Pls help me decide Pass Labs X250.8 or Luxman M900u

VACs need to be powered on for Cinema bypass. ModWright preamps can be left off for HT bypass if that matters.

VAC preamps with the Pass Labs X250.8 is a wonderful combo btw. I used that with my Maggie’s and YG’s. However you can turn the Luxman stereo amp into a monoblock should you require more power.

Looking at the impedance curve for 803D4, I don’t see it dipping below 2ohms? I see 3ohms listed as the minimum.

Fwiw. I run my pass 250.8 into my B&W 803 D3 and it is terrific on all accounts. I’ve not used the Luxman amp so I can’t compare the two amps. 

The three brands I’ve heard of (I think) that allow you to run the HT bypass with the pre turned off are Backert, Rogue, and maybe VAC. Considering what you’re looking for in detail and price I think you’re on the right track with the Backert. I will mention that the LTA I recommended above is designed for very long tube life, and the tubes are cheap to replace so may still be worth exploring, but I also think you’ll be thrilled with the Backert as well. Member Terry London compared them in a review I think in Stereo Times a while back and slightly preferred the LTA by a small margin but not sure that outweighs the ability to turn the Rhumba off for HT, which is really nice.

You’re welcome.
You can configure “Processor” through the Ref’s menu and assign any input to it. Keep in mind Ref will turn that input into unity gain so HT processor is all you want to have hanging off that input.

@audphile1 what is the input on the Ref 6 labeled, as I have been looking at the back panels and only see Bal 1-4 and SE 1-4 inputs.

Thanks again for all your great info!

@garynospamm …Ref 6 SE does have a processor feature but the Ref must be powered on to utilize it. If you use your HT a lot, using Ref in that system would just result you in shortening tube life by running the unit unnecessarily. 

@soix I have 803D4’s (not D3’s) but you are correct about the upper registers. I’d like as much imaging, 3dimensionality and life like presentation as possible. I find magic in the small details and how notes can hang in the air.

@audphile1 I would consider a Ref6 SE but (maybe because of my lack of knowledge) thought it would be best to buy a pre amp which has Home Theater Bypass as 60% of the time the system is used for that.

You can turn the Backert off for HT , also it’s much more affordable than the VAC. Have not found a store that had both so I can so listen side by side. 

@OP Late reply as I am no on USA time.

Just two final comments - once the specs don't show any red flags - listen!

Secondly, I wouldn't get hung up on technologies and suggest that you also listen to a comparably priced Passlabs preamp before making a final decision.

@ghdprentice LOL I’m sure. I’m enjoying a Ref 6 now paired with my X260.8 monos, courtesy of my buddy who let me play with it for a week. Sweet combo!

@audphile1 

+1 I agree. I used an Audio Research Reference 5SE for many years with a Pass x350. Is a great combo… although, to me, a way better combo was with a REF 160… but that is another conversation.

@garynospamm if you end up with Pass Labs amplifier, consider Audio Research Ref 5SE or Ref 6 in your price range. Audio Research tube preamps pair extremely well with Pass Labs amps. Speaking from personal experience. 

The Backert Rhumba Extreme really interests me- unless I can find a used VAC Signature MkII SE

These two have different sonic signatures, so at this point it’d be good to ask what sound characteristics you’re looking for as that will make all the difference. Given what you’ve said about wanting to keep the upper detail of your D3s I’d skew to the Backert and also mention the Linear Tube Audio MicroZOTL or MZ3 preamp (depending on your connection needs). I’ll also reiterate my prior recommendation for checking out the reviews of both the Atma-Sphere and AGD GaN amps that are getting rave reviews as being a wonderful combination of tube goodness with solid state control and are upgradeable. Best of luck.

I own M900u along with C900u. I also have Focal Sopra speakers that my friends told me would sound too bright with Luxman, mainly because of the beryllium tweeter. Room treatment is important as others have noted, but  in my book the front end and property matched cables are even more so. Bottom line: look at your system as a whole and not just the two mentioned components to see what will sound best to you. Try to work with a dealer that will allow you to work with multiple set ups until you are happy.

If you decide to look at the M900u, mating it with C900u may possibly be your best option, as they were designed to work together. 

Warmest, regards

I really appreciate all of the responses here!

I’ll update once I make my purchase and have the amp in my system. Will start to focus more on the Preamp now.

The Backert Rhumba Extreme really interests me- unless I can find a used VAC Signature MkII SE

Impedance is fine. 

You’re fine as long as the sound characteristics work for you. 

@audphile1

So, I found this on the Backert

Input impedance: 34,000Ω
Output impedance: Below 80Ω

On the Pass Labs X250.8 specs

So thoughts? Input 100,000 on amp

output on Pre 80ohms so looks good?

@garynospamm

I’ll chime in and I’m sure @yoyoyaya will as well…

few things to consider -

1. The input impedance of the amplifier should be at least 10x the output impedance of the preamplifier.
2. The amplifier input sensitivity and gain - pair a high gain preamp with a high gain amp and you’ll be losing some of the finesse of the preamp volume conttol as well as the volume range.
3. Figure out if you want to use XLR outs on a preamp - most preamps will double the voltage output on the XLR outs compared to their single ended outputs.

If you take the specs of the amp and preamp and reach out to their respective manufacturers, they’ll give you an idea if the pairing will work and or what aspects of sound quality may be compromised 

@yoyoyaya thank for the response , @audphile1  you make a very good point.

what specs do I need to look at to understand if the Backert Rhumba Extreme 1.4 would pair well with a Pass Labs X250.8 ?

https://backertlabs.com/tube-bias-adjusted-automatically/

https://backertlabs.com/more-goodies/

@OP  - audphile1 makes a very important point - it is critical to listen to the pre power combination, even moreso if a tube pre is being contemplated.

@ghdprentice ​​​​@yoyoyaya I’m with you. Not sure what @mtdining heard or heard of but my experience after owning 3 different Pass amps (X250.5, XA30.8 and X260.8) and running them with 8 different preamps (tubed, hybrid and solid state) and 5 different sets of speakers - dynamic and electrostatic, is that the Pass amps are as dynamic and transparent in bass, mids and highs as the signal you feed to them.  There is no lack of high frequencies or any difficulties in the bass. Excellent mids as well. 
Mismatch the impedance between a preamp you’re using and the amps, and you will get crappy, lifeless sound.
Find a synergistic match and you get explosive dynamics that will make the hair on your ⚽️ ⚽️ stand up.

Boulder amps start at what, $20,000? They better be better!

Take this with a grain of salt as I am a dealer for T+A Elektroakustik, but look into the T+A A 3000 HV amplifier. It has the richness of a Luxman or Pass but will control speakers much better than either of them at the frequency extremes. It is stable down to 1 ohm and can drive the lowest sensitivity speakers. It is part of a modular system as well, where you can get a second and them into mono mode, or you can get an optional external power supply which separates the input stage power from the output stage power and give double its capacitance to 240,000uF. 

I use this amplifier as my personal reference and they pair wonderfully with Vivid Audio Kaya 90, designed by Laurence Dickie who designed the B&W Nautilus.

Happy to answer any questions should you have them. 

OP - I also agree with ghdprentice. One particular point of difference ref. mtdining - Pass amps are very refined in the top end, which some may interpret as "a lack of high end". Unamplified acoustic music has an apparent lack of top end compared to most "hi fi" reproduction. It depends on what one's point of reference is.

OP,

Just to point to the reality that your own values and system are the most important aspects in choosing an amp. I completely disagree with @mtdining on every point he makes. This does not mean he is wrong for him. I have 50 years of experience in pursuing high end. I have owned Pass amps for over thirty years and spent a lot of time auditioning Luxman, Boulder, and Spectral. My conclusion is exactly the opposite. Pass exceeds in bass extension, and particularly rhythm and pace… making his amps far more compelling.

This is why you must audition amps in your own system. I am not doubting @mtdining has not experienced what he advocates… just that our values and systems are different.

Pass amps suffer in bass, dynamics, and a lack of high end I normally associate with British sound, compared with Luxman, Boulder, Spectral, Ayre, which are all more lifelike.

Great to hear from you soix!

We have a group of 3 other local audiophile friends, we get together periodically to enjoy a few hours of music and food. It's always casual - nothing extravagant but an enjoyable few hours.

We rotate at each other's house. You are welcome to join us.

I'm seven three two seven seven nine one too five seven.

@tjassoc Very interesting stuff and perspective and hope you post more often.  I’m in North Jersey and going through a similar situation so I sympathize greatly.  Best of luck with everything.  If/when we both get our systems back up and running maybe we can trade some good listening sessions. 

I hardly contribute because of all the negative responses, so I hope I don't regret this.

My experience was with Pass amplifiers, all driving a pair of Wilson Watt Puppy 5.1 speakers - which present a very difficult load, are very efficient and reveal everything upstream. 

One caveat, 3D imaging with a wide, deep and natural soundstage is everything to me. Bass is great but not nearly as impressive or important to me.

- XA-30.5 - amazing imaging, bass was it's weak point but by no means objectionable.

- X - 250.5 - strong bass, what others define as a fast amplifier. Poor imaging in comparison. Both amp's are highly resolving.

- XA-200.5's - had these connected to Sasha I's before going back to the 5.1's. Anyone who hears the system is amazed. Bass is still the weak point but nothing like the difference of the 30.5 amplifier, and the 250.5 still has noticeable better bass - but only when making a direct A/B comparison. Otherwise I never heard anyone complain or even make a comment about the bass because everything is so well integrated.

It's the closest I've heard (with a few exceptions) of being at a live performance (with great recordings of course).

Of what I heard, the X.8 series (I heard the 350.8) has much better imaging than the .5 series but still not the XA series equivalent.

This based on experience.

I never heard a Luxman amplifier. I've heard Gryphon, Constellation and a few other "exotic" brands I expected to be better than what I had. My audiophile associates told me they preferred my system (prior to me making any comments) for it's life-likeness.

Please - I'm not trying to boast as I could care what anyone else thinks. I stive to enjoy the illusion of a live performance in my home. I normally invite anyone in the central NJ area to stop by for to enjoy music for themselves but at this time my system is not operating because my wife serviced me with divorce, and I'm uncertain how things will be settled and my system is currently being dismantled for either storage or sale.

Best, TJF

Had an X250.5, not the .8 and a M800A, not the 900. Both smooth, the Luxman like butter on a hot day.  But, overall (broad brush) it was too smooth and if choosing again for my gear, the Pass would be the choice of the two.

Presently using a Coda 8 and prefer it over all 30 other amps I have used in almost 20 years. I'd get a Coda16 if I could swing it.

Best of luck.

@yyzsantabarbara can totally see it with benchmark ahb2. 
it’s dimensions are 11.04" W x 3.88" H x 9.34 " D - Including feet and binding posts

and it weighs 12.5lbs

The power transformer in my XA30.8 was bigger than this entire amp.

Think quality vs. quantity and this is a case in point. 

With my Thiel CS3,7, a speaker that went down to 2 Ohm a lot, my Benchmark AHB2 did not have a very propulsive or powerful sound with dynamic music. It sounded great with slower stuff.

With a CODA #8, KRELL Duo 175XD, Parasound A21+ the sound was explosive with the same music that was not so great with the AHB2.

Another amp that will drive hard load and is rather good for a low price is the Peachtree GAN400.

Saying all of that I have another AHB2 on its way next week.

The CODA #16 is an amp I would recommend if you like Luxman and PASS. I moved up from the #8 to the #16. It doubles from 150 | 300 | 600 @ 8 | 4 | 2. 

@mtdining can you elaborate? What are the signs the amplifier is not able to manage impedance dips?

Nelson Pass’s heyday was decades ago.

Pass Amos do not do well with difficult to drive speakers. The Luxman is definitely the better choice, at least based one driving Wilson Audio speakers. I can’t abide the B&Ws lack of coherence- the brutal tweeters. All the remaining talent left that company and founded Vivid.

Luxman has trouble with certain speakers....Pass doesn't.

Try a Modwright integrated amp. 220w into 8 400 into 4. I use that on my YG’s and Vivid Giya G2. It has the tube preamp built in! So you will save 10-20k in cables and preamp! I will put this integrated up against 50 grand of separates!

I have experience with Luxman and B&W.  My recommendation would be to find a retailer that sells those brands and get a demo.  I don't think you will like that combo.  Google Ohm's law and you will see that Luxman meets the criteria of how low they go; however, with the combo of B&W I think you will be disappointed and feel like you are missing something. 

The 803D4 has a couple of tough dips in its modulus of impedance but nothing that Pass X250.8s can't handle.

Years ago I owned B&W N803 and drove them with Pass X250.5 and Audio Research LS-25 and Ref1 preamps. B&Ws love power and the X250.5 had zero issues driving them.
I now have Wilson Sabrina that dip to around 2ohms and have no problems with X260.8/XP22 combo. The amps, at normal listening levels below 90db, don’t even leave Class A.

Also, I had XA30.8 driving Martin Logan Montis and the Sabrinas. The MLs have nasty dip to below 1ohm if I’m not mistaking.  The XA30.8 didn’t care. It wasn’t as dynamic and didn’t have the control over the speakers the X260.8 possess with the Wilsons but it still had the midrange and treble magic. 
I have no experience with Luxman amps.

I think you need to find great retailers that have no risk home trials. I have the 250.8 w Wilson Sabrina speakers and Reno HiFi made it possible to try various Pass products. 
 

The best I’ve heard BW 803’s sound was w a McIntosh MC462. Very full and sweet but ridiculously clear. Not fatiguing. 
 

Odyssey audio

Bryston. 

Take a look at the Anthem P2 amp it will go down to 1ohm or less.

I’d take a look at the newer and highly-regarded GaN amps from AGD and Atma-Sphere.  A lot of people are putting these in the “end-game” amp category.  Not only are they getting top marks for sonics, they’re upgradeable as technology improves going forward, which is pretty nice.  Neither quotes power below 4 Ohms so that’d be something to look into given your speakers I’d think.  Just another option, and best of luck. 

Do not look at the XA series of Pass. Yes, they are warmer and fantastic.

However, if you look at measurements, they don’t do quite as well at lower impedances.

But they are fantastic if your speakers’ s minimum impedance is 4 ohms or greater.

I have heard the Luxman u and must agree would not be a good match with the speakers. Having owned a X350 for nearly a decade I would find it hard to believe it would show any negative sonic qualities because of the impedance. However, at least since I like more musical vs detailed / slam amps I would look at Pass XA.

KRELL Duo XD lineup

Are there other amp's you think I should look at?  I understand the Pass XA's are warmer (but also with less dynamic bass).  I think the D4 series overall is less bright that the D3 series and I like the Top End sound already with my 803's from the X5, but I know it can get significantly better.

Definitely not the Pass Labs (which, otherwise, are wonderful sounding) if your speaker’s impedance dips that low.

I had X260.8 monos and now I use the Parasound JC1+ monos for the same reason you mention.

The Luxman M900U should work, but, IMHO, I’m not sure if it is a good match with B&W sound. The resultant sound might be a bit bright and thin despite your tube preamps - but I guess that depends on your room as well.