik U300 and still no noise at all.
Just my opinion and best of luck.

dsper,

If you are hearing 'hiss' 3 feet away then something else is also contributing to that noise.  Unless you favor Krell sound over the rest of the aforementioned components I would not recommend Krell amp in your setup.  

In my setup, I only hear 'hiss' sound when I draw my ear close to my 800D2 tweeter. I used to own Classe SSP-800/CA-2200/CA-5200 components that were dead quite.  Call me crazy, but I prefer Krell sound over Classe, even with that faint 'hiss'. 

Good luck with your search! 

I would find that unacceptable. This awkward, as I've been pushing a Krell audition for your CS 5's for some time. Perhaps, Al is right. He usually is. IME, most Krells seem to work best when used in balanced configuration, though I can't really comment on Krell's CAST usage. 

Well Stereo5 that is what I am thinking given all the info about noise floor and retrieval of low level detail not to mention something could be wrong with it.

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.

Personally, I would stay far away from any component that causes hissing.   Why would anyone buy a Krell Evolution knowing it produces hiss?

dsper, 

I also own Krell evolution series components.  The hiss you're hearing is common among Krell components. As long as 'hiss' sound is not audible 5-7 feet away, you're A-ok. Here is a in-depth article that explains audible hiss,

http://www.gcaudio.com/resources/howtos/systemnoise.html

Hope this helps! 

I assume, given the preamp you are using, that you are connecting it to the amp via RCA cables. Are jumpers in place between pins 1 and 3 of the amp's XLR connectors, as called for in the manual when the RCA input connectors are being used? If not, that could very conceivably account for the problem.

Also, can you provide some indication of how loud the hiss is?

Regards,
-- Al