about op amps

[km-r]

what are the major tonal difference between op amps?
well, specifically, im refering to the stock boss IC's M5218's
im planning to replace them with RC4558 or a TL072.
disregard packaging style please.

thanks!

[petemoore]

M5218's
  I'm guessing this is a modern' standard dual opamp.
  Alot like other MSDOA's. Check data sheets...
  But you may notice slight to moderate to mojo differences when swapping OA"s.
  Most modern duals are fairly 'high performance', using LM741 as example of 'not so modern' single opamp.
   I put a standard dual once in a BOSS DS-1, [which had an inline originally, I had to hack/n'/squeeze to fester it in there]...wasn't worth the trouble since the DS-1 just wasnt' really my thing anyway...I heard a sample of a modded one sound good though.
  As far as 'difference',  a change of diode or voicing cap may make a more discernable change in tone than one good oa to another...YMMV.

[brett]

Hi
op-amps don't "sound" like anything.  It's a bit like asking what the speed of a car is.
In general, op-amps do a very climical job of amplifying a signal - they rarely add much or deplete much.
When can different op-amps might affect the tone of a circuit?
If they have low input impedance (e.g. NE5534) they can "load" the pickups.  The TL072 has a JFET input stage that makes for a minimal load in most circuits, which probably explains its popularity.
cheers

[JHS]

Most cheap opamps stray a lot in terms of slewrate, gain and frequency response.
If you buy for ex. 5 4558D from the same lot they can sound, due to the manufacturing tolerances, quite different in the same circuit.

The Lovepedal  Eternity is factory equipped with a 4558 and comes with an extra 4559 so you can swap them, would not make much sense if if the IC has no influence on the sound.

If buy a TL 071 form JRC, TI and STM and put them in a IC booster circuit (for ex. Rustdriver) and listen to the sound, the tonal results will be different too. A TS with TI 4558P sounds softer than the same TS with a RC4558P or a JRC4558D.
A Dist+ equipped with uA741C sounds different compared to a LM741. A NE5534 or TI 071C in a Dist+will produce a complete different sound.

JHS

[R.G.]

Most cheap opamps stray a lot in terms of slewrate, gain and frequency response.

Just to be clear for a beginner's question, both Brett and your answers are correct, but different parts of the elephant.

Modern opamps are essentially tone-free; that is, highly accurate reproducers of whatever you put into them (1) as long as you do not drive them to clipping and (2) as long as you do not demand full power supply swings at the highest audio frequencies.

This was not true of early opamps. The first internally compensated opamps like the 741 and the 748 are essentially silicon fossils. They were designed back when we as a race could barely get transistors to work. As such, they suffered a lot in terms of full power swings and funny behaviour on transients. The RC4558, the LM1458 and others were second generation devices and had better response to transients. This accounts for much of the JRC4558's mojo in the tube screamer.

In succeeding generations we got high slew rate and very high input impedance with the JFET input devices of which the TL06x/07x/08x and LF35x families are examples. These opamps are essentially nonloading to audio signals, able to slew full power supply at 20kHz, and very forgiving in recovering from transients. You really have to work at it to get a "tone" out of these.

There are even more modern devices which are even more transparent.

Yes, you can get different transient and slew response out of different opamps in a distortion pedal if you compare first and second generation opamps with themselves and with more modern devices. But that's an issue of the imperfections of the first devices, not a characteristic of opamps in general, especially modern opamps. And that's why swapping opamps in distortions may make a difference. Also why it may not.

[Ben N]

That was great!  FAQ material--Aron? Peter?

BTW, RG, I'm sure you meant "we as a species"--the common, but imprecise, usage of "race" is probably not worth the potential slight of some hypersensitive or misunderstanding individual down the road.  JM2C

Ben

[lovric]

variety in input impedance:
lower -> loads the guitar -> less highs

variety in possible voltage swing:
rail to rail -> more voltage swing -> later clipping -> good for oscilators

noise:
less noise -> better

transient handling:
pls study the 'technology of TS' at www.geofex.com 

[R.G.]

BTW, RG, I'm sure you meant "we as a species"--the common, but imprecise, usage of "race" is probably not worth the potential slight of some hypersensitive or misunderstanding individual down the road.

Yeah - I meant the "human race" as an extrasolar visitor might perceive it. Frankly, it doesn't occur to me to distinguish between "races" of humans. That'll probably get me in trouble some day. Politicians and their droids love to use "race" as a wedge.