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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
dwest1023
209 posts
 
I have a similar issue with my pass int 60. Sounds ok at startup, but takes maybe 3 hrs or more of playing time to sound its best. I just put up with it.
chungjh's avatar
chungjh OP
265 posts
 
@Iwin 
I think expecting 1 1/2 hr for warm up is something I can live with.But not 6 hr.
elliottbnewcombjr
5,461 posts
 
I could not enjoy music in a small hot room.

I suggest it’s time for you to find some high efficiency speakers that you can then successfully use with a ’not too hot’ tube amp.

SOUND LAB / ELECTROSTATIC OWNERS?

what efficient speakers have you found and like/love that you can recommend OP try?
stringreen's avatar
stringreen
6,468 posts
 
open a window...use a fan.....    You seem to like your sound: don't mess with it.
decooney
2,031 posts
 
I think he’s also referring to how much time it takes to warm up the Pass amp before he’s ready to enjoy it. It’s a regular topic. Not unique to Pass amps. My former dual mono class A/AB SS amp was the same way at 6-8 hours, it transformed into a gem once the transformers were good and saturated with heat at 6-8hrs. Parasound has made some progress with 1w standby pre-warming, and even then I demo’d one and still had to run it for a while before it sounded right to me. My mono tube amps I run now take a lot less time to be ready for listening.

@chungjh,
My local dealer sells Sound Lab and tube amps only. I’ve heard various SL model speakers there over the past 20+ years. In every case they were running two mono tube amps with the SL speakers. At 86db and 8ohms for your 545s, you’d likely need a (pair) of tube amps if you do decide to go to tube. More output tubes = more heat there too. Last time I was there, he was running a set like the larger 845s (huge) powered by two Quicksilver Mono 120 tube amps with dual KT150s in each, only 100wpc. One mono amp per speaker. While it sounded very nice, seems like many with your speakers run above 250wpc solid state amps regularly. If I had 545s and could not keep the 250.8, tube amps would be my choice. They do sound quite amazing with good tube amps. Maybe not as dynamic as your 250.8 Pass amp, unless you bought some with lots of tubes and back to heat again, IMO.

Pros/Cons:
While you only need one amp now to power your 545s with the Pass 250.8, you’d likely want/need a very large stereo tube amps or monos, and either case, still generating some heat but maybe less time for warmup.

Warmup:
The advantage I’ve found with my QS Mono 120s with two KT150 output tubes per amp, they have fewer tubes, don’t run hot, and never take more than 1hr to fully heat up, even at 45 min they start to sound pretty good.

Having heard a few different tube amps with your speakers, you’d need to choose wisely with tubes before you could effectively displace a Pass 250.8 amp I’d bet. Would mono tube amps be enough power and dynamics for you without buying some heat-monster tube amps, hard to say. Your speakers call for 50-600w. It really also depends on your room. At lower listening levels, sure might get away with 100w tube amps. Or, fans for the 250.8 and call it a day. Good luck.





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