Help with hiss

A couple of things to try.. first, re-route all cables making sure that the low level cables (interconnects) are at 90deg to any power cable they need to cross. Make sure speaker cables are kept away from power cables.

If that doesn't help, turn everything off, disconnect any interconnect to the mono blocks and then turn them on. If you still hear the hiss, then it's from the amps. If you don't, then connect the interconnects but do not turn on the preamp. If hiss, then it's the connection (interconnects or the input of the amp). If no hiss, then connect the preamp (test first without it on and then with it on). And so on, work your way backwards until you identify the source.

I went through this exercise only to find that if I plugged in my integrated amp to a different outlet on my PS Audio PowerPlant, any and all hiss went away.

@erik_squires Oh, I did not take it that way at all!🙏🏻 I think I was trying to address the very real issue of shielded vs. unshielded. I’m not sure which of the cables are which, but it will be very easy to get that information. I’m afraid my Brick Wall is loaded with wall warts, but there has been no recent addition, unless one is beginning to fail (which is possible). I’ll end up systematically unplugging each one and seeing if that has an effect.

I don’t want to jinx it, but since I got up on this quiet Sunday morning, the system is absolutely silent. I’m thinking you guys may have scared away the gremlin!! He knew I called in the big guns!

@audiojan Thank you so much for that! I do what I can to route the cables that way. It’s quite a mess back there without a lot of room to spread things out like they should be. I am cognizant of it, though. I will also do as you suggest and disconnect the interconnect to the amp. I agree that isolating the amp from the rest of the system may provide some answers or direction. 

@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.