understanding star grounding

[farmerjack61]

Originally Posted by pacificblue

Yes.


Depends on the speaker impedance and how much capacitance your power supply has. Something like 12 W into 8 Ohm.


You will not be able to control that.


If the transformer is rated for 3 A, you can use a 3 A slow-blow fuse on the secondary side. You don't gain any safety by using a smaller fuse.


Use a split supply. You save on the virtual ground circuit and the output capacitor.


If you regulate it down to 13 V, you will only get 7-8 W into 8 Ohm, instead of 12 W. The regulators will produce a lot of extra heat, extra consumption, and they will increase the cost, size and complexity of the project.


No, you would skip the center tap, so your transformer will have 1x24 V instead of 2x12 V and the regulated voltage could be 26 V, too.


Split supply is better, but the difference is not that big. You basically add a big capacitor to the signal path, and that can or cannot have an influence on the sonic signature.

Why do you suggest a T3A fuse as opposed to the one mentioned in post #478 Blue? What about the primary fuse? Would you reccomend one of them?

Cheers Cobber.

[pacificblue]

If you have a transformer rated for 2,8 A, use a 2,8 A fuse, if you find one. If you have a transformer rated for 3 A, use a 3 A fuse. Using a smaller fuse than nominal does not hurt, but it does not help either. On the contrary, although it appears strange, transformer secondaries are usually fused with the next higher fuse, e.g. a 3 A transformer would get a 3,15 A fuse, not a 2,5 A.

Why is that so, when we usually always take the next smaller fuse? Because the power rating of a transformer is a guaranteed performance promise. If you use a smaller fuse, the transformer cannot deliver that power, because the fuse will prevent it from doing that. Accordingly transformers are designed to work on the next higher available fuse size.

It is quite common to find a recommendation for the primary fuse on the transformer itself. Sometimes you also find it in the datasheet.
If the transformer manufacturer does not recommend a primary fuse, you will have to determine it by trial-&-error.