I have finally made some progress here. I set everything up in our spare room where I build things. When I had the DCB1 with it's signal inputs shorted and it's outputs connected to the FE's I got near silence, had to put my ear right up to the drivers to hear the faintest hum.
Next I connected my passive source selector/attenuator unit to the DCB1 and got bad hum so I decided to concentrate on that unit. I ended up completely rewiring it and when I came to re-connect the miniature rotary switch I use for source selection one of it's weedy little input pins came away in my hand (I had heat shrink sleeve over them and I hadn't noticed any problem with them previously)
Anyway I had to fit a heavy two way toggle switch because I had no other rotary selector switches, I also changed the 20k miniature DACT attenuator to a 10k Tokos carbon pot. The wire I used to rewire the unit with was too heavy for the little DACT attenuator.
I can now listen to everything with almost no hum, with the source paused I have to turn the volume up to a level I'm not allowed to listen at (when she's at home
) until the hum returns. Strangely it gets quite bad when I reach 2/3 to 3/4 volume, then disappears completely when the pot reaches full volume position
Anyway, I'm going to use the setup for a bit now before I try to do anything else to it. If anyone has any ideas why a volume pot should cause hum to get progressively louder (until it reaches full volume position when it goes silent) I would like to hear them.
It did this with the miniature stepped attenuator too, it beats me as to why
Next I connected my passive source selector/attenuator unit to the DCB1 and got bad hum so I decided to concentrate on that unit. I ended up completely rewiring it and when I came to re-connect the miniature rotary switch I use for source selection one of it's weedy little input pins came away in my hand (I had heat shrink sleeve over them and I hadn't noticed any problem with them previously)
Anyway I had to fit a heavy two way toggle switch because I had no other rotary selector switches, I also changed the 20k miniature DACT attenuator to a 10k Tokos carbon pot. The wire I used to rewire the unit with was too heavy for the little DACT attenuator.
I can now listen to everything with almost no hum, with the source paused I have to turn the volume up to a level I'm not allowed to listen at (when she's at home
) until the hum returns. Strangely it gets quite bad when I reach 2/3 to 3/4 volume, then disappears completely when the pot reaches full volume position Anyway, I'm going to use the setup for a bit now before I try to do anything else to it. If anyone has any ideas why a volume pot should cause hum to get progressively louder (until it reaches full volume position when it goes silent) I would like to hear them.
It did this with the miniature stepped attenuator too, it beats me as to why
Strangely it gets quite bad when I reach 2/3 to 3/4 volume, then disappears completely when the pot reaches full volume position
If anyone has any ideas why a volume pot should cause hum to get progressively louder (until it reaches full volume position when it goes silent) I would like to hear them.
It did this with the miniature stepped attenuator too, it beats me as to why
I have had one do the same thing. It was a breadboard, so not together anymore, and I never got it to go away. I don't know why it did exactly what you are describing, but you are not alone.
You put the shield to the PSU star? Yes, that will hum like angry bees.
The shield is nothing more than a permeable metal strip wrapped around the transformer to 'catch' some of the spurious magnetic field, and sink it somewhere - chassis ground in this case. Taking it to PSU GND will couple that into the PSU.
To make things really quiet, lift the PSU GND off the chassis ground with a CL-60 or similar NTC power thermistor in the same manner as the Pass PSUs.
Sadly it seems that antek has discontinued 3 and 400va transformers in the 22 and 24v flavors that don't have the shield. I tried many configurations with the shield wire when I was troubleshooting my hum problem and it did not seem to matter where it was connected(iirc). I ended up connecting them together at the front of the chassis with their own lug. The pgnd tabs are wired to the same chassis connection as the iec. I only get a very minute amount of noise with my ear to the tweeter (heil). Otherwise it is my favorite amp.
Pics Please.
It's all back on the rack now Bob but since it was your good self that asked
Voila - some more atrocious pic's
I have had one do the same thing. It was a breadboard, so not together anymore, and I never got it to go away. I don't know why it did exactly what you are describing, but you are not alone.
Thanks, glad i'm not the only one to have come across this wierdness. Maybe someone will provide some answers, then again maybe not........
Yes.
I've connected it to the star ground and no trace of hum unless you put ears directly on drivers.
Fine, so it seem you identified the problem.Strangely it gets quite bad when I reach 2/3 to 3/4 volume, then disappears completely when the pot reaches full volume position
Really weird... Never had such problem so I've no ideas to share... Sorry.
Absolutely!
I'm happy you're finally enjoying you FEs and DCB1.
Yes, they're a very good combination indeed but with the wrong parts selection you risk to have a too much deep bass...
naah, there's no such thing as a too much deep bass... Your photos are fine. If you need some help with brightness I suggest you download XnView. It's free and top notch. There are both auto and manual correction tools in the image drop-down. I pass almost everything I post through it.
What are the boxes at the back of the bottom shelf - and are they in the FE system?
Please define the three units on the shelf above the FEs. Looks like the right-most is not connected.
First thing that comes to mind is the DCB1 that incorporates the source selection element. Ya, I know - More $$$$$
What are the boxes at the back of the bottom shelf - and are they in the FE system?
Please define the three units on the shelf above the FEs. Looks like the right-most is not connected.
First thing that comes to mind is the DCB1 that incorporates the source selection element. Ya, I know - More $$$$$
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Bottom/ground floor shelf, on the left of the FE's is a 12vdc powersupply with a DAC sitting on top of it. On the right of the FE's is a V-LINK (external digital clock) with a phono stage sitting on top of it.
First shelf, on the left is my source/volume selector (passive preamp). In the middle is my DCB1. On the right and not switched on at the moment is my diy dual chip C-moy headphone amp.
Second shelf, is a Samsmug 250Gb netbook with upgraded RAM for playing digital files (mainly FLAC)
Top shelf, Project RPM5 turntable with Denon DL160 cartridge fitted.
The 12v powersupply on the floor level shelf powers the DAC, the phono stage and the headphone amp.
To the right of the rack is a mains filter/surge protector which everything is plugged into.
Lastly speakers are REGA R3 Floorstanders which do very well in this small 5x4 meter square room.
Room treatments are two fat cats, the missis, me and some curtains, furry rug (for cats ofcourse
) and any visitors which might be lolling around on the sofa.Think thats about it, for now
Thanks, you probably already know - but power and signal wires should intersect at right angles, if possible. That can be difficult in a setting like yours.
So glad that your efforts paid off. Enjoy the music !!!
P.S. I'm really looking forward to getting my turntable back in the system later this winter.
So glad that your efforts paid off. Enjoy the music !!!
P.S. I'm really looking forward to getting my turntable back in the system later this winter.
Go for it Bob, my vinyl sounds amazing through this lot. For a little while the digital setup ran it close and in some cases bettered it, especially when I added the external clock.
The addition of the DCB1 and FE's has turned things around again though, when I play decent vinyl now all I can say is WOW!!
I probably should have two racks for that lot but domestic restraints have to be met, what goes in the room is not just up to me
The addition of the DCB1 and FE's has turned things around again though, when I play decent vinyl now all I can say is WOW!!
I probably should have two racks for that lot but domestic restraints have to be met, what goes in the room is not just up to me