What would this L.F. Choke be used for?

[SurreyNick]

I’d like to understand the role of this type of choke.

It is marked L.F. Choke and is built like a transformer with a laminated iron core so I think it must be an Audio Frequency choke. What I don’t know (and I can’t find any reference to this particular choke on the internet) is what type of circuit it would be used in i.e. AC only, DC only, or AC/DC, and what role it would fulfill.

For example was it intended to be used as a form of AC resistance, or alternatively for smoothing in a DC power supply to filter out hum, or as part of a rectifying circuit to remove ripple at the output of the rectifier?

I'm intending to sell it on, but I’d still like to know more about it and it’s purpose before disposing of it.

Thanks

Nick
           

[Framer Dave]

A choke of this type was commonly used as the anode load for the audio output stage in early receivers. Typical connection was between HT+ and the anode of the audio output valve, the high impedance (moving iron) loudspeaker being connected via a capacitor between the anode and HT-.

Regards,

[Ed_Dinning]

Hi Nick, used as Dave suggests. It would have a mixture od AC and DC currents in its windings and probably quite a low current rating but highish inductance.
Not really suitable for power supply smoothing applications. Sometimes used in reflex circuits in series with an RF choke.
Close examination of the lams may well show a small airgap.

Ed

[unrealdave]

Hi - its used for choke capacity coupling in the LF stage - probably in a 20's battery radio. It goes from the anode through to HT+ , the anode also goes to the grid condenser (cap) of the following LF amplifying valve.

There are example circuits in Camm's encyclopaedia

It works well but you don't get the same amplification as with transformer coupling.

[SurreyNick]

Thanks guys. That is really helpful.
N.