is "floating phase" system having proper safety gnd potential ?
I resume not ..... it's more likely "nulled" ( which is term for tying neutral and safety gnd in home electrical installation) ?
if that is the case ...... that's just dummy safety gnd , having some safety virtues but certainly not working as proper drain of mains related nuisances
I resume not ..... it's more likely "nulled" ( which is term for tying neutral and safety gnd in home electrical installation) ?
if that is the case ...... that's just dummy safety gnd , having some safety virtues but certainly not working as proper drain of mains related nuisances
did we established - is it hiss , or sort of buzz ?
hiss is , someone already wrote , as upper part of noise from FM tuner between two stations
buzz is much lower - and considering that PL factory amps are in question , gnd issues are out of question ..... but some mains related dirt is possible .......
is that single phase power grid , or multi-phase ?
if later , did you tried other phases , for amp(s) feed ?
hiss is , someone already wrote , as upper part of noise from FM tuner between two stations
buzz is much lower - and considering that PL factory amps are in question , gnd issues are out of question ..... but some mains related dirt is possible .......
is that single phase power grid , or multi-phase ?
if later , did you tried other phases , for amp(s) feed ?
aha , I found it
did you hear same buzz , mechanical , from amp cases ?
disconnect speakers for that
maybe you need DC blocker ........
regarding AC from wall , that's same everywhere - if anything else , having pure AC is a dream
often there is also some DC , riding all around AC , mostly residue from modern switching appliances , refrigerators etc.
if that's the case , toroid trannies will sweat much more then old EI ones .... most probably passing through at least some of that trouble to secondary side
there is no other way to test that then either try to observe mains with scope , measure with DVM ( set to DC) or simply making quick and simple DC blocker (DC block filter) and try with it ( you can make it as mock-up , on wood or plastic platform , as part of short extension cord ; be careful - mains voltage ! ........ if it helps ........ make nice box , with several of these , each feeding one precious apparatus )
look at pic
often there is also some DC , riding all around AC , mostly residue from modern switching appliances , refrigerators etc.
if that's the case , toroid trannies will sweat much more then old EI ones .... most probably passing through at least some of that trouble to secondary side
there is no other way to test that then either try to observe mains with scope , measure with DVM ( set to DC) or simply making quick and simple DC blocker (DC block filter) and try with it ( you can make it as mock-up , on wood or plastic platform , as part of short extension cord ; be careful - mains voltage ! ........ if it helps ........ make nice box , with several of these , each feeding one precious apparatus )
look at pic
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superlian, I have a similar setup, just not as pretty. 
I had a buzz and a hum. Tried cheater plugs one at a time. Made a small different in lowering the noise, but it also affected the sound some how. It was dry. Best I can describe.
System had an interconnect that was not shielded from XO to bass amp. Installed a shielded ICs on XO to bass amp and the noise was almost all but gone in the full range amps, but not the bass amp. The hum is a bit lower in the bass amp. Almost tolerable, but still wish it were gone.
Have you tried different ICs? Just a thought.
Vince
I had a buzz and a hum. Tried cheater plugs one at a time. Made a small different in lowering the noise, but it also affected the sound some how. It was dry. Best I can describe.
System had an interconnect that was not shielded from XO to bass amp. Installed a shielded ICs on XO to bass amp and the noise was almost all but gone in the full range amps, but not the bass amp. The hum is a bit lower in the bass amp. Almost tolerable, but still wish it were gone.
Have you tried different ICs? Just a thought.
Vince
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Here's the spectrum of that noise from the midrange section:
Makes sense if your line frequency is 50 Hz in Norway.
What's interesting is that it is barely audible from the woofer section, which I would expect to be strongest around 100 Hz.
I'm doubting any of this is amp related.
Also, based on the clip with the microphone close to the speakers, it doesn't seem terribly bad really, but worth continued experimentation if only for fun and education.
A lovely setup, by the way.
Edit: Do you know the frequency response of your microphone? Just wondering if that's why I can't hear the woofer section.
Makes sense if your line frequency is 50 Hz in Norway.
What's interesting is that it is barely audible from the woofer section, which I would expect to be strongest around 100 Hz.
I'm doubting any of this is amp related.
Also, based on the clip with the microphone close to the speakers, it doesn't seem terribly bad really, but worth continued experimentation if only for fun and education.
A lovely setup, by the way.
Edit: Do you know the frequency response of your microphone? Just wondering if that's why I can't hear the woofer section.
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I made a video with ipad. I think the noise here is easy to analyze:
https://www.youtube.com/watch?v=7d4AgwQkC5A
https://www.youtube.com/watch?v=7d4AgwQkC5A
So, let's say you're getting 54dB from .1 meters away from one speaker, that's 32dB from two speakers at your listening chair, which is just above a whisper as you described. 32dB at your listening chair from 95dB speakers requires about a microwatt from each channel, which would take a couple of millivolts of noise to produce, which more closely matches your description of being tube amp-like. So whatever ground loop or other line related phenomenon is present, it is certainly above the intrinsic noise of the amps themselves. Which just means it's probably worth tracking down.
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