Recapping an ARC LS-5 mkiii

So I have done an exhaustive Internet search on this, and have some answers (but not all).

Every piece of audio gear I have from the 80's and 90's has had some sort of issue and needed mods and/or repairs. Some of this wasn't audible, but showed up when the equipment was put on a test bench.

Every piece of classic/vintage equipment I have (Aragon, Sonic Frontiers, Audio Research) has been updated except for my LS-5 mkiii preamp. With ARC gear, I know lots of people tend to think of them like classic cars and look down anything ARC didn't do originally.

At the same time, I know ARC offers a Stealth Cap upgrade (roughly $800 IIRC) and I also know Steven Huntley at GNSC used to modify ARC gear (including the LS-5), but I can't really find anything out there on what that process involved.

I am interested in getting the Stealth Caps done, however, outside of that, I don't want to change the sound signature too dramatically (like shoehorning an LS V8 motor into a Mazda RX-7). I'm sure there are some gains to be made (Rel Caps to Infinicaps?), but want to make sure I do things the right way.

BTW, the preamp sounds good (to me), but as I've learned, that doesn't always mean it would test completely within spec.

Thanks in advance.


Slim to zero chance ARC will work on the unit if it has obsolete semiconductors (they can't take the chance they'll accidentally damage an irreplaceable good one while in their care). 

The Rel Caps are top quality films which ARC uses as bypasses in the power supply. I don't know what they use in the signal circuit. I think you may be doing a sideways upgrade if you replace the Rel Caps. I look for old damaged ARC gear to harvest the Rel Caps.

LS 5 mk 3 one of the all time great pre from ARC a true classic believed to be the first REF. Pre they made. I always wanted one and would buy the right one in a heart beat and would also upgrade the caps. Extremely rare to fine one for sale showing how treasured they are.

Agree you have a great preamp. No doubt caps have come a long way since that baby was made. As mentioned I’d start with ARC but I’m sure there are many techs more than capable and some here that will use better caps than what ARC uses and not take your head off on the labor. If you’re not confident you can do this personally, then don’t make this your first project. 

Have you checked the tubes recently , if not you should as the maybe ready.

@gs5556 appreciate the heads up. I’m still learning all the ins and outs on caps/etc., so thanks for clarifying.

@tecknik Thanks. Yeah, I jumped on it last year because I know they don’t come up very often and I really wanted to see how well it paired with my Vandersteen 3A Sigs (it works pretty darn well).

@adg101 I certainly have a tech who is capable...and that ain’t me lol (A guy I know who has rebuilt my Aragon equipment and has a pretty good reputation on DIY Audio).

I’ve reached out to ARC on what may be involved. I contacted Pyramid Audio who resurrected my "unserviceable" (per ARC) D400mkii and it sounds pretty darn good...but Pyramid hasn’t seen a ton of LS-5’s and they’re risk averse to modding or changing anything.

I took out the original Sovteks and bought some "platinum matched" gold pin EH tubes from Upscale Audio because they’re basically the only 6922 they recommend for ARC gear. I have 4 Amprex 7308’s, but those I haven’t personally put on a tube tester and didn’t feel like sporting for four more at the moment. (I have 2 Willsenton integrated amps I’ve rolled tubes in and, well, don’t feel like spending more than the $400 I’ve already spent on those EH tubes).

@spatialking thank you. I have a guy who is pretty knowledgeable, and has some advanced test equipment. Appreciate the heads up.

I’ll update this thread when I hear ARC’s response. I know a lot of this classic gear (regardless of brand) from the 80’s and 90’s at least needs to be looked at because what sounds okay and what measurements show are probably two different things (for example, the DC offset was completely wack on my Aragon 4004, and that was after it had been serviced by the factory recommended repair shop...turns out it was a bad transistor).

Changing coupling caps isn’t modding if you are changing caps with the same values. I did that with my ARC LS5 Mk2 by an ARC authorised tech local to me. Changed the caps to TRT Dynamicaps which greatly improved the SQ.

Modding is when you change the value of the caps to something else or other components on the PCB or PSU to different values.