Switch preamp?

Whoever told you stats work best w/tubes is nuts. Stats place giant demands on amps w/crazy impedances. Plus they need big volts, not watts. Best amp for stats is a Sanders Magtech. Built esp for them.

A tube preamp would be the way to go. Since you have found memories of Conrad Johnson, why not go with that brand ?

Tube preamps with stats are magical. :)

However, OP, you have one cold system! :)

AR and Krell to my ears are pretty analytical and lack warmth. Maybe consider a CJ preamp if you want something mellower, and juicier. I find they are IDEAL with ESL's.

Best,

E

I remember hearing Krell electronics with a chrome faced preamp with three large chrome knobs with blue lights are the controls.  Cannot remember the brand name, maybe some else can help me out. It was a very nice match.  Probably can find one used some where.Happy Listening.

@scott_w   Your statement against using tube amps with Electrostatic transducers is not true in all circumstances.  The best Martin Logan experience I have ever had was listening to a pair of Montis driven by a top notch all tube Audio Research amp. Dynamic, sweet and open!

Before going to far, check the manual of the Krell.  I use to have an older Krell 200 FPB stereo amp.  When I added a tube pre, I had to open the amp up and remove a small jumper(manual switch) connector.  Something about tubes damaging the amp.  The information was in the manual but the location was not so I called Krell and I performed the job with the tech over the phone.

I had Maggie 3.6Rs powered with a Blue Circle 2.1 pre. Absolutely golden. Check into blue circle. 

Ih, and my amp was an ARC VS-110, so all tubes can go well with stats and planars, if there's enough wattage and voltage. 

I guess it is just of these audiophile myths. I would stick with solid state, as did Quad's Peter Walker, once he had designed his first solid state amplifier. I drive my Quads with a Quad 606-2, and that is fine, even if I might one day upgrade to the QMP monoblocks for more power (power is king).

Yes, Erik, outside of the speakers the system is old and maybe it's time to bite the bullet and replace both the amp and preamp.
Vegas, the manual makes no mention of altering the amp to accommodate tubes, although I would call Krell before installing.
The Krell is probably in the 25 year range and I suspect AR LS 10 equally old. The Krell performs flawlessly -- no hum -- and has plenty of power, rated 500 watts per channel into 4 ohm, so the question then becomes will the sound be appreciably richer/ better if I switch out both the amp and preamp when compared to just replacing the preamp. (An audiophile recommended I sell the Krell and go with Prima Luna's Dialogue Premium HP mono blocks.) 

I appreciate my knowledge is notch above a layperson, nevertheless my ears are good and I spend at least 2 hours a day listening. Consequently, because of my age and the amount of time I devote to my passion it is crucial for me to get it right this time around. Your comments are greatly appreciated.

No reason to expect any sonic improvement from changing the Krell (your electricity bill will be lower with a pair of bridged Benchmark AHB2s, however). Just get it recapped and you are good for ages again.

OP:

When I said the system was "cold" I really was talking about the sound of the gear you purchsed, not so much the age! :)

Best,

E

 I use to have an older Krell 200 FPB stereo amp.  When I added a tube pre, I had to open the amp up and remove a small jumper(manual switch) connector.  Something about tubes damaging the amp.  The information was in the manual but the location was not so I called Krell and I performed the job with the tech over the phone.

Despite Krell's remonstrations this bit about tubes damaging the amp is a myth. Its based entirely on a single customer's preamp having a failed coupling capacitor; which is the sort of thing that can blow up an amp whether the preamp is tube or solid state!

Regarding the ability of tubes to drive ESLs and Martin Logans in particular:

The issue is that of impedance- Martin Logan makes ESLs (which normally work best with tubes) but to try to get better solid state compatibility (and thus a larger market) they keep their impedances down. The typical Martin Logan is 4 ohms in the bass and 0.7 ohms at 20KHz.

You can correct this with a set of ZEROs (www.zeroimpedance.com) and then a wide variety of tube amps could be used. Of course, many tube amps will work with this speaker if you use the 4 ohm tap even without the ZEROs.

notesaddict
 I am happy with the sound but ...

Sounds like audiophilosis. I have it too. My system sounds better now than ever before. Yet I keep looking at tonearms and lately, tube  amps. Before that tube preamps. I can give good reasons for wanting to change. My tonearm  (OL Illustrious) was suppose to be temporary til I could get better. That was 7 yrs ago. My amp & preamp are opposite of the audiophile standard. Tube amp and SS preamp. Never mind the preamp is a Stereophile class A (CJ PFR)....its old too. My amp is too cheap to be audiophile approved  (Bob Latino ST-70). But it replaced a $4k SS amp and put it to shame. I have a feeling that despite the system sounding fantastic now, I'm going to change something. So far all my changes have been for the best. But the odds are against me at this point. Surely I'll make a change at some point which will destroy every bit of the synergy in my system. Even though I know this, I keep looking.  
FWIW, I like CJ gear. I'd also consider the Primaluna.  Also, Don Sachs makes a tube Preamp which gets rave reviews by its owners. He also makes a KT-88 Tube amp which he claims is better than the Citation 2 amps he rebuilds for Jim McShane. Both will cost you a little over the $5k budget. He may even give you a short audition period. He is very personable and easy to talk too
Also, Bob Latino makes an M 125 Tube mono blocks which get very good reviews and are about $2800 with tubes. Again, great sound and Bob builds a good product and is very good with customer service.
Good luck with whatever direction you go.

Artemus, yes, a case of the perpetual audiophilosis with diminishing returns. I perused Sach's comprehensive website; compelling. I am going to give him a call. Thank you.

Artemus, I communicated with Don as suggested and just made a deposit on a preamp that should be ready in 12 weeks. 

notesaddict. Glad I could help.  It sounds like Don is quite backed up. Did he offer you an audition period? From my remembrance he uses top quality parts in his amps and preamps. I probably should have bought one of his preamps last year when I talked to him. I believe he has raised his prices since then though I believe he has upgraded some parts he uses since I talked to him.
Please keep us posted on your impressions of the preamp after you get it.

I didn't ask to audition, being that he's custom (I ordered all the upgrades) making it for me I figure it should be my risk. I'll keep you posted. Thanks.

I am going to second Scott_w's recommendation for a Sanders Sound Magtech amp.  It's especially made for electrostatic speakers like the 13a's.  I have been using one with my Martin Logan Montis speakers and the combination is a true dream!  I have tried amps that are thousands more from my local dealer and only have to send them back, because none could touch the Sanders Sound.  The Magtech has been an Absolute Sound best buy for many years.  Mr. Sanders builds them in CO and has a generous 30 day trial period.  At $5500, it is truly a best buy and likely the last power amp you will ever buy.  

For preamps, there are more options I feel.  I personally use a Classe Sigma SSP processor since I also need home theater duty in the same room.  It works great for my needs.  But eventually, once I move to a larger house with a dedicated hifi listening room, I will likely get a true two channel preamp.  Top contenders are ModWright LS 100 ($3750), PS Audio BHK Signature preamp ($5999) or if I am on a tighter budget a Backert Labs Rhumba 1.1 ($2250 on clearance).  I've listened to the Backert and ModWright at HiFi audio shows, so I know they are good.  The common thing among all of these is that they have tubes in the output stage.  I think a tube preamp like these marry well with the solid state Sanders Sound Magtech.

Kind regards and best of luck,
Jason

Jason, thank you. At the end of the day I couldn't part with my Krell KSA 250s. I spoke with Krell tech support and they said due to its age recapping is a must; +/- $1,000 plus shipping. At the end of the day it should sound far superior after 25 years of degradation. Then, based on Artemus suggestion, I started a dialogue with Don Sachs. He knows his stuff and I felt I was in good hands. Because of my age this will probably be my last chance -- I've said this with each upgrade -- to get it right and consequently ordered the best he has to offer for my system. So, some time within 3 months I should have a Don Sachs tube preamp (it's well worth checking his Web site) feeding a rebuilt Krell powering ML 13a. A lot of angst, a lot of reading.... we'll hear.

If you enjoy the sound of the Krell (great product), then a recap is going to bring the life back!  Getting over 25 years out of something is an awesome feat and shows the value you have received from such a product!  

Looking forward to your thoughts on the Don Sacks pre.  I'm always open for good recommendations.  

In the end, it's your ears and no one can argue with that.  :-)  

To my ears the best combination with my Martin Logans was Cary tube preamp with pwerful class A solid state power amps.  I tried several different power amps matched well in this scenario

Well, I finally have my Don Sachs preamp along with an entirely new system. What started as simply replacing KEF, Polk bridged speakers with Martin Logan 13a ended in a completely new system comprised of the Sachs preamp, PS Audio’s DAC and CD player and Krell 575 monoblocks (while I was getting my Krell KSA 250s recapped, I received a trade-in promotion e-mail that resulted in the monoblocks).

It should not go without saying that what was a stressful endevour was made palatable by the fine people at Krell, PS Audio and Don Sachs. If I was ever to jump back on the merry-go-round, which I won’t, I’d undoubtedly go back to the mentioned companies due to their service being above reproach. Fine people.

Humbly, my system is fantastic. In good measure I have the Audiogoners who recommended Sachs to thank. It was well worth the 4 month wait. The preamp far exceeded my expectations.

After 50 years my rabbit hole is filled, well, almost, there’s still some interconnects and power cords to consider...

I am going to second Scott_w's recommendation for a Sanders Sound Magtech amp. It's especially made for electrostatic speakers

@jasonsim Sanders loudspeakers use a conventional woofer for the bass. In this way they avoid the high impedance in the bass that is often associated with ESLs. It is that reason why the Sanders amp works with ESLs; and because of the low overall impedance of the Martin Logans, why it works with your speakers. Other ESLs such as the Sound Labs challenge the amp as it does not make power into higher impedance load, like most solid state amps.

notesaddict,
Congratulation, looks like you went all out and didn’t make any compromise in your selections. Aside from the power cords for those beasts, you should also consider dedicated 20amp circuits so their feeding is not shared with other parasitic consumer electronics or lights in the house. Those pesky promotional emails work...

Thank you. When it dawned on me that this is my last system, the days of upgrades are a thing of the past, compromising was not in the cards. Fortunately, I don’t have annoying hums to contend with so a dedicated circuit board is unnecessary, although tomorrow I am ordering Krell’s Vector power cables.