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Help and Advice Pass Labs X0.2
Help and Advice Pass Labs X0.2
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Old 11th January 2019, 05:05 AM   #1
nooshinjohn is offline nooshinjohn  United States
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Default Help and Advice Pass Labs X0.2

I have a new(to me) Pass Labs X0.2, that was just serviced and given a clean bill of health at the Lab just this past week. It was sent in because it had a loud and very audible "pop" between steps on the volume, and an audible "hiss" similar to what you would hear on a cassette tape back in the day. This hiss gets louder with each step up in volume and once an increment of 10 is achieved, the hiss steps back down again.

A large shift away from factory settings for DC offset were found and corrected, as well as a handful of capacitors found to be out of spec and replaced. The popping sound has been diminished by about 50 percent, but I find that the hissing noise is still there and very much a distraction to listening.


I sit 10 feet away from my speakers, and use Polk Audio SDA-SRS 1.2TL's, which have crossovers that have been recapped. The speakers are 91db efficient. Driving them is a set of Carver 350 watt tube amplifiers. All connections to source components are made through XLR cables made by Audioquest.

My previous preamp was a Pass Labs X1, which exhibited none of the noise issues I have described. I do understand the pop sound is a function of the volume control and is a characteristic of it's design, and I am more than ok with that.

All functions of the pre work as intended and it sounds great otherwise. The only issue that really concerns me is that hissing sound. It is present regardless of source selected and can be heard some 20 feet away from the speaker even if nothing is playing. Is there something that can be done to reduce or eliminate this noise?

Last edited by nooshinjohn; 11th January 2019 at 05:48 PM.
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Old 11th January 2019, 04:55 PM   #2
Nelson Pass is offline Nelson Pass  United States
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Help and Advice Pass Labs X0.2
I'm a little confused. Is this a X0.2 or X1?

In either case we need Wayne to chime in. As he is out at Sea Ranch today,
I will ask him.

That it goes up and down with volume tends to indicate source.
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Old 11th January 2019, 05:08 PM   #3
nooshinjohn is offline nooshinjohn  United States
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We are talking about an X0.2 Mr Pass. I do have an X1 as well. The X1 works well with my system. The X0.2 does not.

I was thinking along the lines of an impedance issue between amps and pre. The amp's specifications are....

The amplifier specs...

2 Hz to 85 kHz (–3 dB)
Distortion: Less than 0.5%
Power Bandwidth: 24 Hz to 28 kHz without filters
Line Inputs: 1 RCA
Input Impedance: 100 K ohms (RCA)
Gain: 30 dB (8 ohms)
Tube Complement: One 12AX7, one 12AT7, one 6AL5, six KT120
Hum and Noise: Better than 120 dB, referred to 350 watts, A-weighted

Last edited by nooshinjohn; 11th January 2019 at 05:19 PM.
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Old 11th January 2019, 05:49 PM   #4
nooshinjohn is offline nooshinjohn  United States
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I am deeply grateful for your help Mr. Pass.

Last edited by nooshinjohn; 11th January 2019 at 06:02 PM.
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Old 11th January 2019, 06:37 PM   #5
nooshinjohn is offline nooshinjohn  United States
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Some more information if it helps... it does this independent of source selected and is still present even with no source connected to the preamp. The hiss is present even if the attenuation is set to zero. It is also present in both left and right channels. In my mind, that eliminates cables or source components from being an issue.

It would appear to be exclusive to the preamp itself, or in the match between amps and preamp.
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Old 12th January 2019, 05:13 AM   #6
wayne is offline wayne  United States
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Help and Advice Pass Labs X0.2
The 0.2 shouldn’t have noise like that. I am not sure I saw that in for service but will check Monday so we can get it taken care of.
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Old 12th January 2019, 05:59 AM   #7
nooshinjohn is offline nooshinjohn  United States
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I spoke to Kent around 1pm today... They are sending me some shorting pins for the RCA's and XLR's. He wants me to unplug the sources from positions one and two, then report back and let him know if the noise changes. I agree however, the noise should not be there.

Thank you Wayne for looking into this for me, and thank you Mr. Pass for getting Wayne involved.

Hissing aside, I am in AWE of how much more resolving and detailed this preamp is in my system. Once it gets dialed in, I will be a happy camper until I can convince my wife an XP-32 is in order.
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Old 12th January 2019, 06:29 AM   #8
dtaylo3 is offline dtaylo3  United States
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That's what I call some impressive customer service!!! Most cool.
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Old 12th January 2019, 05:39 PM   #9
Nelson Pass is offline Nelson Pass  United States
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Help and Advice Pass Labs X0.2
We are fortunate that service problems are few enough that they don't
tax our resources.

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Old 12th January 2019, 06:04 PM   #10
dtaylo3 is offline dtaylo3  United States
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While I take that fact as 100% true, it is evident that your personal philosophy on quality, transparency and an obvious high level of integrity, serve to place you and your companies on a far different level than most. It is rewarding to witness and deserves commendation.
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