The chip (LM3886) and the board are on the opposite side of the enclosure from the mains input and wiring, I moved the other wires so that the feed and return from the mains switch all run together across the front panel. I twisted the wires as much as they would reasonably allow but I might manage to force another couple of turns in them. I wonder if it's because of the close proximity of the transformer to the front panel. I even removed the feed from the board to the power switches inbuilt LED. None of this made any difference.
The other thing I wondered about is the casework, the individual sections are probably quite well insulated from each other by paint, even the screws which hold it together are painted. I might try sandpapering the paint off where the panel edges meet each other to make a better connection between them.
To be honest the hum is very low, I'm probably just being fussy in trying to reduce it further.
The other thing I wondered about is the casework, the individual sections are probably quite well insulated from each other by paint, even the screws which hold it together are painted. I might try sandpapering the paint off where the panel edges meet each other to make a better connection between them.
To be honest the hum is very low, I'm probably just being fussy in trying to reduce it further.
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The "New & Improved" all metal mini chassis is almost done. There was no hum in the Old Wooden Bucket that failed, so we'll see if being super close is a problem.
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That might actually be worth a try. Mind you the transformers have an inbuilt screen which appears to make no difference, however I think it's between the windings although I have been wrong in the past
An external copper screen might work better.
Then again, I have not tried as Dario suggested, rotating the transformers. I thought since they are toroid's that sort of thing was not an issue. I might try lengthening the leads on them to allow me to rotate them
Thanks rredline, link works now. I remember reading that article before, I wonder if it might be worthwhile fitting that ground breaker circuit at some point.
Anyway, I just tried back to back comparisons with and without the DCB1 in circuit and to be honest, I don't think it's making any difference now except to add further hum. This could in part be due to me changing from a 20k pot in my passive pre to a 10k one. Or it could be due to the FE's having 'burned' in now. Either way if it's not doing anything useful it's not wanted in my setup. The hum without it in circuit is so low as to not really be an issue to someone without OCD. You can still hear it with your ear hard against the drivers but I've yet to hear an amp through these speakers which is totally silent.
I think I might just call it a day at that and enjoy the FE's, they are brilliant after all.
Anyway, I just tried back to back comparisons with and without the DCB1 in circuit and to be honest, I don't think it's making any difference now except to add further hum. This could in part be due to me changing from a 20k pot in my passive pre to a 10k one. Or it could be due to the FE's having 'burned' in now. Either way if it's not doing anything useful it's not wanted in my setup. The hum without it in circuit is so low as to not really be an issue to someone without OCD. You can still hear it with your ear hard against the drivers but I've yet to hear an amp through these speakers which is totally silent.
I think I might just call it a day at that and enjoy the FE's, they are brilliant after all.
Today is a good day, well so far anyway lol.
I tried moving the transformer but that made no difference.
When you rule out the complex, it must be something simple, and it was.
A dam noisy switch mode power supply for a modem on the same ring mains which feeds the HIFI, DOH!
Oh well, at least it wasn't my build at fault.
Bob your layout should be fine, the FE is not much bothered by having a transformer very close to the board.
Thanks everyone for helping me, I should have realised far sooner than this.
Cheers
Davy
I tried moving the transformer but that made no difference.
When you rule out the complex, it must be something simple, and it was.
A dam noisy switch mode power supply for a modem on the same ring mains which feeds the HIFI, DOH!
Oh well, at least it wasn't my build at fault.
Bob your layout should be fine, the FE is not much bothered by having a transformer very close to the board.
Thanks everyone for helping me, I should have realised far sooner than this.
Cheers
Davy
Glad to hear of the progress. Just a note, a shortcut to those results was implied in the suggestion to "Use the living room floor " and add one piece at a time. It works for me usually after my knees are sore from crawling behind the stack or trying to focus while standing on my head - but eventually....
Great perseverance. You should try bronco busting
" and add one piece at a time. It works for me usually after my knees are sore from crawling behind the stack or trying to focus while standing on my head - but eventually....Great perseverance. You should try bronco busting
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I wonder if it's possible to tell whether the SMPS was sending air waves or copper waves to the stereo system?
If air waves, then good screening would help. Good twisting also helps a lot.
If copper waves, then attenuation at every cable entry is required. That attenuation is best if it can go screen to chassis. This is achieved if you use the can encased RFI mains connectors. As much of the can should make electrical contact around the perimeter of the hole through which it passes.
You can also add common mode attenuation from poles to chassis. Even the TWO speaker terminals can benefit from this.
Who says SMPS are "best"?
All smps should have rfi attenuators between the mains and the smps.
The very small plugtop style may not have any RFI attenuator.
Maybe these should be plugged in via an attenuator !
Does anyone make a suitable flat pack attenuator to fit between the mains socket and the plug top appliance?
If air waves, then good screening would help. Good twisting also helps a lot.
If copper waves, then attenuation at every cable entry is required. That attenuation is best if it can go screen to chassis. This is achieved if you use the can encased RFI mains connectors. As much of the can should make electrical contact around the perimeter of the hole through which it passes.
You can also add common mode attenuation from poles to chassis. Even the TWO speaker terminals can benefit from this.
Who says SMPS are "best"?
All smps should have rfi attenuators between the mains and the smps.
The very small plugtop style may not have any RFI attenuator.
Maybe these should be plugged in via an attenuator !
Does anyone make a suitable flat pack attenuator to fit between the mains socket and the plug top appliance?
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Bob, I think it's because of our ring mains system, when I tried the amps in a different position, it appears that the different socket I used shared the same ring as the one I normally use AND that dam SMPS is also plugged into.
Cheers Marra, I'm glad to have found the source of mains evil. It seems the FE's are more sensitive to mains pollution then my previous amps were, I didn't notice this in the past.
Andrew, good points. Can encased RFI mains sockets would definitely be a good idea with these amps. I often read audiophiles posts preaching the evils of SMPS, this is the first time I have really had an issue with them. My DAC & phono stage are powered by one but it's made for purpose by Musical Fidelity so I suppose it's better filtered than the wallwart causing the problem.
A further point is that I did also have an issue with a pin on my passive input selector which was held in loose contact by the heat shrink sleeve I fitted when I first wired it up.
Having two sources of hum threw me to say the least, I was doubting my sanity for a bit there. I'm just glad to have finally resolved this issue. Even having the system plugged into a mains isolation/surge protection block didn't help with this. Be wary of SMPS folks!
Cheers Marra, I'm glad to have found the source of mains evil. It seems the FE's are more sensitive to mains pollution then my previous amps were, I didn't notice this in the past.
Andrew, good points. Can encased RFI mains sockets would definitely be a good idea with these amps. I often read audiophiles posts preaching the evils of SMPS, this is the first time I have really had an issue with them. My DAC & phono stage are powered by one but it's made for purpose by Musical Fidelity so I suppose it's better filtered than the wallwart causing the problem.
A further point is that I did also have an issue with a pin on my passive input selector which was held in loose contact by the heat shrink sleeve I fitted when I first wired it up.
Having two sources of hum threw me to say the least, I was doubting my sanity for a bit there. I'm just glad to have finally resolved this issue. Even having the system plugged into a mains isolation/surge protection block didn't help with this. Be wary of SMPS folks!
I just tried changing that optical link between my V-LINK and V-DAC back to the original coax and I got some noise back as long as my netbook is running on it's own SMPS. The system is now silent when running on it's battery.
The optical link went back in fast. I can't tell that much difference between them sound quality wise anyway.
It would appear that in fact I actually had THREE sources of noise entering my HIFI originally and they all added up to quite a racket
Conclusion - non HIFI specified SMPS are indeed the devils work
The optical link went back in fast. I can't tell that much difference between them sound quality wise anyway.
It would appear that in fact I actually had THREE sources of noise entering my HIFI originally and they all added up to quite a racket
Conclusion - non HIFI specified SMPS are indeed the devils work
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