Hi, I have recently acquired a Pass Labs X2.5 Preamp and X150.5 power amp, both just 5 years old. I'm not having much luck with either I'm afraid.
The pre developed this cracking/popping sound accompanied by this 'electronic rushing wind sound' in the right channel. It's very hard to describe in words.
Here's a recording of it - click here for video
The level it's at is quite loud, and it's not affected by turning the volume between 1 and 30. However at a volume of 0, it cannot be heard, and turning the volume from 0 to 1 (which you can hear me doing towards the end of the recording) seems to trigger the sound.
It's been at my tech for over a week now and he's not heard it again, but after hours of playing when it first happened for me, once it started it would only stop for a minute or 2 then it would begin again.
Any ideas on what this could possibly be?
The pre developed this cracking/popping sound accompanied by this 'electronic rushing wind sound' in the right channel. It's very hard to describe in words.
Here's a recording of it - click here for video
The level it's at is quite loud, and it's not affected by turning the volume between 1 and 30. However at a volume of 0, it cannot be heard, and turning the volume from 0 to 1 (which you can hear me doing towards the end of the recording) seems to trigger the sound.
It's been at my tech for over a week now and he's not heard it again, but after hours of playing when it first happened for me, once it started it would only stop for a minute or 2 then it would begin again.
Any ideas on what this could possibly be?
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if swapping UGS modules between channels leaves problem in same channel , then problem is after them
so - most probably (right channel) volume circuit itself , counting on fact that PSU for volume is shared between channels
I resume that noise will go in both channels , if you activate mono function ?
it seems temperature dependent problem , so - put some cushion on top of preamp , trying to provoke it
so - most probably (right channel) volume circuit itself , counting on fact that PSU for volume is shared between channels
I resume that noise will go in both channels , if you activate mono function ?
it seems temperature dependent problem , so - put some cushion on top of preamp , trying to provoke it
Problem is after I dropped it off to the tech, he's not heard the noise again! We'd discussed swapping the UGS modules over and seeing if the noise followed.
He tried running it in proximity of a space heater to get it a bit warm, but to no avail. Once we get it to produce the noise again, we'll be able to continue the troubleshooting process. I was just posting this up here with the sound clip in case someone could say yes I've heard that exact noise and it was xxxx failed.
He tried running it in proximity of a space heater to get it a bit warm, but to no avail. Once we get it to produce the noise again, we'll be able to continue the troubleshooting process. I was just posting this up here with the sound clip in case someone could say yes I've heard that exact noise and it was xxxx failed.
whatever it is , it isn't from components/positions common for both channels
so , either UGS or attenuator stage
presuming that you're using balanced route to amp , SE output module is out of suspicion
so , either UGS or attenuator stage
presuming that you're using balanced route to amp , SE output module is out of suspicion
Well actually I was using RCA's (SE) with the XLR shorting pins in place. Is that the same as using XLR's or not? If not, that could be something to try.
I'm not sure how intimately you know it but if you can indicate anything that is active with RCA's + shorting pins that is not active when RCA's without shorting pins are used, this could really help pin things down.
The noise was independent of volume setting 1-31 but was silent at volume 0 . I was leaning towards it not being in the attenuation circuit but I could be wrong. What do to the UGS modules do?
I'm not sure how intimately you know it but if you can indicate anything that is active with RCA's + shorting pins that is not active when RCA's without shorting pins are used, this could really help pin things down.
The noise was independent of volume setting 1-31 but was silent at volume 0 . I was leaning towards it not being in the attenuation circuit but I could be wrong. What do to the UGS modules do?
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preamp is having dedicated buffer stage , just for SE/RCA drive
however , with no popping with attenuator on "0" , I resume that problem lies in preceding , so - attenuator stage
though , only Wayne and Papa can confirm that with 100% certainty
edit : with presumption that swapping UGS modules result in conclusion that they're not problem
however , with no popping with attenuator on "0" , I resume that problem lies in preceding , so - attenuator stage
though , only Wayne and Papa can confirm that with 100% certainty
edit : with presumption that swapping UGS modules result in conclusion that they're not problem
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Thanks. I had another thought. The preamp hasn't put a foot wrong in 1.5 weeks of up-time alone. My X150.5 is making a reasonably loud 'thump' on power on only when the XLR shorting pins (for pins 1 & 3) are used. When purely single ended with no shorting pins, there is a very soft turn on/off sound. If I turn it off then turn it back on within a second or so with the XLR pins in place, it thumps loud enough to feel the bass impact in your chest and the current meter swings 3/4 of the way across the dial.
I had the thought that the X150.5 could somehow be influencing the X2.5 causing the sound?
I had the thought that the X150.5 could somehow be influencing the X2.5 causing the sound?
possible ...........
but your tech must be capable of concluding that , with simple elimination process
though , it certainly will need some time
but your tech must be capable of concluding that , with simple elimination process
though , it certainly will need some time
I'm not much on troubleshooting amps, and I'm sure the Pass Posse will be along to help, but none of my Pass amps make even a hint of thump at turn on or turn off.
Does it make the thump when connected to something other than the X2.5?
yes, I have another preamp and when connected single ended with XLR pins in place it thumps on power on (not on power off). Even when nothing is connected to the X150.5 at all (but XLR pins in place) it thumps, however when I removed the XLR pins it makes a barely audible pop at power on and power off.
what's the DC offset between output (+ and -) output terminals ?
same thump on both channels ?
if yes ....... PSU caps issues come to my mind
same thump on both channels ?
if yes ....... PSU caps issues come to my mind
No idea but I have a multimeter, how do I measure it? Yes as far as I can tell same thump on both channels.
The amp is not even 5 years old, PSU caps already? Thought this was a premium brand and it even says in the manual it's expected lifespan is 15-20 years. I would have thought something like PSU caps would have a global effect and if they were on the way out, then it wouldn't make any difference having the XLR shorting pins in place or not.
The amp is not even 5 years old, PSU caps already? Thought this was a premium brand and it even says in the manual it's expected lifespan is 15-20 years. I would have thought something like PSU caps would have a global effect and if they were on the way out, then it wouldn't make any difference having the XLR shorting pins in place or not.
I can't tell anything being 100% sure , so take everything as half-educated guesses , my crystal ball being not so shiny , lately 😉
your gear , being SH , is possible having dark history ....... there are many temperature abused amps around , and caps don't like excessive temp.
as said - nothing which good tech can't solve , in vivo
DC offset - let amp heat for an hour , put your DMM in DC voltage range , either 200mV or auto range , stick probes on speaker outputs (red to red , black to black) , one channel , then other
write here what you got
your gear , being SH , is possible having dark history ....... there are many temperature abused amps around , and caps don't like excessive temp.
as said - nothing which good tech can't solve , in vivo
DC offset - let amp heat for an hour , put your DMM in DC voltage range , either 200mV or auto range , stick probes on speaker outputs (red to red , black to black) , one channel , then other
write here what you got
The guy I bought it from was an older gentleman with other very expensive gear. He was the first owner, the amp and pre had their own shelves in his listening room, and he traveled a lot for business and only really used the gear on weekends. As far as I can tell, they've had a very easy life. Aesthetically they appear brand new.
I have no preamp connected, is it OK to measure DC voltage across the speaker terminals of a power amp with no preamp connected to it?
I have no preamp connected, is it OK to measure DC voltage across the speaker terminals of a power amp with no preamp connected to it?
Turned on from cold and measured:
L = 15.5mv
R= -8.5mv
If I put the red probe in the black speaker terminal and black probe in red terminal I get (positive) 8.5mv for the right channel so it appears to be less than 0mv.
L = 15.5mv
R= -8.5mv
If I put the red probe in the black speaker terminal and black probe in red terminal I get (positive) 8.5mv for the right channel so it appears to be less than 0mv.
Can I measure DC voltage across the RCA inputs on the power amp in the same way? Center to outer I mean.
regarding offset - everything looks just completely normal
so , if that thump is too much of worry , your tech need to check all caps ( especially PSU ones)
thump is usually saying that some cap(s) aren't keeping with others , in time domain
so , if that thump is too much of worry , your tech need to check all caps ( especially PSU ones)
thump is usually saying that some cap(s) aren't keeping with others , in time domain
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