Pass Labs amps. Help me choose.


Speakers: Focal JM Labs Electra 1037BE
Room: 15 x 20 x 10 (w x d x h)
Listening Volume: typically 70 - 80 db at listening position. occasionally peaks at 90 db with symphonies (Mahler, Tchaikovsky). Rarely if ever above 100 db.

First a little background. I had an opportunity to audition X-150.5 at home, and I instantly fell in love. I have a stereo + multi channel music system, and I need five channels of amplification. I have immediately acquired X-3 for center and rears, and have been looking to get X-150.5 or X-250.5. In the mean times I was using X-3 for fronts and center duties. I had B&W Nautilus 804 speakers back then.

Fast forward a few months, I have replaced B&W with Focal Electra 1037BE. Focals are wonderful speakers, but it turned out they are a mismatch for X-3. When driven with X-3 the tonal balance is noticeably lean. X-3 couldn't control the bass and dynamics, and loud transient became muddy. Not a big deal, as my intention was to use X-3 for center and rear anyways, but I still needed amplification for the fronts. I've then acquired Levinson No 335 to drive Focals. With Levinson the bass control and dynamics are back.

Objectively, No 335 is an excellent amp and I could happily live with it for a while. However I am still partial to Pass Labs, and I would like to get a proper Pass amp for my speakers and compare against my Levinson. I do miss the musicality and the ease of flow with the previous set up with Pass amp. The amps I'm currently considering are the following:

X-350.5
XA-100
XA-100.5

X-350.5 and XA-100 are within my budget. XA-100.5 is a somewhat more than I would be willing to spend on amps. But if it comes down to only XA-100.5, then I am willing to take a leap.

Obviously my primary concern is whether the amp can drive my 1037BE. They are not an easy load where the impedance swings from 3 ohm in low bass to 18 ohm in upper midrange. X-3, a sibling of X-150, had problems driving my speakers. Personally I would choose XA-100 if it doesn't show the problem X-3 did and can drive my speakers with correct tonal balance. I don't know if it can or can't. X-350.5 looks great too. Two concerns with X-350.5 is that I don't want to pay for the powers that I may never need (350W @ 8 Ohm and 700W @ 4 Ohm is really a lot of power), and I may later regret not getting the XA series and just "settle" with X series. Then XA-100.5 would probably be perfect, but with about 2x the cost.

That's where I'm at right now. If you own any of the models listed above please let me know what speakers it's driving, and how you like / dislike about your amp. Thanks,

jlee
jylee
You don't need the power of an X250.5 or X350.5 with the 1037 BE. The sensitivity is sufficiently high enough and the impedance is relatively flat at 8 ohms.

A pair of XA60.5 will do the job just fine.

Dealer disclaimer.
Completely agree with Bill (Audiofeil). For your stated application the XA60.5 will offer the most refined sound for the dollar. The key is the tame impedance curve at 8 ohms coupled to the high sensitivity... You get 60 wpc rms clean class A power (120 wpc peak) versus the ~20 of the 250.5 or ~40 of the x350.5. Visit the website to learn more specs. The XA.5 amps are the pinnacle of Pass Labs and will have a leg up sonically, given appropriate system match. In your medium room with those speakers the XA60.5 should be the bomb.
French fries,

I had a ML 333 for 8 years driving a pair of Thiel 3.6s. I had thought it was a good combo, but slightly veiled. For 3 years, I had thought maybe the Thiels were the weakest link in the system, and that they would be the next item for me to upgrade.

My 333 had suffered blown capacitors three times during those 8 years. Twice under my ownership, and once under the dealer's care (I bought it as a demo, and found out last year from Harmon that the dealer had sent it in for repair once for the same issue). Harmon had switched their capacitor supplier after taking over from Madrigal. And the amp sounded better with the new cap. But after the third incident, I was ready to part with ML amps. (I still do have high regards for the 33 and 33H. I think they are miles ahead of the regular 33x series)

But the 33x series is nowhere near the Pass X350.5. I was in awe when I first hooked it up to the Thiel 3.6. With the X350.5, the Thiels had bigger soundstage, deeper (and more) bass, and the midrange sparkle. It made the ML 333 sounded like veiled, flat, and uninspiring. (And the amp has not even been broken in) I had a few friends come over to listen. These guys are very familiar with Thiel 3.6s, either through listening to my and other friends', and/or they had lived with a pair of their own. Everyone was scratching their heads, as they had all thought before that I had pushed the Thiels pretty much to "its limit" with my old setup.

For a while, I had seriously thought about keeping the Thiels longer. But my upgraditis was acting up, so I traded them in for a pair of used Parsifal Encore. (After 15 years of Thiels 2.2 + 3.6) The Parsifals are easier to drive than the Thiels, and sometimes I think the X350.5 is an over kill. But it's better to have more power than not.

FrankC
Thanks all for the recommendations. I was under the impression that 1037BE is not an easy load. Just how does one determine whether the speakers are an easy load or not? The impedance curve at stereophile web site looks pretty nasty to me. The average impedance may be 8 Ohms, but the impedance swings from 3 Ohms to 19 Ohms.
Jylee,
The impedance is frequency dependent. Which of course is music dependent. Given your favor of classical (and not pop or rap with high rms (average) energies of 30-40 hz) and the fact that we are talking about Pass amps (very stout) the recommendation still stands that the XA60.5 would be more than enough power for your application.
3 ohms is not a big deal; it's not like its the average. In fact the average is higher than 8 ohms. But they have to dial it in to an industry standard for marketing. Again, the key is (mainly) the higher than market average sensitivity and relatively benign impedance curve.

The only TRUE way to know is to buy the amps and see if you have a match in your system (acoustic space), but I would bet real money they have enough juice to satisfy your listening habits.