This can be complex. First question is: is it pure 50/60Hz sine noise or is it a more rattle-like supply ripple? I assume the latter.
Are you driving the tube amp (I assume it is a power amp) with a preamp? If so, is the rattle still there if you 1) remove one of the input plugs from the power amp and/or 2) if you remove both?
Jan
Are you driving the tube amp (I assume it is a power amp) with a preamp? If so, is the rattle still there if you 1) remove one of the input plugs from the power amp and/or 2) if you remove both?
Jan
Yes the noise is not depending on the source and also not changed by volume. In other words I hear it softy when near to the speaker and playing very low level music. Playing louder doesn't change the volume of the noise. Once I connect the (power) amp with a electric plug with no earth pin the amp is dead silent again
I am assuming here the op didn't intentionally use a design that injects noise through the ground.
ok, first we need to make sure nothing is touching the chassis metal (like stacking units).
Then we need to measure the leakage current of the chassis:
disconnect earth ground on the unit. place a ac current meter with one lead connected to the outlet's earth ground. Then with the other lead touch all of the signal output grounds and any other exposed metal.
if you have more than 100 micro amps, then the design needs to be reviewed (provide schematics) and/ or transformers need to be either removed (input/output transformers) or replaced (power transformer)
ok, first we need to make sure nothing is touching the chassis metal (like stacking units).
Then we need to measure the leakage current of the chassis:
disconnect earth ground on the unit. place a ac current meter with one lead connected to the outlet's earth ground. Then with the other lead touch all of the signal output grounds and any other exposed metal.
if you have more than 100 micro amps, then the design needs to be reviewed (provide schematics) and/ or transformers need to be either removed (input/output transformers) or replaced (power transformer)
An audio system really just needs one earth connection to the zero volt line.
Two connections can cause an earth hum loop.
If the pre amp is earthed to zero volt line then don't earth the amp to zero volt line or vice versa.
In my systems the amp is always earthed and everything else has no zero volt line connection to earth.
Two connections can cause an earth hum loop.
If the pre amp is earthed to zero volt line then don't earth the amp to zero volt line or vice versa.
In my systems the amp is always earthed and everything else has no zero volt line connection to earth.
...when made by a peasant.
When made properly no matter how many connection it has. The example is, a good sound console, with multiple inputs and outputs. No dirty currents through ground loops = no hum.
I think he said it doesn't depend on the source, I assume he means it is just the power amp connected to nothing else.
In this scenario I guess the only ground loop can exist from live and/or neutral mains somehow to protective ground. Possibly a bad transformer leakage?
Then again, 'near the speaker with soft music' may be just background we all hear.
Jan
In this scenario I guess the only ground loop can exist from live and/or neutral mains somehow to protective ground. Possibly a bad transformer leakage?
Then again, 'near the speaker with soft music' may be just background we all hear.
Jan
if you post your as-built scheme, we can have a closer look...
tubes have heater cathode specks that must be observed,
lifting the heater to some b+ if there is a chance it will be exceeded,
and we can not tell that without looking at your schematics...
looks like the two bass only amplifiers are monoblocks. These are easier to wire up and not have an error that causes excess hum.
The Melody, like all multi-channel amplifiers, needs more care to avoid excess hum.
Do you have sch for the Melody?
Or detailed pics of how it is wired up.
Is there an error in your diagram? You show one output from the Melody even though it has two inputs. Is it summing two channels to create a mono output signal?
We need some extra information on which interconnections cause the hum and which do not cause a hum.
The Melody, like all multi-channel amplifiers, needs more care to avoid excess hum.
Do you have sch for the Melody?
Or detailed pics of how it is wired up.
Is there an error in your diagram? You show one output from the Melody even though it has two inputs. Is it summing two channels to create a mono output signal?
We need some extra information on which interconnections cause the hum and which do not cause a hum.
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The crux of the matter is: does it do that too when NOTHING ELSE is connected to it (except speakers of course)? If not, you'r back to square one - it may or may not be the power amp.
Why is it so hard to do some logical diagnosis??
Jan
It's not Jan, like I wrote in the previous post "Thanks you all for the advise so far. I'll try the suggestions this week and I'll post an overview of my setup"
No need for irritation
Jock
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