hey thanks bud.
actually this is the one I was looking for (guess I was using wrong search terms)
http://www.diyaudio.com/forums/attachment.php?s=&postid=16083&stamp=1012084233
the original thread's subject is 'dc filter' and its in the solid state forum.
actually this is the one I was looking for (guess I was using wrong search terms)
http://www.diyaudio.com/forums/attachment.php?s=&postid=16083&stamp=1012084233
the original thread's subject is 'dc filter' and its in the solid state forum.
Hi,
the link in post3 uses a cap in each of the live and neutral supply lines.
It is safer (and it works just as well) to combine the two anti-parallel caps in one line only and use dual anti-parallel diodes (1.4V or use a 25A bridge) to keep the start up and fault currents out of the caps.
Decide if you want the caps on either the live line (both ends and the cap body are live) or if you want to put them in the neutral line but at the risk of the neutral becoming open circuit and leaving the amplifier "live" but inoperative.
Safety is a big issue here. Consider mains DC blocking carefully.
BTW. the bridge diodes can be wired as follows:- mains into ~ and mains out of the other ~.
Add a shorting link from + to -. This gives a series pair of anti-parallel diodes developing 1.4 to 1.6V when passing current.
the link in post3 uses a cap in each of the live and neutral supply lines.
It is safer (and it works just as well) to combine the two anti-parallel caps in one line only and use dual anti-parallel diodes (1.4V or use a 25A bridge) to keep the start up and fault currents out of the caps.
Decide if you want the caps on either the live line (both ends and the cap body are live) or if you want to put them in the neutral line but at the risk of the neutral becoming open circuit and leaving the amplifier "live" but inoperative.
Safety is a big issue here. Consider mains DC blocking carefully.
BTW. the bridge diodes can be wired as follows:- mains into ~ and mains out of the other ~.
Add a shorting link from + to -. This gives a series pair of anti-parallel diodes developing 1.4 to 1.6V when passing current.
Hi,
the DC on the mains varies from one moment to the next.
It is, in part, caused by non linear current draw from the mains. It also tends to be worse when the mains are heavily loaded.
As a result the DC can be measured and found to be negligible, then when you listen you hear noisy transformers.
Listen over a range of your common listening times and hear if you have a regular problem.
the DC on the mains varies from one moment to the next.
It is, in part, caused by non linear current draw from the mains. It also tends to be worse when the mains are heavily loaded.
As a result the DC can be measured and found to be negligible, then when you listen you hear noisy transformers.
Listen over a range of your common listening times and hear if you have a regular problem.
I've also been looking at a DC filter solution...
There is an simple apparently simple solution from Nelson Pass in a previous thread. It states:
"If you are experiencing mechanical hum from your
transformer, it is often caused by the presence of
DC on the line. Usually this comes from some appliance
using current asymmetrically, such as a lamp dimmer.
The hum comes usually from toroidal transformers, which
saturate easily with DC, and when they recover, they
draw an extra pulse of current, causing the noise.
You can put a pair of back-to-back electrolytics in series
with the AC power line to block this, and it works fine.
Makes sure the current rating of the electrolytics is
high enough, and the they are joined at a like polarity,
such as + to +."
However, if anyone could explain to a complete eejit what "a pair of back-to-back electrolytics in series with the AC power line... joined at a like polarity, such as + to +" actually means, that eejit would be most grateful
Any suggestion on capacitance would be also be appreciated...
There is an simple apparently simple solution from Nelson Pass in a previous thread. It states:
"If you are experiencing mechanical hum from your
transformer, it is often caused by the presence of
DC on the line. Usually this comes from some appliance
using current asymmetrically, such as a lamp dimmer.
The hum comes usually from toroidal transformers, which
saturate easily with DC, and when they recover, they
draw an extra pulse of current, causing the noise.
You can put a pair of back-to-back electrolytics in series
with the AC power line to block this, and it works fine.
Makes sure the current rating of the electrolytics is
high enough, and the they are joined at a like polarity,
such as + to +."
However, if anyone could explain to a complete eejit what "a pair of back-to-back electrolytics in series with the AC power line... joined at a like polarity, such as + to +" actually means, that eejit would be most grateful
Any suggestion on capacitance would be also be appreciated...
Hi,
this DC blocker is different from the description posted by Nelson Pass, but it does the job
http://www.diyaudio.com/forums/attachment.php?s=&postid=328821&stamp=1077146064
The parts you need are the two caps and the 4diode bridge on the left of the diagram.
Bryston have installed this DC blocker in the Neutral line (which I believe is a safer option), but some others would insert the DC blocker in the Live line (claiming that it is safer due to avoiding the risk of the neutral line becoming open circuit).
The DC blocker works just as effectively whether it is in the Live or Neutral line.
But do not fit it to both lines as shown in some other "balanced" mains input which adopts the unsafe practices of both without any additional benefits.
There is a slight problem with mains plug and sockets that are reversible, since either line can be live depending on which orientation one inserts the plug.
SSmith,
if the diagram is still unclear just shout out again.
this DC blocker is different from the description posted by Nelson Pass, but it does the job
http://www.diyaudio.com/forums/attachment.php?s=&postid=328821&stamp=1077146064
The parts you need are the two caps and the 4diode bridge on the left of the diagram.
Bryston have installed this DC blocker in the Neutral line (which I believe is a safer option), but some others would insert the DC blocker in the Live line (claiming that it is safer due to avoiding the risk of the neutral line becoming open circuit).
The DC blocker works just as effectively whether it is in the Live or Neutral line.
But do not fit it to both lines as shown in some other "balanced" mains input which adopts the unsafe practices of both without any additional benefits.
There is a slight problem with mains plug and sockets that are reversible, since either line can be live depending on which orientation one inserts the plug.
SSmith,
if the diagram is still unclear just shout out again.
Hi,
re DC blocker diagram.
The live comes into the amp, throught the IEC socket. Passes to a fuse (not shown) then through a switch (double pole in the UK) then to the transformer primary.
The neutral comes from the IEC socket into the DC Blocker at the top, out of the DC blocker at the bottom and then to the transformer primary. In the UK the neutral is also switched, but not fused.
The DC blocker is on the neutral so that all the components are near ground voltage.
Note the shorting link across the diode bridge from +ve to -ve.
re DC blocker diagram.
The live comes into the amp, throught the IEC socket. Passes to a fuse (not shown) then through a switch (double pole in the UK) then to the transformer primary.
The neutral comes from the IEC socket into the DC Blocker at the top, out of the DC blocker at the bottom and then to the transformer primary. In the UK the neutral is also switched, but not fused.
The DC blocker is on the neutral so that all the components are near ground voltage.
Note the shorting link across the diode bridge from +ve to -ve.
Percy,
Does your audio equipment have toroidal input transformers?
You say you have no hum problem. The dc blockers are not trivial; I would avoid them unless the combination of toroids and hum was present, AND the presence of DC was known to be causing problems...
The the potential for hum problems will be most acute in gear where the toroid is marginally sized (read commercial). DIY stuff with lavish margins on core size will be less affected.
Does your audio equipment have toroidal input transformers?
You say you have no hum problem. The dc blockers are not trivial; I would avoid them unless the combination of toroids and hum was present, AND the presence of DC was known to be causing problems...
The the potential for hum problems will be most acute in gear where the toroid is marginally sized (read commercial). DIY stuff with lavish margins on core size will be less affected.
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