How to add a high / lowpass to an IGC / GC? - Page 3

Rick NL · 2nd December 2003, 03:31 PM

Hi, the attachment did not seem to come through, here another try,
Rick

Raka · 2nd December 2003, 04:00 PM

and what if I simply put a passive net in the amp input, of course buffering the general input? If I go second order, I won't get more than a Bessel, but I thinK I can live with that.

I've been thinking about the substractive in the Pass paper, trying to get passive also, but didn't get something tangible, any hint?

theChris · 2nd December 2003, 05:41 PM

won't this design ossilate?

ThorstenL · 2nd December 2003, 05:54 PM

Konnichiwa,

Quote:

Originally posted by Rick NL
One thing is important with this topology: the feedback resistors shall be low ohmic in comparison to the filter resistors.

As also clearly spelled out in the Application note.

Sayonara

Rick NL · 2nd December 2003, 09:01 PM

Kuei Yang Wang wrote:
As also clearly spelled out in the Application note.

Kuei Yang Wang,

Yes it is spelled that the impedance around the negative i/p is around 100 Ohms but it is not stated why and what is the consequence when you don't comply to this rule.
It is important as on this forum many contributions state that around 220k/10k or even 470k/15k are sonically best for the gainclone. Not in this topology!

Rick

Nappylady · 2nd December 2003, 09:18 PM

The LM3875 datasheet typical app note includes a feedback capacitor that "ensures unity gain" for DC signals... so there must be some caveat to the "if gain < 10 then oscillate" rule...

ThorstenL · 3rd December 2003, 07:47 AM

Konnichiwa,

Quote:

Originally posted by Rick NL
It is important as on this forum many contributions state that around 220k/10k or even 470k/15k are sonically best for the gainclone.

Inverting topology, not non-inverting....

Sayonara

Cradle22 · 8th December 2003, 09:31 AM

Hi!

Could someone please check out, if this setup would work (and not oscillate)?

Non-Inverting XO with a gain of 22, circuit like in AD's online calculator (link above)..., low pass Bessel 75 Hz (or Butterworth with different values)

C1 2.2 nF
C2 47 nF
R1 1050 K
R2 35.7 K
R3 2.21 K
R4 105 ohm

Non-Inverting XO with a gain of 22, circuit like in AD's online calculator (link above)..., high pass Bessel 75 Hz (or Butterworth with different values)

C1 2.2 nF
C2 2.2 nF
R1 3320 K
R2 243.0 K
R3 2.21 K
R4 105 ohm

I know that inverted design is more stable, but I don't know how to calculate (didn't find a tools for this) the values for inverted design...

Thanks,

Arndt

2nd December 2003, 04:00 PM	#22
Raka diyAudio Member Join Date: Aug 2002 Location: Close to Oistrakh	and what if I simply put a passive net in the amp input, of course buffering the general input? If I go second order, I won't get more than a Bessel, but I thinK I can live with that. I've been thinking about the substractive in the Pass paper, trying to get passive also, but didn't get something tangible, any hint? __________________ What is beyond the speaker?

2nd December 2003, 05:41 PM	#23
theChris diyAudio Member Join Date: Dec 2001 Location: SIUE, Illinois, USA	won't this design ossilate? __________________ if only it could be used for good, not evil...

2nd December 2003, 09:01 PM	#25
Rick NL diyAudio Member Join Date: Sep 2003 Location: Gouda	Kuei Yang Wang wrote: As also clearly spelled out in the Application note. Kuei Yang Wang, Yes it is spelled that the impedance around the negative i/p is around 100 Ohms but it is not stated why and what is the consequence when you don't comply to this rule. It is important as on this forum many contributions state that around 220k/10k or even 470k/15k are sonically best for the gainclone. Not in this topology! Rick __________________ After all it's the music

8th December 2003, 09:31 AM	#28
Cradle22 diyAudio Member Join Date: Jan 2003 Location: Dortmund, Germany	Hi! Could someone please check out, if this setup would work (and not oscillate)? Non-Inverting XO with a gain of 22, circuit like in AD's online calculator (link above)..., low pass Bessel 75 Hz (or Butterworth with different values) C1 2.2 nF C2 47 nF R1 1050 K R2 35.7 K R3 2.21 K R4 105 ohm Non-Inverting XO with a gain of 22, circuit like in AD's online calculator (link above)..., high pass Bessel 75 Hz (or Butterworth with different values) C1 2.2 nF C2 2.2 nF R1 3320 K R2 243.0 K R3 2.21 K R4 105 ohm I know that inverted design is more stable, but I don't know how to calculate (didn't find a tools for this) the values for inverted design... Thanks, Arndt __________________ ************************ A Sacrifice For Freedom

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2nd December 2003, 09:18 PM	#26
Nappylady diyAudio Member Join Date: Feb 2003 Location: Salt Lake City	The LM3875 datasheet typical app note includes a feedback capacitor that "ensures unity gain" for DC signals... so there must be some caveat to the "if gain < 10 then oscillate" rule...

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