2. amps-preamps
  3. 161353-98013

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
jmbumgarner01
64 posts
 
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.
johnto
1,025 posts
 
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.
keegiam
731 posts
 
**** 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.
sofos
3 posts
 

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

sofos
3 posts
 

.. 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..

 

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