The Ratstortion (Modified Kokko Distortion clone)

[pettert]

have you considered trying some KR140UD1408?
indicated as a soviet reverse engineered LM308, and after seeing drunk beaver's investigation with scope evidence, it looks pretty convincing that they behave identically. (have breadboarded a few of these against motorola & ns lm308hz and they sound the same to me)

they're quite cheap too.

Absolutely, since yesterday after I read that article you posted!

I have been playing with the TS271IDT programmable opamp a little. It'll do the thing. No compensation (iSET resistor, not a cap)is something like 0.02V/uS. At that point GBW is something like 500Hz.
Just got a bunch of ICL7614s in yesterday. it's CMOS based but can slew as low as 0.016
Recently OOP but they're around. The 7614 is the only chip in the series that is externally compensated

Oh,thanks, I didn't know about these!

 

[moonlighter]

Just a reminder, the LM358 and LT1490 are dual opamp devices and the LM308 is a single opamp device.
Another option for a low slew rate single opamp is the LT1008 - Slew Rate: 0.2V/µs (and a bit pricey).

I've been using the AD/LT chips for a bit, and I can say the LT1008 is nearly identical to a 308 in performance, and offers the compensation cap to tweak as well. It's much closer "in spirit" to the 308 than the OP07 is. The cost per unit is unfortunate, but considering how abundant fake 308s are, $10 for a genuine chip that is currently fabbed isn't the worst the market has to offer (if only I had a decommissioned submarine laying around).

One I haven't seen mentioned and I'd like to recommend is the LT1013. It's a dual precision amp (same family as 308/OP07) with a 0.3V/us slew rate.
It has a Class AB output stage unlike the LM358, so crossover distortion isn't an issue. The 1013 can also swing its output to ground, so the distortion is a bit different than an OP07, but the slewing effect is there. Just like most other AD products though, wallets will prefer TI, ON or STMicro.

 

[jwin615]

I like the 1008 as well. The low-end stays a little tighter than some others. I did a semi shootout last here with some unusual suspects

View attachment 98334
Rat opamp shootout
Findings playing a loop through an EL ACHE build max gain, filter wide open
1)Harris HA2-5130-2 best note articulation, good low end, nearing unobtanium, not a CA5130 varriant
2)Linear LT1008 close second, a little less saturated but full tight low end
3)LM308 yep
4)Raytheon RV4077FDE a little less saturation, less fizz/sizzle than a 308 but bottom extension is lacking but what is there is tight
5)OP07 ... There's a weird ice pick 1khz harmonic, boxy low end, less harmonics but more crossover distortion?
6)OP02 meh fizzy, less balls, flubby bottom

1 2 and 4 are all improved OP07 types, per the datasheets