Pass Labs XP 22

kswanson27

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Nov 21, 2018
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In the digital audio forum I've been discussing my setup which has no preamp but runs a Berkeley Alpha DAC 2 directly into my Boulder 2060. There seems to be a consensus that a preamp adds something beyond functionality. Ack feels the Berkeley is not suited to drive an amp directly because of issues with its digital volume control. Later today I'll be trying hard to duplicate the sound variations others have heard related to that volume control but in the meantime I've started researching possible preamp options to try. I have no need for more functionality than the Berkeley provides so a straight line stage preamp will do. My first choice is a late Boulder but that's probably beyond my means. Recently I've read a review in Stereophile for the Pass Labs XP 22. Austin liked the sound and Atkinson liked the measurements. Anyone here have any thoughts or experience with the XP 22?
 
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BlueFox

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I have had the XP-22 for about two years, and love it. Prior to that I had the XP-20, and the XP-22 was an improvememt.
 

ack

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@kswanson27 More than digital volume controls, amplifiers need a minimum amount of current to be driven properly. The Alpha puts out a mere 1mA which works for some amps, but not all. All in all, 1mA is minuscule. My amps require some 180mA for rated output; not sure about yours. Be careful to audition worthy preamps already broken-in, so as to eliminate that variable, and of course, they need to be able to properly drive your amp. My friend Al M was one of those driving his amp directly, until he plugged in a great preamp. One of many, many such examples.
 
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kswanson27

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Nov 21, 2018
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The XP 22 I'm considering is a demo so it is broken in. The Boulder has a balanced input impedance rating of something like 200k so just about anything will drive it. I believe the Berkeley achieves its 1mA at a 54 volume setting hence that is the recommended setting for downstream volume control. At that setting my system is operating at 95+ dB with "normal" recordings so that's a no go here.
 

analogsa

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Apr 15, 2017
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The Alpha puts out a mere 1mA which works for some amps, but not all. All in all, 1mA is minuscule. My amps require some 180mA for rated output; not sure about yours.

I am quite confused with these mA figures. Where do they come from?

Fet or valve input amps require no milliamps at all, bipolar inputs get minimum distortion when fed from a low impedance, but really needing substantial current is very unusual. 180mA? A lot of speakers need less :)

I have never heard of amps with an input impedance of less than 50ohm and even this requires an order of magnitude less current.
 

ack

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I am quite confused with these mA figures. Where do they come from?

You are quite confused - no surprise - probably because you do not read the manuals like we do, and seem assertive based on vapor information. Just a thought.
 

analogsa

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You are quite confused - no surprise - probably because you do not read the manuals like we do, and seem assertive based on vapor information. Just a thought.

Would you kindly clear the vapor for me good Sir? Any kind of link to the mysterious 180mA required for rated power would be indispensable. Much obliged. Is this for the Spectral amp?
 

ack

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Yes it’s for the Spectral amps. It’s the reason why the preamp puts out a max of 1A (http://spectralaudio.com/30SV web pkg/DMC30SV Spec.htm). They do not publish manuals online. I have run across such similar, but lower, specs from other manufacturers in stereophile or TAS articles, in the past
 
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ack

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So I just took a picture of the amplifier manual - it ought to help clear vapor

IMG_3716.jpg
 

analogsa

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Apr 15, 2017
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Thanks a lot for taking the trouble to scan and publish this. Really appreciated.

From where I am standing it is marketing BS. Apparently the issue has previously been discussed here with some amusing contradictions.

Marketing aside, this cannot be a universal consideration when pairing pre with power amps.
 

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