Field coil DC power supply help

[Jazid]

And does that field coil hummmmm?

Still not convinced field coils will sound their best heavily damped or under-damped, but what do I know


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[Jazid]

I modeled an RCRC and with available bits it had under 1mV ripple at 300mA. I presumed this would be adequate as a starting point, the speakers aren't that sensitive (if memory serves me - unlikely)

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[disarmamant]

And does that field coil hummmmm?

Well there is some hum, but this is a wartime radio probably built some 75 or more years ago. And how would one tell if the hum was from the field coil?


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[Jazid]

Now that is a very good question!

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[Barry]

Well there is some hum, but this is a wartime radio probably built some 75 or more years ago. And how would one tell if the hum was from the field coil?


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Disconnect the connections to the driver coil?

[paulf-2007]

Disconnect the connections to the driver coil?

Depends where the hum can be heard coming from. If it comes from the cone then disconnecting the voice coil will kill it anyway, switch off the field coil and see if that kills it,

[Jazid]

I presume if it is ripple in the field coil circuit you might leave that energised but short out the voicecoil? That would show any hum, but some precautions necessary in some equipment of course!

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[Barry]

I presume if it is ripple in the field coil circuit you might leave that energised but short out the voicecoil? That would show any hum, but some precautions necessary in some equipment of course!

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Agreed - disconnect the audio connections to the driver coil and terminate them with, say, 10 Ohms (assuming the radio is valved and uses an output transformer). Then short out the speaker driver coil, or terminate it with, say, 1 Ohm.

[bumpy]

The DC supply must be very well smoothed, otherwise any 50 or 100Hz component will beat with the bass frequencies leading to low level intermodulation distortion.

I agree with this. A valve based power supply just sounds better than solid state (to me) but has associated hum issues. This hum can be sat on at the expense of overall sound quality. This is why I have not progressed down this route.

[Jazid]

For others coming down this route I have a suggestion. The PSU is a doddle, hum is not a major issue in anything working adequately on PSUdesigner.

I have found the impedance of the power supply to be rather more important, if you use 1-3 ohm impedance the sound falls into place, this with the silver Aero 8 only since I have tried no other models.

Sounds rather fine actually

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