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
schematic and inf o here
http://sound.westhost.com/project09.htm
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
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
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.
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.
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
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
LT1469 = Yes ... http://www.linear.com/pc/productDetail.do?navId=H0,C1,C1154,C1009,C1022,P1845
( LT1604 = No, don't bother with 16 bit A to D.)
( LT1604 = No, don't bother with 16 bit A to D.)
Member
Joined 2006
Member
Joined 2006
Hi there gainphile.
Yes, opamps do sound different. But TL074?!!
I am trying to figure out what's best for our Pluto
I have used opa2134, then LM4562, and later LME49860 - each trial was an improvement.
And now I need to make a decision on whether LT1352 or LT1469 which will be next for the filter stages...
LT1352 is recommended by Jim Williams for EQ circuits (with low input bias current), but the quiescent current is really low (250 uA....), on the other hand LT1469 is also promising......(not sure it's capacitive load capability is an issue, or is it an issue?)
Yes, opamps do sound different. But TL074?!!
I am trying to figure out what's best for our Pluto
I have used opa2134, then LM4562, and later LME49860 - each trial was an improvement.
And now I need to make a decision on whether LT1352 or LT1469 which will be next for the filter stages...
LT1352 is recommended by Jim Williams for EQ circuits (with low input bias current), but the quiescent current is really low (250 uA....), on the other hand LT1469 is also promising......(not sure it's capacitive load capability is an issue, or is it an issue?)
" ... I have used opa2134, then LM4562, and later LME49860 - each trial was an improvement. ..."
I bet you installed a socket so you could easily swap out the op-amps ... Good show.
BTW: that LT1469 from Linear Tech. ... It is a mistake for Linear to associate a linear device with the 16-bit digital protocol = same as saddling up a cow.
But from what I can read, it is a good op-amp for this purpose. No personal experience here, but Linear generally makes about as good as it gets.
I bet you installed a socket so you could easily swap out the op-amps ... Good show.
BTW: that LT1469 from Linear Tech. ... It is a mistake for Linear to associate a linear device with the 16-bit digital protocol = same as saddling up a cow.
But from what I can read, it is a good op-amp for this purpose. No personal experience here, but Linear generally makes about as good as it gets.
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