Hey,
I've been looking at a few projects and I've seen that they require a JRC 4558. As I've said a million times before, it's impossible to get odd parts in New Zealand and I wondered if there was a substitute. I've read that substituting other IC's will alter the sound, but to be honest, I don't really care, I just wanna make pedals that do their job 'cause I can't afford the real thing.
Tim
Subs are among others:
TL072,TL082,NM5532,TL062,LF353....and the list goes on.
They all share one thing,pinout.
Aharon
You can use any dual opamp I think, just watch the pinout. You can use two single opamps like the 741, or half of a quad opamp.
Sweet as, I knew all this, honest...I was just checking :oops:...Are some replacements better than others? I mean, who decides whether a 4558 is better than a TL072?
Tim
QuoteAre some replacements better than others? I mean, who decides whether a 4558 is better than a TL072?
YOU do, dude.
In this case your personal ears are the only ones that matter.
Every eight pin DIP dual opamp I've ever seen had the same pinout, so use a socket, and substitute parts until you like the sound.
First off, JRC = NJM. Same company. JRC = Japanese Radio Company. The NJ is *New* Japanese something or other.
In truth, many things that list a 4558 (and often they do not name the manufacturer but just say 4558, since there are various alternate manufacturers of that basic chip) do not *require* a 4558. Rather, the 4558 meets the minimum requirements for whatever needs to fill that slot, and has the appropriate pinout if there is a board layout. A 4558 could conceivably be replaced with a TL072 or 62, an LM358, an OP275, a pair of NE5534's or CA3140's, or half of an LM4136 quad op-amp if you were building on perfboard.
Elektor magazine, for years, used to have a nomenclature in their published schematics of TUP, TUN, DUG, DUS for "transistor-universal-PNP", "transistor-universal-NPN", "diode-universal-germanium", and "diode-universal-silicon". In that spirit, the 4558 ought to be listed as DUO for "dual-universal-opamp".
What makes an op-amp "better" can depend on many circumstantial factors. For instance, is the entire circuit hanging just at the border of being battery-operable vs needing a power supply? Well, then a lower power op-amp would be recommended. Is there something about the role of that op-amp that requires it to be able to "swing from rail to rail" (i.e., outputs very close to both the negative and positive supply voltages)? Then a different op-amp might be selected. Does the circuit stand to generate a lot of noise unless the op-amp has a very high input impedance? Then another would be preferred. Does the circuit need you to be able to adjust (compensate) the gain-bandwidth product of a given op-amp so that it deliberately sluggish with respect to high end (e.g., the Rat)? Then another one is prefered.
And so on and so on. For a whole host of reasons, many of which have to do with how legends make things seem better, the JRC4558 has acquired a reputation, primarily via the TS-808 Tube Screamer, and primarily through Stevie Ray Vaughan's use of it. It was not selected for duty in the TS-808, however, primarily because of tone, but because it was cheap, commonly available and met minimum criteria. People came to *like* the tone produced by that musician with that pedal with his setup and style and guitar, but that is a far cry from the chip itself having any sort of special sonic qualities.
On my site, I have a fairly thorough (though admittedly not entire up to date or comprehensive) listing of op-amps and their specs-of-interest, scanned from the Hill and Horowitz book "The Art of Electronics". Look for "Ops, I did it again" at http://hammer.ampage.org and you can see a bit about the range of op-amps out their and what compares with what else.
Check out my post on op amp evaluation. It has a list of duals that work. I tried them all.
Some opamps use different circuitry, which may contribute to a certain sound - JFET, CMOS, Butler front end, etc.
There are some who claim that chips with a high bandwidth (~10mHz) sound really good. I suppose that is because in theory, they should produce a lot more of the higher harmonics, which are usually virtually absent in solid state devices. Most people would interpret that as "more warm sounding" or "more like a tube".