Interesting video on fake chips

[CheapPedalCollector]

What was the sign? Slow slew rate?

Very noisy and had distortion.

[Paul Marossy]

What was the sign? Slow slew rate?

Very noisy and had distortion.

Was this a single case, or consistent with several? Could be that the chip got damaged by an electrostatic discharge or something like that.

My only experience with a TL074 was with a squealing Classic EQ preamp module for my Seymour Duncan Convertible amp. When I replaced the TL074 the squealing stopped. From that experience I've always felt that the TL074 was kinda dodgy but I suppose my one negative experience doesn't mean they are bad IC chips. Could have been any number of reasons why that went bad inside a hot tube amp chassis.

[Kevin Mitchell]

Yeah I wouldn't say "they sold me a fake chip", but rather "the chip I got was defective", but I know that doesn't sound much better  . Or does it?
But I'm a biased fanboy. What can I say.

I've seen reports of fake TL071 chips around the web in recent years. Looked ok phyiscally but when it was put to task as a non-inverting amp for a multiplexed signal (don't know exactly what speed, likely 20kHz or so - wasn't clocked too fast) the output would just look like a swiggled line on the scope and would not stabilize fast enough to represent the multiplexed channels. Such poor quality chip would make a pulse look like an ugly sine. That's prof of a poor slew rate.

[CheapPedalCollector]

I bought 10, they came in a chip tube so likelyhood they all got static damage is low. They all were like this, I bought some from Mouser and they work fine. Comparing the chips, both Ti, the ones I bought from SB are not the same and look suspect, I can take pics if you want.

I just figure they got a bad batch from whoever the supplier was. This was before they changed hands btw.

I've had a couple of order goof ups since then, but they were quickly resolved which I attributed to growing pains.

[Paul Marossy]

I bought 10, they came in a chip tube so likelyhood they all got static damage is low. They all were like this, I bought some from Mouser and they work fine. Comparing the chips, both Ti, the ones I bought from SB are not the same and look suspect, I can take pics if you want.

I just figure they got a bad batch from whoever the supplier was. This was before they changed hands btw.

I've had a couple of order goof ups since then, but they were quickly resolved which I attributed to growing pains.

Around 15 years ago I built guitar effects for a certain well known "boutique" manufacturer. At the time they offered a buffer circuit, and sometimes they would have weird problems and sometimes not. As I recall they used a TL072 (maybe it was a TL071?), and one of the sections remained unused. They followed the normal conventions with respect to how to treat an unused opamp section. In spite of all that end results were somewhat unpredictable. So much so that I heard they eventually stopped making that pedal (sometime after I had went back into consulting engineering following 16 months of unemployment 2009-2010). I have also tried using them in unity gain circuits and they just don't seem to like that environment. They sound good/work OK most of the time but those TL072s seem to be very quirky in some situations, in my experience.