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Old 9th November 2004, 07:08 PM   #1
hihopes is offline hihopes  South Africa
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Default Upgrade IC's & caps in active crossover

I have a Prosound DR66 12v (car audio) active crossover in my hi-fi system. I had it open today and noticed 2 x TL074 op-amps in it (14pin DIPs). There are also a number of cheap-looking electrolytic caps in it.
SO! I was thinking:- "074's? Couldn't they have done better than that? Couldn't I do better than that? And what about all these c*aps? I know this is a cheap unit with a reasonable sound, but I have a SPARE one too!
So, question time.
1) I was thinking of replacing the 074's with possibly OPA4134's or OPA4227's (if I can get either in 14pin dip) I know there might also be OPA4228 and/or OPA4132, but I don't know if they would be stable in this unit. Actually, I don't know if 4134 or 4227 will either. (And before someone tell me to put caps on the power pins, this is a PCB and there is no place for that) So, are these the only / the best choices, and will they work? (Just remember, there are no sockets involved. I will have to do some fancy desoldering, so I can't really experiment with this)
2) I am thinking of putting in some Rubycon extreme low ESR caps in place of these cheapies.

So if anyone has some ideas, advice or comments to make, please do so before I a) waste my time or b) mess this thing up.
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Old 10th November 2004, 06:19 PM   #2
hihopes is offline hihopes  South Africa
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O.K. then - no replies yet. But I have been busy in the meantime. I have taken out the old 074 chips, put in DIP 14 sockets and ordered some OPA4227's to try. (I would have preferred OPA4134's, but they are only available in SOIC form now.)A browse of the TI website shows that these are pin-compatible, and since they are supposed to be stable at unity gain, they should be a safe bet as far as oscillation is concerned (the unit has some gain anyway, though I don't know how much) The only question remains whether they will work with a 12v single supply, but if they can't then I will just have to live with the 074's.
I really would like some other options to try if at all possible, so please put on your thinking caps and post some suggestions, for chips and for caps. (Just please don't say Black Gate - I know they are good, that is a bit too much for my pocket)
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Old 10th November 2004, 06:45 PM   #3
Cobra2 is offline Cobra2  Norway
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Default Crossover

I did similar update to a RANE-crossover...used 4134...
-a well invested upgrade!
Also check quality of filter-caps, and take notice if any of them electrolytics are in the path....(replace with bi-polar, or your favourite).

Arne K
Don't believe everything you think...
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Old 10th November 2004, 07:59 PM   #4
hihopes is offline hihopes  South Africa
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That would have been my choice, but it is only available in SOIC from TI now. I hope the 4227's will prove to be good.
Thanks for the tip re the caps. Of course it make sense now that you mention it. I guess polyrops will be way too big, but perhaps metallized will still be better than what is in there now
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