Tweakers' Asylum

Posted by Vynuhl.Addict (A) on November 08, 2006 at 14:38:33

In Reply to: Which op amp posted by jmall on November 6, 2006 at 12:55:07:

As for changing op amps in the output I would be influenced to first determine how they are being used, chances are if its 2 dual op amps one half handles the IV conversion while the other half drives the line out as a unity gain buffer. Study the datasheets and weigh your new choice against the existing in areas such as open loop gain and closed loop gain frequency response, unity gain stability, you would be suprised to see just how bad some better known op amps appear to be the high frequencies at certain gains. In this case there will be tradeoffs to make as/is, typically something such as an opa2604 will be used here due to its capability to drive lower impedence loads and act as a decent iv stage. I personally have found the ad823 best for the IV stage as a drop in, but at the sacrifice of drive capability which is its weak point so to get around the issue I would add a buffer after the ad823 output, I personally love the ad744/811 (slightyly modified) Walt jung composite stage. I have found by giving the line out plenty of drive capability it produces unflinching sound and superb dynamics and clarity..I used to be into the "Drop It In" mindset, but through extensive listening and datasheet studying there were always changes to make to get it to work its best, some op amps tied pin to pin into unity may require a low value resistor for stability and or frequncy compensation. Someone elses choice for "best" may wreak havoc on your circuit.

Regards
Colin