ARC LS25 with PASS X250 - bad match? Seems bright.

I just switched my amp from an arc VT100mkII to the PASS X250. Upon doing so, I heard more brightness and even harshness in my system. I have heard that the PASS amps are not bright, so I am suspecting either a system mismatch, or that the X250 is more linear and is revealing another source of brightness in my system, that the tube amp perhaps was masking.

Rockport Mira Monitors
Wisdom SCS Subwoofer
Audio Research LS25 mk I
Bryston 10b Sub crossover
Cambridge DacMagic
J.A. Michell Tecnodek
Dynavector 10x5
Cardas 100b microtwin balanced interconnects
Cardas Cross speaker cables

I am having a feeling that maybe my source components are not up to par with the rest, and that may be the cause of the harsh brightness at times. Or, that the PASS does not like the ARC LS25. What do you think?

Do you hear the brightness with all your sources equally? There could be a potential impedance mismatch. ARC suggests that the minimum load the LS-25 sees is 20 Kohms, abd the X250's input impedance is 22 Kohms. So you are threading the needle. Do the X250s have single-ended inputs or only balanced (XLR) inputs? I ask because the output impedance of the LS-25 is higher via balanced vs. single-ended connections, so it could have less control over the X250 via balanced connections. My guess is the LS-25 has a highish output impedance in the bass region and you are getting attenuated bass as a result of the mismatch and so the sonic picture sounds tipped up and bright. If all your sources sound equally bright, my bet is that is what's going on and you would be better off switching back to an ARC amp or if you want to stick with a SS amp, you should get one with a minimum input impedance of 50/60 Kohms. Of course the best way to do it is to audition whatever amp you get to replace your X250. The other option is to replace your LS-25 with perhaps a PASS pre amp that has a very low output impedance and keep the X250.

GGood luck.
I don't know the VT100, but the X series Pass amps, in my experience, will produce more treble energy than many tube amps. I recommend you live with it for a while and experiment with small adjustments to your system and see if maybe you can get it to a place you like before making a major change.
The Dacmagic is known to be a little on the bright side. You can look for a warmer sounding digital cable, but the fact remains your DAC is not up to the level of the rest of your system, so the sound will always be compromised even if you tame it down. Also, you never know what you will get when mixing amps and preamps from different manufacturers. If you are still not satisfied after improving your source you should either go back to an Audio Research amplifier or get a Pass preamp. When the amp and preamp are matched there is always a rightness to the sound that cannot be achieved by mixing brands.
Interesting, thanks guys. I was considering replacing the arc preamp with the pass x1. Originally, I thought the tube preamp would warm up and tubify the sound a little. But If the reality is different, and I am just mismatching the system, perhaps a pass preamp is the way to go. Thoughts?
- Mark
X1 is not the right choice to warm up your system. The xp series would be a better choice. Or BAT or Cary or Conrad Johnson for tubes.
The Rockports certainly aren't your problem, and I doubt its your cabling. I will assume what you describe is on all sources, with and without your sub. I have heard an ARC pre, and Pass amp once, with what I consider to be a warmer speaker. It did sound a bit forward for my taste, to be polite. I heard Rockport Ankaa's about 3-4 years ago, and they sounded great. Source was digital, an Audio Aero Capitole Classic. Preamp was a Shindo Monbrison, amp was believe it or not, an ARC Classic 60. I was wanting for very little. Again, assuming your cartridge is properly matched...! I hope this helps. Very nice system, BTW!
Swanny, what do you mean exactly? Is the x1 bright? From the grapevine, it may be the mismatch between the x250 and the arc LS25 that is causing the unwanted harshness/brightness. Would a perfectly mated X1 & X250 be less bright than a mismatched x250 & ARC LS25?
I used an ARC LS25ll with Pass X250 without any brightness issues, and thought it was a great combination. Have alsoi owned a Dacmagic and agree it is not up to the quality of the Pass or ARC.
I owned a VT100mkII, & it's pretty neutral sounding "for a tube amp", but still, it's unmistakably a tube amp. Why did you want a different amp?

I looked at your cables, they're on the "budget" end of Cardas cables, is that right? My experience is that the "budget" Cardas cables are not that great, you have to go to the higher end Cardas to really get the sound Cardas is known for. So I'd really put cables on the list of possible upgrades, along with the DAC, apparently.
I own an LS 25 mk1 and sometimes find that it tilts the sound a bit to the "dry" (rather than "bright", per se) side, depending on the character of the the balance of the system. Relative to my Joule preamp, for example, the ARC sounds a fair bit less tube-like thru the upper registers. If the Pass leans that way, too, it's possible that the combo could sound a bit bright/dry/analytical for some tastes.

Just one more data point for you to chew on.

Marktomaras, about the X1, the only way to know how it might interface is to try in your system. Too many variables to know otherwise--cables, speakers, room, etc, in addition to the impedence of the pre to the amp. I will say that the X1 is voiced to the cooler side of neutral, based on my own experience with it in my system. I used the X1 for about a year. It does many things very well, but I prefer the overall sound and lower gain structure of my current XP10, in my system, and IMHO. Of course, YMMV. Good luck and keep us posted.
let's first establish that brightness is the perception of excess sound pressure level in the upper midrange/lower treble.

it may be the result of subtraction in the upper bass/lower mids or a peak somewhere in the range 1000--3000 hz.

ok, what could be responsible for this. ?

i assume you did not notice this with the vt 100.

it is possible that there is an impedance mismatch between amp and pre. it could be that the ls25 has problems. it could be that the pass has problems. or, as you say, there may be something else about the pass/ ls25 combo that is creating the problem.

i would try other preamps, to see if the problem persists.

as has been suggested, there may be problems with other components, which the pass, being less "colored" than the audio research is revealing.

my experience with solid state is that there is also a speaker amp relationship which needs to be considered.

does the rockport have a metallic tweeter and where is it crossed over from midrange to tweeter ?

why did you replace the audio research with the pass ???
Some people may disagree but I think part of the problem is the X250. I had one in my system and complained that it had too much midrange and high energy. Great bass control WOW!!! I have also heard the VT100 and loved it. Night and day difference between it and the 250. The X .5 series is supposed to be much smoother than the original series from my understanding. Overall I didn't keep the X250 very long. Also I think it depends on other factors but your cabling is on the smoother side so its hiding even more of the brighter aspects of the 250. Personally I would keep the VT100 and try more neutral cabling to open things up more. You might be surprised. I had the Cross speaker cables and while they were a step up from my older cables they are not known for neutrality or openness. Cabling is very important or at least has been for me. Just my 2 cents.
Steveaudio makes a good point about the Cardas cabling. Once I upgraded to better cabling the sound really opened up. The VT100 is a very nice amp.
Thank you very much for the advice and thoughts. I thought I would try the pass x1 with the x250. The sound is still harsh in the highs. I thought that is what bright means, but perhaps my lingo is not precise or accurate.

We are talking the high frequencies of vocals, some high drums, definitely cymbals, and other treble. It sounds harsh, and well, bright!

So, enter the X1. Still sounds similar. Harsh highs. But now I am lucky, that though my audio research amp and preamp are for sale, they haven't sold yet. So I will set all of them up and do a proper comparison between the arc amp & preamp and the pass amp and preamp.

My sources still may be contributing, but at least I'll know which amp-preamp combo I prefer. I sort of really want to love the pass gear. I am attracted to the significantly less maintenance they require over the tube gear. But who knows, if the audio research stuff sounds way better, maybe I have to rethink about which units to sell!

I'll do this test on Friday, and I'll let you know what happens.
ARC products are bright sounding, more like solid state. Pass is not a bright amp.
Agree with Samzx12. I have an ARC LS25 Mk I with GNSC ref mod driving the Pass X350.5. Speakers are Verity Parsifal Encores. No problem with impedance issue. Prior to getting my amp, I had listen to it in a side-by-side comparison with the X-350 at a friend's house. Speakers were Avalons. We had also compared the ARC Ref 2 Mk I and the Pass X0.2 driving the X350.5 at a later date.

Next to the X350.5, all 4 guys conducting the test that day agreed that the X350 sounded bright, cold, and "solid state", while the .5 version had the signature warmth and musicality that Pass had been known for. The difference, we all thought, warranted more than a ".5" upgrade status.

The X0.2 preamp sounded more tube like than the stock ARC Ref 2 Mk I. All the other 3 panelists voted for my friend to keep the Pass pre and ditch the ARC. But I voted for the ARC. My reason was that if he replace the Sovtek tubes with some NOS tubes, the ARC would have more of that tube magic in the midrange.

I've just had that experience myself. I had just moved back into my house in May after a 2-year major remodel. My system now sits in a dedicated room. I had plugged in some early Rusian tubes into my LS-25 and forgot all about it. I thought my system sounded a bit lifeless and dry in my new room. About a month ago, while I was cleaning I realized that I had Russian tubes in my pre. I swapped them out with some Amperex 6DJ8s and now it sounded much better.

Phillyb I have to disagree 100% that ARC is bright. My buddies VT-100 is anything but bright. The Pass X .5 series is smoother than the old series for sure.
Did Marktomaras ever come back with his comparisons? I would like to know how it turned out.