Hello all, this is my first post in your very interesting forum.
I design and build tbe amps and preamps as a hobby, but for a phono preamp I changed and purchased a mint second hand Pass Labs XP-17.
I design and build tbe amps and preamps as a hobby, but for a phono preamp I changed and purchased a mint second hand Pass Labs XP-17.
The PX-17 sounds great but I have a right chanel hum when the volume control is above 12 0'clock.
In my system I have a Linn Sondek LP12 Klimax, self made tube amps (PP 2a3, SE 845) and preamps, Naim Nap 250 whith his preamp,, Audio Research Reference 3,, Nagra bps phono, Avantgarde Duo Grosso speakers and much other collective stuff.
My system is dead quiet.
The Pass Labs XP-17 has a right chanel hum due to electro magnetic field radiation of the power transformer.
I have rotated the transformer a quarter turn clockwise and solved 90 per cent of the problem, but replacing the top cover on the hum is back but not so bad as before.
I think this is due to a faulty power transformer, I have sent a mail to Pass Labs for help.
Any suggestions or advice?
Thank you
In my system I have a Linn Sondek LP12 Klimax, self made tube amps (PP 2a3, SE 845) and preamps, Naim Nap 250 whith his preamp,, Audio Research Reference 3,, Nagra bps phono, Avantgarde Duo Grosso speakers and much other collective stuff.
My system is dead quiet.
The Pass Labs XP-17 has a right chanel hum due to electro magnetic field radiation of the power transformer.
I have rotated the transformer a quarter turn clockwise and solved 90 per cent of the problem, but replacing the top cover on the hum is back but not so bad as before.
I think this is due to a faulty power transformer, I have sent a mail to Pass Labs for help.
Any suggestions or advice?
Thank you
In the case I do not replace the transformer what do you think about the Trafo shielding sheet from Don Audio?
Ciao, benvenuto.
I cannot help much, if the trafo is your problem, you may also look for top audio grade Toroidy transformers from Poland..
I cannot help much, if the trafo is your problem, you may also look for top audio grade Toroidy transformers from Poland..
if content with need for xformer replacement, it'll be best to definitely confirm hypothesis
remove xformer from case and temporary connect it with long wires, placing it 30-40cm away
if hum is gone, hypothesis confirmed
remove xformer from case and temporary connect it with long wires, placing it 30-40cm away
if hum is gone, hypothesis confirmed
There is no doubt because rotating the trasformer the hum is greatly reduced.
There must be a great radiating lobe from the toroid that is not normal.
Maybe the electro magnetic field radiation can be reduced with a trafo shielding sheet from Don Audio.
Any experience with shielding sheets?
There must be a great radiating lobe from the toroid that is not normal.
Maybe the electro magnetic field radiation can be reduced with a trafo shielding sheet from Don Audio.
Any experience with shielding sheets?
I'm getting all my Donuts from local winder (asked, they're not willing to send abroad), with exact specs as said for PL - static shield, magnetic shield
more or less, that's standard for low and line level signal stages, whatever construction in case
I know that magnetic shield on mine is made of same magnetic strip (several turns) as used for xformer toroid core
Anyhow - I don't know what happened with your exact xformer to start spraying bad vibes, so I can't predict how much of that spray could be suppressed using any type of shielding
instead of applying any sort of cure, best to simply replace it with proper quality one - either gotten directly from PL (whatever you agree with them) or ordering locally, by data given by PL
in general, whatever type of shielding, count that thickness of shield is very/most important; so - chunky it must be; even piece of steel tube with thick wall will do the job, nicely wrapped with fabric Tesa tape
more or less, that's standard for low and line level signal stages, whatever construction in case
I know that magnetic shield on mine is made of same magnetic strip (several turns) as used for xformer toroid core
Anyhow - I don't know what happened with your exact xformer to start spraying bad vibes, so I can't predict how much of that spray could be suppressed using any type of shielding
instead of applying any sort of cure, best to simply replace it with proper quality one - either gotten directly from PL (whatever you agree with them) or ordering locally, by data given by PL
in general, whatever type of shielding, count that thickness of shield is very/most important; so - chunky it must be; even piece of steel tube with thick wall will do the job, nicely wrapped with fabric Tesa tape
Did anyone have problems of electro magnetic field radiation with toroidal transformers that causes hum?
Yes, when I build the AlephX and this post from Nelson did the trick:
https://www.diyaudio.com/community/threads/industrial-alephx-high-power-version.14979/post-289095
Adding "one rectifier bridge for each rail polarity" fixed the problem.
It's hard to imagine this would be your problem on a factory made Pass amp.
https://www.diyaudio.com/community/threads/industrial-alephx-high-power-version.14979/post-289095
Adding "one rectifier bridge for each rail polarity" fixed the problem.
It's hard to imagine this would be your problem on a factory made Pass amp.
I hooked up an older XP17 set at 60dB to a headphone amp via RCA cables. With the volume set to max level, I did not hear any hum on either channel on the headphones.
(Obviously I wasn't playing a record when I did that. 🙂 )
On the odd occasions I contacted PL's service dept via email their responses were very quick, so I imagine you will hear back from them after the weekend.
I hope you have this hum issue resolved soon.
(Obviously I wasn't playing a record when I did that. 🙂 )
On the odd occasions I contacted PL's service dept via email their responses were very quick, so I imagine you will hear back from them after the weekend.
I hope you have this hum issue resolved soon.
Thank you, using headphone or speakers is the same.
I am convinced that the power transformer is faulty.
I am convinced that the power transformer is faulty.
Hi 6L6, you performed the mod on a XP-17?
Moved the trasformer in a separete power supply, but the connection cord is in ac or dc?
Thank you
Moved the trasformer in a separete power supply, but the connection cord is in ac or dc?
Thank you
