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Old 4th February 2011, 10:53 PM   #1
gixxer is offline gixxer  Canada
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Unhappy NJM4556a opamp

Good Day
Help !!!!

Where can i get a hold of 4 - NJM4556A opamps ? If not available is there a good equivalent to same . I am building a Phono Preamp .
Thanks
Gixxer
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Old 5th February 2011, 02:57 PM   #2
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The 4556 has high current drive, which would be useful for driving a headphone, but not as useful as a pair of NEC575C2 which are an 8 pin dip with a little heat sink on the end. The 4556 has no noise specification, and is only specified at 150 ohm load, which is still not enough for an 8 ohm headphone. For the rest of the input functions I would use RC4560, or ST33078, which are modern,stocked, durable (no latchup like TIL072) and very low noise. For a single IC solution to driving the headphone, farnell.com had TO220 package op amps with modern numbers. TO220 has a big heat sink. Just use their selector chart for IC and pick a cheap TO220 one with at least ft of 3mhz. You don't specify the package, the 4556 comes both in DIL and straight 8. You need to download the datasheet from datasheetcatalog.com and figure out which suffix you are looking for. My disco preamp was modified for low noise and uses +-8 off a 18 VDC wall transformer. See the following thread for my hiss and hum war on the RA88a, Improving a "Disco mixer" to mid-fi performance. If you can find a Herald RA88a at the flea market, it has superb slider pots and a nice SS front panel.
If you use fast op amps with ft 10 mhz or higher like these, make sure you put a .01 uf to .1 uf disc cap between + and - supplies at the op amp socket or within an inch, and a 20 pf cap or so across the feedback resistor, to eliminate the tendency to oscillate. This is in addition to the x00 uf electrolytic caps on the power supplies on the board. Electrolytic caps are wound up and too slow for megahertz signals to penetrate.
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Last edited by indianajo; 5th February 2011 at 03:13 PM.
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Old 6th February 2011, 02:56 AM   #3
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Default headphone driver

Okay, if anybody is listening, and has a schematic for a magnetic phono amp using NJM4556's, the only reason to use that IC is for high current for the headphone driver. A modern op amp in a TO220 package with big heat sink is TI OPA453. +-10 to +-40 v power supply, 50 ma drive capability, 7.5 Mhz Ft, 23 v/microsec slew rate. $5.16 2/5/11 in North Carolina. You want a little slower amp, OPA452, Ft 1.8 mHz. Both have 21 nv/sqrtHz noise, about 5 times the 33078. The pinout will be different than the NFM4556, and it may require more power supply & feedback resistor bypass caps, but it should drive your headphone. The high gain signal amps I would still use the RC4560 (TI or NJM) or ST33078 for the low noise. The 33078 is driving an 8' cable to my power amp just fine.
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Last edited by indianajo; 6th February 2011 at 03:06 AM.
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Old 6th February 2011, 05:25 AM   #4
Michel is offline Michel  Canada
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Future Electronics has them at 27 cents each!
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Old 6th February 2011, 06:32 AM   #5
Mooly is offline Mooly  United Kingdom
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Quote:
Originally Posted by gixxer View Post
Good Day
Help !!!!

Where can i get a hold of 4 - NJM4556A opamps ? If not available is there a good equivalent to same . I am building a Phono Preamp .
Thanks
Gixxer
Which preamp are you building ?

I would imagine the LM4562 would be an ideal choice.
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Old 6th February 2011, 01:11 PM   #6
gixxer is offline gixxer  Canada
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Default njm4556a

I believe it is a Grado knock off .
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Old 6th February 2011, 02:48 PM   #7
Mooly is offline Mooly  United Kingdom
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Quote:
Originally Posted by gixxer View Post
I believe it is a Grado knock off .
And you mean phono preamp as in record deck, not headphone amp
Just with everyone else talking of driving H/phones.

If it's an RIAA phono preamp or M/C head amp the LM4562's have to be the one to try.
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Old 6th February 2011, 04:11 PM   #8
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The reason I was talking the headphone part is that the 4556 has a spec that it can drive 150 ohm load, and all these other numbers do not have that much drive current. They are fine for the mag phono cartrige pickup, the cd player input, and the driver of the cable to power amp , however. 4562 looks fine, I have the NJM datasheet from datasheetcatalog.com. I have some physical 4560's in the CS800s, they are very quiet, and interchange with the ST33078's I put in the disco mixer RA88a with two mag phono inputs, a CD, and a mike (now FM radio) .Be sure to use disc caps locally on P.S. & feedback resistor as 4562 will oscillate just like the 33078 did without them.
TH3 something (in Romania) bought a Velleman Pro disco mixer where they had used 4558 op amps for all functions including the headphone drive, and besides hissing, it was pretty feeble at driving headphones too. So a 4556 had a reason to live at some time, although it is quite obsolete now.
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Last edited by indianajo; 6th February 2011 at 04:27 PM.
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Old 6th June 2011, 08:40 PM   #9
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What about the NE5532?
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Old 8th June 2011, 06:45 AM   #10
Mooly is offline Mooly  United Kingdom
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Quote:
Originally Posted by eliaselias_0 View Post
What about the NE5532?
Why... do you like it ?
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