Anybody using Wilsons or Soundlabs with Pass Labs?

I have a customer who had the Pass 600s driving the Sound Labs UB-1s and it worked well....The Parasound JC-1s worked enough better on the U-1s and UB-1s that the Pass 600s went away as did the OTL amps he used above 150hz.....

1. Fdriver I agree with your well-stated points. The aleph series if I recall correctly has a higher output impedance than the X which *may be* a better match for the SL in the low frequencies. However with the old crossovers I found the low power ones clipped with heavy brass, etc. That being said the Wolcott or the OTLs are the best amps, IMHO, for the SLs. I was going to biamp with Alephs but got Wolcotts instead.
2. Why doesn't Stereophile,etc. test the FR, etc.,of the amps under test with the speakers that the reviewer is using? This would show true system interaction. The dummy IHF load is only somewhat germane to the system context. The tests they do now are at best academic and irrelevant...ok, they do reveal the basic quality of the amp but if the amp shows 10% distortion it should be sent back to the manufacturer before it is reviewed. Sounds like Fdriver's own tests are more relevant and systematic, even though the results cannot be used to make universal statements, but why should they?

The purpose of my post was not to "insult" the Pass Labs X600. I was mearly pointing out that the amplifier's bass performance (Sound Labs can hit 50 ohms or higher here!) is not acceptable. This includes playing the same recording on other speakers and taking into account the expected bass on a variety of other speaker / amp combinations. I also use test CDs that put out bass tones; the Pass just didn't like the Sound Lab impedance. That does not mean the Pass is a bad amp; in fact, when paired with the appropriate speaker, it is an outstanding amplifier.

The true test of being a real Audiophile is acknowledging that not every component in Stereophiles "Recommended List" will work correctly with other products on the list. The key is to build a system where each of the components compliment each other, instead of exposing weaknesses such as impedance issues - low or high. This is not an easy process, but very rewarding when done right.

Fdriver has an interesting perspective. One could order/update with the SL biamp option. One could then put Alephs or X series amps on the top end and perhaps Wolcotts on the bottom, or MAs if you wish. Or even 4 channels of Pass amps, if your electrical system is up to it. I believe the new crossover configuration offered as an update by SL would lessen the bass taste issues some of the correspondents cite. I feel recordings vary in bass impact much more than the excellent electronics all the correspondent refer to. Others, credible others, have used the Sunfire 300 watt on the bass and the Wolcotts on the top. HAve fun!

Ferrari, Did you see Roma's post (Should I sell my Diva?) Could it be there is a dichotomy in perception when it comes to bass response? Shall we say, hi-fi bass, found only in audio, epitomized by truck bed mounted mega woofers, versus natural bass - like the baritone and kettle drum. I would want an amp that gets the texture and timbre of these big wave producers right rather than an amp that will substitute accuracy for cracking the plaster. My X-600 is of the former.

I have a pair of Wilson W/P 6 and tried a Pass 350 when I was looking for amps. The Pass was a very nice amp but just didn't do it for me. There was nothing wrong but I felt the magic wasn't there. I ended up with Atma-Spere MA1. The only thing I can suggest is giving them a listen.

Wow! what a lot of interesting responses. I would have never guessed the Aleph models could give satisfactory service on the big speakers.

Yes - I did. I tried a Pass Lab X600 with a pair of Sound Lab Auras (similar to Milenium series, but made of steel like Ultimate).

I also got to compare the X600 with Krell KSA 300S and Atma-Sphere MA1 mkII.2 OTL tube amps.

The results:
Atma-Sphere had the overall best performance, with the Krell a distant second. The Pass amp had NO BASS whatsoever to speak of. I suspect the Pass amps do not like the high impedances that occur in the mid-bass region.

DO NOT recommend you pair the Pass amps with Sound Lab speakers. However, I will say that the midrange and upper frequency performance was outstanding.

I'm using Aleph 1.2's with a pair of Apogee Duetta Signatures. These replaced a pair of Krell KMA100 Mk 2's.

They are a very synergistic match. Bass is slightly less in quantity but much better in definition. The mids and highs are far superior and sweet.

I use a Pass Labs X-1 preamplifier and a pair of Aleph 2 with Wilson Watt/Puppy 5.1. If you're no bass fetishist this is an excellent combination.

jameswei, my understanding of the P is that your left and right gain should be set to as far left or 0 as possible while the volume should be as far right or 9.9 as possible making certain that the amp is not being overdriven.

The purpose of these settings is to minimize distortion while receiving maximum volume through the volume control with the shortest signal path possible. The volume control can then likely be wound right out to 9.9 without ever using up the amp.

The gain settings you describe are adding distortion to the listening material and the sound levels I suspect are on the order of minimum 107db @ 16watts continous and a mind numbing/ear killing 119db @ 256watts. So I suggest that you back the gains to 0 or left and the volume further right or 9.9 for improved clarity. I would not be concerned about getting to 9.9 and system integrity, I might be concerned about my ear components.

My P settings are .5mv Helikon, 64db Krell phono stage, 0 gains and full on P volume providing 88-95db intermittent @ 1 metre via 87db efficiency speakers in a 8x16x26' half live/half dead room driven by 10% of the power of your mammoth amp with an Aleph 5. Room RT60 is approximately calculated @ 125hz/.44... 250hz/.68... 500hz/.69... 1Khz/.68... 2Khz/.55... and 4Khz/43

My sound levels are high enough the only thing my system is missing that yours has is the incredible dynamics the Wilson's deliver and almost a full octave of depth.

Way off topic here but the gains should be addressed... otherwise I love the combo!

I tried the Aleph series on sound lab A3s and they were excellent within their power rating. Very natural, detailed, with good imaging. If one could find a pair of 1.2s one would be happy indeed.

In my primary system, I am driving a pair of WATT/Puppy 6.0s with a pair of Pass X600 monoblocks. The sound is smooth and seamless.

All frequency ranges are well presented, with extended highs, even midrange, and OK bass. The best is the midrange. The Pass' liquid control of the midrange plus my particular room acoustics work to tame the slightly hot upper midrange character of the WATT/Puppy 6.0s. The bass is fine, in good proportion if not really socko. The speakers tend to roll off in the bottom octave, so I have two Sunfire True Sub Signatures filling out the foundation. (Reputedly, the WATT/Puppy 7s go the distance in the bass.) With the right subwoofer blending, I feel no lack in the low bass.

The relative efficiency of the speakers combined with the high power of the amps provides for plenty of headroom and a very dynamic sound, which is an aspect I personally find especially appealing. I don't sense anything is lost in terms of detail and delicacy at low and mid volumes either. Soundstaging and imaging are solid and stable, leaving me nothing to be desired.

A Pass Aleph P preamp has been a good fit with the X600s. Notably, this one has left gain, right gain, as well as an overall volume control. The sound is noticeably more dynamic with the gain controls set past 11 o'clock, independent of the volume control setting. To improve the dynamics, I have set some of my source components to lower output levels in order to turn up the gain controls to 12 o'clock or higher without losing my control range with the volume control. I don't understand why -- theoretically, there shouldn't be any difference between high gain control settings with a low volume control setting versus low gain controls with a high volume control, should there? Is this what they're saying about loss of dynamics with passive preamps? Does the patented volume control that is used on newer Pass preamps address this? Dunno.

The Pass X600s replaced a pair of Bryston 7B ST monoblocks, which in comparison sounded punchier in the bass, a little warmer/brassier in the midrange, and very slightly harsh in the treble (through the same speakers). Perhaps my Audioquest Dragon silver conductor speaker cable exacerbated this last. (Also using Audioquest Amazon silver interconnects.) Best Regards.