Suggestion from Elsewhere for Grounding

[networkn]

I was posting in another forum about the buzzing I have been trying to locate. Someone suggested the following:

Try the ground loop isolator from trademe to verify that it is a ground loop problem. If you don't want to use it permanently. The best way (I think) is to modify the crack amp. What you need to do is have separate audio ground and mains ground. Connect the metal panels, Transformer case ect to the earth pin On the crack amp. Insulate the ground of the RCA connections and the headphone connections from the case if not done already. Make sure that no other audio grounds are connected to the case. Get a high current bridge rectifier such as http://jaycar.co.nz/productView.asp?ID=ZR1324&w=bridge+rectifier&form=KEYWORD Connect the +and - terminals together. And the 2 AC terminals together. Then connect 1 side to your audio ground. And the other side to the mains ground. This will block any small circulating currents because the diodes in the bridge rectifier will only start conducting if there is more than 0.5V difference. But if mains power somehow livens the audio ground, The diodes which can handle 70A (2X35A in parallel) will easily conduct it to ground so the circuit breaker / fuse will still cut the power as normal.

Would this be a worthwhile addition to the crack amp? Is it safe and unlikely to modify the sonic properties of the Amp?

[Doc B.]

I strongly suggest that you resolve the issue you have been discussing on another thread before you modify anything on the amplifier. You must be sure that the amplifier has been properly assembled as described in the manual and that there is no fault which may be making the chassis live. Only after you have ascertained that and made any necessary corrections for safe operation should you address any issues of noise or consider any modifications from the stock design.

[networkn]

I strongly suggest that you resolve the issue you have been discussing on another thread before you modify anything on the amplifier. You must be sure that the amplifier has been properly assembled as described in the manual and that there is no fault which may be making the chassis live. Only after you have ascertained that and made any necessary corrections for safe operation should you address any issues of noise or consider any modifications from the stock design.

Don't worry, I know the order in which I need to do this, I'll make sure the basics are right before anything else, I promise

I was just starting the conversation in the meantime.

[Paul Birkeland]

Would this be a worthwhile addition to the crack amp? Is it safe and unlikely to modify the sonic properties of the Amp?

Not particularly.  The best solution is to fix the issue causing the ground loop.

Installing this modification in the Crack will also be extremely difficult, and will create an incredible safety hazard if not done properly. 

[Paul Joppa]

I'll just add that the described mod is the way the original Foreplay was built in 1998. We learned fairly quickly that it had much more hum and buzz in most situations, so we moved to the (safer) present system of tying the safety and signal grounds together at one point. The diodes are an attempt to solve the intrinsic safety problem of separated grounds; they will not affect the hum or buzz.