New op amps, good idea?


I have recently acquired an old crossover which was highly rated in its day (early 1990's). I know technology has improved dramatically since then in many regards but assuming I want to keep and potentially improve this particular one rather than buy a newer version of it (not available), is it worth sending it to a trusted local electronics shop who specializes in such things and asking him to upgrade the op amps with newer/faster/better...? I realize I am not helping its resale and will probably hurt it but if that's not a big concern... I've been told it was a great unit in its day but that it may be considered less transparent than today's similar offerings...
My technician assured me it was not going to be a lot of money (perhaps $100-$200 or so ) and that he was quite confident he could make a noticeable improvement in its performance...If I decide to let him take it what should I be knowledgeable about in order to speak with him intelligently about the work?? Would there be any other mods he could do "while he's at it" that would be reasonably cost effective and sonically helpful as well? Any input would be appreciated as my technical knowledge in all this is limited.... Thanks in advance for any and all opinions. Regards,
lissnr

Showing 2 responses by bombaywalla

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.
Thanks for all the additional input. I think the power supply will be targeted as well as the bridge rectifier, caps and resistors, as per Bombaywalla's great advice (really nice Scinnies by the way and the Cat/Symphonic must make an outstanding combination... very nice rig). .....
Thanks for your kind words, Lissnr. Indeed the combination is very enjoyable.
You had asked about approx total cost - it's very hard to give you such a number as the costs vary depending how far you want to take the upgrades/modifications. One simple example: if you choose Kimber Kaps when replacing caps everywhere, you might end up paying an avg. of $15/cap. OTOH, if you choose, say, Mundorf, you could end up paying 2X or 3X more per cap. That could escalate your costs very quickly. Same deal with the other components.
All the best & I/we hope that it all works out for you. The Apogee DAX are very well regarded. Keep us posted on this forum. Thnx.