Audio Research LS2B mk2 cap ugrade

I used an LS2 with Classe CA-300 for several years so I can relate somewhat to your situation. I tried several cap upgrades on my LS2 which mostly brought it up to MkII status, i.e. replacing a number of RelCaps with MIT caps. Your preamp already has the MITs which are a pretty good sounding cap IMO. I have no doubt, however, that V-Caps would sound better based on my testing V-Caps in several components (but not the ARC). There are a couple issues though. First, if you are using the LS2B in balanced mode, you have 4 output coupling caps to replace. As I recall, the output caps were a 5uf MIT (with a .01uf MIT bypass) for the single-ended outputs and either a 1.0 or 2.0uf MIT for the balanced output (also with a .01uf MIT bypass). You do NOT need to use the same values for replacement caps. The Classe amp has a pretty high input impedance so a 5uf is total overkill. If I were you, I would replace the 5uf caps with a single 1.0uf V-Cap per channel and no bypass cap. If you are using the preamp single-ended, you do not need to replace the output caps on the balanced outputs. If you are using it balanced, then replace the 1.0 or 2.0uf caps with again a single 1.0uf V-Cap without a bypass cap.

There are other caps in the LS2 circuit that affect the sound quality such as the bypass caps in the power supply, but you will get the most bang for the buck with the output coupling caps. Therefore, I would do them first and get a good feel for how they sound before tackling any other parts. It is possible to have too many V-Caps.

Here's another factor to consider: The ARC circuit boards are double-sided and each cap lead is soldered on both sides. This makes for a very reliable connection but also makes it difficult for the average solderslinger to replace parts. It can be done but it's not as easy as you might expect.

Dave

I disagree with that. You should retain the same coupling cap values. Changing the value of the coupling caps to smaller values may cause the low frequency bandwidth to shift and possibly cause more phase shift below 10Hz. Keep the values the same. I have updated many ARC products and I don't stray from their values. Also, whatever cap you decide to use for the 5 mfd., change out the .01 as well with the same brand cap. Don't mix them. Were you planning on replacing the film bypass caps in the power supply as well?

Hifigeek1, That's why I mentioned the Classe amp's input impedance which is fairly high. As I recall, it is 68K. It is true that a lower value output coupling cap will cause the bass to roll off sooner, but in this case it won't have any practical effect. A 5uf cap into a 68,000 ohm input impedance will have a -3db roll off frequency of 0.46 Hz. That's virtually DC. Lowering the cap value to 1uf will increase the -3db frequency to 2.3 Hz. Not a problem. It could be a problem with a very low impedance amp but the LS2 isn't really designed to drive low-Z loads.

A more practical issue is the cost of V-Caps. For the TFTF V-Caps, a pair of 1uf caps will cost $405. A pair of 3.3uf caps (the largest value) will cost $1050.

Replace the caps on the power supply bypass, I could yes. Trying to get ideas of what to do with this thread and articles that are on the net. There are caps on the board listed as 625 and the equivelent with V Caps are rated @ 600v, I dunno if that will be an issue, I have no knowledge of electronis except what I can edjucate myslef with. Upgrading with sheilding and other stuff may not be anymore than a tweak, I have talked to a company does upgrade work and that is some of the upgrade work they can do. I am lookin for the best impact, I'm thinking it will be in the caps. But I don't wanna go overboard too much with stuff like sheilding and this and that when I can put that money towards a ARD Ref 1 when the funds come into great supply, I had a chance to get a Ref 1 a few years back for $3200 and I am still kicking myself for not doing it. But when I say get a Ref 1 the LS2B can be run on the SE part of the amp, I always use 2 preamps, with it, SE and BAL.

The voltage rating isn't an issue. The voltage is a maximum rating; as long as you operate the caps at less than the maximum, you're ok. The highest voltage in the LS2 is around 425v. A cap rated at 450v or above will do fine.

I still think you will get the most bang for the investment out of a pair of 1uf V-Caps on the output. Beyond that, I would be thinking about replacing the preamp with something else. By the way, I would also recommend using the V-Caps without a small bypass cap. That's what the V-Cap mfr recommends, and I prefer them that way in my own equipment.

The input, I think if it follows suit with the rest of Classe amps because Classe does not list the manual and without sending a email to Classe, the 100-101 and 200-201 are 75 kohms while the 300-301 and 400-401 are 16 kohms.

I have also used AR LS9 with it with a Krell Showcase DVD, that was a nice combo but I did not like the stepped volume on the LS9 as it did not have enough steps.