GC 0,22R output resistor - Page 2

Peter Daniel · 2nd March 2004, 12:00 AM

I've seen some people experiencing problems with wrong choice of speaker wires (mostly distortions at high frequencies). Zobel didn't help at all, changing wires did.

In all the amps I built (always without resistor), the resistor was not needed.

Arius · 2nd March 2004, 12:55 AM

Do not use a 0.22R series resistor at the output by itself. This resistor is only meant to be used in conjunction with an output inductor.

1) Output inductor is used to to provide a stable load when driving highly capacitative loads, e.g. long speaker wires.

2) Series resistor (paralled with the inductor) is to damp the LC combination.

Zobel network is for a totally different purpose. It's to provide a load at very high frequencies (where the speaker is no longer 8R).

For highly stable amplifiers like these (if used correctly), output inductor/resistor combo is not needed. Neither is Zobel.

Upupa Epops · 2nd March 2004, 05:19 PM

These resistor is mandarory only in case, if you can connect two channel in parallel mode. In another cases you may let it. But remember on this - if you connect two amps in parallel without this resistors, it will be deadline for both.

tbla · 2nd March 2004, 06:57 PM

Quote:

But remember on this - if you connect two amps in parallel without this resistors, it will be deadline for both

and by that you don't mean bi-amping but having several chips in parallel sharring the same load....right.....?

Upupa Epops · 3rd March 2004, 02:27 AM

Right

.

2Bak · 3rd March 2004, 07:19 AM

I just wonder why the all schematics I've seen on
http://www.ampchipdiy.com/phpBB2/viewforum.php?f=2
includes this resistor...?

Also the most updated one http://ampchipdiy.com/invertedLM3875_r2_1.gif

But perhaps I should ask this question on the ampchipdiy.com forum itself...

I guess quite a few who have build this variation of the IGC have included this resistor. At least those not so experienced DIY builders like me, who stick to the book to be on the safe side

If one uses this resistor, and since it's more a part of the speaker system than the GC circuit, a good non-inductive resistor must be an advantage then, and maybe my Caddocks was not such a bad pick after all...

/Jan

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2nd March 2004, 12:00 AM	#11
Peter Daniel diyAudio Member Join Date: Jul 2002 Location: Toronto, Canada	I've seen some people experiencing problems with wrong choice of speaker wires (mostly distortions at high frequencies). Zobel didn't help at all, changing wires did. In all the amps I built (always without resistor), the resistor was not needed.

2nd March 2004, 12:55 AM	#12
Arius diyAudio Member Join Date: Mar 2004 Location: California	Do not use a 0.22R series resistor at the output by itself. This resistor is only meant to be used in conjunction with an output inductor. 1) Output inductor is used to to provide a stable load when driving highly capacitative loads, e.g. long speaker wires. 2) Series resistor (paralled with the inductor) is to damp the LC combination. Zobel network is for a totally different purpose. It's to provide a load at very high frequencies (where the speaker is no longer 8R). For highly stable amplifiers like these (if used correctly), output inductor/resistor combo is not needed. Neither is Zobel.

2nd March 2004, 05:19 PM	#13
Upupa Epops diyAudio Member Join Date: Aug 2003 Location: Prague,Czech Republic	These resistor is mandarory only in case, if you can connect two channel in parallel mode. In another cases you may let it. But remember on this - if you connect two amps in parallel without this resistors, it will be deadline for both.

3rd March 2004, 02:27 AM	#15
Upupa Epops diyAudio Member Join Date: Aug 2003 Location: Prague,Czech Republic	Right .

3rd March 2004, 07:19 AM	#16
2Bak diyAudio Member Join Date: Apr 2002 Location: Denmark	I just wonder why the all schematics I've seen on http://www.ampchipdiy.com/phpBB2/viewforum.php?f=2 includes this resistor...? Also the most updated one http://ampchipdiy.com/invertedLM3875_r2_1.gif But perhaps I should ask this question on the ampchipdiy.com forum itself... I guess quite a few who have build this variation of the IGC have included this resistor. At least those not so experienced DIY builders like me, who stick to the book to be on the safe side If one uses this resistor, and since it's more a part of the speaker system than the GC circuit, a good non-inductive resistor must be an advantage then, and maybe my Caddocks was not such a bad pick after all... /Jan

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