Nuuk said:
I haven't checked it out thoroughly, but I suspect the chassis has almost no effect in my circumstance anyway. The amp in chassis with the screened toroid is completely free from the line ticks and pops with its lid off.
The other remedies (more caps, snubbers, or series impedance) may have unwanted effects or desirable benefits depending on your individual taste.
I agree Jeff.!
There are two types of interference in my book. The first is the one that I get when I switch on the lamp near the GC to choose a CD. There is a small pop. But as it only happens when I am putting on a CD, it doesn't bother me and I can live with it.
The other type is the interference that I used to get from my old fridge-freezer. I had no control over when that occurred so I dealt with as described on Decibel Dungeon.
But I would always try and treat the source rather than add extra components to the amp!
Re: Re: noise / hum
If you have a "good" regulator -- (one which has a fast, low noise error amplifier) it will catch the "pop" if it is transmitted through the mains. The further problem is, however, that the mains act as a radiator, not just a transmission line -- particularly for this kind of problem (some time when I pull out a bottle of Vinho Verde we can discuss RFI caused by a lightbulb which was not completely screwed in.)
Placing a cap across the +/- inputs of the overture chips -- 100nF is way, way too much -- we are talking maybe a few hundred picofarads --
Aside from the bifilar choke and caps on the mains input -- consider placing a ferrite bead on each input lead. Still a problem -- use a differential input amplifier to a common output -- place a ferrite bead on each of the inverting and non-inverting inputs.
And the supply bypassing is very important -- no matter what the minimalists say it is good design practice -- or at least from the perspective of the folks from Analog Devices and Burr Brown who make the opamps for ultrasound equipment, sonobuoys etc -- 100nF ceramics placed as closely to the V+/- supply pins of the Overture chip.
carlosfm said:
If you have a "good" regulator -- (one which has a fast, low noise error amplifier) it will catch the "pop" if it is transmitted through the mains. The further problem is, however, that the mains act as a radiator, not just a transmission line -- particularly for this kind of problem (some time when I pull out a bottle of Vinho Verde we can discuss RFI caused by a lightbulb which was not completely screwed in.)
Placing a cap across the +/- inputs of the overture chips -- 100nF is way, way too much -- we are talking maybe a few hundred picofarads --
Aside from the bifilar choke and caps on the mains input -- consider placing a ferrite bead on each input lead. Still a problem -- use a differential input amplifier to a common output -- place a ferrite bead on each of the inverting and non-inverting inputs.
And the supply bypassing is very important -- no matter what the minimalists say it is good design practice -- or at least from the perspective of the folks from Analog Devices and Burr Brown who make the opamps for ultrasound equipment, sonobuoys etc -- 100nF ceramics placed as closely to the V+/- supply pins of the Overture chip.
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