Pass Labs x250.8 vs tube amps


I have a beautiful system. Lumin X1 > BAT Rex 2 pre > Pass Labs x250.8> Sound Labs M545 (ESL) in a tiny room (9x 11 ft).  This system has the most glorious SQ: smooth, detailed and powerful , along with great bass. I would say this sound equals or betters any ultra high end system. HOWEVER, I have a problem. My system takes 6 hours of music playing to sound this good. I had X250.5 and I had the same issue. Leaving it on idle overnight doesn’t solve the problem. It is 15 W class A, so it generates quite a bit of heat, and yet I have to still play music. Because my room is small, I don’t crank up too much- maybe this is the problem, but the temperature doesn’t complete stabilize for 5-6 hours. The top reaches 107 deg in 2 hours, but the front plate doesn’t reach 107 until the 6 th hr when it starts to sound glorious. I have never had a tube amp and I am wondering if I can reach that thermal equilibrium and the glorious SQ faster with a tube amp? I worried about the heat generation with a tube amp in this small room, but X250.8 generates 450 W just idling. This is no worse than tube amps like Audio Research 150 Se, which I demo’d and was impressed by. BTW, I need power in the amp because of the esl speakers.
What do you all think?

128x128chungjh
@chungjh
BTW, I need power in the amp because of the esl speakers.What do you all think?

To: @chungjh
I don't typically recommend dealers, in your situation it could be worthwhile to correspond.  A local home audio dealer (Deetes) here in northern California USA has been in business since 1967, offers SoundLab speakers, sold Pass, more AudioNote and QuickSilver today.  Primarily traditional TUBE amp systems only - that's his real passion, and specific electrostatic speakers.  He's actually been selling SoundLab speakers as long as anyone around the world.  I've known him for 42 years, seen and heard a lot of gear there new, used, trade-ins. A real treat to hear Soundlab there.  Its a special place, last of its kind. 

The first time I saw and heard my own mono block tube amplifiers they were playing with massive SoundLab speakers there. Deetes is a big fan of your SL 545s too.  Email and by appointment only.  In business 53+ years.  

Deetes Sound Room
Deetes Andersen deetessound@hotmail.com
Former related thread four years back, some good replies by Agon’ers, @atmasphere

Thread: "Why Warm Amps Sound Better".

https://forum.audiogon.com/discussions/why-warm-amps-sound-better
decooney,

Thanks for the info. I will look into it. Since last night, I left my X250.8 on. This afternoon, it started sounding good around 2 hr mark. Less sibilance and harshness.
Sounds like you all need to take a look at Pathos Acoustics and the impolite units.
@chungjh
I left my X250.8 on. This afternoon, it started sounding good around 2 hr mark. Less sibilance and harshness.

Similar situation with my prior dual-mono MOSFET SS amps I ran for 20+ years. Mine did still keep sounding better at hour 4, and more dimensional at hour 8 when they are on all day long. Similar to Pass .5 and .8 amps. There are several threads on this, owners debating this.

Tested and made notes today on my own tube mono amps with big transformers. 60 minutes was listenable, but hour 2 became plush and 3-dimensional. I cannot listen to them until at least 1hr warm-up. Kinda reconfirming again its just so much better at hour 2 with my tube amps too. Once it hits that bias set point, becomes very musical, enjoyable.
I leave my Pass amp on all the time now and still warm up for a couple of hours to sound GREAT. But, I still hear sibilance in Diana Krall's tracks and some others. As I get older, this sibilance thing bothers me more and more. At my volume of playing, I am still deep in Class A, and yet still sibilance. Does this mean I have to bite the bullet and go for a high end tube amp? This review on Conrad Johnson's ART150 sounds good: inner detail but smooth. Of course, it is close to $20,000. Do you think the reviewer is exaggerating and do you think CJ is worth the price?
Hi @chungjh`
"worth the price" is in the eyes and ears of the beholder and a person’s wallet I’d guess. CJ has a huge following just like Pass or Cary or Audio Note, etc. I’ve not heard the new Art150 or Art300 myself. I have been reading comparisons as I run two mono amps with KT150 tubes myself - wondering how and why the Art150 costs $15,000 more. Knowing CJ through colleagues, I’m sure it sounds``wonderful.  I’d have to hear that amp in my own system on my speakers before I’d conclude its worth it.

A buddy owns that $20k GAT preamp by CJ. He compared it to my same $4.5k tube preamp with upgraded caps in it, and reported he’s selling the GAT preamp pocketing the difference. Don’t forget that Art150 amp will need a worthy preamp to go along with it. The cost adds up quick.  I was at the same point you are now about "ears" and led myself back to tube amps, different interconnect cables, a tube DAC, and even changing coupling caps to smooth things out even more. There may be some things to try with your own 260.8 before going all tubes.

My own KT150 based amps were still a tad bright to me until I installed good NOS small input/signal tubes and changed coupling caps in them.  Upgrading a standard build tube amplifier with standard upgrades used can be amazing when done by a good tech who knows how to improve a line. A good friend just had two different CJ" amps upgraded lately and likes the difference quite a bit.  Everything I’ve heard myself at Deetes with SoundLab speakers has always been pleasant, yet it’s always been tube preamps and tube amps powering them. You could also try a proper tube preamp with your 260.8 in an effort to keep it. I’ve had email conversations myself with Nelson on this topic, he has many customers running tube based preamps with his XA and X amps. Feel free to send me a PM.  
Yes, I am running BAT rex2 tube preamp with my Pass Labs. It sounds better with it than without it when I go direct from Lumin X1 streamer/dac which has outstanding LEEDH volume control. One option is to get rid of rex2/Pass and go directly from Lumin X1 to a tube amp, to get the tubes smoothness. If I do this, I can go for a much more expensive tube amp.
Hi there.  I had the ARC Reference 10 pre and Ayre MX-R monos.  They turned my audio room (16' x 18') into a hot yoga facility after about 3 hours of play.  Also, I wasn't that pleased with the sound after a visit to the Munich Hi-End Show and hearing what other systems at the same or slightly less price were delivering.  When I returned I continued my research and testing.  I landed on the Octave Jubilee (a hybrid with a solid state power supply) and the Octave MRE 220 w/ the "Super Black Boxes", which are external capacitance power devices (one per mono amp).  They are leagues above my old components in their build quality and sonic performance across all parameters of measurement and evaluation.  To single out just a few qualities: incredible inner detail and nuance - check; accuracy in tone and musical pace - check; a vastly bigger, deeper and more defined soundstage - check; and, a much fuller, deeper and more articulate bass - check again.

But moving to your concerns.  The components need no more than an hour to achieve full potential and the tube pre and tube monos together give off far less heat than just my ARC Reference 10 did (a two box unit with a tube power supply).  Tons of power from the MRE 220 amps with and without the SBBs. 

There is so much great gear across the pond providing far better performance and value.  You only need to visit a handful of European countries to quickly appreciate how much more they are into music than Canada and America.  They've had a head start and it shows.

Ray
Ray

One option I was thinking is to take out the expensive tube BAT Rex2 preamp and connect Lumin X1 streamer/dac directly to a high gain tube amp, using the LEEDH volume control on X1. However, I found with my Pass X250.8, which has gain of 26, some albums weren't loud enough at LEEDH max volume. I was thinking that 3 db additional gain would be just enough. Well, MRE220 has 29 db gain and got good reviews. There is a used one on the market (without SBB) at around $10,000. It should have plenty of power to drive my SL speakers.

1.What is the power consumption at idle? My Rex2/x250.8 combined put out 900W of heat at idle.
2. Sibilance and edgy sound bother me a lot. How does MRE220 do on this?
3. How do you like Jubilee vs. MRE220? The person selling MRE220 is also moving to Jubilee.
OP.  There is a problem.  I have a 150.8 and it 'only' took an hour to get best performance, from off.  I leave it on standby and get best performance in minutes.  An amp that takes five or six hours to sound best is defective.  
As for tubes: If your Pre is tube based then in my humble opinion that is enough.  
Hi Chung, 
we have similar small room and if you not get bother with heat then go try tube amp .The heat from power tubes is hotter than pass amp !!! But winter is coming so no worries 😁.
me also use Pass before but 250.5 And their INT.
my experience with tube amp is pretty fast to warm up , at 15 min I can do listening But getting better in 30 min or so.
I try some prima Luna ,Line magnetic & Audio research Then settle with Air Tight .Tube amp also look better in my opinion 👍.
Have great evening 🙏



@chungjh@chungjh 



 McCormack and odyssey

idle is enough for warmup, if you need more than 6-10 hrs for warm up, that’s not good.

some newer caps may need more warm up time.


The Sound Labs are a different sort of beast. Like most ESLs, they don't work so well with amps that can double power as impedance is halved, since the Electrostatic principle doesn't rely on a driver in a box...

The impedance curve of the speaker varies by about 10:1 from the bass (peaks at 30 ohms) down to about 3 ohms at 20KHz. But the efficiency of the speaker is about the same though that entire range; for this reason most *but not all* solid state amps will tend to sound bright on them. A Brilliance control is provided to help tone this down a bit, as well as jumpers to allow for more bass, since all solid state amps struggle to make power in the bass region. This is why a tube amp of 140 watts can easily keep up with a solid state amp of 600 watts on that speaker!
Tube amps will stabilize much quicker than solid state (in terms of warming up to get where it needs to go to sound right), so with a good tube amp you should be having the system very near its ultimate warm-up in only an hour, and really sounding quite good in only 15-20 minutes.
@chungjh, 
Thinking about your 260.8 amp.  55 degrees celsius measured at the heat sink is often referred to as optimum operating temp for many Pass amps.  Reportedly,  55c is also a setup tuning point where Pass Labs sets the bias on many of their X/XA amps. It's re-checked many times during the first week of build validation testing.  Bias is not set or checked until hot right at 55c. Some manuals note 55c as the sweet spot for warmup and listening time.  

Last year I recall someone who finally sent their amp back in, found out it was not reaching optimum bias and temp. Simple adjustment fixed it.   

Gotta infrared thermometer (heat gun) to check how fast it gets to 55c? 


Oh, I haven't checked the heat sink. Last time I got inconsistent results. But, after constant idle and then playing for 3 hours, the top and front plate reach around 110-115 F and stays there.
All,

Great informative reading. I learn a lot about matching and challenges one doesn’t always think of when getting new equipment. 
I am currently running Magnipan 3.7 and Thiel CS2 (depending on m6 mood) from ole school Classe DR-15 amp/DR4 pre. Very happy overall with the  sound on both but considering what going to the 250.8 might bring. Or maybe an upgrade to preamp?
(Also have Rega P8/Alpheta3/Rega Aria mk3/California Audio Labs CD).
 I know the Classe stuff is dinosaur so maybe not much experience here with that but it has served me remarkably well. 
any thoughts would be appreciated....also don’t want 6 hours of warm up time....ha...thanks.
I have Maggie 3.7i paired with a Pass 250.8 and it sounds terrific. When I can I'll turn it on from standby about one hour before listening. On occasion I've listened from startup and the sound is still very listenable.
**** all solid state amps struggle to make power in the bass region. ****
This runs counter to everything I've learned over the past 50 years.

Hello all

Have been building amps for 40 years and built/auditioned a lot of circuit topologies both ss and tube.

 

Re warmup time- it should not be more than 15-30 mins for tubes depending on the ambient temp and 1 hour for pure (very rare) class A for ss.

 

Re sound quality, nothing beats thermionic emission in sound reproduction, nothing (in my experience). You could go pure class A SS with the best topology million dollar components in the signal path and still fall short of a lousy mediocre Chinese built tube amp running pentodes in ultralinear class AB. Go with more bias, SET and triodes and you are in heaven. Want more bass reproduction fix your psu. Matching tube impedances with transformers, and different tubes is a way to fix any topological issues.

 

Wont even touch tube OTL designs as those are unique and sound 10 times better than any tube transformer amp but more moody than an angry woman

.. and to avoid misunderstanding I would advise as follows:

a) if you are a purist and would not accept a "fly on your sword" then it is obvious where to look

b) if you want a plug and play solution which would give you the very good results in a low maintenance environment for with SS class A

c) if you want a excellent solution on a plug and "pray" scenario which will require biasing, tube rolling, and more hands on work go with tubes

Subjectivity does not win over physics..

 

The most important thing is you love the sound after the warm up.  That is hard to achieve and I wouldn't want to risk losing it by switching components.

The problem seems to be the long warm up and the heat.  A "cheap" solution would be to leave the amp on all the time and buy an air conditioner for a couple hundred dollars.  Presumably, your listening room has a window for the heat exhaust.

You could leave the amp on all the time with the door closed and turn on the air conditioner half an hour before you want to listen.  And of course turn it off while you listen because it's noisy.

It’s not the amp, it’s your ears and what’s between them.  Listening to music that you enjoy will release hormones like dopamine. Listening to songs you like, and more importantly, allowing yourself to relax and enjoy the music will speed up the process. The amps casing and heat sink temps that you seem to be measuring  have nothing to do it. But you guys go ahead and disagree, I enjoy reading many of the different explanations and recommendations. 😄

Nope, the placebo effect has nothing to do with this on a blind AB test. Topologies do matter (a lot), and distortion as well as harmonics which are more enhanced in some designs are both received and acknowledged by the human brain.

The heat that is mentioned before by jwei does impact the sound in a class A environment but within a few minutes of powering up again depending on the design of the amp. Heat affects also, inter alia, the impedance of components sometimes materially.

The only mistake people make in this is treating it as an overly simplified subjective affair. It is extremely complicated that sound engineers may spend a lifetime to master. Even the room construction topology merits attention with sound interference patterns being closely monitored and with millions of budgets invested in serious philarmonic venues.