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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
decooney
1,908 posts
 
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
chungjh's avatar
chungjh OP
265 posts
 
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.
skypunk's avatar
skypunk
499 posts
 
Sounds like you all need to take a look at Pathos Acoustics and the impolite units.
decooney
1,908 posts
 
@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.
chungjh's avatar
chungjh OP
265 posts
 
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?
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