| ampage Tube Amps / Music Electronics |
For current discussions, please visit Music Electronics Forum. |
ampage archive
Vintage threads from the first ten years
| previous: lion OK, I know it took some time – but ... -- 1/8/2000 4:24 PM |  |
|---|
Re:Thanks RG and Randall!
 1/8/2000 4:33 PM |
|
Randall Aiken | Re:Thanks RG and Randall! Glad to be of help! To get rid of the effects loop hum, disconnect the ground on the return jack on the amp. Be sure to use isolated jacks for the send and return. By lifting the ground on the return, you are creating what is known as a "telescoping shield", i.e. a shield that is grounded only at one end, usually the sending end (in this case, it is grounded only at the sending end of the effect in use). This allows the effects unit to have a ground reference from the send jack, but not another to the receive jack, so it prevents a ground loop through the shields. It is usually a good idea to add a 0.01uF cap from the receive ground to the amp chassis ground, in order to bypass the shield for high frequency noise. Ideally, a transformer-coupled send and return should be used for complete isolation and hum removal, but the telescoping shield method works in most cases. If you still have hum after lifting the receive jack ground, you can make a cable that has the shield grounded on only one end, and use it for the connection between the send jack and the effect input. This is used only for cases where the effect is run from a 3-prong AC cord, to eliminate a ground loop through the shield and the AC cords of the amp and effects unit. Randall Aiken |
|---|---|
| Replies: |
| lion Randall ! |