Hi, I built the following reamp box.
The purpose of the Ground Lift switch is to connect/disconnect the shielding of the transformer to Sleeve/Pin 1 of the XLR right? I am concerned that as is it will not have a difference since the audio transformer signal depends on pins 2 and 3 right? Am I mistaken to think that grounding or not the transformer will not have any effect?
Thanks
The purpose of the Ground Lift switch is to connect/disconnect the shielding of the transformer to Sleeve/Pin 1 of the XLR right? I am concerned that as is it will not have a difference since the audio transformer signal depends on pins 2 and 3 right? Am I mistaken to think that grounding or not the transformer will not have any effect?
Thanks
Loop currents can travel between equipment through the cable shield and cause noise problems. Suggested default is to leave switch in the 'ON' position, and use the RC network only if there is actual noise detected.
Even if both equipment are individually earthed, it is best to leave the shields connected unless noise is detected. Also, the alternative is to use parallelled RC, not series.
Even if both equipment are individually earthed, it is best to leave the shields connected unless noise is detected. Also, the alternative is to use parallelled RC, not series.
That is the chassis ground on the schematics, and the transformer should be tied to that. The switch is separate to this chassis / transformer connection and connects the pin 1 to the chassis. Chassis, through the pin 1, is then connected to ground and protects the innards from outside stray electromagnetic fields which would be heard as noise. This is the important thing here, chassis grounding.
Inside the box I would think the transformer shield is not needed since the box protects it, unless you've got more electronics in the same chassis. You'll quickly find it out if listening / scoping the noise if it is required or not
The most problematic noise picking antenna is the guitar cord hanging on the high impedance side. Keep that short.
Inside the box I would think the transformer shield is not needed since the box protects it, unless you've got more electronics in the same chassis. You'll quickly find it out if listening / scoping the noise if it is required or not
The most problematic noise picking antenna is the guitar cord hanging on the high impedance side. Keep that short.
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Hi guys thank you for your answers! Oh so it's purpose is for EMI shielding/Chassis grounding? I missed that unfortunately. When the Switch is ON (GND), pin 1 and the transformer are Grounded to the enclosure. Thus any EMI noise picked up is grounded? And if GND noise is audible then the Lift switch is used.
Some other concerns:
1. Is it ok if it output jack is not grounded to the enclosure?
2. Also I've seen other schematics of Reamp Boxes where the GND Lift works as a connection between XLR Pin 1 and the Output Jack Sleeve. The purpose in this case is to shield the enclosure through the output jack I think rather than the transformer.
Oh so it's purpose is for EMI shielding/Chassis grounding? I missed that unfortunately. When the Switch is ON (GND), pin 1 and the transformer are Grounded to the enclosure. Thus any EMI noise picked up is grounded? And if GND noise is audible then the Lift switch is used.Some other concerns:
1. Is it ok if it output jack is not grounded to the enclosure?
2. Also I've seen other schematics of Reamp Boxes where the GND Lift works as a connection between XLR Pin 1 and the Output Jack Sleeve. The purpose in this case is to shield the enclosure through the output jack I think rather than the transformer.
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The author of that App Note (perhaps Deane himself) knew more than almost anybody here. Build it just as documented. If it "dont work", either you didn't build it as documented or are not using it for the intended purpose.
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