Where are you guys getting your LM308s? Small Bear doesn't have them anymore... what is the world coming to? I don't trust eBay. Mammoth want 3$ a piece for them and I don't want to give them my money if I can help it.
It appears that Jameco has them, but they are $7 a piece.
https://octopart.com/search?&q=LM308N&start=10
Smallbear has the metal can version if you can fit that in your design.
I got some at a local Radio Shack for a reasonable price not to long ago.
They might have them online
I got a bunch of eBay metal can ones not too long ago. Extra mojo 8) if they work :o
If you can't find anything I could send a couple along (assuming I can find them). Let me know.
Looks like PPP still has them. Sheesh. $4 though.
http://www.pedalpartsplus.com/product-p/4023.htm
I have a bunch, 8 pin DINs. Lemme know if you can't find one reasonably priced.
I got my last couple (metal cans) from an old electronics store. They're NTE labeled, but all they did was scrub the production label off and print "NTE 938" on. $2.50 a pop.
So far:
Small Bear: Not stocked anymore; Can version is $5.50
Mammoth: $3
PedalPartsPlus: $4
Futurlec: $2.30 (Probably fake)
Mouser: Call for quote (No thanks Mouser, if you're not gonna list your price I'll just go elsewhere)
Jameco: $6.95
PM me.
I'm looking for a LM308 in the UK to do this project - http://tagboardeffects.blogspot.co.uk/2015/10/giant-hogweed.html - does anyone know a supplier preferably in the UK?
Quote from: Philtre on February 02, 2018, 09:06:58 AM
I'm looking for a LM308 in the UK to do this project - http://tagboardeffects.blogspot.co.uk/2015/10/giant-hogweed.html - does anyone know a supplier preferably in the UK?
There is a store here in Paris that has them. But it costs 4 Euros. I can pick you up one if you want. With shipping to the UK it would be about 6 or 7 Euros.
If not. http://www.diystompboxes.com/smfforum/index.php?topic=33493.0
Thanks for the offer :-) I might check out alternatives first. I wonder if a TL071 would work?
I think so. Check the pinouts. IIRC you should omit the 30pf compensation cap between pin 1 and 8.
without looking at the schematic, I couldn't say if the pedal is making good use of the lm308 or not(rat-like behavior), I would say the OP07 is a compensation cap adjustment away from working like the lm308. the lm301 is mushy by comparison. lm741 should work so long as you omit the comp cap same for ne5534
Give this a read. http://www.davidrolo.com/2014/09/28/giant-hogweed-fuzz-octave-up-octave-down/
He says the 308 does matter. Closest is a tl070.
Quote from: bsoncini on February 02, 2018, 12:37:50 PM
Give this a read. http://www.davidrolo.com/2014/09/28/giant-hogweed-fuzz-octave-up-octave-down/
He says the 308 does matter. Closest is a tl070.
Right, that's interesting. Thanks for finding that. 8)
Yeah, while technically speaking the circuit would FUNCTION with some other single op-amp, it would not SOUND the same.
See, the LM308.... sucks. Its old, slow, worn out, obsolete technology. And that is why we love it in the audio world. That slow sluggish get-off-my-lawn response gives it this fantastic growl in distortion circuits.
Newer tech, its too precise. It keeps up with your signal too well, and you get this scratchy, sreechy sorta tone in circuits that were designed around the old bludgeoning curmudgeon of a chip.
If you can't find an authentic LM308, try for an NTE938 (same part re-badged). The next best I've heard of is an "over-compensated" TL070/TL080. So put a ~150-200pF cap between pins 1 and 8 and it will drop the slewrate right down to... close-ish.
BUT the key is what sound you prefer (I personally dislike Rat style distortions). If its not true-to-classic, but you like it, screw the haters and do what you want.
I found these over on BG Micro:
(https://www.dropbox.com/s/kz7zhqt7t1cvfgh/2016-04-27-09-02-57.jpg?raw=1)
The website incorrectly advertised these as UA308's, so I wasn't overjoyed when they arrived.
Oh well, the packaging is nice. I haven't tried them in a rat, so I can't vouch for their performance.
The chips in the background are LT1054's. $1.20 a pop.
Quote from: stringsthings on February 03, 2018, 04:05:01 PM
I found these over on BG Micro:
(https://www.dropbox.com/s/kz7zhqt7t1cvfgh/2016-04-27-09-02-57.jpg?raw=1)
The website incorrectly advertised these as UA308's, so I wasn't overjoyed when they arrived.
Oh well, the packaging is nice. I haven't tried them in a rat, so I can't vouch for their performance.
The chips in the background are LT1054's. $1.20 a pop.
108s are the Mil-spec equivalent of 308s. Same function, but tighter tolerances and wider operating temperature range.
I thought so. When I get around to it, I'll pop one in.
.... so much mojo! :)
Just think, if you have to troubleshoot, you get to scream at it, "What is your major malfunction?!?!"
So I built the Giant Hogweed circuit here - http://tagboardeffects.blogspot.com/2015/10/giant-hogweed.html
The schematic is here - http://www.davidrolo.com/wp-content/uploads/2017/07/GiantHogweedSchematic_zps445f5a36.png
I still haven't found an LM308, so I popped in an OP07. The pedal works, but so far I don't know how it compares to an LM308 or a TLO70. Also, I'm not sure whether the 30pf compensation cap between pins 1 and 8 of the OP07 needs to stay, be removed, or the value changed.
OP07 datasheet: http://www.analog.com/media/en/technical-documentation/data-sheets/OP07.pdf (http://www.analog.com/media/en/technical-documentation/data-sheets/OP07.pdf)
The OP07 does not need the 30 pf external compensation capacitor. It uses those pins for offset nulling (which is something that never gets used in pedals AFAIK), and the cap probably won't do anything if you leave it in.
Quote from: reddesert on June 08, 2018, 05:52:11 PM
OP07 datasheet: http://www.analog.com/media/en/technical-documentation/data-sheets/OP07.pdf (http://www.analog.com/media/en/technical-documentation/data-sheets/OP07.pdf)
The OP07 does not need the 30 pf external compensation capacitor. It uses those pins for offset nulling (which is something that never gets used in pedals AFAIK), and the cap probably won't do anything if you leave it in.
Yep, you're right, thanks. The 30pF cap does nothing if I leave it in. Wonder if it will do any harm leaving it in, just in case I ever slot in a LM308 or TL070?
I'm intrigued by trying out an actual LM308. There are some on eBay. Anyone have any experience of eBay LM308s? Fake? Unreliable?
https://www.ebay.co.uk/itm/LM308N-DIP-8-Integrated-Circuit-UK-SELLER/273271724172?hash=item3fa043988c:m:mRRRNL-ddJXw4RDEq0XRW7A
I've been burned by Ebay chips too often, but I have gotten lucky occasionally with domestic vendors. Avoid Chinese sellers and throw the dice.
Banzai also has them in stock for about 3 euros a pop:
http://www.banzaimusic.com/LM308N.html
Quote from: somnif on June 10, 2018, 04:13:43 AM
I've been burned by Ebay chips too often, but I have gotten lucky occasionally with domestic vendors. Avoid Chinese sellers and throw the dice.
Banzai also has them in stock for about 3 euros a pop:
http://www.banzaimusic.com/LM308N.html
Cheers for that.
I've ordered this one from eBay - https://www.ebay.co.uk/itm/LM308N-DIP-8-Integrated-Circuit-UK-SELLER/273271724172?hash=item3fa043988c:m:mRRRNL-ddJXw4RDEq0XRW7A
I'll update soon when I test it.
If you ordered one from ebay (or anywhere that's not trustworthy infact) how would you know if its real or not?
Quote from: chromesphere on June 11, 2018, 12:20:29 AM
If you ordered one from ebay (or anywhere that's not trustworthy infact) how would you know if its real or not?
I don't know, TBH. What would a fake one do or not do?
I suppose I can compare with an OP07. And check if the 30pF compensation cap between pins 1 and 8 makes any difference in sound.
Quote from: chromesphere on June 11, 2018, 12:20:29 AM
If you ordered one from ebay (or anywhere that's not trustworthy infact) how would you know if its real or not?
Measure resistance between pins 1 and 5 (the offset null pins). Single op-amps like TL071 or LM741 will have a resistance (around ~2k for the 741, higher for the TL071), the 308 will show no connection.
And if its a dual-opamp re-painted, the pinout won't match and it won't actually work in the circuit.
Quote from: somnif on June 11, 2018, 12:41:40 AM
Quote from: chromesphere on June 11, 2018, 12:20:29 AM
If you ordered one from ebay (or anywhere that's not trustworthy infact) how would you know if its real or not?
Measure resistance between pins 1 and 5 (the offset null pins). Single op-amps like TL071 or LM741 will have a resistance (around ~2k for the 741, higher for the TL071), the 308 will show no connection.
And if its a dual-opamp re-painted, the pinout won't match and it won't actually work in the circuit.
Good call, thanks. Do I measure this with voltage applied to the chip?
(Just had a despatch notice from eBay. Soon....)
No just carefully touch your DMM leads to the chip.
(http://static.righto.com/images/741/schematic_raytheon_rc741-w1416.png)
Thats the 741, but the 071 has a similar topology with some different resistor values. You can measure resistance between those pins straight away.
Excellent information Somnif! To be honest i wasnt sure there was an easy way to check, i hope this info helps folks source genuine parts (tonnes of fakes out there...)
Note this trick doesn't work for externally compensated chips like the TL070, since it uses a similar compensation scheme to the '308. There is a diode between pins 1 and 8 in the 070, though, so that's something you could look for.
It arrived.
I measure no resistance between pins 1 and 5, and about 17k between pins 1 and 8.
Quote from: Philtre on June 13, 2018, 03:06:10 AM
It arrived.
I measure no resistance between pins 1 and 5, and about 17k between pins 1 and 8.
Does it work in circuit? I'm not sure you should be seeing a resistance that low between 1 and 8, but I don't have one on hand to check. In the 308, 1 and 8 are connected via a 5.6k resistor in series with a bunch of transistor junctions. I have no idea what the resistance of that would be off hand I'm afraid.
An OP07 just has a couple resistors between 1 and 8, but their value is determined on-die, and isn't a published stated value, so no easy way to check there. .
Real way to check is just chuck it in a Rat. If you can, leave the compensation cap out. If it doesn't work, its a 308, if it does work, its something else.
ALL THAT SAID, there isn't really a huge profit margin in faking 308's. Rat aficionados may love the things, but pedal builders are a drop in the bucket, and they aren't really super special niche market chips like old BBDs. Chances are its probably real. And hell, if it sounds good, who cares?
It works in the Giant Hogweed circuit - http://www.davidrolo.com/wp-content/uploads/2017/07/GiantHogweedSchematic_zps445f5a36.png
I have an OP07 here and there is 16k between 1 and 8.
So if I snip the 30pf Cap should it not work if it's real?
It works the same in that circuit with no compensation cap.
Quote from: somnif on June 13, 2018, 03:33:30 AM
ALL THAT SAID, there isn't really a huge profit margin in faking 308's. Rat aficionados may love the things, but pedal builders are a drop in the bucket, and they aren't really super special niche market chips like old BBDs. Chances are its probably real. And hell, if it sounds good, who cares?
Scammers have faked chips and transistors of far less value so i wouldn't be so sure of that.
I think it would be very handy to have in this thread the values measured on a confirmed lm308 so people can check there chips against it. Amazingly i dont have one that i would trust as being 100% genuine.
Ok, yeah, sounding like you got a re-branded op07, that sucks >:(
Rat's without a compensation cap can pass through sound, but they end up sounding sputtery and broken. If its behaving the same without a cap, and showing a similar resistance, I'd say its probably the same chip. Boo.
I dug out a metal-can 308 (ok, technically its a 108, but that just mean it works in cold weather) I had and see a 1-8 resistance of about 40 Megaohm. Not sure how that would compare to the DIP8 version, unfortunately.
A/B testing between the "LM308" and an OP-07 and it sounds almost exactly the same. 30pf cap makes no difference in or out.
I'll claim a refund, on principle.
Well, if you want some vintage mil-spec mojo I found a UK-ebay auction for a pair of metal-can LM108's, 8 pounds for 2 of them. They actually include pictures, so that something.
I requested a return from the eBay seller. He just refunded, no questions, quibbles or even wanting the chip back. Perhaps he knows they're fake?
I think I'll stick with my OP07 in the Giant Hogweed circuit.
If its a small amount the eBay seller probably just refunded to avoid any headaches. eBay favors the seller in most cases and if you disputed that the chips were fake through the dispute resolution process chances are eBay would favor you over the seller.
For those reading this thread and are new to the hobby and electronics I should just reiterate here, ebay is not recommended for electronic parts.
Quote from: chromesphere on June 13, 2018, 07:29:36 PM
If its a small amount the eBay seller probably just refunded to avoid any headaches. eBay favors the seller in most cases and if you disputed that the chips were fake through the dispute resolution process chances are eBay would favor you over the seller.
For those reading this thread and are new to the hobby and electronics I should just reiterate here, ebay is not recommended for electronic parts.
True, but I have bought AC128s from eBay and they've been fine. Resistors and caps can be OK.
Buying this "LM308" was an experiment. It was a case of "I gots to know". No loss financially, but experience gained.
Mainly ICs and Transistors. Things that have a bit of worth. J201's, BBDS, etc. Germanium transistors are usually ok.
Banzai in Germany sell LM308s. How would one know upfront if these are genuine?
http://www.banzaimusic.com/LM308N.html
Quote from: Philtre on June 13, 2018, 10:42:38 PM
Banzai in Germany sell LM308s. How would one know upfront if these are genuine?
http://www.banzaimusic.com/LM308N.html
They'll be real if they actually have them. The problem with Banzai is they are either fantastic or fantastically useless. Basically if you submit an order and they have everything you'll get it in about a week from Germany to the uk. If, however, one of the items is actually out of stock (though was probably showing as in stock when you ordered) they'll hold the entire shipment and not contact you until you harass them by email 3 or 4 times then they'll ship the parts they do have and either offer a refund on the outstanding one or ask if you want to wait and ship it separately.
That's been my experience.
I have to go here often for work. I can pick you one up if u want. http://www.stquentin-radio.com/?page=info_produit&info=5052&color=3&id=0&act=0
It's pretty sure they are legit. I've bought a few from them. €4 plus maybe another €2 for shipping.
Quote from: bsoncini on June 14, 2018, 09:26:47 AM
I have to go here often for work. I can pick you one up if u want. http://www.stquentin-radio.com/?page=info_produit&info=5052&color=3&id=0&act=0
It's pretty sure they are legit. I've bought a few from them. €4 plus maybe another €2 for shipping.
Many thanks for the offer. But I'm going to stick with OP07s. :-)
No problem. Let me know if you change your mind.
I've been playing in a group as a duo recently. Me on guitar and a drummer. I've been using this pedal a lot to have some more bass.
I've been researching LM308 vs OP07.
The tech sheet for the OP07 has pins 1 & 8 as an offset nulling option where it seems a variable resistor can be connected. Yet, on various forums discussing the ins and outs of OP07 vs LM308 some people swear that adding a compensation cap on 1 & 8 on the OP07 makes a difference to the sound (example - https://www.thegearpage.net/board/index.php?threads/rat-op-amp-chips.1326447/)
What do the experts think?
I mistrust thegearpage as a source for technical information, generally (although I don't read it often and may be a grump).
The LM308 is a really old op-amp. Back then, fabrication techniques made it hard to put an internal capacitor on the chip. So op-amps like the LM308 relied on an external compensation capacitor. The point of this cap is to avoid oscillations at high frequencies (above the audio band) that would make the op-amp unstable. For complex reasons, the amplifier has a phase shift that changes with frequency, and at the frequency where it is 180 degrees out of phase, the negative feedback would change to positive and cause oscillation. The compensation cap rolls off this behavior.
Later op-amps like the 741 and OP07 were made with a small capacitor on the chip, so the external compensation is not necessary and the pins are used for offset nulling (which is AFAIK something to use for precision DC differential amplifiers and irrelevant for audio circuits). If you compare the schematics of the LM308 and OP07 in the gearpage thread, the OP07 has a small cap C1 from V+ to the collectors of Q9 and Q10, while the LM308 has no capacitor on-chip.
For more information about the history behind this, look at section 4 of the History of Op-Amps book chapter at http://www.analog.com/media/en/training-seminars/design-handbooks/Op-Amp-Applications/SectionH.pdf (http://www.analog.com/media/en/training-seminars/design-handbooks/Op-Amp-Applications/SectionH.pdf). By the way, Sections 1-3 will happily lead you down a rabbit-hole of reading about early vacuum-tube and discrete op-amps. Here's a screen-cap of a footnote about the internal compensation capacitor:
(https://s19.postimg.cc/6odjzvs73/Screen_Shot_2018-06-16_at_12.23.34_PM.png) (https://postimg.cc/image/6odjzvs73/)
I don't think adding a cap between the offset null pins of an OP07 or similar is going to do anything to modify the high frequency behavior, nor is it necessary.
However, I've not been convinced that the LM308's low slew rate is what gives it the mojo sound. Its slew rate is still quite adequate for audio signals.
Thanks for that info, redderset, very informative. :-)
For my own part I've tried an OP07 and an LM741 and, to me ears, there's very little in it. I might try a LM301 at some point but I'm fast coming to the conclusion that it's just not worth the bother fretting over this, and just bung in an OP07 without a compensation cap and be done with it. I believe that modern Rats use them.
Very interesting thread. When I swapped an lm308 for an Op07 a few months ago I was surprised that I could barely hear a difference. And I'm pretty sure I took out the 30pf with the OP07 and it made no difference either.
I've often found that AliExpress is good for rare parts. Yes, I know they are fake, but if you order some and then test them you can generally find the good sellers pretty quickly. I get a lot of SMD parts from there, especially the transistors and diodes because either I can't source them elsewhere or the minimum quantanty is rediculous.
But like I say, I test the parts before using them to ensure that they are within spec of the original ones, and haven't had an issue so far.
Sent from my SM-G955F using Tapatalk
I did an experiment. I built a RAT clone (http://tagboardeffects.blogspot.com/2012/01/proco-rat.html) and ordered some LM301s from Tayda and tried the following:
- OP07 (no compensation cap)
- LM301 with 100pf compensation cap
- LM301 with 33pf compensation cap
I know it's subjective but, for me, the last option won. Sounded a bit grittier.
(BTW - the Tayda LM301s are genuine as they squeal like a pig without the cap unlike the "LM308" I bought off eBay which was a repainted OP07)
Quote from: stevie1556 on June 20, 2018, 05:20:30 PM
I've often found that AliExpress is good for rare parts. Yes, I know they are fake, but if you order some and then test them you can generally find the good sellers pretty quickly. I get a lot of SMD parts from there, especially the transistors and diodes because either I can't source them elsewhere or the minimum quantanty is rediculous.
But like I say, I test the parts before using them to ensure that they are within spec of the original ones, and haven't had an issue so far.
Sent from my SM-G955F using Tapatalk
Just be wary of the places that sell end of life parts with a listed production capacity of 10,000 pieces per day. ;-)
My 2 cents on "fake" parts (I know we've been around this before): It's common in the electronics industry to "second-source" parts. This means that there is some other manufacturer making, say, a dual op-amp that works like a JRC/NJM4558 and calling it a 4558. This is not considered a fake (unless they counterfeit the manufacturer logo).
Then there's the parts that either grossly fail to meet spec or are just some other random IC with the name of a hard-to-find chip like a CA3080 printed on them. These are fakes (real fakes? fake fakes?) and will lead to frustration.
As a generalization, I would consider buying an easy to find item on ebay or wherever (of course, if it's easy to find, I can probably get it from a regular suppier), but if it's exotic and the price is too good to be true, it probably is.
Quote from: reddesert on June 30, 2018, 05:11:02 PM
My 2 cents on "fake" parts (I know we've been around this before): It's common in the electronics industry to "second-source" parts. This means that there is some other manufacturer making, say, a dual op-amp that works like a JRC/NJM4558 and calling it a 4558. This is not considered a fake (unless they counterfeit the manufacturer logo).
Then there's the parts that either grossly fail to meet spec or are just some other random IC with the name of a hard-to-find chip like a CA3080 printed on them. These are fakes (real fakes? fake fakes?) and will lead to frustration.
As a generalization, I would consider buying an easy to find item on ebay or wherever (of course, if it's easy to find, I can probably get it from a regular suppier), but if it's exotic and the price is too good to be true, it probably is.
In China, there are a lot of second tier electronics houses where you can buy parts. I deal with folks in China on a regular basis and asked somebody to get some JFETs for me from one of the local houses that had stock (this was soon after they went EOL). I ordered 2n5457 and J201. Not only were they all out of spec, some were actually P-Channel. They were marked with the right names, but the logos were off. Oh well.
Personally would not trust Banzai, After catching them out selling fake HA1457W Hitachi op amps at a great price, then I notified them to as much that they were selling fakes, they said we will look into it, A year later they are still selling the same fakes as real NOS, Totally unscrupulously oblivious to what constitutes ethics
https://www.banzaimusic.com/HA1457W.html
Don't purchase these, I asked Banzai for an up to date image of actual item being sold back in late 2021, and the image they sent to depict their item was an exact same image and detail as fake Chinese HA1457W IC's I had previously purchased of which none of them worked all duds from a lot of around 50 out of China, All non original fake copies, and bad copies at that.
The actual image Banzai sent me to depict their HA1457W is shown here as 8M4 HA1457W identically marked.
2nd image is an original Hitachi HA1457W, its not hard to spot the fakes with the HA1457W op amps
And while it is, I have purchased a few working fakes of these op amps, the lot of those marked same as the Banzai, from China were all duds, non working, I cant use them, and wont resell them.
And yet Banzai did nothing after I notified them they were selling fakes, likely to this day they are still selling the same