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tINY · 19th January 2005, 08:49 AM

Actually, putting a small capacitor across the feedback resistor reduces the closed loop gain at higher frequencies and can make the loop stable if chosen reasonably.

The difference you hear (perhaps) has to do with the gain-bandwidth of the op-amps. Since the typical GBW of the OP27 is 8MHz, the most gain you can have at 16kHz is about 54dB. If you run the gain higher than that, you will actually attenuate the high-frequencies relative to the rest of the audio spectrum. The OP37 is "decompensated" and has a GBW of almost 64MHz. That will give you about another 18dB before this starts happening.

-tINY

19th January 2005, 08:49 AM	#21
tINY Lives for gear Join Date: Jul 2004 Location: Orygun Posts: 6,017	Actually, putting a small capacitor across the feedback resistor reduces the closed loop gain at higher frequencies and can make the loop stable if chosen reasonably. The difference you hear (perhaps) has to do with the gain-bandwidth of the op-amps. Since the typical GBW of the OP27 is 8MHz, the most gain you can have at 16kHz is about 54dB. If you run the gain higher than that, you will actually attenuate the high-frequencies relative to the rest of the audio spectrum. The OP37 is "decompensated" and has a GBW of almost 64MHz. That will give you about another 18dB before this starts happening. -tINY