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Digital Drive Upsamplers, DACs, jitter, shakes and analogue withdrawals, this is it. |
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Digital Drive Upsamplers, DACs, jitter, shakes and analogue withdrawals, this is it. |
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In Reply to: AD827JN op-amp in IC sockets? Is this okay? Help! posted by Dan on March 31, 2000 at 12:41:26:
Let's put this in perspective. This is a video OpAmp. It has a 300V/usec slew rate (very fast). It has 15 nV/root Hz input noise- not all that quiet. It does have low power consumption, and low input offset. To have a power amp which matched it's GBW and SR, scaling for gain, it would have to be about 6000V/usec slew rate. You're going to have trouble finding that.
Is the 827 the best choice for a CD Player output stage? That's a personal call, I could probably argue otherwise, though I certainly wouldn't fault the DC characateristics (0.5 mV offset) or GBW and SR. However, using high GBW video amps requires special techniques just to make sure they don't turn into an oscillator. I've discussed some of that in another MSB DAC upgrade post recently. If you don't have a scope and the experience to measure and trouble shoot the circuit, I would proceed with caution. Since I don't know what the existing opamps in the Link DAC are, I can't tell you if BurrBrown OPAS2134's would be an upgrade, but their DC characteristics, GBW and SR, and very low distortion make them an eminently reasonable choice for experimentation, as long as the existing design uses some good local bypass for the OpAmps; they work fine in sockets. There are a host of other design issues, including power supply bypass, radiated noise, use of coupling caps in the output stage (a no-no in my opinion), and other matters (such as the DAC's themselves) which will probably frankly swamp the sonic differences between those two parts, in a product at the Link DAC's price point. The OPA2134 are moderately low noise, and are JFET inputs, so input bias current related offsets will be non-existent, as well as most other input impedance effects, unless the associated circuitry is very high impedance, (unlikely), in which case the nonlinear JFET input capacitance will cause some rise in HF distortion.
Unfortunately my favorite "cheap" OpAmp is not available in a dual, but try the 2134's and see what you think- it's a no risk proposition, compared with the 827. The 2134's are popular retrofits for recording mixers, and I've yet to hear a PCM playback device that could equal a good live mic feed. But, don't expect the opamps, whatever you use, to turn your DAC into SACD.Regards,
Jon
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- Re: AD827JN op-amp in IC sockets? Is this okay? Help! - Jon Marsh 14:42:40 03/31/00 (0)
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