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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
stanwal's avatar
stanwal
3,147 posts
 
This is the one I meant, you said you had been on the old ones previously.
http://www.apogeespeakers.com/
magfan
1,583 posts
 
Just for some reading material....
I've built a CMOY pocket headphone amp.
I used the OPA2134 series.

http://tangentsoft.net/audio/cmoy-tutorial/parts.html#op-amp

Somewhere in the documentation is a long list of opamps and how the author feels about them. Some are very good while others have audible flaws which some may find acceptable, others not.
ait
480 posts
 
I just converted the output stage on the low frequency EQ unit for my Infinity RSIIb speakers from cap-coupled single-ended mosfet to direct coupled with OPA827 opamps, and the new output stage is much more transparent and clear sounding. The entire signal goes through this stage after equalization.

I know single-ended mosfet stages have a much better audio rep than lowly opamps, but the SiGe OPA827 is very nice sounding, and its exceedingly low DC offset lets me rid the circuit of the output coupling cap - the best cap is no cap, IMHO.
lissnr OP
365 posts
 
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). I'm looking fwd to getting this into the shop soon and will post results asap.
bombaywalla's avatar
bombaywalla
1,958 posts
 
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.
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