Air core inductor for audio amp

tomchr

Member
Paid Member
2009-02-11 12:58 am
Calgary
www.neurochrome.com
Folks,

Does anybody here know of a manufacturer of air core inductors suitable for audio power amp applications? Something like 1.0 - 1.5 uH capable of handling 10 - 20 A RMS.

In the output of a power amp, you often see a Thiele or Zobel network consisting of an inductor in parallel with a resistor. For distortion reasons, it is desirable to use an air core inductor. Winding an inductor for a DIY amp is no big deal, but if one wants to do automated assembly, having a ready made part would be really handy.
I've tried the high-current iron core inductors commonly used in Class D amps, but they distort pretty badly, especially at high frequencies (>10 kHz).

Thanks,

Tom
 

Elvee

Member
2006-09-08 2:04 pm
To be precise - I asked for measurements, not for opinions. Are there any numbers available?
I made a quick check on a 5µH/10A choke like this one:
[IMGDEAD]http://www.newark.com/productimages/standard/en_US/06J0263-40.jpg[/IMGDEAD]
With a 1KHz, 10A^ current (7.07Arms), the voltage appearing across the choke had 0.8% distortion.
Of course, that is not the distortion value for the current, because of the HP filtering effect on harmonics.
Taking this into account, the parasitic resistance, plus the fact that it's mostly 3rd harmonic translates into ~0.25% distortion for the current.
 
Just wind 20 turns of 1.2mm enamelled wire around a pencil (and then pull said pencil, it's just a winding core) .

Since wire diameter and turns is constant, all will measure the same, so you can consider it a commercially bought part and design your PCB accordingly.

Some wind said inductor around a 1W to 2W 10 ohms resistor, but if you want not the least iron inside, so be it, mount them side by side on the PCB.
 
air core inductor

Folks,

Does anybody here know of a manufacturer of air core inductors suitable for audio power amp applications? Something like 1.0 - 1.5 uH capable of handling 10 - 20 A RMS.

In the output of a power amp, you often see a Thiele or Zobel network consisting of an inductor in parallel with a resistor. For distortion reasons, it is desirable to use an air core inductor. Winding an inductor for a DIY amp is no big deal, but if one wants to do automated assembly, having a ready made part would be really handy.
I've tried the high-current iron core inductors commonly used in Class D amps, but they distort pretty badly, especially at high frequencies (>10 kHz).

Thanks,

Tom