Messages

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 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. :-)

That's it! Thanks!

Time for coffee!

This is one of those probably simple things that I just cannot get my head around (maybe lack of coffee).

I'm building a circuit that has a standard wired stomp 3PDT for Bypass. The wiring I use is this:



I also need to include another 3PDT switch that simply makes a connection in the circuit, on or off (it's Octave On/Off), so just two wires for this. This should have its own LED to indicate on or off. (I know I could use a DPDT but I don't have one).

I know how to wire them so the LEDs have their own make/break loops but I want the Octave LED to switch off when the Bypass stomp is off.

Banzai in Germany sell LM308s. How would one know upfront if these are genuine?

http://www.banzaimusic.com/LM308N.html

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.

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.

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.

It works the same in that circuit with no compensation cap.

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 arrived.

I measure no resistance between pins 1 and 5, and about 17k between pins 1 and 8.

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....)

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.

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.

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