New tubes or new preamp?

There were two versions of the LS15. If you have the older version (most easily identified as it has a captive power cord) then the cap and power supply upgrade by ARC is a very cost effective improvement.

Brrgrr,

After reading your 2nd post, I don't know if you will get the results you want by getting a new preamp. It looks like you want something to deal with your 3.7's not having a "sweet" type of sound. Getting an LS27 most likely won't help. If anything, its a more transparent preamp and will further enhance what you don't like about your speakers.

Given that, I think you have 2 choices. The first choice is to buy equipment in an effort to cover up what you don't like about your speakers. Its a very tempting option, but almost never works. You'll just end up spending a lot of money. The 2nd choice is recognize that you may have bought a pair of speakers that are not for you. If thats the case, deal with the issue directly and get a different pair of speakers. For me, personally, that would be the way to go. Deal with the problem and be done with it.

"Still not getting the sweet sound I prefer"..........If by 'sweet' you mean rolled highs or midrange warmth, I'd agree with Zd542. It is very hard to change the fundamental sound of speakers by changing amps etc. That said, however, IMHO the electronic's you seem drawn to are not noted for their warmth. Detail, transparency, speed, etc, for sure. Warmth, not so much.

FWIW I've never thought that panel speakers matched to SS amps, etc, were a match made in heaven for folks who want warmth/sweetness. But if you think a tubed pre-amp will do it look for something that is noted for it's warmth/sweetness
not its transparency etc. ARC would not be my first choice buy some margin, neither would a Modwright, fine though they may be.

I am an inveterate tube roller who can tell you that in some cases of ARC gear, - tube rolling is not useful. I own a highly modded ARC SP6B which uses 6 12AX7s. It was very difficult to tame the glare I sometimes got using this pre. I had all sorts of tubes to roll none fixed the problem. In the end I just put in some good tubes of no special merit and gave up.
I don't know if that is the case with your ARC pre but even ARC would tell you which tubes were likely to change the sound and which did not.
You can buy a tubed pre that may be to your liking, but I have to agree with some others and say, that more ARC gear is not a going to cure your system's ills. I can't comment on the other brands you mentioned but you may want to check out 6SN7 based pre amps from Cary, such as the SLP-05. You can put a whole host of different tube brands and vintages in that pre.

I have had that preamp and the sound is dated even with vintage tubes Good for the money but not a Ref 3 or 5. Sell and replace it if you want a bigger step forward. Tube rolling is way overrated. Tubes only do so much. Jallen