Bias Resistor for AX

PsykoK · 30th March 2004, 05:44 PM

I search some good 0.33R 3W resistor to build an AX.
I found this:
http://www.caddock.com/Online_catalo...000_Series.pdf
www.distrelec.ch ref: 721705 or 720703

What do you think about these parts?
With 1% tolerance must I match them?

Tanks in advance.

Alex

jwb · 30th March 2004, 05:49 PM

Seems like a very nice resistor. I wouldn't bother matching them at 1% quoted tolerance.

Personally, I just used four 1.3Ω 1W BC Components metal film resistors in parallel to get 0.33Ω. Only costs US$0.34.

SGregory · 31st March 2004, 04:08 PM

In my AX, I needed .4ohms. In order to do that I found .82 ohm 2watt MOX resistors. Used two per device. Since they were 5% tol, I measured them.

What was interesting was looking at the actual tolerence. Out of 200 resistors, only 4 were over 1% deviation. Infact the general population of the the groups was better than 0.5%. This supports not needing to measure 1% tol resistors. Of course we are DIY, why not measure them.

I used a method I saw on the forum of attaching 10 in series and passing 1 amp of current through them. The voltage drop across each device is equiv to the resistance in ohms. I was able to measure all of them in about 4 hours.

By selecting the resistors to use, the effective tolerence for the resistors is theoretically 0.01%. In reality, I think my meter has more error than that.

I did a similar thing for the current sense resistors and the ground resistors as seen in the photo

Scott

jwb · 31st March 2004, 04:40 PM

I love the half-circle terminals you built on those capacitors. Bravo.

PsykoK · 31st March 2004, 04:59 PM

SGregory> Nice work!
Thanks for your information!

Alex

jam · 31st March 2004, 05:10 PM

Scott,

I like the way your construction looks. How about more close up photographs.

Regards,
Jam

30th March 2004, 05:44 PM	#1
PsykoK diyAudio Member Join Date: Sep 2002 Location: Mulhouse, France	Bias Resistor for AX I search some good 0.33R 3W resistor to build an AX. I found this: http://www.caddock.com/Online_catalo...000_Series.pdf www.distrelec.ch ref: 721705 or 720703 What do you think about these parts? With 1% tolerance must I match them? Tanks in advance. Alex

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30th March 2004, 05:49 PM	#2
jwb diyAudio Member Join Date: Mar 2002 Location: San Francisco, USA	Seems like a very nice resistor. I wouldn't bother matching them at 1% quoted tolerance. Personally, I just used four 1.3Ω 1W BC Components metal film resistors in parallel to get 0.33Ω. Only costs US$0.34.

31st March 2004, 04:40 PM	#4
jwb diyAudio Member Join Date: Mar 2002 Location: San Francisco, USA	I love the half-circle terminals you built on those capacitors. Bravo.

31st March 2004, 04:59 PM	#5
PsykoK diyAudio Member Join Date: Sep 2002 Location: Mulhouse, France	SGregory> Nice work! Thanks for your information! Alex

31st March 2004, 05:10 PM	#6
jam diyAudio Member Join Date: May 2001 Location: Charlotte,NC,USA	Scott, I like the way your construction looks. How about more close up photographs. Regards, Jam

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