Why does my SS amp need to warm up?

[topspeed]

I recently replaced my PS Audio HCA2 (switching amp) with a Pass X150.5 and was hoping someone can explain to me why the sound of this solid state amp changes so much as it warms up? Tubes need to warm up, I get that...but solid state? When I first plugged it in, I was concerned I'd made a mistake, but helpful advice from Mr. P and others assured me that 24 hrs of feeding it juice would make all the difference, and it did. Now I leave it in stand-by, but even then I've got to give it a good half hour or so before she brings her big guns out to play. I've never encountered this before in a ss amp. The nerd in me wants to know why this happens

[Feanor]

I'd like to know too. I also have a Pass X150.5 and agree that it takes a good 30-40 minutes to warm up close to potential from Stand-by. Maybe it's the transistors coming up to the temperature they need for stable operation, but that's only a guess. According to Pass, the X150.5 draws about 30 watts on Stand-by but 200 watts powered On but idle.

But I note the may Class D Audio SDS-258 required a warm-up time to sound best; in its case it was only 10-15 minutes but even so.

[topspeed]

I'd like to know too. I also have a Pass X150.5 and agree that it takes a good 30-40 minutes to warm up close to potential from Stand-by. Maybe it's the transistors coming up to the temperature they need for stable operation, but that's only a guess. According to Pass, the X150.5 draws about 30 watts on Stand-by but 200 watts powered On but idle.

But I note the may Class D Audio SDS-258 required a warm-up time to sound best; in its case it was only 10-15 minutes but even so.

The PS Audio consumed so little power while idling, I simply never turned it off. Warm up? What warm up? Gotta love that Class D efficiency!

[Mr Peabody]

My X250 also sounded better after 30+ minutes of play time. I can't explain it but I believe it has to do with the Class A type topology Pass uses. Coincidentally, my 532h sounds better after some play time. Now I wonder if it's a solid state thing where you need high resolution system to hear it or if it's just the character of certain amps. The 532h is quite a bit different topology. The Pass warm up time was more apparent to me, just like when I had my CJ tube amps.

[Hyfi]

Don't big Caps need to be charged all the way before optimum performance?

My Stratos amp as well as a Rotel Receiver both get louder and start sounding better after about 30 minutes.

[blackraven]

Don't big Caps need to be charged all the way before optimum performance?

My Stratos amp as well as a Rotel Receiver both get louder and start sounding better after about 30 minutes.

Yes, caps need to charge up but that takes a second to do so. It probably has something to do with the temperature as well as polarization.

TS, welcome to the Pass club. How do you like the amp? What are you using for a preamp?

[topspeed]

Yes, caps need to charge up but that takes a second to do so. It probably has something to do with the temperature as well as polarization.

TS, welcome to the Pass club. How do you like the amp? What are you using for a preamp?

Hi BR,

I like the Pass quite a bit. I had never purchased an amp before without auditioning it, but knew Nelson Pass has the same JBL's for his own system, so it was safe to assume they would be a synergistic match, which they are. Once warmed up (which is key), the X150.5 has terrific grip and extension on the bottom end while the mid band and treble are both very smooth without the slightest hint of grain or glare. It isn't as fast in transient response as the HCA2 and the edges are softened in comparison, but its not a matter of better or worse, just different. While both are rated at 150wpc, the Pass seems to pull harder (car-guy parlance). The greatest attribute is the complete lack of fatigue. It just makes you want to turn it up, which the JBL's love! Once she's really cooking, the sound has meat on the bones and the dynamics simply bloom. I'll spin tunes for hour after hour. I went from Porcupine Tree to Stan Getz to The Eagles and relished every second of it.

My pre-amp for now is a Marantz SR5010 used in Pure Direct with all room correction and audio/video processing shut down. Sometime down the road, I think I'll add a pre-amp/dac w/ theater bypass. Before I purchased the Pass, I was negotiating on a CODA CSX integrated that Mr. P spoke highly of, which would have saved me the trouble of finding a good line stage, but I've always wanted a Pass so that's what ended up in my room.

[blackraven]

Congrats on the Pass. You described the sound perfectly. My X250 has a soft top end but tremendous grip and bass extension. I find transients are very fast but I am using a BAT VK-51se preamp which is just an explosively dynamic preamp.

[Mr Peabody]

What I notice after some play time the sound seems to have less of a glare and opens up more, warmer sound. The Pass just gets into a more relaxed character and more open.