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Old 4th January 2016, 11:23 PM   #1
britshc is offline britshc  Canada
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Default Pass Labs x.150 Problems

I recently purchased an x.150 ( circa 2000 build date) for a second audio system. I admired an was curious about the build philosophy of the Pass products and have aways gravitated towards audio electronics with simple and minimal gain stages (and simple crossovers in speakers). To my ears they sound more like music and typically are more dynamic and life-like.

I also happen to own a balanced DAC/Pre (made/distributed by K&K Audio) and though the balanced output would match a Pass Labs amp well.

I have had the amp for a fews days now but have not had much luck with the amps performance in my system. While the amp is quite tonally correct and runs quite - it is dynamically flat and lifeless. If i didn't know better it sounds to me like a 10 watt amp might present and not the rated 150w of this model.

I have tried switching from XLR to RCA inputs ( little difference) . I have tried switching out different speakers ( both of which are 84-86 db small monitor 2 way speakers with very simple crossovers). No luck with either.

When i replace the x.150 with my Naim 250.2 amp ( 70 watts) i regain the dynamic presentation and the small monitor speakers once again sing.

Before i pass this off as an audio experiment gone wrong, or poor matching to my pre-amp - perhaps there is something i am missing? Would the caps beginning to age on the now 15 year old x.150 present like this? Would a bias issue present like this?

Or perhaps these 'x' series amps are just not as dynamic as some of their counterparts and there are not issues with the unit?

My, pre amp's specs are: Output voltage: 2vRMS at 0dBfs;
Output impedance: 350 ohms


Thanks in advance for any advice forum members may have.

Im located in Canada so delivery the manufacture would be a logistical nightmare.

Britshc
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Old 5th January 2016, 12:08 AM   #2
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any pictures of innards possible , at least to try to see was there any fiddling with it ?
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Old 5th January 2016, 12:16 AM   #3
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Hmm, The amplifier cannot reduce dynamics unless it is horribly compressing things. Not heard a modern Naim, but the older stuff was coloured in a way to enhance their famous 'PRAT'. I would listen to it for a week and see how you feel then. Totally possible caps are in need of replacement, but something doesn't feel right.
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Old 5th January 2016, 01:50 AM   #4
britshc is offline britshc  Canada
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Zen,

i cannot figure out how to attach images to this website, but the insides look entirely stock and unmolested.

I looked at some prior posts of yours and while i had the lid off did a few measurements with a digital volt meter and got the following readings after the unit had been powered up (fully) for about 30min:

Main board pins: 0.106 for one side and 0.109 for other ( slightly higher than the 0.94 referance)

Right speaker term output: btw 0.218 - 0.224 btw positive and negative; and 2.48 & 2.25 against ground (the housing of the amp)

Left output: 0.0 btw positive and negative; and 0.15 & 0.15 against ground (the housing of the amp).


Not sure how helpful this information is. If you send me an email adr - i will send you pics directly if you like.

Build date seems to be 2001.
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Old 5th January 2016, 02:04 AM   #5
britshc is offline britshc  Canada
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Bill,

thxs for your reply. It feels like an impedance or component mismatch. Or something about the speaker crossover that is unfriendly to a Pass design. it not a small difference, its striking. I was under the impression that these amps are know for their attack and PRAT.

One item of note. I had to increase the volume on the preamp significantly to achieve the same volume from the speakers. My Naim amp is rated 29db gain. Where the x.150 is 30db gain. So in theory they should be a similar output, no? Im out of my depth here - so bare with me....
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Old 5th January 2016, 02:34 AM   #6
Zen Mod is offline Zen Mod  Serbia
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feel free to toss as many pictures you can on >sasica5@gmail.com<

leave them unshrinked/original size

even better , if you have dropbox or some other way of putting big and plenty pictures on similar server , that would save us e-mailing procedures/limits

regarding hum/buzz and similar nastiness - I understand none of them are present , having X150 in system ?
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Old 5th January 2016, 02:42 AM   #7
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hm..
I have an x150, should be a thread here about the poor thing. Pass X150 Where does it sit in the overall line up ??
Even before the minor reno I did, it still seemed very happy to drive the few speakers I have to throw at it.

With every speaker it's always been really really nice.

But I don't know what your Naim sounds like..

If you can post pics, the brains trust here should be able to pick out which version it is and advise from there.

At least my fussy memory thinks theres more than one version ?

Last edited by Old'n'Cranky; 5th January 2016 at 02:46 AM.
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Old 5th January 2016, 03:00 AM   #8
britshc is offline britshc  Canada
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Zen,

i sent some pics to you via a Drop Box invite. I can add any further pics of any other parts that is helpful if there is not enough detail in the pics i provided.


No noise from the unit. It runs quite ( no hums and no pops). The x.150 seems to just not have much gain, or much capacity to render transient passages of music with any authority.
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Old 5th January 2016, 04:03 AM   #9
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to shorten things - send invite for DB to >choky@neobee.net< , as such I'm recognized at DB
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Old 5th January 2016, 04:58 AM   #10
Zen Mod is offline Zen Mod  Serbia
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got 3 pictures in DB

but , now I need some sleep ...... it's dawn already
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