Ultimate noise rejection

[annex666]

I'm in the process of making an integrated dual mono amp with circuit boards care of ESP.

As the design of the beast in question entails there to be 3 toroidal transformers inside the same box as the pre-amp and power amps I want to employ internal shielding as well as earthing the case.

I've already decided to shield the pre-amp in it's own aluminium box inside the main case as this is probably the most prone to interference. I'll also be using a "zero volt line" - as described on the ESP website.

One final thing I was wondering about was sheilding the toroids?

Would it be benificial for me to source individual boxes for them for inside the main case or could I wrap foil around them or would this break the continuity of the lux lines?

Any help would be appreciated, also ideas how to reduce any kind of interference.

 

[MRehorst]

Be careful about how you box the toroids. Most toroids mount with a bolt through the center and a large metal washer on top. If you put the thing in a box, and the box and the bolt connect to a conductive chassis, you are making a very low resistance, shorted, 1-turn secondary and it will blow fuses (assuming you use them- you are going to aren't you?) or destroy the transformer.

Make sure there is no way the bolt can come into electrical contact with the shield box.

MR

 

[Elso Kwak]

Use of Toroids

Hi Annex666,
Better use two chamber or split bobbin transformers in the preamp. I have researched this in my DAC and preamp and the latter type of transformers gave better sound. Not a day and night difference but worth the effort. To mininise hum pickup I placed the trannie for the preamp in a separate box. In the DAC hum is not a issue. The twochamber transformers have much <I><B>lower interwinding capacitance</B></I> making transfer of hash and garbage from the mains to the circuit more difficult