LM308AD 14 pin

[Nicklsm1]

Hey all!  Newcomer to both the forum and to pedal building. 

Got a small number of these chips laying around at work, and was wondering if they can be used for a distortion pedal build.  Looked all over for pinouts and specs, but having a hard time.  Would appreciate suggestions for some circuits to build these into, if they can even be used.

Thanks!  Nick

[GGBB]

Welcome to the forum. LM308s are obsolete but not uncommon in DIP-8 format. The DIP-14 variant is supposedly rare and could be valuable if there's demand. To your question, the RAT is probably the most famous distortion pedal that uses the LM308. Another pedal is the PAiA Gator (auto-swell/noise gate). You could probably use it in most pedals - distortion or otherwise - that use a single op-amp - for example MXR Distortion+ or DOD 250. It's very unlikely that you'll find existing layouts for DIP-14 though, so you'd need to manage that yourself.

Pinout here: https://pdf1.alldatasheet.com/datasheet-pdf/view/572861/NSC/LM308.html

[PRR]

Welcome!

Did you search the web for "LM308 pedal"? I thought we had long '308 discussions "here", but it seems there is a big thread at TheGearPage.

As an audio chip, the '308 is so bad it is good. Do hi-fi violin or percussion through it, it schmears all the transients and rosin-tone to mush. Use it to dirt-up a guitar, it avoids the worst ear-bleed screech.

We see the 8pin DIP and 8-pin round packs more, but the 14-DIP is the same guts with a few useless legs. The gold is real mojo (in your mind). G is right: a sale could be lucrative.

It is also a good accurate DC amplifier. Good for 1975. It would be a waste today because even better DC chip are really cheap. And as audio people, we don't do much DC, and not accurate.

[PRR]

I see, there's no 14-pin pinout for '308 at the usual places.

Opamp marketers are VERY eager to upgrade/invade sockets of other chips. So 99% of the time they use the SAME package and pinouts.

Iain here scored some 14-DIP '741. And in fact the '308 was sold as a "better '741", with drop-in pin-out. So your 14DIP will echo Iain's 14 leg '741.

DIP14 ua741pc? (Semi-off-topic)
Note correction at replies 9 and 10.

[GGBB]

308/108 14-pin pinout here:

Pinout here: https://pdf1.alldatasheet.com/datasheet-pdf/view/572861/NSC/LM308.html

[Govmnt_Lacky]

EDIT: Deleted because I responded and obviously do not have enough coffee in my system yet 

[duck_arse]

geeze, I wouldn't even bother thinking about it - get them on evilbay as fast as you can write the copy - GOLD - hermetic -  old old old - extra pins!

with the money you rake in, you can buy a heap of good real lm308's with less pins. then, get back to those drawers and scrounge, there must be some more goldmines in there. and another welcome.

[iainpunk]

hey, welcome to the forum

i do indeed have five or six uA741CP chips in my collection. im really glad they got spared the leg snipping the previous owner gave to the round metal can 741's (he cut of the NC and offset null pins off of the chips).

its basically just a normal chip in a bigger box. if you want to use it in a pedal, you can use a really tall socket and leave the legs just hanging over, or if you use bigger or upright components, you have to design the layout around the chip

cheers

[Kevin Mitchell]

Wow nice lot!!

Funny enough I had just ordered a few LM308 chips from my "secret" vendor just yesterday. Been looking into how to authenticate them.

[iainpunk]

just remembered that an ca3130 or 3160 with a large compensation cap also sounds really good in a distortion pedal. i have experimented with using the strobe/comp pin to start a feedback loop back to the noninverting input, to let the output stage work open loop, or atleast with way less feedback. the output stage itself is a cmos inverter, so you can get that smooth cmos feel with opamp usability.

cheers, Iain

[GGBB]

its basically just a normal chip in a bigger box. if you want to use it in a pedal, you can use a really tall socket and leave the legs just hanging over

Actually that wouldn't work - the pinout is different.

[amptramp]

If you want to speed up the glacial response of an LM308, you can use the application note in the original National Semiconductor Linear Applications Handbook.  It is Linear Bulletin LB-14 near the end of this manual:

http://www.bitsavers.org/components/national/_dataBooks/1972_National_Linear_Applications_Handbook.pdf

There are no pages, only application note /  linear bulletin pages in the pdf so you have to go almost to the end of the book to see it.  Feedforward uses a capacitor to bypass the input stage and boost the slew rate from 0.3 V/µsec to 1.3 V/µsec and the small-signal bandwidth gores up to a dizzying 3 MHz.  The gain at 1000 Hz goes from 500 to 10,000 so you might not even be able to tell the difference between an LM308 and more modern amplifiers.  There are some good things about it - the supply current is only 300 µA and it has low input offset voltage and low input bias current (for a bipolar amp) And we used to use a lot of them for DC circuitry.

But I agree that these can be sold to fund the acquisition of better amplifiers unless you want to claim them as mojo parts for high-dollar builds.

[Govmnt_Lacky]

This reminds me. I have an MC1747G metal can (two matched 741s in a can with shared V+ and V-) and have no idea what to do with it. 

[Kevin Mitchell]

This reminds me. I have an MC1747G metal can (two matched 741s in a can with shared V+ and V-) and have no idea what to do with it. 

Differential circuits of course!
There will come a time 

[iainpunk]

This reminds me. I have an MC1747G metal can (two matched 741s in a can with shared V+ and V-) and have no idea what to do with it. 

stereo rat?
ive heard studios using a rat to spice up everything from drums to vocals, so a stereo rat would be a novel option to replace 2 separate rats for stereo tracks.

or a super fancy tube screamer.

cheers

[Nicklsm1]

Thanks everyone!  Great honesty and knowledge here.  Being a newbie to electronics (still learning how to read schematics), I will just look for a simple rat circuit to copy.  I will probably uses an 16 pin socket, and drop on of these in.  There also may be a sale on "special" chips if I am uninspired with my prototype. 

[iainpunk]

its basically just a normal chip in a bigger box. if you want to use it in a pedal, you can use a really tall socket and leave the legs just hanging over

Actually that wouldn't work - the pinout is different.

ow, sorry for the wrong information
i expected it to be the same as with the 741.

sorry and cheers