RAT 2 questions. LM308AN, missing battery screw.

[Psychophonic]

I have acquired a used ProCo RAT 2. Boss-type power jack, which I assume makes this one of the latest versions?

The screw for the battery cover is missing. Are these available for purchase anywhere?

The OP07CP is not what I was expecting to find, but I'm no RAT expert. I have a couple of LM308AN chips on hand. I realize this isn't a Motorola LM308N, but is it worth swapping out?

The pedal sounds great as is, but can it improve with the LM308AN? Leave it alone unless I can find the Motorola chip? I'm also very curious about the mods I'm seeing on YouTube, with the 3 position toggle switch.

[Kevin Mitchell]

I have acquired a used ProCo RAT 2. Boss-type power jack, which I assume makes this one of the latest versions?

I believe so.

The screw for the battery cover is missing. Are these available for purchase anywhere?

The original takes a hex key but I couldn't tell you the size or threading. Be that guy and bring it into a hardware store and see what fits.

The OP07CP is not what I was expecting to find, but I'm no RAT expert. I have a couple of LM308AN chips on hand. I realize this isn't a Motorola LM308N, but is it worth swapping out?

The pedal sounds great as is, but can it improve with the LM308AN? Leave it alone unless I can find the Motorola chip? I'm also very curious about the mods I'm seeing on YouTube, with the 3 position toggle switch.

You can find topics across the internet about the Rat's opamp and substitutes. I'd encourage you to socket the IC and see what you like!

But to be honest - I believe most of the character from an effect is the circuit around the opamp and not the opamp itself. In most cases anyhow.

I should probably mention that I'm also half deaf.  So I'll leave the subtleties to you.

-KM

[EBK]

The screw for the battery cover is missing. Are these available for purchase anywhere?

Yes.

http://smallbear-electronics.mybigcommerce.com/thumbscrews-for-rat-battery-door/

[Psychophonic]

Nice! Thanks for the link. Sometimes it's the little things haha.

[willienillie]

I would put the 308 in, even if I didn't expect the sound to change.

[Psychophonic]

I would put the 308 in, even if I didn't expect the sound to change.

What would be the point?

[GGBB]

I have a couple of LM308AN chips on hand. I realize this isn't a Motorola LM308N, but is it worth swapping out?

Yes if you want to hear the difference between OP07 and LM308. I'll avoid stating that all 308s sound identical regardless of manufacturer or package type to avoid war, but they all sound far closer to each other than any one of them does to an OP07 (and not really a huge difference there either). The OP07 is the stock chip since mid-2000s.

Make sure your C8 is the correct value - looks like it is in the pic (double-check C5 too):


Pro Co RAT Schematic - "Multi-RAT" Comparison

[amz-fx]

The original LM308 was made by National Semiconductor. There were subsequently versions also made by Motorola, Raytheon and Fairchild. Later on came versions from PMI and Linear. The schematics of all of those versions are in their datasheets and they do not match each other. In fact, the original LM308 had 30 transistors but the Fairchild version had 48. To complicate matters even further, the later National Semi LM308 chips were made with dies that match the Motorola schematic, and have additional parts that allow the die to be used as an LM11. Not at all like the early NS parts.

regards, Jack

[GGBB]

And for the record, the early RATs used National chips. Motorola chips started appearing in the small-box black-face RAT shortly before the RAT2 came out. I can't speak to the consistency of this rule.

[willienillie]

I've built 4 rats so far, two with old (1984?) Motorola metal can 308s, two with recent (2010?) NS metal can 308s.  They sound different for sure.  The newer NS sounds more like I remember an actual ProCo sounding, but that's a 30+ year old memory.  Best I can describe it, the NS is more "snarly" while the Motorola is smoother.  I also have an older metal can Fairchild from Small Bear, but haven't tried it yet.

[GGBB]

I've only done one 308 comparison. I have metal can Motorola and National and plastic dip Fairchild and National. One of the metal can chips wasn't part of the test - I think it was the Motorola but I'm not sure. Same pedal, guitar, amp, cables, strings, ... - I couldn't hear any difference. But we generally hear what we expect to hear unless the tests are controlled blind tests.

[willienillie]

I didn't do a blind comparison, but at one point had both (Motorola and NS) pedals in line, both true bypass, and was able to switch between them immediately.  I *think* the NS metal can sounds just like the dip8 version that was in my friend's ProCo back in the 80s (the only actual ProCo Rat I've ever played), whatever brand 308 that would have been.  But the Motorola can is different, just doesn't have that same "snarl" at any tone (filter) setting.  And I've done two of each now, same results.  I like both sounds, I guess I prefer the Motorola, but the NS is much more of a "correct" Rat sound IMO.