Help with hiss

@forestg Wrote:

 I didn’t so much change any cables, but I did add a cable around Christmas time. I got a Schiit Loki for Christmas, so I broke out a pair of Raven Audio cables to use to put the Loki in the system.

Just a thought, the Loki does have a wall wart style power supply. The two most common reasons for hiss is either a grounding issue or a gain staging issue.

I know this may sound silly but my guess is check the amplifier bias, maybe it's drifting, causing the hiss. Wish I could be of more help. See Odyssey Audio below:

Mike

https://odysseyaudio.com/kismet-reference-amplifiers/

@ditusa Hi Mike, The Loki does have a wall wart. I’ll unplug it to see if that helps. I have several components that use wall wart style power supplies. I’ll check them all while I’m at it.

I had thought of the bias issue. I’ve read several discussions, especially pertaining to Odyssey, about adjusting bias to change the sound. The only thing perplexing about the bias drifting is that both amps exhibit the identical behavior at the identical time. Can drift in one effect the other so directly? I understand that bias exists and that it is a “thing”, but that is the extent of my knowledge. It is not anything I would attempt myself. You’ve been very helpful. Thank you so much.

This is a natural phenomenon. You can spend the rest of your life trying to figure this out. Based on the writings of Stereophile and others, this hiss is originating from your components. The noise floor is poor and this hiss is symptomatic of poorly measuring components. 
 

if your amp has gain adjustments try lowering the gain. Stereophile has written about this before.

good luck. 
 

Try a cheater plugs on the Amps and Preamp. 
 

Cheater = 3 prong to 2 prong adapter. 

Hiss is random noise generated by active electronic components. It is not induced nor due to grounding issues like a 60Hz hum. Nor is it impacted by cables, AC power or external electrical components. Are you familiar with ’gain staging’? Basically, your amps are running at max gain and your preamp isn’t required to run at a level very far above its noise floor. Solution: Reduce the input sensitivity on your monoblocks and drive your preamp harder.

As well if you are using a low-gain MC phono cart the signal to noise ratio of the MC preamp may be 10-20 dB noisier than a MM input. You can check this by switching to an unused line input, and if the hiss drops, that’s the contributor. The solution is the same - gain stage your preamp and monoblocks, and now your MC preamp as well, to raise the signal (variable) to noise (fixed) ratio.

Gain staging is a basic survival skill in live sound and recording studios, (it was one of the first things I was taught, along with grounding theory) but is rarely mentioned in HiFi. Here’s are two good good tutorials: https://www.izotope.com/en/learn/gain-staging-what-it-is-and-how-to-do-it.html

From Sweetwater Music: https://www.sweetwater.com/insync/gain-staging/