Rat op-amp

[mremic01]

I've tried a few (LM308 both RCA and Chinese, metal can and op07cp) and hear a difference too...and I'm not usually that fussy.

Are you hearing a difference between the individual ICs or between the versions of the Rat? I briefly had a Chinese-made Rat and traced the circuit. Built one identical. That build, and all my others, were ballsier. The op-amp didn't seem to have anything to do with it. Maybe the Rat I had was just on the thin side of things from component tolerance. But I couldn't match the tone in any of my builds, which was frustrating. The thinner Rat had its own thing going that I liked.

[Guitarmageddon]

I've never actually owned a real rat!
...but built many.
The first being the BYOC mouse which is what I've used to compare the opamps. I'd never suggest using two separate pedals for this type of comparison, far too many other variables.
Just like Rej, I'd suggest to use a socketed part and a looper. (what I've done)
If you really want a proper scientific comparison, record and play them back in a double-blind test.

[GrindCustoms]

I've tried a few (LM308 both RCA and Chinese, metal can and op07cp) and hear a difference too...and I'm not usually that fussy.
The metal cans kill the others IMHO.  I use them in my personal rat and "shmancy' expandra builds.

Still got a few of these if anyone here is interested... (only$5 ea, shipped anywhere!)

I also notice a difference between the LM741 in DIP8 package vs Metal, sounds rounder to me.

Grabbed couple of these from you before, might need to get a little lot

[selfdestroyer]

I've tried a few (LM308 both RCA and Chinese, metal can and op07cp) and hear a difference too...and I'm not usually that fussy.
The metal cans kill the others IMHO.  I use them in my personal rat and "shmancy' expandra builds.

Still got a few of these if anyone here is interested... (only$5 ea, shipped anywhere!)

PMed.

Cody

[wgc]

I think different op amps sound different ... in a Rat. It's not that any one is better than another, but there are differences. LM301, for example, sounds to me to have a bit less gain at some mid and higher frequencies. It's a bit more mellow than a 308. I suspect that some of that has to do with the value of the compensation cap, but I haven't done extensive testing.

I just recall the first time I really did some testing between the op amps, I was very surprised that I could hear a difference that was definite.

What would be awesome would be a Rat PCB with two op amps and a trimmer cap. That would make testing a lot easier.

I was also surprised, and pretty much agree with your comments all around.   Though I tried other op amps, 4558, etc, and prefer the 5534. The difference to me is the type of crunch, and how it fades. The gain and mids seem to be a more subtle thing.

Sort of goes without saying, but the clipping diodes make a difference here too