Have you considered the Modwright KWA100SE or KWA150SE? Just an aside, if you haven't considered this for the LS100, might want to try Black Treasure CV181s (6SN7 equivalents) takes the sound to another level
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All good. It's going to come down to what you like. Everything noted on your shortlist is very nice stuff. I own a LS36.5 so I'd say start with ModWright and Pass if you're staying SS. If you're thinking tubes then I think it gets more difficult but can pay off. If you're thinking a tube amp, don't overlook maintenance, heat and tube replacement. If you're leaning towards SS, with your speakers I'd maybe move ARC and Bryston to the bottom of the list. Personally not a big fan of current ARC SS amps and not sure I'd go with Bryston, although very nice amps, with your speakers. I'd look at at one of the lowered power Pass XA amps - XA30.8 to start with or a ARC Ref 75SE; if new is a little outside your budget they are often on the used market. As much as I love my Pass, I'd say look into the Ref 75 with your speakers. Good luck.
I’ve been running a Pass x250.8 with great results. I’ve also tried the Black Treasure CV181’s ( 2 different pairs) in my LS-100 and have nothing but noise after a couple months use. Now have a set of Psvane CV181’s running which are almost as good as the Black Treasures, but are starting to get a little noisy after just a few months. I’ve gone through the old rectifier tube that was in when I got it in May of last year, plus a new one I replaced the old one with. This also blew the Synergistic Red fuse I was running in it. I’m done playing with tubes. Just the other day I bought an Ayre K-1xe to replace the Modwright. It arrives Thursday.
Good luck in your quest.
I have a Pass X250 with my ModWright LS36.5. My experience with a big SS amps with a tube preamp it's best to run balanced cables. My previous ModWright SWL 9.0SE was a little noisy too which is why I sold it and got the LS36.5. Your formerr LS100 has an XLR out, but it's just a cheater - not balanced. Pass X250.8 with the Ayre K1XE should be very nice. Run balance cables if not.
I wouldn't think the LS100 would be noisy. Larger Pass amps can get a little noisy because of their high gain running single ended cables, so balanced is highly recommended on them. Both Pass and ModWright make great equipment and as always it's all about the synergy between any two components. I spoke to Dan before buying my LS36.5, and he stated on my Pass the LS100 would not be any quieter than my former SWL 9.0SE because the XLR Jack on the back of the LS100 is only a jack on a single ended output. Abucktwoeighty mentioned his LS100 was noisy on his Pass X250.8 which doesn't surprise me. As far as his misfortune of tubes goes, that probably comes down to not buying from a reliable source maybe?
Back to Bluejeans on the amp search. What is your budget? I don't believe your Harbeths are a difficult load, so I would recommend quality of power over buying a bigger cheaper amp.
A decent amp is just as important as rest of the components in the system. I wouldn't skimp or settle on a cheap amp given what you're trying to put together.
I highly recommend KWA150SE, you can buy one used at 50% or less off full retail.
I own a pair of KWA150SE and it's a fabulous sounding amp especially when you pair it with a tube preamp.
I owned the LS 100/KWA 100se combo. Its was nice but might be a little warm for the Harbeths. I would go with something less warm than the KWA 100se or the Pass (but the .8's are not as warm as the .5's right?). If you can stretch to try the KWA 150se, it is not as warm as the 100 and might be better for the SHL 5+. Or try AR.
@bluejeans, what did you settle on?
I have my LS100 (with Psavane tubes) paired with Hypex Ncore 400, amps, Eminent Technology LFT8b's and Vandy subs. Happy chappy!
The KWA 150se seems like a winner, but my speakers are not efficient and not sure if there'd be enough grunt (though the Ncore's are only 50w more).