LM108 vs LM308.. do they perform the same in a rat clone?

[Bornhorst]

I just picked up a metal can LM108 from a local electronics shop. They informed me that the LM108 was just the military spec LM308.

I was wondering if I could use the LM108 and expect to get the classic rat tone,
or if the higher tolerance of the LM308's contributed to the sound of the rat?

Thanks!!

[MikeH]

I don't know but you could probably get an idea by comparing the datasheets.

And then there's always the "put-it-in-a-socket-and-see-if-it-sucks" test. 

[rogeryu_ph]

LM108/LM208/LM308 Operational Amplifiers
General Description
The LM108 series are precision operational amplifiers having
specifications a factor of ten better than FET amplifiers
over a -55C to 125C temperature range.
The devices operate with supply voltages from g2V to
g20V and have sufficient supply rejection to use unregulated
supplies. Although the circuit is interchangeable with and
uses the same compensation as the LM101A, an alternate
compensation scheme can be used to make it particularly
insensitive to power supply noise and to make supply bypass
capacitors unnecessary.
The low current error of the LM108 series makes possible
many designs that are not practical with conventional amplifiers.
In fact, it operates from 10 MX source resistances,
introducing less error than devices like the 709 with 10 kX
sources. Integrators with drifts less than 500 mV/sec and
analog time delays in excess of one hour can be made using
capacitors no larger than 1 mF.
The LM108 is guaranteed from -55C to 125C, the
LM208 from -25C to 85C, and the LM308 from 0C to
70C.
Features
Y Maximum input bias current of 3.0 nA over temperature
Y Offset current less than 400 pA over temperature
Y Supply current of only 300 mA, even in saturation
Y Guaranteed drift characteristics

[Bornhorst]

So.. in other words, it'll probably work?

Thanks, I greatly appreciate the info guys!!

[StephenGiles]

I tell you something else, I built a Bi Filter Follower type unit and for good measure put a Rat on the same veroboard. I used the first IC pulled out of a tin which was a 4558, and the sound was the same - and I had half an opamp spare!

[appliancide]

My first pedal (that I just finished about a week ago) is a Rat and I used a LM108. Works great! I compared it to my friend's Rat (glow in the dark graphics) and mine sounds more vintage while his sounds more meaty. That could be any number of things, but it doesn't matter to me because they both sound awesome.

[Bornhorst]

Interesting.. I own the vintage rat reissue, which is alright, I'm not terribly pleased with the sound, hence me building the original.. in fact, I'm not even sure what the difference is between the original and the vintage reissue.  I guess my ear will decide upon completion of the clone.

Since my LM108 is a metal can, I'll probably make a little adapter on perfboard, to adapt it to dip size.  That way I'll be able to try different op amps as I come across them.

Thanks for the comments guys!

[grolschie]

You can try a CA3130EZ in a Rat. I really like this IC in the Rat.

[doitle]

What Rat Clone schematic are you working from? I don't think I've ever seen a schematic of one. I'm scouting around to maybe figure out what my next attempt will be once I get my Valvecaster all boxed up.