op amps for active crossover

deriver23 · 18th October 2006, 08:44 PM

i plan on building rod elliots 4th order LR active crossover. What high quality opamp shold i use in the output buffer? What should i use to change the gain?

schematic and inf o here
http://sound.westhost.com/project09.htm

preiter · 18th October 2006, 10:54 PM

Do a search, there are many threads with people expressing opinions on their favorite crossovers.

To add gain, you could reconfigure the input stage to have gain.

FastEddy · 18th October 2006, 10:59 PM

Analog Devices just released a very interesting book (in pdf format). My sub title would be "everything you ever wanted to know about op-amps ... and then some." ... lots of filter circuits and op-amp recommendations, etc.

I got it by subscribing to their new letters re: op-amps ...

Calvin · 19th October 2006, 06:15 AM

Hi,

I recommend FET-type OPs. Since in filter circuits almost always high impedance values exist, FET-types are imo better to couple out the signal. There are many useful types starting from BB´s OPA604/2604, 132/2132, 134/2134/4134 to AnalogDevices AD711/712, 8510/8512, 8610/8620. Using double and Quad-OPs reduces stray effects and keeps the layout compact. With the suggested OPs sound is rather more a function of proper layout, grounding and power supply than anything else.

As an output buffer with gain, I suggest something like in Fig.3c of the BB OPA604 datasheet. This circuit shows more flexibility and clearly better results in driving capacitive loads than just a simple resistor at the output. With this circuit You can tune in on Your´re load situation. Giving best possible signal behaviour (best rectangular wave). The influence of cabling is minimized vastly and You can use even very highly capacitive and/or very long cables. For critical loads like very long cables You should use a OP thats capable of delivering some mA at the output, or use a additional Buffer like the BB BUF634 or an dicrete Buffer circuit.

jauuu
Calvin

AndrewT · 20th October 2006, 07:06 AM

Hi,
look up WaltJung's site.
He describes (in detail) cascading two opamps to create a composite that has excellent input and precision characteristics of a single opamp combined with the output capability of a true IC buffer for driving any sensible cable & load.

He also has a comprehensive article there, for building a high quality discrete buffer. This would replace the buffer in the composite or could be used on it's own if all you need is impedance conversion and no voltage gain.

If you don't fancy implementing these, at least read the articles for the knowledge and then ask the informed question that you aren't aware of at the moment.

nilsomat · 20th October 2006, 07:53 AM

Quote:

Originally posted by FastEddy
Analog Devices just released a very interesting book (in pdf format). My sub title would be "everything you ever wanted to know about op-amps ... and then some." ... lots of filter circuits and op-amp recommendations, etc.

Hello! Does anyone have a link?
AD site has loads of information, but can become a bit confusing...
Greetings,
Nils

dougmorse · 30th October 2006, 07:46 PM

My short answer is 5532. I use 'em.

I do think there is some advantage to using FET types where there is expectation that there is EMI. FETs have less opportunity to demodulate RF, and thus cause interference problems .

By the time any audio signal get to the user, it's alredy been through 100 5532s in the recording process.

Doug

Ryssen · 30th October 2006, 08:19 PM

Quote:

By the time any audio signal get to the user, it's alredy been through 100 5532s in the recording process.

Spare them from one more an use LT1469..

FastEddy · 30th October 2006, 08:45 PM

LT1469 = Yes ... http://www.linear.com/pc/productDeta...09,C1022,P1845

( LT1604 = No, don't bother with 16 bit A to D.)

deriver23 · 30th October 2006, 09:55 PM

While were talking about active filters what is are good passbands and stopbands for a two way crossover?

18th October 2006, 08:44 PM	#1
deriver23 diyAudio Member Join Date: Aug 2006	op amps for active crossover i plan on building rod elliots 4th order LR active crossover. What high quality opamp shold i use in the output buffer? What should i use to change the gain? schematic and inf o here http://sound.westhost.com/project09.htm

20th October 2006, 07:06 AM	#5
AndrewT diyAudio Member Join Date: Jul 2004 Location: Scottish Borders	Hi, look up WaltJung's site. He describes (in detail) cascading two opamps to create a composite that has excellent input and precision characteristics of a single opamp combined with the output capability of a true IC buffer for driving any sensible cable & load. He also has a comprehensive article there, for building a high quality discrete buffer. This would replace the buffer in the composite or could be used on it's own if all you need is impedance conversion and no voltage gain. If you don't fancy implementing these, at least read the articles for the knowledge and then ask the informed question that you aren't aware of at the moment. __________________ regards Andrew T.

30th October 2006, 07:46 PM	#7
dougmorse diyAudio Member Join Date: Oct 2006	answer to what kind of op-amp My short answer is 5532. I use 'em. I do think there is some advantage to using FET types where there is expectation that there is EMI. FETs have less opportunity to demodulate RF, and thus cause interference problems . By the time any audio signal get to the user, it's alredy been through 100 5532s in the recording process. Doug

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18th October 2006, 10:54 PM	#2
preiter diyAudio Member Join Date: May 2006	Do a search, there are many threads with people expressing opinions on their favorite crossovers. To add gain, you could reconfigure the input stage to have gain.

18th October 2006, 10:59 PM	#3
FastEddy diyAudio Member Join Date: Jun 2006 Location: North Californie	Analog Devices just released a very interesting book (in pdf format). My sub title would be "everything you ever wanted to know about op-amps ... and then some." ... lots of filter circuits and op-amp recommendations, etc. I got it by subscribing to their new letters re: op-amps ...

19th October 2006, 06:15 AM	#4
Calvin diyAudio Member Join Date: Nov 2004 Location: close to Basel	Hi, I recommend FET-type OPs. Since in filter circuits almost always high impedance values exist, FET-types are imo better to couple out the signal. There are many useful types starting from BB´s OPA604/2604, 132/2132, 134/2134/4134 to AnalogDevices AD711/712, 8510/8512, 8610/8620. Using double and Quad-OPs reduces stray effects and keeps the layout compact. With the suggested OPs sound is rather more a function of proper layout, grounding and power supply than anything else. As an output buffer with gain, I suggest something like in Fig.3c of the BB OPA604 datasheet. This circuit shows more flexibility and clearly better results in driving capacitive loads than just a simple resistor at the output. With this circuit You can tune in on Your´re load situation. Giving best possible signal behaviour (best rectangular wave). The influence of cabling is minimized vastly and You can use even very highly capacitive and/or very long cables. For critical loads like very long cables You should use a OP thats capable of delivering some mA at the output, or use a additional Buffer like the BB BUF634 or an dicrete Buffer circuit. jauuu Calvin

30th October 2006, 08:45 PM	#9
FastEddy diyAudio Member Join Date: Jun 2006 Location: North Californie	LT1469 = Yes ... http://www.linear.com/pc/productDeta...09,C1022,P1845 ( LT1604 = No, don't bother with 16 bit A to D.)

30th October 2006, 09:55 PM	#10
deriver23 diyAudio Member Join Date: Aug 2006	While were talking about active filters what is are good passbands and stopbands for a two way crossover?

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