Pass Labs X350.5 Stereo Power Amplifier Review

A

admin

Audioholics Robot
Staff member
The Pass Labs X350.5 350 watt/ch stereo amplifier has the appearance like it was sculpted by Cybertronians. It portrays a commanding presence that just draws your attention. The X350.5 is built like a tank, pegging the scale in the pride of ownership department and weight (132 lbs). Its pristine sonic virtues and ability to drive even the most challenging of speaker loads beyond reference levels is even more impressive than its overall excellent bench test results. But, its power hungry demeanor and luxurious pricing isn't for the faint of wallet. However, I'm confident if Optimus Prime were an audiophile, it's a sure bet the X350.5 would be his amplifier of choice. Audiophile & Audioholics recommended!


Discuss "Pass Labs X350.5 Stereo Power Amplifier Review" here. Read the article.
 
Irvrobinson

Irvrobinson

Audioholic Spartan
Wow. Look at that 1W FFT plot. Distortion is about 20db *less* than the Emotiva XPA-2. That's amazing. I'm not sure the difference is audible, but that's very good performance.

If you want to test amps like this, Gene, you need to run a 30 amp circuit. ;)
 
gene

gene

Audioholics Master Chief
Administrator
Wow. Look at that 1W FFT plot. Distortion is about 20db *less* than the Emotiva XPA-2. That's amazing. I'm not sure the difference is audible, but that's very good performance.

If you want to test amps like this, Gene, you need to run a 30 amp circuit. ;)
Yea I wish I had that luxury. 30A wouldn't help in this case though b/c the real limitation is the 1.5KVa transformer when driving 4 ohm loads. Also, the amps max power consumption is 1800 watts so running a continuous power test for 4 ohms, both channels driven at 700 watts would consume roughly 2500 watts which this amp cannot do steady state.

At low power levels, you are seeing the advantages of Class A. This amp sounds great but it's also a bit power hungry b/c of the heavy Class A bias.
 
Irvrobinson

Irvrobinson

Audioholic Spartan
Yea I wish I had that luxury. 30A wouldn't help in this case though b/c the real limitation is the 1.5KVa transformer when driving 4 ohm loads. Also, the amps max power consumption is 1800 watts so running a continuous power test for 4 ohms, both channels driven at 700 watts would consume roughly 2500 watts which this amp cannot do steady state.
Which is odd, because Pass rates this amp as 700W/ch into 4 ohms, and I suppose the naive (like me) just assume they mean both channels driven.
 
gene

gene

Audioholics Master Chief
Administrator
Which is odd, because Pass rates this amp as 700W/ch into 4 ohms, and I suppose the naive (like me) just assume they mean both channels driven.
As I stated in the review, they don't really specify both channels driven. Regardless, still lots of power on hand.
 
ImcLoud

ImcLoud

Audioholic Ninja
Ill take 2!!! Oh wait they are $11000.00US each, never mind, how much just to rub my XPA5 on it for a couple minutes, maybe some of that non audible 20% will rub off... :D

Good job with the review..
How would it compare to 5 XPA1's and a brand new Jetski? lol, I really like the look of it, but I think I could pay a local metal artist $500 to make me a new enclosure for an EMO..., stainless with blades on it, and a bottle opener for my BEER..
 
Adam

Adam

Audioholic Jedi
I love the looks of it. The reality is that I'd snap my back trying to lift it, all while cutting off a hand on the heat sink fins. That just might be worth it, though...

Richard Marx...wow...that's a trip back in time right there. :D

Of course, I'm jealous. I suspect that I'll never buy an $11k amp, even if it was going for the outrageously good price of $5k. Give me a second...okay, I've made my piece with it. :)
 
Irvrobinson

Irvrobinson

Audioholic Spartan
Ill take 2!!! Oh wait they are $11000.00US each, never mind, how much just to rub my XPA5 on it for a couple minutes, maybe some of that non audible 20% will rub off... :D
Not 20%, 20 decibels. That's 10,000%.
 
Steve81

Steve81

Audioholics Five-0
This amp sounds great but it's also a bit power hungry b/c of the heavy Class A bias.
You can say that again. 500-600 watts just to idle is quite a lot by any measure. Still, if you can afford it and you are environmentally conscious, you can probably afford the means to offset the usage.
 
Irvrobinson

Irvrobinson

Audioholic Spartan
You can say that again. 500-600 watts just to idle is quite a lot by any measure. Still, if you can afford it and you are environmentally conscious, you can probably afford the means to offset the usage.
Having owned amps that sink a lot of current like these (Krell class A mono blocks, so I had two of them), the truth is that having them turned on a couple of hours per day was invisible on my electric bill.
 
Irvrobinson

Irvrobinson

Audioholic Spartan
Damn......Rich.........People. :D
Yeah, they just buy premium products that generate higher-paying jobs to make and sell them. ;)

But seriously, how many people have a second refrigerator or a freezer, or drive a huge pick-up truck to the office? Very middle class behaviors lots of people do that make these Pass amps look positively green by comparison. Of course, what about those new 90" LED monitors so many AH folks covet? They sink about 400W too, every minute you have them turned on.

Not that I'm defending the Pass Labs stuff per se. I'm just injecting a little perspective into the conversation.
 
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Steve81

Steve81

Audioholics Five-0
Yeah, they just buy premium products that generate higher-paying jobs to make and sell them. ;)
I always found it somewhat ironic that people would bash the rich for spending conspicuously during a recession, because you know...when people who have money are guilted into not spending it, that's fantastic for the economy. :rolleyes:

Not that I'm defending the Pass Labs stuff per se. I'm just injecting a little perspective in the conversation.
Like I said, if you can afford the amplifier, and you're concerned about the environment and global warming, you can afford the carbon credits and a few solar panels too. Not a deal breaker in my book.
 
Steve81

Steve81

Audioholics Five-0
Having owned amps that sink a lot of current like these (Krell class A mono blocks, so I had two of them), the truth is that having them turned on a couple of hours per day was invisible on my electric bill.
I wouldn't really expect it to. It's not in the same category as running your AC on a 100+ degree day to keep your home at a nice comfortable 70 degrees. That'll run up the bill a bit quicker.
 
jinjuku

jinjuku

Moderator
Not 20%, 20 decibels. That's 10,000%.
And almost every speaker out there will have mechanical distortion above either amps.

My Parasounds had a claimed (I believe A-Weighted) 116SNR as an example of a very good looking #. Still didn't help keep them in the stack vs my Crown.

It may be a great amp but I still can't square it with $11K MSRP. I guess if I had a pair of $50K speakers I would give it serious consideration.
 
Irvrobinson

Irvrobinson

Audioholic Spartan
And almost every speaker out there will have mechanical distortion above either amps.

My Parasounds had a claimed (I believe A-Weighted) 116SNR as an example of a very good looking #. Still didn't help keep them in the stack vs my Crown.
No argument; I mentioned that I thought the difference might not be audible, (especially in an SBT or DBT). I do wonder though if a difference like that could explain some of the longer term fatigue differences I perceive. Of course I'm reaching, but 20db of difference is so huge if money weren't a factor I'd be hard-pressed not to have it affect a buying decision.

As for the mechanical distortion of speakers, you're correct of course. Very few reviews test speaker distortion (except with subs), but any speaker that gets much under 1%, or 40db above where the Pass amp is at, seems to be considered a superstar. Nonetheless, the signature of solid-state electronic distortions versus mechanical distortions is different enough (odd versus even harmonics) that it seems a worthy goal to minimize both.
 
Steve81

Steve81

Audioholics Five-0
And almost every speaker out there will have mechanical distortion above either amps.

My Parasounds had a claimed (I believe A-Weighted) 116SNR as an example of a very good looking #. Still didn't help keep them in the stack vs my Crown.
Not to mention the noise floor of most rooms, especially with an HVAC running.
 
GranteedEV

GranteedEV

Audioholic Ninja
I observed the 3rd harmonic (35.251 + 37.57) dBV being 72.8dB down from the fundamental. This unusually high distortion product is likely somewhat a deliberate result of employing minimal feedback in this amplifier design.
"Unusually high"... come on now. I mentioned in another thread that I can barely if at all even identify a decorrelated noise signal at -65db down, on headphones. A 3rd harmonic is something the music, and the speaker, will have at a higher level already.

That's a great measurement at 420 watts.
 
gene

gene

Audioholics Master Chief
Administrator
"Unusually high"... come on now. I mentioned in another thread that I can barely if at all even identify a decorrelated noise signal at -65db down, on headphones. A 3rd harmonic is something the music, and the speaker, will have at a higher level already.

That's a great measurement at 420 watts.
Perhaps I'm a bit too picky at times :) It is a pretty good measurement especially since I was driving the amp above its rated output. :D
 
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