pucho812
Well-known member
what is the purpose of a ferrit bead on the line input of a piece of gear? I have seen it a few times usually after the connection and before the differential opamp.
pucho812 said:what is the purpose of a ferrit bead on the line input of a piece of gear? I have seen it a few times usually after the connection and before the differential opamp.
I've never seen a ferrite bead saturate at audio frequncies in mic or line level applications. Anyway, their reactance at audio frequencies is so small even huge variations would have no consequences on distortion.user 37518 said:There are mixed feelings about ferrite beads, on one side they help suppress RF noise, on the other side they tend to saturate and distort, pick your poison.
Same here. But if concerned about it useful to note that placing a ferrite around current balanced conductors cancels out the effect on the differential signal. The likely common mode rfi does see the impedance.abbey road d enfer said:I've never seen a ferrite bead saturate at audio frequncies in mic or line level applications.
It depends on the RF environment the SKU is exposed to, and the design of the input stage. It is possible to design an input stage that harmlessly LPF RF input but many older designs will slew limit and rectify the RF.pucho812 said:which brings up the follow up questions as to how necessary they are and if they can be left out?
Common-mode chokes. They used to be expensive when they started to appear, at the time manufacturers were made conscious of EMI/RFI regulations.JohnRoberts said:It depends on the RF environment the SKU is exposed to, and the design of the input stage. It is possible to design an input stage I recall some specialized input common mode filters, that became popular to fix RF problems in a high volume mixer designed by a competitor . IIRC it was something like a transformer that passed differential audio but rejected common mode noise.
JohnRoberts said:"These days there are more RF sources everywhere than back when I was in the trenches."
Yup, everything was better back in the good old days...
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