irb
pfm Member
I have the dreaded buzzing toroid problem, in two different power amps. I reckon I need to do something about it. I've read a fair bit here on pfm and elsewhere, and here's what I've learnt:
1. The most likely cause is DC offset on the mains, and the prescribed cure is a mains DC blocker of some sort.
2. There are several commercial products available but some of these are expensive, and most get mixed reviews. Some include other filtering, which may or may not be a good idea.
3. A DIY solution is possible, as a DC blocker is not terribly complicated. Rod Elliott's pages describe a possible circuit, here: https://sound-au.com/articles/xfmr-dc.htm. Several sources, including ATL Audio and Sjöström Audio, will supply a suitable PCB or even a built module, using Elliott's circuit or a variation on it.
5. The heavy duty DC blocker by Sjöström Audio (their DCT03) is a particularly well-liked incarnation of this type of circuit - more than one fishie has good things to say of it.
So, why not just buy a Sjöström DCT03 board, along with the necessary diodes and caps, and build my own DC blocker? Well, because the web has offered up a different DC blocking circuit, which might be somewhat smarter. It was suggested by a regular poster on AoS some years ago - see here: https://theartofsound.net/forum/showthread.php?11219-DIY-DC-blocker
The circuit looks like this:
DC_Blocker01 by grilled snapper, on Flickr
If it will work, it offers two advantages: first, it is simpler (why build a blocker with sixteen diodes if only two are needed?); and second, it should block all DC votages, whereas the other circuit has a limit of about 0.7v for each diode in the chain (so something like 2.8v for the DCT03).
What do others reckon - will it work, or is there a good reason why so many people use the more complex option?
1. The most likely cause is DC offset on the mains, and the prescribed cure is a mains DC blocker of some sort.
2. There are several commercial products available but some of these are expensive, and most get mixed reviews. Some include other filtering, which may or may not be a good idea.
3. A DIY solution is possible, as a DC blocker is not terribly complicated. Rod Elliott's pages describe a possible circuit, here: https://sound-au.com/articles/xfmr-dc.htm. Several sources, including ATL Audio and Sjöström Audio, will supply a suitable PCB or even a built module, using Elliott's circuit or a variation on it.
5. The heavy duty DC blocker by Sjöström Audio (their DCT03) is a particularly well-liked incarnation of this type of circuit - more than one fishie has good things to say of it.
So, why not just buy a Sjöström DCT03 board, along with the necessary diodes and caps, and build my own DC blocker? Well, because the web has offered up a different DC blocking circuit, which might be somewhat smarter. It was suggested by a regular poster on AoS some years ago - see here: https://theartofsound.net/forum/showthread.php?11219-DIY-DC-blocker
The circuit looks like this:
DC_Blocker01 by grilled snapper, on Flickr
If it will work, it offers two advantages: first, it is simpler (why build a blocker with sixteen diodes if only two are needed?); and second, it should block all DC votages, whereas the other circuit has a limit of about 0.7v for each diode in the chain (so something like 2.8v for the DCT03).
What do others reckon - will it work, or is there a good reason why so many people use the more complex option?