Pass Labs X5

In fact class A amp maximum theoretical efficiency can achieve is 50%.

I know I’m resurrecting a 13 year old thread, but just felt like I had to correct the assumptions in here for the record, since I own an X5. The X5 idles at 200w and provides 40w x 5 of Class A power per channel before crossing over to AB.

It is a legitimate space heater, brutal in the summer, and has necessitated the addition of a mini-split AC unit just for my Stereo/HT listening space.

I believe the X series amps, which are class A/AB, are biased in full class A to 20% and then switch to class AB. For the X5, that means 25W into 8 ohms Class A and thereafter up to 125W into 8 ohms Class AB.

I believe Nelson Pass used this same percentage on the Threshold S series amps as well.

Mlawitm- I believe the main difference between the X5, the X150 and the X150.5 have to do with bias current. Both the X5 and X150 idle at 200 watts. As such, I believe the X150 if biased further into Class A (being a two-channel amp) then is the X5 being a five-channel amp. The further (more watts) an amp is biased into Class A, the less the crossover distortion all else being equal.

The X150.5 idles at 250 watts and therefore I believe is biased further still into Class A. Just guessing at all this but Nelson is a big proponent of Class A.

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New retail was $4500 for that amp.
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Hi Flrnlamb
Do you remeber what the x5 was selling for I thought they just stoped producing that amp?

Thanks
John

The older amp was a bit relaxed sounding, but otherwise smooth, detailed, and pretty dynamic for what it was. It's not as good as the 2 channel X150, but still a bit more refined and smoother than, say, ATI series amps, Adcom, Parasound, etc.
I used to sell that amp retail. Not sure on new amps, but they're likely an upgrade, possibly...?