I'm very interested in this as grounding and RF are two of my pet hobby horsesIs there a thread showing how your problem occurred and how it was solved? I'd like to read it. 'Leaking RF' does not sound to me to be the whole story...
Yes, it's this entire thread, but began to find solution by this post http://www.diyaudio.com/forums/chip-amps/208261-first-build-dual-mono-lm3875-4.html#post2949838
It still boggles my mind. I am still curious to know about building a better line between psu and amp... It looks like a big antenna doesn't it?
Also I want to research and learn about balanced inputs. All my other equipment only has two prongs on its mains (no earth), and I've also read that class 1 & 2 earthed and double insulated equipments don't always play nice together... I wonder if that's a part of the puzzle.
Fascinating thread, thanks for pointing me over to it. What made me most curious was the 'pokie wire' used by farmerjack61 to fix up his buzz problem. I wonder if your problem is just an external version of that problem he fixed. I don't know the details of the '10cm away' grounding of the input wire but I suspect that 10cm might not be just a wire, it may have at least one other connection to it. If so then this becomes a common ground impedance coupling issue. In my own experience these issues are very common (ooops pun not intended ). When he put the pokie wire on the input RCA ground he was diverting current direct to the central ground and then it wouldn't flow through the 10cm long connection (which I figure was higher impedance). But this is all speculation
Your raising of balanced inputs is highly pertinent - these solve the common ground impedance coupling issues. When unbalanced connections are used with only two-prong powered kit, there's a mains leakage current which flows down the screen of the RCA cable. This current isn't pure 50/60Hz these days as mains supplies are pretty noisy. If that current is carried directly to the central (star) earth then that's out of harm's way and no issues arise. But normally it isn't - it goes on to the amp PCB and that's where the buzzing starts to rear its head because it induces small voltage drops around the sensitive amplifier input terminals. This is why grounding/layout is one of the primary issues for amps in my experience.
). When he put the pokie wire on the input RCA ground he was diverting current direct to the central ground and then it wouldn't flow through the 10cm long connection (which I figure was higher impedance). But this is all speculation Your raising of balanced inputs is highly pertinent - these solve the common ground impedance coupling issues. When unbalanced connections are used with only two-prong powered kit, there's a mains leakage current which flows down the screen of the RCA cable. This current isn't pure 50/60Hz these days as mains supplies are pretty noisy. If that current is carried directly to the central (star) earth then that's out of harm's way and no issues arise. But normally it isn't - it goes on to the amp PCB and that's where the buzzing starts to rear its head because it induces small voltage drops around the sensitive amplifier input terminals. This is why grounding/layout is one of the primary issues for amps in my experience.
Thanks for reading my thread Abraxalito. Yes, I believe you're right, that the problem was an external version of a simular problem that another member was having with a different kit. Let's be clear that this external problem was created by myself making unusual connections between my equipments.
To clarify, the "Receiver" that I am using is designed with 5.1 theatre sound in mind. The "SACD" player I mention is actually a DVD player, which I bought solely because of it's SACD capabilities.
Because of a pre-existing problem of the "video switching" in the receiver not working anymore; I made some unusual connections. The "cost" was that I would have to use more than one remote to change channels (select input/output), the "benefit" was that I could use the best sounding connection to get sound from the DVD/SACD to the Receiver for two channel listening sessions.
From DVD/SACD, I was running HDMI to receiver for sound, then running component-video connections to the TV. I also had the Cable-DVR running on HDMI to TV, then a SPIDF from Cable-DVR to Receiver for sound.
This describes the "Loop" that I created with all the back and fourth cables from DVR, to TV, from TV to DVD/SACD, and from each of those to Receiver as well.
The set-up that worked in the end is connecting it more like it was origionally designed to be connected in the first place.
Now I use HDMI from SACD to Receiver. I use HDMI from Cable-DVR to TV. All other conductive connections between TV, DVD, and Receiver have been omitted (no more Loop). Getting sound from TV back to receiver must be done with a non-conductive cable, digital optical here works great.
I just wanted to clarify that there was nothing wrong with my kit, and nothing wrong with it's design. I am very pleased with my Audio Sector kit, and would reccomend it to others.
Furthermore, for a first-build, the Audio Sector LM3875 kit in my opinion is ideal, because of the very few number of parts, excellent instructions -including pictures. I really learned a lot by putting together this kit. It is deffinately a high-light accomplishment for me.
Did I mention that it sounds AWESOME!!
Best Regards,
AlexQS
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