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Climbing the opamp ladder

Over the course of the past five or so years, I have been upgrading my active crossovers. Initially, the input buffer, which also converts balanced input to single-ended, was populated with OPA2134. The sound was very musical but somewhat dull and flat without much detail or sparkle.

Not satisfied, I next installed LM4562. There was a considerable increase in high frequency detail, with tighter bass and somewhat better soundstage and depth. At times there was almost too much detail with a bit of stridency and occasional sibilance. Tonality was just barely on the realistic side of too hi-fi, with a somewhat thin midrange.

After a couple years of that, I decided to take the plunge and try OPA627. My crossovers were designed for stereo, but I am using them inside monoblock amplifiers so I need only half of the dual opamp design. I used a BrownDog DIP adapter to fit the single 627 into the dual circuit. I also improved the power supply bypassing, which may have contributed. The sound improved considerably, with much more realistic tonality without any extra brightness. Depth and soundstage improved, with increased sense of air around instruments. Midrange was excellent, and voices became more realistic.

However, our tweaker motto is never good enough, so I next went to OPA627 in SOIC format, soldered onto another BrownDog with smaller footprint and shorter signal paths. This provided a minor refinement of sound, with slightly better depth and bass control.

Still not good enough, so I have recently installed a Sparkos discrete opamp. Since I need only a single, I still had to mount it to yet another BrownDog, this time back to the DIP format. It takes up a bit too much real estate compared to a standard opamp, so I needed to move the Vishay naked Z-foil resistor to the bottom side of the board. Okay, this might be enough. The tonality is every bit as good as, if not slightly better than, the OPA627, but what has improved dramatically is the spatial characteristics of the sound. There is no longer any sense of sound coming from inside or on or anywhere near the speakers. There is no front or back or side to images, just an infinite layering of varying shades and depths, existing free in space, filling the space between the speakers with that ultimate goal: an aural hologram.

I admit I was on the fence about the worth of discrete opamps, somewhat cynical that any circuit twenty or more times larger than a chip could perform better than a device with 0.00003% distortion. Now I'm convinced that there is something to it, at least with the Sparkos in this rather straightforward application. I've fiddled with enough components inside circuits to know that careful parts selection makes a significant difference to the overall character of sound, and this discrete device is a big step up from the little plastic boxes.

Peace,
Tom E
berate is 8 and benign is 9


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Topic - Climbing the opamp ladder - madisonears 20:00:00 08/13/17 (3)

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