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?
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?
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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
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
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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.
It would appear to be exclusive to the preamp itself, or in the match between amps and preamp.
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.
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.
We are fortunate that service problems are few enough that they don't
tax our resources.
That's why Pass is world class stuff. I have built my own tube amps, and nothing has solidified my setup quite like a Pass Labs preamp did.
Attachments
The shorting pins did nothing to resolve the hissing issues in my new preamp. Today I removed the Pass Labs X0.2 from the rig, pending an all expenses-paid trip back to the factory where Wayne himself will be going through everything from top to bottom, and re-installed the Pass X1.
UPS will be here tomorrow sometime to pick it up and we shall see what the wizard finds within. Hopefully the fix won't compromise the incredible detail this beast was delivering.
UPS will be here tomorrow sometime to pick it up and we shall see what the wizard finds within. Hopefully the fix won't compromise the incredible detail this beast was delivering.
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