Floating input
Bert,
With a single ended input source like some of the old tube preamps the whole case could go to 1/2 the line voltage as they weren’t grounded. This was usually a fairly high source impedance but not always. Doing a single ended to balanced conversion with an adapter cable would connect this sources case to the amps ground through the 10 ohm resistor. It might cause enough I/R drop to blow the chip due to excessive common mode input voltage. This can't happen with a direct connection or if the diodes are used. Diodes are very cheap and would only take a couple of minutes to install. IMHO well worth the cost and effort.
Roger
Bert,
With a single ended input source like some of the old tube preamps the whole case could go to 1/2 the line voltage as they weren’t grounded. This was usually a fairly high source impedance but not always. Doing a single ended to balanced conversion with an adapter cable would connect this sources case to the amps ground through the 10 ohm resistor. It might cause enough I/R drop to blow the chip due to excessive common mode input voltage. This can't happen with a direct connection or if the diodes are used. Diodes are very cheap and would only take a couple of minutes to install. IMHO well worth the cost and effort.
Roger
Re: Floating input
Aah....now I understand. This is a non issue in my power amps/preamps because I never use mains ground in amps. This is to avoid ground loops. The ground only comes from the source....if its mains grounded. So I never have this problem...well I never had it anyway.sx881663 said:
Ground potential?
Burt,
If you plug in all the various pieces and turn them on without any connections in between or any ground connections then measure the AC voltages between the various grounds I think you will be surprised. I think that most of it is generated because of the power transformers leakage inductance. That stored energy has to go somewhere. This voltage is greatly affected by the polarity of the AC power connection. Mark which way it is plugged in that generates less voltage and use them connected it this direction. As I stated the source impedance of this voltage is usually high. In your case high enough that the 10ohm res. is a low enough value to short it out. Still it would be interesting to do the above measurements and then do it again with a 10ohm res. shorting out the meter and see how much is left and see if it is worth doing anything about.
Roger
Burt,
If you plug in all the various pieces and turn them on without any connections in between or any ground connections then measure the AC voltages between the various grounds I think you will be surprised. I think that most of it is generated because of the power transformers leakage inductance. That stored energy has to go somewhere. This voltage is greatly affected by the polarity of the AC power connection. Mark which way it is plugged in that generates less voltage and use them connected it this direction. As I stated the source impedance of this voltage is usually high. In your case high enough that the 10ohm res. is a low enough value to short it out. Still it would be interesting to do the above measurements and then do it again with a 10ohm res. shorting out the meter and see how much is left and see if it is worth doing anything about.
Roger
Very low voltages
Burt,
Was this done without the interconnects and the pieces just plugged in and turned on? If so very surprising and certainly no problem. If not it doesn't mean much as these low numbers are the limit of measuring ability and it would be a measurement of the quality of your connections anyway.
Roger
Burt,
Was this done without the interconnects and the pieces just plugged in and turned on? If so very surprising and certainly no problem. If not it doesn't mean much as these low numbers are the limit of measuring ability and it would be a measurement of the quality of your connections anyway.
Roger
Re: Very low voltages
BTW computer is mains grounded.
My passive preamp switches the ground line of the inputs. So now the radio plays and this is the only one grounded to the preamp-poweramp.
The areal input is cable so this is grounded somewhere in the house.
Everything connected and on...music playing.sx881663 said:
BTW computer is mains grounded.
My passive preamp switches the ground line of the inputs. So now the radio plays and this is the only one grounded to the preamp-poweramp.
The areal input is cable so this is grounded somewhere in the house.
Re: Re: input current problem
Sorry, it is the ucd diagram from Hypex's.
The Hypex modules can run without problem, but does it have some built-in solution of the problem?
e.g. a small capacitor tied between input and GND, and a resistor series on the input terminals to isolate the preamp from capacitive load.
Sorry, it is the ucd diagram from Hypex's.
The Hypex modules can run without problem, but does it have some built-in solution of the problem?
e.g. a small capacitor tied between input and GND, and a resistor series on the input terminals to isolate the preamp from capacitive load.
Bgt said:
phase_accurate said:
Still think if you use an unbalanced input, ground your inverting input at the input socket on the UCD pcb and not at the rear of your housing at the input plug. Especially with higher gain than standard the input tends to become capacitive sensitive when the - is treated balanced for an unbalanced system.
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