EM sheilding for Homemade AMPS??

[Hoads2047]

I was wondering if there was a way to make EM shielding for a Headphone amp that i an planning to make.

 Thanks.

[Enderman]

Build the case out of metal.

[DrMacintosh]

EM shielding can range from your hand to a CD

[Unimportant]

9 hours ago, Hoads2047 said:

I was wondering if there was a way to make EM shielding for a Headphone amp that i an planning to make.

 Thanks.

I'm assuming this is about keeping EMI out, not so much about preventing your device from radiating itself ?

While grounded metal shielding like mentioned above can help, most EMI comes in trough the power supply. You'd want to use or build a power supply that filters out the noise and suppresses voltage transients. Proper decoupling and picking parts with a good power supply rejection ratio in the relevant frequency ranges. Proper shielding of connector and cables off course, especially on the high impedance input side, while making sure to prevent ground loops. Design the amplifier with a input impedance not higher then it needs to be. Most ppl think the higher the better, but more input impedance means more noise. (I guess adding a low pass filter after the input high pass (DC blocking) filter, effectively creating a band-pass, would help with this). PCB design is also important, but more of a art then a hard science, even in commercial design some things are simply tried and tested rather then calculated/modelled. Large uninterrupted ground/power planes help (thus, low impedance all round, no thin connections between planes), pass ground traces in between critical traces, etc.

 

[Guest]

6 hours ago, Unimportant said:

I'm assuming this is about keeping EMI out, not so much about preventing your device from radiating itself ?

While grounded metal shielding like mentioned above can help, most EMI comes in trough the power supply. You'd want to use or build a power supply that filters out the noise and suppresses voltage transients. Proper decoupling and picking parts with a good power supply rejection ratio in the relevant frequency ranges. Proper shielding of connector and cables off course, especially on the high impedance input side, while making sure to prevent ground loops. Design the amplifier with a input impedance not higher then it needs to be. Most ppl think the higher the better, but more input impedance means more noise. (I guess adding a low pass filter after the input high pass (DC blocking) filter, effectively creating a band-pass, would help with this). PCB design is also important, but more of a art then a hard science, even in commercial design some things are simply tried and tested rather then calculated/modelled. Large uninterrupted ground/power planes help (thus, low impedance all round, no thin connections between planes), pass ground traces in between critical traces, etc.

 

 

By filtering out the noise from the power supply, do you mean to make galvanic isolation or use something like a linear voltage regulator (like a LM78xx)?

[Unimportant]

28 minutes ago, Willi said:

 

By filtering out the noise from the power supply, do you mean to make galvanic isolation or use something like a linear voltage regulator (like a LM78xx)?

Line filter on the primary; X/Y filter capacitors, common mode choke, mov transient suppression. One can buy premade line filters tough. Proper smoothing capacitors on the secondary, along with smaller capacitances to handle the higher frequencies. A linear voltage regulator helps with power supply rejection, offcourse. If you find one that has good rejection for audible frequencies (upto 20Khz) then that would be a great choice for a audio amplfier. Proper bypass capacitors near any active components throughout the circuit.