Hiss at addition in system LAMM L2

I have soft, low-level hiss in my system with the Lamm L2. Yes, it can be heard from the listening chair 8 feet away. It's very slightly more hiss than I heard with an Atma-Sphere MP1 MK III linestage or Audio Research Reference 3 preamp in the system. It's *less* hiss than was present when using the Atma-Sphere's phono section. The hiss is not audible during quiet passages of music playback (although obviously it's still present).

The hiss goes away when the L2 is muted.

I often wonder if some of us are more sensitive to hiss than others, and were we to listen to the same system at the same time if some of us would object to hiss we hear whereas others would not.

The question is, how do we compare in writing the loudness of the hiss we hear unless we each measure the decibel level with the same model sound pressure level meter, at the same distance from the drivers, and after having established a baseline test tone decibel level? IMO, this is nearly impossible.

To directly answer your question with a few suggestions...

Using the L2 in balanced mode with balanced amplifiers reduces hiss level, as does changing old tubes to new tubes and re-biasing the preamp. Re-biasing according to the owner's manual must be done after tube changes in the L2 power supply. A multi meter, and a small flat head screwdriver is required.

If you still have excessive hiss after you change the tubes, re-bias the preamp, and run it in balanced mode, then perhaps the issue is one of personal preference for less hiss and another preamp is in order.

I owned a L2 Ref 2 years ago. Had the same issue which drove me nuts. I did everything I could (bought new tubes, rebiased numerous times, changed cables, got balanced cables, moved my rack (thinking it might be and RF issue), took both isolated both pieces from the rack, swapped in another amp. You name it I tried it as I did love what it did in terms of musical presentation. Spoke to Lamm and on their advise shipped both crate "air express" from western Canada to NYC - OUCH at almost $500 return. They could not find anything wrong with it. Since it was there I had them upgrade all the toggle switches to the current version.

Got it back and still the noise but mine was more than a hiss it was more like a sizzle. Had my buddy John Wright of Museatex fame give it the once over - still the same problem.

While it bettered my resident Hovland preamp the Hovland was dead quiet in comparison. In the end I sold it. I could not justify its "issue" for what I had in it.

As Grant advises it may not be for you which was my case...

Hiss can be annoying, no doubt.

I will add that using different power conditioners and cords has affected the
L2's level of hiss in my system. It seems to be fairly sensitive to power cords
and power conditioning, IMO. You don't necessarily have to spend a fortune,
either. I'm presently burning in an Alan Maher Reference Power Center V2
that retails for $750 including a captive power cord. The hiss level is the
same, or slightly less, than when I was using a Shunyata Hydra 2.

In my system, the L2 is better (more transparent, alive, and lacking
coloration) than the ARC Ref3, despite the ARC being nearly dead quiet.
However, this is likely due to better impedance matching with my amplifiers
than anything else.

The only other balanced preamplifier I'm aware of that has an output
impedance somewhat close to the L2 is the Modwright LS36.5. I'd like to hear
one in my system since Modwright products are famously quiet, but the
price including the PS36.5 power supply puts it out of my comfort zone.

forgot to add that I threw mine on a BPT balanced conditioner and also ran it on its own dedicated 20A line - still had the problem. Got an email from a gent in Europe after I posted my findings and his L2 Ref had a similar problem. I would imagine what could be this preamp's "best" match is a Lamm amp(s) but that was not in the cards for me...

The L2 Reference is an outstanding match with Pass Labs XA-.5 series.

IMO.