Source for 708N chip to upgrade Rat 2?

[oc disorder]

Multi- RAT Revision G with details on changes
from DIY Stompboxes Created By G.Tranter 2011



"So does anyone recognize the logo in that picture? "


On September 23, 2011, National Semiconductor formally became part of Texas Instruments as the "Silicon Valley" division.

The LM 308 was replaced in the RAT with the Analog devices OP 07 IC in 2002~2003.

(perhaps this is where the "7" is infiltrating G-One !)

In 2010 a reissue was made using the LM 308 again = ProCo Limited Edition ’85 Whiteface RAT Pedal

[g1]

And when I searched Google for "lm708n rat" the only hit I just got was to this thread! What the heck is going on???

That's what I keep trying to tell you .
Try instead googling for lm308n rat. (if you don't see the difference copy and paste).

[Steve A.]

That's what I keep trying to tell you .
Try instead googling for lm308n rat. (if you don't see the difference copy and paste).

Yikes- I got my numbers mixed up again! I wish I could say that was an unusual occurrence for me but it happens to me every day. Over and over again. - And not just numbers but nouns and names as well. I used to say that my mind was like a steel trap but it has become more like a rusty old birdcage that cars keep driving over on the freeway.

Steve

[Jazz P Bass]

[Chuck H]

disturbing

[Steve A.]

OK here are the results

I ordered one National Semiconductor NOS LM308N on Amazon, three 1984 Motorolas from a surplus electronics site plus five of the new ones from China which were less than $5 with free shipping. I finally got around to testing them yesterday and here are my observations...

The new Chinese chips with the National Semiconductor logo are total crap. This could create problems since they are labeled with the NS logo so unscrupulous people might try to sell them as NOS chips at NOS prices. One difference between the new chips and the old: the numbers are embossed deeper and sharper than the originals- if you hold them at most angles you can see the printing. (With the NOS chips you have to hold them just right to see the numbers.)
The markings on the new Chinese chips are:
[NS] M65AP
. . . LM
. . . 308N

The NOS National Semiconductor was "da bomb!" Very smooth and rich overdrive which responded well to playing dynamics and guitar volume settings. I have a hunch that these were the chips that Proco used when they were designing the Rat.
The markings on the NOS chip were:
[NS] JR11ARE
. . . LM
. . . 308N

The 1984 Motorola chips were very good- almost as good as the NOS NS which I thought was just a little bit richer and with more dimensions.
The markings are:
LM308
[M] N
K8426E

The original chip in my Rat 2 was a National Semiconductor 0P07C which did not have the very rich sound of the NOS LM308N's. But compared to the new LM308N's from China they weren't really *that* bad.
The markings are:
[NS] 1AA6079 (?)
. . . OP07CP

BTW [NS] and [M] represent the logos of the two companies. The Motorola logo has the stylized M inside a circle. The NS logo can be seen in the picture I posted previously.

Enough Rat talk! I also tried all 4 chips in the 2002 Fulltone Distortion Pro pedal that I acquired recently on eBay at a price I couldn't refuse. It is considered to be a boutique version of the Rat, with 6 controls on top and 2 trim pots inside. I wasn't that crazy about it and with most reviews saying to get a Rat instead I decided to go with the vermin. With the LM308N Rats going for $120+ I got a used Rat 2 for under $50 figuring that I would replace the chip and be dollars ahead.

The original chip in the Distortion Plus was painted over so I have no idea what it was. I suspect that Mike Fuller used a socket for the chip and the two trimpots so that he could use different chips and tweak the trimpots for that chip. As with the Rat the NOS NS chip sounded the best with the 1984 Motorola a close second. The NS OP07C didn't sound bad- I liked it better than the mystery chip. The new LM308N's from China sounded terrible. Since I wanted to put the NOS NS chip in the RAT I put one the 1984 Motorola ones in the Distortion Plus which IMO is a big improvement.

My recommendation when looking for NOS chips is to avoid the National Semiconductor ones unless you are 100% sure that it is not a new one from China. The Motorola ones with the M in the circle would be the safest bet.

Steve Ahola

P.S. I will be posting sound samples of the different chips once the ring finger on my fretting hand heals completely. Warning: if you are wondering if the coiled spring on the holder for an 80 watt soldering iron is hot do NOT test the temperature with your finger. (The iron wasn't actually touching the spring so I figured that it wasn't THAT hot.)

To insure that the sound samples are accurate I will be using my Boss RC-3 Loop Station to output the exact same signal to the RAT with each of the 4 chips.

[oc disorder]

Steve that's interesting , I'ts good to have your perception on these chips.
I might point out that before Nat Semi were National Semiconductor
they were National Semiconductor Corporation with the squiggle logo.
It appears these may have been the original chips .. not the ones with the rounded logo.
I suspect that's what you are referring to as the NOS National Semiconductor chip.
I found this too

http://www.songofwind.com/?p=424#more-424]Landgraff MO-D?????????? « Song of Wind

(no atonal fart jokes please!)
and it appears he did some sound samples which don't seem to exist now.

In the attached photo one is from a early pedal which looks different again....!

[Chuck H]

Hurray Steve!!!

Very nice! Answered a lot of questions for all of us.

I know that most (if not all) the real white face RAT's I've seen inside have the Motorola chip. This IS the tone of that coveted pedal. Not a real smooth pedal either. More gritty and not complex. But it does punch out harmonics while maintaining note definition. If I wanted a smooth, complex distortion I wouldn't be thinking about a white face RAT. But that tone with a little more smoothness and complexity could be a good thing! Would you say that's the difference you heard between the Motorola and NOS NS chips?

P.S. Check this out. I think these are fakes! http://www.ebay.com/itm/Vintage-Moto...-/160607531486

[g1]

Steve: I think most of those on ebay from China are fake/counterfeit. They're getting better with the logo but it's still not right. Another giveaway is many of them are being advertised "for guitar effect pedal", so someone knows of this specific application and that they are obsolete. Why would there be such a stockpile of NOS lm308's in China? Presumably they are NOS as National only built chips in China from 2004 to 2009 and I think lm308 was obsolete before then. So likely they are re-labelling a pin-out equivalent op amp.

As far as the whole question of why there would be a major sound difference, Mark Hammer was mentioning elsewhere how a design may take advantage of inherent weaknesses in certain chips (or strengths I suppose). So substituting a newer "better" chip may actually have a detrimental effect on the sound. To me this makes sense for different types of chips (ex. lm308 vs. op07). However, I don't really understand how it explains the difference in sound between 2 chips of the same type (lm308) from 2 different manufacturers (national vs. motorola). The specs for the same number chip should be pretty much identical. I suppose there is some tolerance variation which may be responsible. As far as those chips you tried from china, they are probably some pin compatible dual op amp with quite different specs than a true lm308, either that or rejects of something compatible like an op07.

Edit: Chuck I think you're right and those are fakes, 1) again, what are nos lm308's doing in China?
2) they are advertising them specifically for rat pedals, seems very suspicious to me.

[Chuck H]

Oh, they're fakes. But they're the first Motorola fakes I've seen so far. Up to now it's all been National Semiconductor fakes. With tubes it's pretty easy to recognize the real deal. Not so much with chips. I wonder what brand ProCo used in the reissue? If Steve reports affirmative to the vintage Motorola vs NS difference I may be accosting him to part with one of the Motorola's. A 1984 RAT is the pedal I owned as a kid and I've never forgiven myself for losing it at a gig. Probably stolen actually.

[Steve A.]

I know that most (if not all) the real white face RAT's I've seen inside have the Motorola chip. This IS the tone of that coveted pedal. Not a real smooth pedal either. More gritty and not complex. But it does punch out harmonics while maintaining note definition. If I wanted a smooth, complex distortion I wouldn't be thinking about a white face RAT. But that tone with a little more smoothness and complexity could be a good thing! Would you say that's the difference you heard between the Motorola and NOS NS chips?

By smooth I meant that it responded very smoothly to picking dynamics and guitar volume control settings. Not that the sound was smooth like a Robben Ford Dumble tone or an SLO.

I thought that the NS and Motorola chips were very similar but to my ears the NS had a fuller sound and response. And I thought that both of them did have a smoother sound than the OP07C, which sounded a bit raspy and one dimensional to me (but not as bad as the new LM308N's from China!)

My Loop Station was not cooperating today but here are two sound samples recorded with the NS chip which might illustrate the smooth grittiness I was referring to:

https://soundcloud.com/sssteeve/rat-sample-1

https://soundcloud.com/sssteeve/rat-sample-2

Steve Ahola

P.S. I don't understand how the Filter control works. I usually keep it set all of the way up (maximum filter.) I would like more filtering so that I could get that sound with the control set to maybe 5 or 7 out of 10. I find 1 to 7 to be pretty useless for me...

[dai h.]

re: the filter, it's a tone control that rolls off highs that works backwards (i.e. clockwise reduces highs). My guess is that using an audio taper there (which gives the right taper but works backwards) was easier and cheaper than sourcing a reverse audio taper pot. For me, filter setting with more highs (and not so much gain) was good for rhythm, while more gain and less highs (more rolloff with the filter knob) was good for solos.

Saw an interesting Rat variant recently which I've never seen before (not that they are a heavy interest but they are classics to me) which had two individual Rats in a big (wide) enclosure and a switch on each to enable switching between different Rat variants (the regular, the Turbo, and something else--"Dirty"?).

[dai h.]

hey Steve, I think your soundcloud links are set to "private" (or something)

[Steve A.]

re: the filter, it's a tone control that rolls off highs that works backwards (i.e. clockwise reduces highs). My guess is that using an audio taper there (which gives the right taper but works backwards) was easier and cheaper than sourcing a reverse audio taper pot. For me, filter setting with more highs (and not so much gain) was good for rhythm, while more gain and less highs (more rolloff with the filter knob) was good for solos.

dai:
Check out the schematics that g-one posted- the filter control is a 100k variable resistor wired in series with the signal path which goes to a 1.5k fixed resistor and a .0033uF cap to ground so I guess that the pot changes the frequency of the RC network to ground. The signal then goes to a .022uF series cap followed by a 1M or 100k resistor to ground at the gate of 2N5438. Very interesting...

g-one: With Tube Screamers there is reportedly a very big difference between the 4558 chips used, even the ones made by the same company. It was a subtle difference I noticed between the Motorola and the NS chips. Perhaps the specs refer to the minimum acceptable values for the parameters. All of that information is above my pay grade...

As you said the counterfeiters in China are obviously aiming at the RAT aficionados (I guess that we could call them the RATketeers if we could get the appropriate clearance from The Walt Disney Company.)

Chuck: The RAT was designed around 1976 or 1977 because the first pedals were sold in 1978. At that time they may have been using the NS or NSC chip (didn't they invent it?) but switched over to the Motorola when they went big-time in the early 80's. Or not.

You know more about the Motorola LM308N chips than me (I knew absolutely nothing until I got the 3 chips from the surplus dealer [thanks for the heads up!]) but the markings on the 1984 chips has "LM308" by itself on the top line and the Motorola logo and the letter "N" on the 2nd line and the date code on the 3rd line. And the printing on the Chinese chips are way too easy to read...

Steve

P.S. I think that the private setting on SoundCloud *used* to mean that you needed the exact link to access a clip (I like!) while "public" meant that people could run across them while browsing the site (I don't like!) Thanks for the heads up- I set them to be public links.

[Chuck H]

In my searching I did find images of some early white face units with the Nat Semi chip. So I would guess that you're right. The NS chip was THE one used for the design and they started using the Motorola chip (presumably for less $$$?) when the bigger orders came. All but the very earliest small box RAT's used the Motorola chip. I can't even be certain now what chip was in mine since it was a "white face" and some of those used the NS chip. So this is new info to me also.