I just measured the inductance of a Hammond 194B choke I recently bought new. Specs say this is a 4H choke. My LCR meter (new battery) measures 2.4H @ 120Hz. So maybe it will be a little higher at 60Hz, but isn't this way out of spec? I bought two of them and the other measures the same.
So then I checked this against a brand new Magnetic Components Classictone 40-18003, which is the same choke --both are essentially the Fender 022699 BF Twin choke. Now I'm all choked up, this one comes in at 6.0H @ 120Hz!!
These chokes look identical otherwise, same dimensions, same weight, same DC resistance.
How is this possible? And the Hammond chokes are NOT made in China.
All Choked Up.
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martin manning
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Re: All Choked Up.
The specified inductance is achieved only if the rated DC current is flowing through the choke, so an LCR meter alone can't measure it accurately. I'm surprised that you are over on one and under on the other, though.
Last edited by martin manning on Sun Aug 30, 2015 10:37 pm, edited 1 time in total.
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David Root
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Re: All Choked Up.
Yes I know that, but this is such a big difference I figured something must be going on between these two.
The only thing I can think of is bobbin construction, but I don't see how that could do this.
Now if the Mag Cpts core was solid nickel, maybe. But it isn't, they are both M6 I believe.
The only thing I can think of is bobbin construction, but I don't see how that could do this.
Now if the Mag Cpts core was solid nickel, maybe. But it isn't, they are both M6 I believe.
Re: All Choked Up.
So, contact Hammond (about the Hammond), tell them what you see, what you did, and ask if they will comment. The same for MC.
Re: All Choked Up.
Inductance can go up and down when comparing values from low signal testers, depending on AC excitation level and DC level (if any).
Also the stacking of laminations can be an influence. Some chokes have a clearly seen air gap, some fill that airgap with a paper thickness to ensure design conditions are met. It could just take one pair of laminations to be perfect (no gap) to give a high inductance at low signal, but to saturate in any normal circuit and so be the same working inductance as another choke that has lower inductance at low signal level. A common example was a swinging choke. Another common example is a weld seam along a stack, instead of the old bolted and bell-end stack clamping style.
Some more info on choke measurement:
http://dalmura.com.au/projects/Choke%20measurement.pdf
Also the stacking of laminations can be an influence. Some chokes have a clearly seen air gap, some fill that airgap with a paper thickness to ensure design conditions are met. It could just take one pair of laminations to be perfect (no gap) to give a high inductance at low signal, but to saturate in any normal circuit and so be the same working inductance as another choke that has lower inductance at low signal level. A common example was a swinging choke. Another common example is a weld seam along a stack, instead of the old bolted and bell-end stack clamping style.
Some more info on choke measurement:
http://dalmura.com.au/projects/Choke%20measurement.pdf
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Stevem
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Re: All Choked Up.
Wire them both into the amp/ build and run the amp up to max RMS output power and compare the DC voltage at that point.
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Not screaming like the passengers in his car!
Cutting out a man's tongue does not mean he’s a liar, but it does show that you fear the truth he might speak about you!