Pass Laboratories XP-32 line preamplifier Specifications

Sidebar 1: Specifications

Description: Solid-state, three-chassis stereo preamplifier with remote control. Inputs: 5 single-ended (RCA) or balanced (XLR), 1 single-ended (RCA) or balanced (XLR) tape, 1 single-ended (RCA) or balanced (XLR) Pass Thru. Outputs: 3 single-ended line-level (RCA) or line-level balanced (XLR), 1 tape (RCA). Maximum gain: 9.6dB, balanced. Input impedance: 42k ohms, balanced; 22k ohms, single-ended. Output impedance: 50 ohms, balanced; 25 ohms, single-ended. Maximum output: 23V RMS at 0.1% THD. Frequency response: 20Hz–20kHz, ±0.05dB; –2dB at 150kHz. Channel separation: >110dB. Total harmonic distortion: <0.001% at 1V, 1kHz. Residual noise: 500nV RMS. Signal/noise: 150dB ref. max out. Power consumption: 70W.
Dimensions: Preamplifier chassis and control unit/ power supply (each): 17" (430mm) W × 4" (100mm) H × 12" (300mm) D. Weight (total): 62.5lb (28.4kg). Shipping weight: 78lb (35.45kg).
Finish: Instrument Gray.
Serial numbers of units reviewed: 37378 & 37379, preamplifier chassis; 37377, control unit/power supply.
Price: $17,500. Approximate number of dealers: 20. Warranty: 3 years, limited, transferrable.
Manufacturer: Pass Laboratories Inc., 13395 New Airport Rd., Suite G, Auburn, CA 95602. Tel: (530) 878-5350. Web: passlabs.com.

COMPANY INFO
Pass Laboratories Inc.
13395 New Airport Rd., Suite G
Auburn, CA 95602
(530) 878-5350
ARTICLE CONTENTS

COMMENTS
Kal Rubinson's picture

A frightening thought:

Can Pass whip up a 6 or 8 channel version of this?

John Atkinson's picture
Kal Rubinson wrote:
Can Pass whip up a 6 or 8 channel version of this?

I believe you can add additional audio-channel chassis, each controlled by the same control unit.

John Atkinson
Technical Editor, Stereophile

Kal Rubinson's picture

John Atkinson wrote: I believe you can add additional audio-channel chassis, each controlled by the same control unit.

I was really thinking of the price tag and the rack space.

Anton's picture

Didn't a prominent Stereophile editor once say that it was the preamp that was the most important part of a system?

;-D

It's out of my budget, but I love Nelson Pass.

liquidsun's picture

Hm, I see Sonus Faber Lumina III used as speakers during the review. Does that mean we can expect the Lumina's to be reviewed sometime in near future? :)

John Atkinson's picture
liquidsun wrote:
Hm, I see Sonus Faber Lumina III used as speakers during the review. Does that mean we can expect the Lumina's to be reviewed sometime in near future? :)

My review of the Lumina III will be published in the April issue of Stereophile.

John Atkinson
Technical Editor, Stereophile

liquidsun's picture

It's a pity that stereophile didn't review the SF sonetto line so we could make a direct comparison between both lines. However it's still good news to hear :)

tonykaz's picture

Didn't you say that you returned it ?

Did you have to purchase it or is it on long term loan?

Tony in Venice Florida

John Atkinson's picture
tonykaz wrote:
Didn't you say that you returned it? Did you have to purchase it or is it on long term loan?

After I measured the MBL N11 for Jason's review, I arranged to hold on to the preamplifier first to use in my followup review of the MBL N31 CD player/DAC in the December 2020 issue, then to use as a reference for this Pass Labs review. It has since been shipped to another Stereophile reviewer to use as a reference for a review of another product.

John Atkinson
Technical Editor, Stereophile

MarkusL's picture

I once connected my Wadia 781 directly to my power amplifiers (Pass X 600). The sound is much better with my preamplifier (Audio Research Ref 5) in between!

Kal Rubinson's picture

I know what you mean:

Quote:

I once connected my Wadia 781 directly to my power amplifiers (Pass X 600). The sound is much better with my preamplifier (Audio Research Ref 5) in between!

I gave up on finding a suitable preamp since I need 8 channels. I run my DACs directly to my power amps and it is, indeed, much better.

LTig's picture

I have some trouble looking at the signal to noise specs. The claim is 150 dB at max output voltage, and 500 nV residual noise, which is more or less what you expect with an output voltage of 23V and 150 dB S/N.

However JA measured 85 dB at 1 V. At 23 V we should then expect 27 dB more which is 112 dB, a whopping 38 dB less (a factor of 80). This would result in a residual noise of 56 mV, more than a factor of 100 higher, Even with bandwidth restriction and A-weighting the measured S/N reaches "only" 124 dB, 26 dB less than claimed.

WayneC's picture

The SN ratio was calculated from max output of 32 Volts with 1uV as the noise. The noise floor is actually lower than 1uV. It all depends how you measure it and the reference. Of course we spec it to look good, the suns output would make a good max reference. Measured on the AP with a 30 KhZ filter it is about 14 uV broadband. John's AP FFT show -120 to -140 dB range. 56 mV would be rather crappy, its a very quiet preamp.

LTig's picture

Aah, there is a typo on the specification page: 23 V max (correct is 32 V). So my calculations are 3 dB off.

14 uV noise broadband (30 kHz) is almost 30 times more than the specified 0.5 uV. May I ask under which conditions you did measure those 0.5 uV?

Regarding JA's FFT plot: one have to keep in mind that the FFT noise floor does not show the S/N value. You have to subtract the FFT gain (3dB per doubling of bin size) to get the real value. I don't know the FFT size of JA's FFT plot. With 16k FFT size the FFT gain is 39 dB. Subtracting 39 dB from 120 - 140 dB we get 81 - 101 dB which correlates quite well with JA's measured S/N.

Michael Fremer's picture

No one else has to tell me that you digitize your analog. You just did! One thing's for certain: we ALL have to analog our digital in order to hear it!

John Atkinson's picture
Michael Fremer wrote:
No one else has to tell me that you digitize your analog. You just did!

Me and my big mouth :-)

John Atkinson
Technical Editor, Stereophile

krahbeknudsen's picture

I hope you don't mind if I point out that your turntable setup is perhaps getting a bit long in the tooth? I love the Linn and all that but at lot has happened since 1991 even in Linn world. That old MDF tone arm board is not exactly known for it's high resolving power. Could it be that your digital setup is outresolving your turntable in the time domain and perhaps that would not be the case with a modern turntable or even an up to date Linn?

John Atkinson's picture
krahbeknudsen wrote:
I hope you don't mind if I point out that your turntable setup is perhaps getting a bit long in the tooth? I love the Linn and all that but at lot has happened since 1991 even in Linn world...

Indeed it has, but I am so familiar, so comfortable, with the sound of my LP12-based LP system that I fear change.

John Atkinson
Technical Editor, Stereophile

a.wayne's picture

Why on earth would you not want to run the pre Amp Direct , favoring the sound of caps maybe ..??
Btw JA ,

Are those stereophile CD’s mentioned still available ..??

Regards

John Atkinson's picture
a.wayne wrote:
Are those stereophile CD’s mentioned still available ..??

Yes, see http://shop.stereophile.com/music-cds/

John Atkinson
Technical Editor, Stereophile

Charles E Flynn's picture

Looking at my test CDs, I found, with no jewel box, cover art, or record of purchase, Stereophile CD STPH-002-2. It was apparently the first test CD Stereophile made, released in 1990.

jahnghalt's picture

I suggest a follow up to address those coupling caps.

"The output is still capacitor-coupled even with the servo but can be bypassed with internal jumpers."

On the back panel - "no user serviceable parts"

Question for Wayne - why not have jumpers accessible to the exterior? Note all those XLR jack jumpers/

(good photos BTW)

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