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?
As@decooney indicated, the heat is not my biggest issue. It is the time to warm up. My logic is that tube amps will reach the optimum temperature more quickly than Pass Labs or other SS. Tell me if I am wrong.
@chungjh You are correct when referring to some of the higher end amps with massive transformers. Most of my tube amps only take less than 1hr. I was a 35-year solid state amp guy, back to mono tube amps now days. Today, 45 minutes of warmup, ready to go. I simply don’t have the extra time or patience to fire up my former solid state amps and let them run for 6 hours of pre-warming for a 1-2 hour listening session. Was not worth it, IMO.
Some of the more modern output tube amp designs and tubes do not get overly hot. I can hold my hand directly on the transformers of my current Quicksilver Mono 120 tube amps for ten minutes straight. Warm, but never hot. The output tubes are warm but not scorching like my older tube amps were at times. Similar to Carver’s amp designs. Ask the designer-mfg-seller to put a laser heat gun on it and tell you what the transformer/tube temps are after 6hrs. Try the same with the Pass 250.8 at 1hr, 2hr, 6hrs and see what you get and when it sounds good to your ears. If you go with tube amps, hang on to your Pass 250.8 if you can, its a lot of fun to rotate.
And, by the way. Since you could sell your preamp, then get Critical Mass 1.0 footers for under the Lumin X1. I also have them under my Carver amps and Niagara 7000 power conditioner. You will be amazed what they do for the image, frequency extensions, soundstage, etc.
chungjh, Carver claims that his design makes the tubes run cooler and the tubes should last longer. I think his claim is something like 20 years. But, that is hard to believe. Bob Carver has always been easy to contact, heck he even flew to my house when I was demoing his speakers. (I didn't like the speakers by the way). The Lumin X1 with the new Leedh volume control direct to the amps is definatly the way to go.
I tried going direct from Lumin X1 to X250.8 and it never sounded as good as inserting BAT rex2 preamp between them. May be it is the tube goodness. If M350 really works for me, I can save a bundle of $. Can you tell me how you like M350? How about reliability, service from Carver?
I own the Lumin X1, fantastic unit! I also owned a Pass Labs X350.5 and also demoed the X350.8. In the end, I preferred the Carver M350 tube Mono Blocks. To me, it is much more musical, open and with greater dynamics. Hard to believe a tube amp can be this dynamic.
I also eliminated the preamp and started running my Lumin X1 direct to the Carver Amps. Best of all possible worlds.
BTW, I don’t think the Carvers put out as much heat as the Pass Labs did. And they seem ready to go soon after turn on.
If you want more dynamics better bass detail and impact and better highs stay with Pass 250.8.If you like lush midrange get tubes.It also depends on the speaker and the system as well.Tubes will definatly run hotter than Pass 250.8.Good luck.
As @decooney indicated, the heat is not my biggest issue. It is the time to warm up. My logic is that tube amps will reach the optimum temperature more quickly than Pass Labs or other SS. Tell me if I am wrong.
The dynamism of X250.8 is unparalleled. With drums in Angela Brown's band, the SMACK is incredible. As I get older, I feel like I wouldn't mind with a bit less SMACK.
Roger West, the owner of Sound Labs, thought Atmosphere MA1 (140W) was powerful enough for room 9x11. Because of lack of space, I was thinking about AudioResearch 150SE stereo. I think heat generation will be similar to X250.8 but will it reach thermoequilibrium by 1-2 hr?
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.
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.
I had a similar issue with my system and it turned out that the pre-amp needed the long warmup. One time try turning on the pre-amp 6 hours before your listening session and see if that makes a difference.
I think part of the issue as you have noticed might be because it is a class A amp and they are designed to handle the excess heat and once they reach a certain temperature they really start to open up. I have a pair of Cary 211 AE amps soon to be FE. They play in class A up to about 75 watts which is more than sufficient to drive my Tekton Design Ulfberhts which are 98 per cent efficient. The amps sound very good from the start but after about an hour and a half of listening when they get hot , they reach a playback level that is simply wonderful and similar to what you are experiencing with your Pass Labs amps. I also have a pair of Odyssey Audio Kismet solid state amps and they barely get warm even after several hours of playing but they sound the same from the time they are turned on to when they are turned off. If I have company coming over for a listening session , I will start the Cary amps about an hour earlier to get them at least warm. The downside to this is tube usage but the upside once they get hot is more than worth it. So in this long winded response is that depending upon the tube amp, you may experience the same issue with them.
Some tube amps , heat might be a issue, with my Defy7, 12 power tubes, heat has not been a problem in summer months, And remember fall temps can make rooms chilly at night, , winters can be frigid, This is when a tube amp can be of an advantage.
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