Grounding problem?

[Bas Horneman]

Hi Dave,

No confusion. I just wanted to make really clear what the situation is/was. And even now I was not 100% clear....because as I mentioned earlier...even with the Slagle autoformers I used to get problems ...the last 3 or 4 volume positions where off limits...cause then the noise started. But only now have I come to realize that this was probably one and the same problem.

So when you inserted the B7 between the passive output and the amplifier, perhaps the connection between the passive output and the B7 did not have a reference.

Or, if the secondary of the passive output was referenced to system ground it was providing a reference to the amplifier, and when you inserted the B7, this reference to the amplifier was lost.

Well that seems to be the problem then. What is system ground? I suppose my definition of system ground used to be.....system ground = signal ground. And every piece of equipment is connected only at one point through signal ground.

I was obviously mistaken that with transformers you can get around each and every ground problem or at least that you need no system ground or reference anymore... because I thought everything was sort of floated now.

[David Davenport]

Originally posted by Bas Horneman

... because I thought everything was sort of floated now.

Hi Bas,

Well, at some level everything is floating – consider a circuit in an airplane. So, as I said before, there is no ground, only references. These references are low-impedance paths where the circuits can get “grounded.” Without these “grounds”, high-impedance points are prone to picking up noise. There can be several of these low-impedance references in a system, and they should be tied together. BUT, it is important that the paths where they are tied together are chosen such that no current flows in them under normal circumstances. For an example of this, take a look at http://www.raleighaudio.com/installation.htm

Dave

[Bas Horneman]

Hallo Dave,

Thanks.

Had a look at the diagrams again.

And I remembered that I've had to install the so called gnd jumpers. Otherwize I had mayhem and noise. But I do know that I've had them not connected for a long time. Something happened somewhere along the line...what I don't know...to cause the system to act in the way it did for me to have to connect those gnd jumpers.

I guess that means in my case I had to connect the external analog ground reference to the internal ground reference (in the case of my RAKK DAC).

Now lets assume I want to add a non-transformer coupled preamp (Which I have tried). In that case the ground reference of the power amplifier will be connected to the ground reference of the pre amplifier via signal ground. The noise is unbearable in this case.

Therefore I assumed I have introduced some kind of ground loop. Which is likely in such a situation.

If I introduce a signal transformer between DAC and poweramp I still get unbearable noise. The reason this time is that I have no " low impedance path" (is that a different name for a wire ) between the various ground references of the various parts of my audio system.

Thing is I can't find the problem in the preamp...i.e. no connection between chassis and rca input and output plugs. And otherwize my standard grounding scheme (buss).

With the signal transformer I could ofcourse try to connect the grounds of primary and secondary. If I have silence then I know that the poweramps would like a better system reference?

[Bas Horneman]

I'm going to build a linear supply for my sp3...since I suspect the switching supply (very near power amps)...of causing a lot of noise.

[Skip_Pack]

A linear supply for my Squeezebox is up on the list for me as well.
A number of reports suggest that it's more important in cleaning
up the noise put back into the power line than it is in improving
the SB3's sound.


Skip

[David Davenport]

Originally posted by Bas Horneman


Therefore I assumed I have introduced some kind of ground loop. Which is likely in such a situation.

Thing is I can't find the problem in the preamp...i.e. no connection between chassis and rca input and output plugs. And otherwize my standard grounding scheme (buss).

Hi Bas,

What I would do is to draw a picture of your system wiring and internal paths and look for the loops. Remember that there are hidden paths, like capacitive leakage between the windings of the power transformers. Thus you will have a loop between two chassis connected to the mains even though there is no safety ground. This loop will include the shield of the unbalanced interconnect and this is where the noise is injected. A transformer will break this path. Without a transformer, the best you can do is to offer the noise current a lower impedance path between the two chassis, that is, a heavy wire between the two chassis.

You say that there is no connection between the chassis and the RCA jack. Thus, now your ground loop includes the signal ground in the preamp. It may actually be better to have a connection between the chassis and the jack instead of having the return noise current flowing through the internal signal ground in the preamp.

Dave

[Bas Horneman]

What I would do is to draw a picture of your system wiring and internal paths and look for the loops

Ok..will do.