ARC LS25 mkII noise level

The hum/hiss is also speaker dependent. The higher the sensitivity of the speaker (92db vs 87db example) the more likely you are to hear the hiss.

What you are hearing is precisely why I have changed over to a solid state preamp. I have the tubes in the amp. It is even more troubling when listening to a tube phono preamp. The tube noise of the phono signal is very noticible. I prefer solid state phono pre for that reason. Amplifying the signal through a preamp is where you do not want extra noise. Finding good tubes that are quiet enough for preamp use is a particularly difficult feat. They may advertise them as quiet, but when you exchange out the tubes for solid state, the difference can be pretty significant.

@ee3: That is what I suspect. I'll check a few more things along with a new set of 6h30 tubes. If that does not do it, I'll send it to ARC for a complete checkup. What amp are you pairing it with and how sensitive is your speakers?

My Focal 1027 Be are 91db.

@tzh21y: The LS25 MKIK does not really use tubes for gain. It is used for cathode following circuit. So, I don't think new tubes will have much effect although you never know. It's interesting in that some people will say their tube preamp is dead quiet and some will say it is much noisier than solid state. I might go passive preamp or solid sate but I'll give LS25 mkII a chance first.

My MKI is dead silent. Nada - even wide open. I'll second ee3, a trip to ARC seems to be in order.

Marty

The only way to know is to use your own ears. To my ears, it is not even close. In your case, maybe there is something going on inside of the pre that is not right. I love the sound of tubes but I have been turned of by the noise, especially from the preamp. There are some good tube preamps. I have never heard the LS25 but Atmasphere, Lamm and First Sound make some great pre's. The Atmasphere uses the 12au7 and unfortunately, it is getting very hard to find quality 12ua7's out there NOS. Both are pretty much handmade and cost well over $5,000.00. Maybe someday I wlll try one of these pres.