| revell |
When I turn on my light while my music is playing, I hear a plopping noise coming from my speakers. At first I thought it was aproblem with ground in my house, so I disconnected the earth from the power distribution block. But this did NOT solve the problem, it just keeps plopping.
Any other gainclone owner who has this problem too? |
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| breez |
| Yes, same 'problem'. Happens also with a commercial amplifier (Hitachi integrated, circa 80s). |
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| revell |
| quote: | | Yes, same 'problem'. |
But no solution?
It is getting weirder: I've run both monoblocks and the pre of an UPS which was not connected to any AC outlet (purely on batterie power), I turn on the light: PLOP
Is this still normal?:bawling: |
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| pinkmouse |
| Radiated RF noise. Check all your cables are screened properly. Other than that, try a 0.1uf cap across the input pins on the chip. |
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| revell |
| Does the cap have to be on the chip or can I put it also on RCA connector (connecting the positive to the negative side)? |
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| Franz G |
The cap must sit directly at the positive and the negative input pin.
Nationals recommendation is 220pF for the LM3875.
Look here, page 4 and top of page 6:
http://cache.national.com/ds/LM/LM3875.pdf
Regards
Franz |
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| Nuuk |
| Or what about doing something about the light switch that is causing the RF? :att'n: |
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| revell |
Thank you for all the suggestions, I'll try putting the 220pf cap between pin 7 and 8.
This won't be easy, I guess because all the components are already soldered to the pcb.
Nuuk: I guess I could listen to the music in the dark;) |
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| Nuuk |
| quote: | | Nuuk: I guess I could listen to the music in the dark |
I'm a big fan of lateral thinking! ;)
But if you get afraid of the dark, I think you can put a capactior across the switch contacts to get rid of the RF thatit generates. Perhaps somebody more knowledgable can comment on the exact cap required. :att'n: |
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| revell |
This is probably a stupid question but I'm going to ask it anyway: is there an other way of saying 220pf. e.g. 2,2uf or 0,22mf
I can't find 220pf on the RS site |
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| Bill Fitzpatrick |
| quote: | Originally posted by Nuuk
Or what about doing something about the light switch that is causing the RF? :att'n: |
Replacing a light switch would be too easy. |
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| Nuuk |
| quote: | | This is probably a stupid question but I'm going to ask it anyway: is there an other way of saying 220pf. e.g. 2,2uf or 0,22mf |
1000 pF =1nF
1000nF = 1uF
1000uF = 1 F (farad)
So 220pF = 0.22nF = 0.00022uF |
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| lazyfly |
Had the same problem a few days ago from a fishtank light and the CC 220pF cap fixed it beautifully.
Try part# 264-4696 at RS
Was reminded after soldering the ceramics to the IC's that a 100R (5W wirewound) resistor and 100nF (Mains rated, AC!) capacitor such as RS part# 210-500 (240VAC) in series between Active and Neutral is meant to help filter out noise which may be easier than trying to stick ceramics onto your mounted amps. |
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| breez |
| quote: | Originally posted by Nuuk
1000 pF =1nF
1000nF = 1uF
1000uF = 1 F (farad)
So 220pF = 0.22nF = 0.00022uF |
Forgot one inbetween ;)
1000uF = 1mF
1000mF = 1F |
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| Nuuk |
| quote: | | Forgot one inbetween |
That was done deliberately! :rolleyes: There was a rumour that everybody in Finland sleeps all day on Sunday and I wanted to find out if it was true! :D |
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| breez |
| quote: | Originally posted by Nuuk
That was done deliberately! :rolleyes: There was a rumour that everybody in Finland sleeps all day on Sunday and I wanted to find out if it was true! :D |
:D
Re-do LM3886 amp internal wiring and grounds = no rest today :xeye: Still a mess, but cured the hum alright.. :smash: |
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| Nuuk |
| I completed my first LM3886 yesterday. I am glad to say it is perfectly silent when not playing music. ;) |
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| carlosfm |
| quote: | Originally posted by Bill Fitzpatrick
Replacing a light switch would be too easy. |
Exactly.
The cap across +In and -In is recommended anyway, but a noisy switch in the house should be replaced.
It's cheap.
Or do you guys feel fine watching a spark on the switch when you turn on the lighs?
Keep the electrical system on your house in shape, as you do with your amps.:cool:
I always tend to attack the source of the problem. |
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