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Old 15th April 2011, 11:54 AM   #1
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Default which opamp for active crossover

Hi guys,
Am planning to build this: Linkwitz-Riley Electronic Crossover still working on the pcb layout.
I am on a college budget and i have a choice of three opamps:NE5532,most expensive and is recommended for the job;TL072,cheaper than the NE;and a "4558",the cheapest option and is flooding the market,used in most electronics from china.
Which will sound decent among the three without eating into my wallet?
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Old 15th April 2011, 12:41 PM   #2
Francec is offline Francec  Australia
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If you could buy all three and do a double blind, there is a fair chance that you won't be able to tell between any two more closely priced. If it was me, the NE5532 unless you have champagne tastes.
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Old 15th April 2011, 01:16 PM   #3
UrSv is offline UrSv  Sweden
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NE5532 are about 1 dollar. That's USD 7 in total.
TL072 are about 75 cents. That's USD 5 in total.
"4558" are about 50 cents. That's USD 3.5 in total.

I would say that the choice of OP-amps from your three candidates is one of the least of your problems. If USD 3.5 is a show stopper then the project is doomed.
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Old 15th April 2011, 01:19 PM   #4
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On a budget:
Use higher GainBandwidth op-amp ( more pricy ) for the two upper ones ( giving High ).
Use lower GainBandwidth op-amp ( cheaper) for the other ones.
High frequencies need good op amps, low frequencies don't.
If I were to build a 3 way LR filter I would use one OPA2134AP ( for the High ) and three NE5532AN ( for the Mid and Low ).
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Old 15th April 2011, 06:43 PM   #5
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Originally Posted by UrSv View Post
If USD 3.5 is a show stopper then the project is doomed.
I need a good sounding system.If the human ear can't differentiate between a 'premium device' and an ordinary "4558",why would i go for a device which is three times more pricey?
What am asking here is the sound quality,which will sound good in this crossover?If its the 5532,i'll have no other choice but to go for it then build the power amps some other time.
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Old 15th April 2011, 07:04 PM   #6
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Quote:
Originally Posted by xeclipse View Post
I need a good sounding system.If the human ear can't differentiate between a 'premium device' and an ordinary "4558",why would i go for a device which is three times more pricey?
What am asking here is the sound quality,which will sound good in this crossover?If its the 5532,i'll have no other choice but to go for it then build the power amps some other time.
It's not about what "the human ear" can hear, but about what you can hear. The differences between 4558, 072, 5532 and 4562 are quite audible to some, but are they audible to you?

BTW, are you building the suggested P05 power supply to feed your board? An extra capacitor or transistor there will bring you more SQ improvement than the difference between a 4558 and a 5532.

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Old 15th April 2011, 07:25 PM   #7
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Originally Posted by MatchASM View Post
BTW, are you building the suggested P05 power supply to feed your board? An extra capacitor or transistor there will bring you more SQ improvement than the difference between a 4558 and a 5532.
Thanks for your replies.
I already have a +/-15v supply from a pioneer receiver,but i'll look into the p05.Does anyone know the current draw of the crossover?
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Old 15th April 2011, 08:04 PM   #8
Mooly is offline Mooly  United Kingdom
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The TO72 is an excellent performer... it's only real limitation is limited output drive into low impedance loads.

The 4558 is not recommended these days for serious listening... use 4558's in say a CD player DAC for output buffer/and/or/ IV conversion and although it may sound good in isolation when you swap for a more modern device the difference is obvious.

As ever it's hard to put into words... a good example is like imagining a $2000 CD player and a $30 portable CD player running through $10'000 worth of amp and speakers. Swap the opamps in the expensive CD player and it will bring it down to the more the performance level of the portable... yet both sound good in their own right.
Its when you hear the subtle differences that there's no going back if you take your music seriously.

Why not use sockets and experiment.
As for current draw... a 5532 pulls around 15ma compared to 3 or 4ma from memory for a TL072 or 4558.
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Old 16th April 2011, 12:54 AM   #9
Francec is offline Francec  Australia
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Hey UrSv,
xeclipse is from Kenya AND a student. Things are vastly different from affluent EU and US standards of wealth and what is achievable. Even a NE5532 is not $1 in Australia; it is about $2. Suggesting to use sockets also doesn't reflect a reality that is achievable; sockets cost too.

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Old 16th April 2011, 01:11 AM   #10
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I swapped out ST33078 for 4558 in my disco mixer (used to play LP's at 50x gain) and there was a noticable decrease in hiss. 33078 has a noise spec closer to a 5532 than a 4558. Takes an additional 0.1 uf cap on the power supply near the IC, to prevent oscillation, so figure that into your costs. 5532 or TL072 might need the caps, too, the more slew rate the more the amp tends to oscillate. You might get some of those salvage from a dead PC switcher power supply or a radio or something.5532 has way better noise numbers than 4558, if you have speakers that can reproduce the high frequencies. If you make mistakes like input voltage too far from the middle, TL072 latches up.
I'm glad I live here, 33078 is $.38, and the ultimate audio op amp right now, LM4562 from national semi is $2.18 this week. All supplies with a minimum $7 freight for up to 5 kilos from farnell. There is no op amp stocked within 300 km of here.
Look at putting your power supply in a different steel box than the op amps, helped my mixer's hum enormously. I'm using an 18 VDC wall transformer from a slot car set with two 1n5344 8.2V zeners in the op amp box to make the center signal reference ("ground").
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