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Help on question for Inductor in CLC Class A amp.
Help on question for Inductor in CLC Class A amp.
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Old 10th October 2020, 03:36 PM   #1
john65b is offline john65b  United States
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Default Help on question for Inductor in CLC Class A amp.

Hey all,

I have a Class A amp power supply on my Krell Clone - Pinkmouse boards)

Anyway, I want to change the CRC to CLC to see power supply ripple reduction.

I saw a few pics that the Pass amps have an iron core inductor (similar to Speaker crossover coils). I did find in my stash two chokes of 4.75mh and .2 ohms DCR (amp rating unknown). These look like vintage Altec Lansing Iron Core Crossover inductors - see pics... look to be 16awg wire...

I remember years ago trying this and the inductors got quite hot (I am pulling around 6A per rail) after a while, but so did the whole damn amp!.

The power supply is a 1KVA Toroid into a 25A Rectifier - 56,000uf - L - 56,000uf and rails are +/- 36VDC.

Anyway, if only .2ohms and 6 amp, 16awg, how to guess at power capabilities (weigh it?)

Whats too hot? Yes, I get that I dont wanna melt the coating...

I see crossover iron core inductors rated at 500W but only .2ohms DCR - how / why? I know there is more to this than Amp x Resistance going into the power rating...
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Old 11th October 2020, 02:00 AM   #2
PRR is offline PRR  United States
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Help on question for Inductor in CLC Class A amp.
AC filter coils want un-gapped cores.

DC filter coils want gapped cores.
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Old 11th October 2020, 02:33 AM   #3
john65b is offline john65b  United States
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I believe these are gapped...no?
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Old 11th October 2020, 03:10 AM   #4
DUG is offline DUG  Canada
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Gapped cores hold their inductance at value for a greater variation on DC current.

Ungapped cores have a decrease in inductance vs DC current that can start happening with very little current...they start to saturate quickly.

Some inductor manufacturers rate their cores at a 10% decrease in inductance at the quoted saturation current.

Inductance and resistance are only part of an inductors' ratings / characteristics.

If you are passing enough current to saturate the core of your inductor you may end up with an effective R...not the L you were looking for.
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Old 16th October 2020, 08:20 AM   #5
Andersonix is offline Andersonix  Sweden
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Help on question for Inductor in CLC Class A amp.
I^2 *R = 36*0.2 = 7W

I think it will dissipate 7W, don't you?
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Old 16th October 2020, 12:23 PM   #6
john65b is offline john65b  United States
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So it is just the resistance? In other words the resistance does not change with a saturated core?

All I was ever seeing was the 7 watts of heat? OK. maybe overly concerned over nothing.

I have 13mH 500W Sledghammers coming and according to PSU Designer, should drop the ripple down to less than half of what it is now.

From PSU Designer adding the 13mH will drop it from 250mv to around 100mv. Still high tho, yes? I can hear a little hum on some speakers, but nothing thru my Quad ESL-988...
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Old 17th October 2020, 10:56 PM   #7
Andersonix is offline Andersonix  Sweden
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Help on question for Inductor in CLC Class A amp.
Yes, 100mV of PS ripple is awful. But I recommend making a one-half drop in ripple every year, so you have time to evaluate (appreciate?) your new sound.
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