Pass Labs XA-25 on all the time?


My Pass Labs XA-25 stays on most of the day. It does sound its best about an hour after it turns on. I'm thinking of leaving it on all the time. Does this help or hurt the amplifier in some way. I  have a PS Stellar S300 in another system that stays on all of the time. It's a class D amp so it uses very little power at idle . PS recommends leaving it on. It sounds better to me that way. Other than the power consumption, is there a downside to leaving the Pass on all the time? Thanks Larry
4fcee8f4 8d1b 473b 8f5e a8283f51a552cooperjack
I would say if you enjoy listening to it everyday then leave it on. If you leave the house for days at a time then I would turn your entire audio system off. 
It doesn't hurt it... each time you power on/off you have some thermal stress which you avoid, so that is better, but all devices wear with use a wee bit.

I also use Class D amps, and they are awful for about 24-48 hours.


Best,

E
If u listen a lot, leave on. It is Pass labs.
i leave my. Amps on. A lot. (Mccormack750’s)
conrad Johnson building McCormack amps, these are my grails!!
Love them.
Leave your preamp on, it more harm for on/off every weekend.

leave on. Enjoy!!,


my B&K pro10MC is on about 300/365 a year.  
Preamp warmed up. Is asportmas a warm amp.
hey cooperjack

I own a Pass Labs XA30.8 and I leave it on all the time. There is a reason I do that. Every time I have to unplug my amp or just turn it off for a long period of time I noticed that when I plugged back in again things just didn't sound "right". It's hard to say exactly what didn't sound "right" but I heard it every time. Then it dawned on me.

When you unplug or turn off an amp for a long time it allows the caps and the transformer to completely drain. You do NOT want to do that. I also noticed that when you turned it back on again it took about 3-4 days until everything sounded correct. You have to realize, the Pass Labs amps are pretty much ALL power supply. Mainly the temporal aspect of the music (timing cues) is what was most affected. A lot of people will think you're nuts if you tell them that. If you're worried about your electric bill then shut it off, if you want it to always sound it's best, leave it on. I hear it every time I unplug it. It takes 3 - 4 days for that big transformer and all those caps to fully charge back up again and come up to speed and stabilize. When that happens everything just comes into focus and the subtle timing nuances that the musicians have taken the time to get just right are preserved and audible. It's a fact that music is a time continuum from start to finish. You can definitely hear it. That's why I leave it on all the time.

Scot
the only downside is the electrical usage, but it is probably not much on the XA25. The XA160.8 left on uses the same electricity as three 100 watt older type light bulbs...I just spoke to Pass about his...no harm to amp and it does sound better, so usually only turn it to standby when not listening for a few days...
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I'm inclined to leave it on. It does sound better after being on for an hour. After that, I'm not sure it's not just me wanting it to sound better. But, heck there does not seem to be much downside. I've owned a  Threshold 400A since new. I did turn it off because it gets a good bit hotter than the Pass. That practice and time probably contributed to the caps ultimately requiring replacement. Time probably had the larger effect.  Thanks for all the answers. The XA-25 is very special. Larry
I always left my XA30.5 on! So yeah, keep it on.
Since the "A" in "XA" means "Class-A", do the math to determine how much A/C will be wasted leaving it on constantly. You may be unacquainted with how a Class-A amp works and get a surprise on your next electric bill.
I have a Bel Canto REF500S amp---should I keep in on 24/7 as well?
The only reason to turn off a SS amp is heat. If it gets too hot, the big caps will age prematurely. I use a separate power supply in another room, so it's not a problem. I use the Class A amps as auxiliary space heaters, so it's cost neutral.
There is a video of Nelson Pass saying to turn off his amps when not in use.  I believe it's the video Steve Guttenburg shot where Nelson gives a tour of his listening room, but it might be a different one.
Moon by Simaudio recommends leaving you amp an preamp on so I do.

If going to gone more than 5 days I kill power to my entire system.

Goo question.
I have Pass Labs 60.8.  When I am not listening I just keep it in standby.  Never turn it off completely unless I will be away for a week or more.
Turn it off:

  1. It is expensive to leave it on.
  2. Nelson Pass says turn it off.
  3. The extra heat will prematurely damage all the electrolytic capacitors
You could always email Nelson and ask. His email is out there.
I agree call Pass Labs. Someone who knows will answer. 
If your planning a big weekend, turn it on Friday morning, turn it off Sunday night. A nice compromise...
chart showing internal impedance of capacitors going up as hours of use go by. this is a primary component of pulse power supply failure.

https://www.researchgate.net/figure/Aging-test-of-electrolytic-capacitors-at-C-values-measured-at-C-...


thus, all sub amps tend to go bye-bye,after a certain point. the caps go off in value and impedance, and then things overheat and the thing goes poof. And are then relegated to the trash bin. Conventional power supplies last much much longer.

the same deal happens to these pulsed units, these class D amps. They start to sound off as they age. Especially true when they have a pulsed power supply hooked up to a pulsed amp circuit.

this is why old gear needs to be re-capped. It is not vintage sound, it is dead slow dark capacitors, on the verge of dying and taking some circuitry with them.

see this chart:
https://www.researchgate.net/figure/ESR-measured-at-C_fig2_3279777
but wait, there’s more...

Thus, not using your SS amps and gear? shut it off. Once or twice a day  (Off-on, etc) is fine. No problemo.

Leave it on all week? Never. Gear sitting in a hot sunroom? Or similar elevated temperature locations? No, don’t go there.

To leave an amp on all the time, the result is...you age the capacitors, over a given time.. by a factor of at least two, or more, maybe four. You dull the high frequencies, close in the spacial aspects, and lose all the fine detail, dull the transients, misalign the circuit’s intended behavior, increase distortion and heat generation, and..well..just generally kill the amp.

the distortions generated as the capacitors age will happen in the area of where we look, with our ears, for ’information’ in the signal. But that thing we hear, on aged capacitor gear..can be and generally is just crunchy noise we mistake as detail. It’s a hardening of the signal, where all of it tends to sound the same. It is actually distortions, and distortion patterns. Which, being in-harmonic, are easier to hear as the ear is designed to hear in-harmonics as separate. Think of the dark screech monotonous sound (everything sounds the same,and all bad) that comes from a 70's Marantz receiver, that has never been serviced. Do you hear it now?

It’s what we use to detect threats, this detail distortion separated from the signal body. it can excite us.  It’s a thing that people with unrefined hearing mistake for detail... as they can make it there, psychologically. Big breast implants and collagen lips ---for those with blunt senses. It’s what Class d and mediocre amplifiers do. Hearing that for what it is, is one of the big steps to getting closer to that unreachable goal.

if you call Pass Labs, let us know what they say please...
I just had my Pass X150 in for service, and I spoke with Kent there about replacing power supply. He said they are just beginning to see the first Alephs coming in for cap replacement, almost 30 years old. Those are monstrous, and monstrously hot, Class A amps. 

He also said no need to worry about premature aging of caps unless large Class A and you leave it on all the time. 

So, if he's right, I guess most Aleph owners don't leave them on much, or if they do, 30 years is premature for Pass Labs caps.  

I leave my X150 on during day (space heater) and off at night, but it doesn't actually run very hot, so I could run it all the time with confidence. It's 150 into 8, 300 into 4.  First 5 watts Class A
If it is a Pure class A amp like the XA30.8 or XA25, turn in off. These amps pretty much draw full power even when no signal is applied. The heat generated with class A will shorten the life of the parts inside, mostly caps, your electric bill will be noticeably higher, and will add extra heat to the room that will be a problem during warmer months. If the amp is a class A/B, Its your call, class D leave on all the time.
I now power up my SMc Audio up one day prior to  listening every week.