1. No need to leave them on all the time. In my system they sound their best after they have been on for at least 90 minutes, and even better as the day goes on.
2. Don't know about the Krells. The JC-1's get pretty warm on LOW BIAS, and pretty hot on HIGH BIAS, but not excessively so in my personal opinion.
3. No regrets at all! These amps have the deepest, tightest, and most powerful bass I have ever heard in my system, as well as exceptional speed, transparency, focus, and detail resolution. They have great image width and depth, and very clearly resolve fine and subtle nuances in the music, as well as reverb trails, etc. They are also notably free from etch, grain, and glare. They also have excellent top-end extension and a very palpable midrange.
All this, and my system is no where near state-of-the-art, nor even that expensive in audiophile terms!
But, they must be FULLY BROKEN-IN to sound their best! This takes about 60 days of 24/7 music signal being played through them. I used an AM/FM tuner, with the volume on my preamp turned just above a whisper for 60 days, 24/7 to break mine in. Simply leaving them on all the time with no music signal for 60 days, 24/7, WILL NOT BREAK THEM IN! They must have a signal to properly and fully break them in.
They sound decent out of the box and up until they fully break-in, but once they do break-in, WOW! They suddenly transform, they are in a different league! They are truly amazing once they hit that stride. Up until they do break-in, they are very unpredictable...a few days they will sound closed-in, rolled-off, dark, excessively warm, and boomy in the bass...then other days they will sound thin, forward, and bright. They also have virtually no image depth at first, but they have it in SPADES after break-in.
Once break-in occurs, they are become exceptionally neutral, and their outstanding sonic characteristics and strengths do not change.
These were MY personal experiences with my JC-1's, in MY personal stereo system. Others experiences with them may vary.
Hope this helps.
2. Don't know about the Krells. The JC-1's get pretty warm on LOW BIAS, and pretty hot on HIGH BIAS, but not excessively so in my personal opinion.
3. No regrets at all! These amps have the deepest, tightest, and most powerful bass I have ever heard in my system, as well as exceptional speed, transparency, focus, and detail resolution. They have great image width and depth, and very clearly resolve fine and subtle nuances in the music, as well as reverb trails, etc. They are also notably free from etch, grain, and glare. They also have excellent top-end extension and a very palpable midrange.
All this, and my system is no where near state-of-the-art, nor even that expensive in audiophile terms!
But, they must be FULLY BROKEN-IN to sound their best! This takes about 60 days of 24/7 music signal being played through them. I used an AM/FM tuner, with the volume on my preamp turned just above a whisper for 60 days, 24/7 to break mine in. Simply leaving them on all the time with no music signal for 60 days, 24/7, WILL NOT BREAK THEM IN! They must have a signal to properly and fully break them in.
They sound decent out of the box and up until they fully break-in, but once they do break-in, WOW! They suddenly transform, they are in a different league! They are truly amazing once they hit that stride. Up until they do break-in, they are very unpredictable...a few days they will sound closed-in, rolled-off, dark, excessively warm, and boomy in the bass...then other days they will sound thin, forward, and bright. They also have virtually no image depth at first, but they have it in SPADES after break-in.
Once break-in occurs, they are become exceptionally neutral, and their outstanding sonic characteristics and strengths do not change.
These were MY personal experiences with my JC-1's, in MY personal stereo system. Others experiences with them may vary.
Hope this helps.