While it is true that technology has improved today compared to 1991, I would have to say that biggest trend today is that things have become more digital - HD TV, HD radio, digital modulation schemes for cellphone over-the-air protocols, digital cameras, Blu-ray DVD players, etc, etc. I.E. there is more & more emphasis put on the digital signal processor (DSP) piece of silicon inside a lot of electronics.
In the meantime, human-beings' audio range is still 20Hz-20KHz. I have looked at Analog Devices', TI's & a few other companies' standard parts catalog. Many of their standard off-the-shelf part numbers are the same as they were 10+ years ago. In fact, many of these companies pride themselves on this part - an off-the-shelf opamp part designed 10+ years ago is still for sale today (because it was a damn good performing part them & remains a damn good performing part today) & is still bringing in revenue. I even know some of the engineers who designed these opamps - they are still designing in the industry not necessarily for that same company.
So, the point here is that it is very likely that it is not your opamp that needs replacement (it very well could & it would be easy to find a similar replacement if your tech looked in the catalog) but you could definitely do with a replacement or upgrade to
* the diode bridge rectifier - use of FREDs or Schottky diodes (the sound of both of these is very different & some people prefer Schottkys over FREDs)
* a change-out of the electrolytic capacitors - use modern day computer grade or audiophile grade caps.
* a change-out of the resistors - use Caddock, Vishay, PRP, Dale, etc brand resistors or the very expensive Tantalum kind that Audio Note UK uses
* Upgrade the internal hook-up wires
* damp the overall metal chassis by using Dynamat (asphalt-based) or Cascade (vinyl based) or you can use the less expensive vinyl based stuff from Partsexpress.com
* upgrade the RCA jacks to any brand that your favour - WBT, Cardas, etc, etc.
* Make sure that your tech uses audiophile grade solder such as Wondersolder or Cardas eutectic solder or something else.
* Make sure that your tech cleans the PC board - all these years could have generated a lot of copper oxidation.
* One other thing to do is for your tech to touch-up all the solder joints just to make sure that there are not old solder joints & no cold solder joints.
I think that once you do all of this, you should have a more transparent sounding x-over.
In the meantime, human-beings' audio range is still 20Hz-20KHz. I have looked at Analog Devices', TI's & a few other companies' standard parts catalog. Many of their standard off-the-shelf part numbers are the same as they were 10+ years ago. In fact, many of these companies pride themselves on this part - an off-the-shelf opamp part designed 10+ years ago is still for sale today (because it was a damn good performing part them & remains a damn good performing part today) & is still bringing in revenue. I even know some of the engineers who designed these opamps - they are still designing in the industry not necessarily for that same company.
So, the point here is that it is very likely that it is not your opamp that needs replacement (it very well could & it would be easy to find a similar replacement if your tech looked in the catalog) but you could definitely do with a replacement or upgrade to
* the diode bridge rectifier - use of FREDs or Schottky diodes (the sound of both of these is very different & some people prefer Schottkys over FREDs)
* a change-out of the electrolytic capacitors - use modern day computer grade or audiophile grade caps.
* a change-out of the resistors - use Caddock, Vishay, PRP, Dale, etc brand resistors or the very expensive Tantalum kind that Audio Note UK uses
* Upgrade the internal hook-up wires
* damp the overall metal chassis by using Dynamat (asphalt-based) or Cascade (vinyl based) or you can use the less expensive vinyl based stuff from Partsexpress.com
* upgrade the RCA jacks to any brand that your favour - WBT, Cardas, etc, etc.
* Make sure that your tech uses audiophile grade solder such as Wondersolder or Cardas eutectic solder or something else.
* Make sure that your tech cleans the PC board - all these years could have generated a lot of copper oxidation.
* One other thing to do is for your tech to touch-up all the solder joints just to make sure that there are not old solder joints & no cold solder joints.
I think that once you do all of this, you should have a more transparent sounding x-over.