Just to finalize this thread a little-
I decided to use the Hafler 9130 as part of my basement stereo and continue to use my DH 200 with my computer/studio set up. No Hum anywhere this way and I'm happy with the amount of juice the little 9130 puts out. Pretty impressive combo with my old DH 101 musical concept modified preamp. I could always buy another and put them into mono if I need more head room.
One last clarification though. Does the fact that my DH 200 amp does not have a third prong on the plug make it vulnerable to the potential shock we talked about with respect to removing the third prong on the 9130? Or, is it simply grounded in some other way? The DH 200 never had a third plug prong.
Thanks!
I decided to use the Hafler 9130 as part of my basement stereo and continue to use my DH 200 with my computer/studio set up. No Hum anywhere this way and I'm happy with the amount of juice the little 9130 puts out. Pretty impressive combo with my old DH 101 musical concept modified preamp. I could always buy another and put them into mono if I need more head room.
One last clarification though. Does the fact that my DH 200 amp does not have a third prong on the plug make it vulnerable to the potential shock we talked about with respect to removing the third prong on the 9130? Or, is it simply grounded in some other way? The DH 200 never had a third plug prong.
Thanks!
Hi,
Pleased you have found a solution of sorts, thats good.
The amp without the "third prong" will be constructed to a "Double insulated" standard meaning it will have passed tests confirming no shock hazard exists if for example a wire were to "fall off the mains switch" . It will be constructed so that if that happened the wire would have nowhere to go where it could do any harm and so on.
The other one will not be to that standard, and if the same thing happened that wire may be able to come into contact with the case or circuit board etc and so this then relies on the earth connection for safety.
Pleased you have found a solution of sorts, thats good.
The amp without the "third prong" will be constructed to a "Double insulated" standard meaning it will have passed tests confirming no shock hazard exists if for example a wire were to "fall off the mains switch" . It will be constructed so that if that happened the wire would have nowhere to go where it could do any harm and so on.
The other one will not be to that standard, and if the same thing happened that wire may be able to come into contact with the case or circuit board etc and so this then relies on the earth connection for safety.
as long as rhe third prong is grounded, the above scenario with a broken line wire is not a problem. if it hits the chassis, it shorts to ground. (you could have a shock hazard if you use a ground lift adapter). with the 2-prong you would have a shock hazard, since the chassis is isolated, and the line touching the chassis would make it "live". both units, however still are made to rhe same UL standard, 1500V isolation between the transformer primary and ground.
Hi Unclejed,
The double insulation standard means that the wire to the switch if it were to fall off ( just an example
) -- would have nowhere to go. The switch may be fully shrouded for example in the double insulated amp and not so in the other. There is lots of equipment (VCR's DVD recorders , Audio gear etc) all with metal cases and no earth wire. These are designed so that in "normal use" it's impossible for the chassis to become live. Of course if you were to physically make the connection ( live and chassis ) it would of course become live, but the point is that in normal use that just cannot happen.
The amp with the earth wire in the mains lead is not to this standard -- the earth wire should never be disconnected for normal use. The "diode earth lift" can still have the chassis connected to ground directly thereby maintaining the safety earth.
The double insulation standard means that the wire to the switch if it were to fall off ( just an example
) -- would have nowhere to go. The switch may be fully shrouded for example in the double insulated amp and not so in the other. There is lots of equipment (VCR's DVD recorders , Audio gear etc) all with metal cases and no earth wire. These are designed so that in "normal use" it's impossible for the chassis to become live. Of course if you were to physically make the connection ( live and chassis ) it would of course become live, but the point is that in normal use that just cannot happen.The amp with the earth wire in the mains lead is not to this standard -- the earth wire should never be disconnected for normal use. The "diode earth lift" can still have the chassis connected to ground directly thereby maintaining the safety earth.
in the US, whether it has a grounded cord, or not, it must pass the UL standard test of applying 1500VAC to one or both prongs of the line cord (not across them) and a ground clip to the chassis and test for a specified leakage current. the wire length and positioning specs, i don't think i've ever seen any, except for the requirement that the ground wire be at least 2 inches longer than the hot and neutral, so that if the cord gets pulled hard enough to break the hot loose inside the cabinet, the ground wire still has some slack in it and remains connected.
Hi,
I think we are thinking of different things here
Two items of equipment, one has a 3 core lead (ground connection) and one a two core lead (double insulated). Both pass all the leakage requirements, but you can't remove the earth on the first one and say it's as safe as the double insulated one.
The double insulated one means nothing live can in any way come into contact with you, nothing to do with leakage.
Edit -- A different thing to leakage
I think we are thinking of different things here
Two items of equipment, one has a 3 core lead (ground connection) and one a two core lead (double insulated). Both pass all the leakage requirements, but you can't remove the earth on the first one and say it's as safe as the double insulated one.
The double insulated one means nothing live can in any way come into contact with you
, nothing to do with leakage.Edit -- A different thing to leakage
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