|
Post by joethearachnid on Mar 22, 2020 17:21:42 GMT
Hi all,
(Very) long time no speak. I've been relatively happy with my audio setup for a while now and also haven't really had much of a chance to enjoy it properly with my current living arrangements, hence why I temporarily lost interest in chasing that hi-fi... high. However, recent circumstances (I'll let you guess what) suddenly mean that I have a lot more time at home with my headphones and amplifiers and it's making me feel enthused to get back into it all again. At the moment I'm re-setting up a lot of bits and bobs and chasing down some lingering issues I've never got around to sorting. So to my conundrum:
My speaker setup is a Fostex HP-A3 connected to a Gainclone powering two Wharfdale 220s. I've always had a faint but audible hum from both speakers when the amp is on. When the source is disconnected the speakers are dead silent so I figured the noise must be amplified from the Fostex. Not a major issue but that's life, or so I thought. However, when playing around today I found that when only one channel is connected from source to amp, both speakers are near enough silent. The noise is only present when both inputs are connected, regardless of which channel I use. I've tried various cables - DIY shielded, cheapo unshielded, all with the same effect (though I can't say I've tried Russ Andrews' latest £6000 interconnects). I have to say I'm completely stumped on this. Any ideas?
Thanks,
-joethearachnid
|
|
solderdude
Administrator
measureutternutter
Posts: 4,881
|
Post by solderdude on Mar 22, 2020 21:19:26 GMT
Sounds like a groundwire issue in the gain clone.
What happens if you connect the L channel with a screened cable and the R channel only using the center contact in the amp and the shield of that cable only connected to the source.
What happens if you connect a normal stereo cable and connect (at the source end) both screens and both pins together ?
|
|
|
Post by joethearachnid on Mar 26, 2020 10:02:46 GMT
Ok, finally got around to jury-rigging something to only connect the pin of an RCA connector. When I connect L with ground and signal and R with signal only, L is basically silent nbut R has significant hum. It's the same when reversed. When I put the grounds together I get no noise. When I put signal together I get the standard hum. When I put both ground and signal together simultaneously I get standard hum. Hopefully that helps pinpoint the issue? I'm only using a single PSU board if that's relevant.
-joethearachnid
|
|
|
Post by joethearachnid on Sept 14, 2021 23:27:38 GMT
In case anyone ever stumbles onto this thread later, I recently did a bit more digging and followed the guidance here on page 29 about having a star ground. I figured well ground is ground, every ground point in the circuit had continuity so how much difference could it make? Regardless, I rigged up a piece of solid core wire between the ground posts for the output and joined the PG+ and PG- from the power board straight to that rather than going through the amp boards. My speakers are now significantly quieter with only the very slightest hum if I press my ear against the tweeter. I may still see if I can replace the (physically) noisy toroidal with a quieter one someday but for now I'm much happier.
|
|