Pin1 does not exist in a two wire connection.
Pin1 is the third wire in a three wire connection.
In a balanced impedance connection, Pins 2 & 3 are the equivalent to Signal and Return in a two wire or coaxial connection.
Pin1 is not Signal Return, nor is it the audio ground.
Pin1 is the Chassis to Chassis connection.
hybrid gnd - RF bypass shield/return to chassis at entry with cap (ring of smt parts)
wire bypassed audio/DC signal gnd to internal signal gnd
same idea, consturction as "EMC XLR" http://www.neutrik.com/en/xlr/xlr-chassis-connectors/emc-series/nc3fdx-emc-spec
wire bypassed audio/DC signal gnd to internal signal gnd
same idea, consturction as "EMC XLR" http://www.neutrik.com/en/xlr/xlr-chassis-connectors/emc-series/nc3fdx-emc-spec
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It seems there is technically no right answer to this, what works best in each case is the right way. I tried connecting the screen to chassis in my DCB1 but it transferred noise, it was definitely quieter when kept insulated. Same thing with my power amps, I was told to keep the screen insulated from the chassis and sure enough it worked best, less noise was transferred that way yet again.
It seems to me that the noise transferred from the mains earth is worse than any RFI the screen picks up from the air. Maybe if the mains was quieter this would not be an issue but in the end I went with what worked best for me.
This would support the theory behind going fully balanced I suppose, but that's not an option for me at present.
It seems to me that the noise transferred from the mains earth is worse than any RFI the screen picks up from the air. Maybe if the mains was quieter this would not be an issue but in the end I went with what worked best for me.
This would support the theory behind going fully balanced I suppose, but that's not an option for me at present.
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feedthru cap and hybrid ground principles are not specific to balanced - just showing the mechanical of the cap ring with the link
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Re: unbalanced. I've used consumer gear (Sony, Denon, Panasonic, etc) single ended for years and never had a hum or noise problem as long as it was all connected to the same power outlet. I've attached Beringer DCX and DEQ 2496 as well and no probs once I corrected manufacturing defects.
So I think looking at whatever they are doing is a good way to go if you're operating unbalanced.
Edit: I use high quality connectors I got from local electronic supply company - $2 each.
So I think looking at whatever they are doing is a good way to go if you're operating unbalanced.
Edit: I use high quality connectors I got from local electronic supply company - $2 each.
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I think you may well be right Frank. In the past I have had quite a lot of kit which was made in Japan, it always seemed to work with no hum issues. It occurs to me that all of that kit was double insulated, having no direct connection to mains earth.
I wonder if problems arise for people when connecting such equipment to other gear which is connected directly to mains earth. I have read articles which state that there can be problems with this, connecting class 1 to class 2 equipment is seemingly known to create problems sometimes, but not always.
I read somewhere that most Japanese manufacturers use a bus system for grounding which has the noisiest items connected at one end and the quietest at the other. The article said that they connect all returns, PGND, signal screen and speaker return to the bus at different points along it. This might be why we sometimes have issues when connecting such equipment to say a diy amplifier which is directly connected to mains earth. My mains is quite noisy and I live in a rural location, however I have a wind farm and a large hydro electric scheme within a couple of miles of my house. Also an electrical sub station within 200 metres and a waste treatment pumping station quite close by too. Lots of potential for mains noise here.
I wonder if problems arise for people when connecting such equipment to other gear which is connected directly to mains earth. I have read articles which state that there can be problems with this, connecting class 1 to class 2 equipment is seemingly known to create problems sometimes, but not always.
I read somewhere that most Japanese manufacturers use a bus system for grounding which has the noisiest items connected at one end and the quietest at the other. The article said that they connect all returns, PGND, signal screen and speaker return to the bus at different points along it. This might be why we sometimes have issues when connecting such equipment to say a diy amplifier which is directly connected to mains earth. My mains is quite noisy and I live in a rural location, however I have a wind farm and a large hydro electric scheme within a couple of miles of my house. Also an electrical sub station within 200 metres and a waste treatment pumping station quite close by too. Lots of potential for mains noise here.
All my gear is connected to the same outlet using a relatively cheap power bar/surge connector. The unspeakable cable company router attached to a different outlet gives me hum - but I haven't bothered to find out what actual cause of that is. I attach computer to hifi using optical connection to kill its noise. I live in urban core half a mile from substation. The environment here is not pristine.
You can have a separate conductor for signal return with an unbalanced connection too; connect the shield to the chassis, but let the signal return conductor pass through. This won't fix ground loops, but it does prevent noise from entering via the shield.
BTW, did anyone work out what caused the original problem?
Pretty much the same here Frank. Wifi router wallwart PSU pollutes our ring mains AND it's on the other side of the house from the hifi, I changed it to another ring, much better now. All hifi gear is plugged into a block like you have too.
Not much else I can do.
Not much else I can do.
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BTW, did anyone work out what caused the original problem?[/QUOTE]
Do you mean the O/P? he seems to have disappeared, probably got a headache like I did from reading grounding articles.
Do you mean the O/P? he seems to have disappeared, probably got a headache like I did from reading grounding articles.
The Screen could be AC coupled to the Chassis at or before the entry.
I posted a question some while back about using some caps from both Hot and Cold to Chassis. Unfortunately no one answered. This was for an XLR 3pin socket with the screen direct to Chassis via Pin1, Pin2 carrying the Hot and Pin3 carrying Return, i.e. unbalanced. Then 3 off 47pF between all three pins.
I am listening to that arrangement now. It's been working virtually continuously for two or so months.
Whitlock on hum
probably got a headache like I did from reading grounding articles.[/QUOTE]
Hi there: Found the answer to my serious hum situation on page 145 of the Whitlock on Audio Grounding an Interfacing, referenced earlier in this tread. A new (to me) audio distribution amp would not connect to an older HK amp without serious hum (although the HK had no problem with other equipment). Just as Bill Whitlock shows on page 145, the ground loop was occurring because the HK is a two prong mains plug and the newer amp is a three prong safety ground (connecting to the same multi bar receptacle). So don't give up on Whitlock too soon, you may find the answer therein. ....regards, Michael
Do you mean the O/P? he seems to have disappeared,
probably got a headache like I did from reading grounding articles.[/QUOTE]
Hi there: Found the answer to my serious hum situation on page 145 of the Whitlock on Audio Grounding an Interfacing, referenced earlier in this tread. A new (to me) audio distribution amp would not connect to an older HK amp without serious hum (although the HK had no problem with other equipment). Just as Bill Whitlock shows on page 145, the ground loop was occurring because the HK is a two prong mains plug and the newer amp is a three prong safety ground (connecting to the same multi bar receptacle). So don't give up on Whitlock too soon, you may find the answer therein. ....regards, Michael
These caps would help for getting rid of RF pickup but not for mains hum. I have been working with some multi-amped active loudspeaker with an external crossover and several long (3-4m) interconnects made from coax with crimp-on RCA plugs leading from the crossover to the speaker. These will make a very nice antenna for hum if you separate two of the coax interconnects on their way to the speaker. I plan to try some of the different schemes mentioned in this thread to see if any will improve the situation. In my case there is no "case" of metal around the amplifier - they are built in to the (wood product) loudspeaker cabinet but there is an earth connection available. When no interconnect(s) are connected, the amps are quiet and there is no hum pickup, so this is definitely coming in on the cable.
I have noticed the the source impedance has a huge effect on the noise pickup - the crossover happens to have a 500 ohm output impedance (!). If I use a low impedance source the noise is much less, or is absent. Unfortunately I need to use this particular crossover unit. I have even considered building a multichannel line driver using NE5532 op amps just so I can reduce the output impedance to a couple of tens of ohms. I would connect this directly at the output of the crossover. This might fix the problem, but I am definitely interested to see how the grounding influences the hum pickup by the cable.
this is probably a hum loop, and not due to noise pick-up by interconnects.
as you said on post 12 about a 4.7R, this should be part of the power amp design to decouple th PAs front end grounding and will elimate hum due to ground loops.
it cant be "added in" from the phono socket to the PAs ov.
Hi there: Found the answer to my serious hum situation on page 145 of the Whitlock on Audio Grounding an Interfacing, referenced earlier in this tread. A new (to me) audio distribution amp would not connect to an older HK amp without serious hum (although the HK had no problem with other equipment). Just as Bill Whitlock shows on page 145, the ground loop was occurring because the HK is a two prong mains plug and the newer amp is a three prong safety ground (connecting to the same multi bar receptacle). So don't give up on Whitlock too soon, you may find the answer therein. ....regards, Michael[/QUOTE]
Interesting! I have come across this issue too, and read about it in the same article. If you don't mind me asking, how did you resolve it, did you change the amp or equipment? or did you modify it?
Pin-1 was short-hand for shield, so let's re-write your statements:
a] Shield is the third wire in a three wire connection.
b] OK
c] Shield is not Signal Return, nor is it the audio ground. (only true in a balanced circuit)
d] Shield is the Chassis to Chassis connection. (true in both balanced and unbalanced circuits)(a Chassis to Chassis connection)
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