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Old 22nd February 2013, 03:04 AM   #71
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Yes, I like them better.
They have the lowest noise voltage of the series.
They claim that the TL082's were for audio but the differences were just that they where acceptable for audio and the TL072 had even less noise.
The differences are very small and is more about the lower frequency's.
I think the TL072's sound better with less change of the character to the sound.

jer
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Old 22nd February 2013, 03:10 AM   #72
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When I do get in to it, I am going to try the NE5532's as well they have an even lower noise level.

jer

http://www.mouser.com/ds/2/405/slos075i-121972.pdf

Last edited by geraldfryjr; 22nd February 2013 at 03:15 AM. Reason: NE5532 not NE5534
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Old 22nd February 2013, 11:51 PM   #73
Bugsi is offline Bugsi  United States
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I think someone already mentioned earlier that NE5532's will draw considerably more current and recommended against it.

Incidentally, congrats for nailing down a shorted diode!
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Old 23rd February 2013, 01:27 AM   #74
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Yes, Very good point.
The data sheet indicates nearly 4 times as much at 8ma vs 2.5ma per chip.
I would consider doing the regulator mod or use a much higher wattage zener diode when using the NE5532's.

I got to thinking about that when I realized that it is using only a 1 watt zener per rail to power 8 dual opamps!!

jer
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Old 23rd February 2013, 01:51 AM   #75
Enzo is offline Enzo  United States
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I mentioned the 5532 increased current draw. It all depends on what you want to do. A couple of them added into a circuit won;t hurt anything, the power supplies are not that marginal as to be affected. But if you had a mixer with 50 of them in there, it would be a different story. In this amp, U6 and U1 are the input stages, so changing them to lower noise should have the most effect. Later stages have higher signal levels and so should be a lot higher above the noise floor.


Think again about the zener. The zener regulates the voltage, NONE of the load current flows through the zener. The zener is parallel to the load, not in series with it. You want the current through the zener - and thus its wattage - to be enough that variations in the load won;t make the dropping resistor make the load voltage drop below the zener voltage. Well, these loads don't vary much anyway.


I don't even keep TL082 in my drawer, The TL072 is a better choice in about any situation, so why have both? Perhaps someone had access to 082s at some point, otherwise they are an odd choice. Maybe it was what the local Radio Shack had in stock. The 4558 may not be the lowest noise of op amps, but it works fine in this circuit. More modern types like 4560 and 4580 probably work even better. But it is really not critical at all, I'd stick an LF353 in there if I had to. I keep 2068s in my drawer, and wouldn't hesitate to use them here. And i am sure the hifi guys have some OPA numbers they like.
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Old 23rd February 2013, 04:44 AM   #76
Bugsi is offline Bugsi  United States
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That's correct that Radio Shack carried the TL082. (I have no idea if they still carry it.)
I believe I've read before that the TL082 chips come off the TL072 manufacturing line, but they may label some chips as TL082 because one chip from a TL072 batch didn't test up to the noise standard of the TL072 spec. I don't believe anyone actually intentionally manufactures a TL082, my understanding is that they are 072 chips that can't be guaranteed for 072 performance, but that people who have tested the noise floor of random 082 chips against 072 chips often find no actual difference, and it is quite common for the 082 to perform exactly the same as the 072 spec.

That being said, if you're buying chips for amp use, you might as well just buy the TL072, the cost can only be a few cents more.
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Old 25th February 2013, 11:26 PM   #77
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The difference I heard was in a very high gain fuzz circuit I made swapping out a TL074 with a TL084, But I could never tell the difference in a regular clean line level signal.

I even used them to invert video signals just to see if it would work and it did.
Great little chip!!!

Yes RS still has them for about $2.49.

TL082/TL082CP Wide Dual JFET Input Op Amp (8-Pin DIP) - RadioShack.com

jer
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Old 26th February 2013, 12:12 AM   #78
Enzo is offline Enzo  United States
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TL072s look to be about 60 cents at Mouser. About 25 cents at Jameco. 47 cents at Digikey.

Mouser also sells the NJM2068 for 40 cents. And NE5532 for 90 cents.

Jameco sells 5532 for 49 cents,
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Old 28th February 2013, 05:49 PM   #79
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Well I ordered all the parts, and new electrolytic caps on Sunday. They will be here this coming Monday.

Pictures and details to come when I start on it.
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