Greetings rsavas,
Would you actually go and purchase just one Op.Amp in the store without being charged customs and import costs (brokerage fees), as happened to me when I ordered directly from Microchip only two PIC MX 32-bit microcontrollers for $7USD, and ended up needing to pay an additional $50?
I consciously took a risk because even if I had received a ceramic MIL-spec 741 for just $5USD, it would have been a good purchase. However, it's another matter if you look on Mouser at how much LF156 or LF256 costs in the MIL CER-DIP version or TO-CAN; you'll see that for those packages, even LF1/2/356 costs more than the PDIP/SOIC AD797.
Greetings, Mark T.,
I agree the OPA1612 is excellent, especially since it's good for low input resistances. It's slightly surpassed by LT1028, but the latter has a drastically higher level of distortion. Indeed, the entire OPA1612/42/52/62 series has proven to be great low THD solutions. It turned out that in my internally developed Wien bridge oscillator, with the lowest THD-N, LF4562/LME49720 showed 0.0006%, closely followed by OPA1612 (though a bit unstable) with 0.0007-8%, then OPA1652 with 0.0009-10% but with a much more stable response, then OPA1642.. and so on.
Honestly, the pure engineering rule applies here: what do you want to achieve, what are the working conditions, and what surrounds it, and the "most expensive music" isn't always what produces the best results.
Without testing and trials in the analog world, it doesn't make much sense to follow simulations and spec diagrams. Often, it seems to me that they are made by people from marketing rather than engineers. For example, who cares about an OP.Amp with -1 amplification and its noise specs when realistically we need it at Av +10, 20, or +40dB.
I genuinely believe that the Japanese, i.e., www.nisshinbo-microdevices.co.jp (former JRC), are the most honest. It often turns out that their components are even better than the specifications they provide
I sincerely recommend them, for instance, NJM8830, even if it operates on just 10V, is fantastic, only requiring a low-cut below 10Hz, or MUSES8832, for example, is clearly a refined and improved NE5532, but much better...
To conclude, based on the documentation, it's clear that someone in China bought LF156/256 Die chips, installed them in ceramic housings, and rebranded them as AD797SQ. The fact is that these chips are in the mil-spec range of -55..+125C, and in a ceramic package, it's still a good purchase for just $5USD. Everything would have been great if only they had stated it was LF256-MIL or 356/357 or whatever, and it would find its use because they operate at +/-40V while not being bipolar but JFET. For instance, LF356 in TO-CAN costs 15EUR at Mouser EU, so you can see for yourself whether it's worth it.
Would you actually go and purchase just one Op.Amp in the store without being charged customs and import costs (brokerage fees), as happened to me when I ordered directly from Microchip only two PIC MX 32-bit microcontrollers for $7USD, and ended up needing to pay an additional $50?
I consciously took a risk because even if I had received a ceramic MIL-spec 741 for just $5USD, it would have been a good purchase. However, it's another matter if you look on Mouser at how much LF156 or LF256 costs in the MIL CER-DIP version or TO-CAN; you'll see that for those packages, even LF1/2/356 costs more than the PDIP/SOIC AD797.
Greetings, Mark T.,
I agree the OPA1612 is excellent, especially since it's good for low input resistances. It's slightly surpassed by LT1028, but the latter has a drastically higher level of distortion. Indeed, the entire OPA1612/42/52/62 series has proven to be great low THD solutions. It turned out that in my internally developed Wien bridge oscillator, with the lowest THD-N, LF4562/LME49720 showed 0.0006%, closely followed by OPA1612 (though a bit unstable) with 0.0007-8%, then OPA1652 with 0.0009-10% but with a much more stable response, then OPA1642.. and so on.
Honestly, the pure engineering rule applies here: what do you want to achieve, what are the working conditions, and what surrounds it, and the "most expensive music" isn't always what produces the best results.
Without testing and trials in the analog world, it doesn't make much sense to follow simulations and spec diagrams. Often, it seems to me that they are made by people from marketing rather than engineers. For example, who cares about an OP.Amp with -1 amplification and its noise specs when realistically we need it at Av +10, 20, or +40dB.
I genuinely believe that the Japanese, i.e., www.nisshinbo-microdevices.co.jp (former JRC), are the most honest. It often turns out that their components are even better than the specifications they provide
I sincerely recommend them, for instance, NJM8830, even if it operates on just 10V, is fantastic, only requiring a low-cut below 10Hz, or MUSES8832, for example, is clearly a refined and improved NE5532, but much better...
To conclude, based on the documentation, it's clear that someone in China bought LF156/256 Die chips, installed them in ceramic housings, and rebranded them as AD797SQ. The fact is that these chips are in the mil-spec range of -55..+125C, and in a ceramic package, it's still a good purchase for just $5USD. Everything would have been great if only they had stated it was LF256-MIL or 356/357 or whatever, and it would find its use because they operate at +/-40V while not being bipolar but JFET. For instance, LF356 in TO-CAN costs 15EUR at Mouser EU, so you can see for yourself whether it's worth it.
Yes, it’s $30.29 for PDIP-8, with the lowest cost option being $24.77 for surface mount. PDIP-8 increased twice since last summer.
I would still never buy outside the authorized supply chain. I can imagine the damage which an unknown opamp and poorly constructed chip could cause downstream to further amplification and speakers.
Greetings rsavas,
yes, I completely agree with you, which is why I always purchase components through Farnell, TME, or local suppliers who still have stocks from the fortunate 1980s and 90s. This option imposed itself when I was desperately searching for a replacement IC for Creative Lab speakers, so I thought I'd give it a try. I figured what the cost would be, even if they "slipped" me a ceramic LM741, I could bake it at 120C. And for that money, up until recently, you could even find an LM741 To-CAN ([https://kelco.rs/katalog/detalji.php?ID=2677]), but even that's no longer available
In any case, everything has its field of application, so even Ceramic LF256/LF257 are useful for something. It really would have been much better and more honest if they had clearly stated that they installed original LF256/356 DIE chips in a ceramic casing and are selling them to us at an extra price. Hm, it seems that this was the option "LF156 MD8 -, DIESALE" sold as a package of 204 pieces... Hm, hm, LF156 is a much better option, now it's clear why it was better than TL072; ah, the mystery is solved ([https://www.ti.com/lit/ds/symlink/l...rl=https%3A%2F%2Fwww.ti.com%2Fproduct%2FLF256])
Great, so LF156 at -55..+125C with a lower noise level and operating at 40V, i.e., +/-20V, and also capable of driving a large capacitive loads up to 5nF.
To conclude, only purchase from verified and honest sellers who will sell you exactly what they specify, because with the others, you never know if you'll get a mouse, a cat, or a tiger in a sack.
Best regards,
yes, I completely agree with you, which is why I always purchase components through Farnell, TME, or local suppliers who still have stocks from the fortunate 1980s and 90s. This option imposed itself when I was desperately searching for a replacement IC for Creative Lab speakers, so I thought I'd give it a try. I figured what the cost would be, even if they "slipped" me a ceramic LM741, I could bake it at 120C. And for that money, up until recently, you could even find an LM741 To-CAN ([https://kelco.rs/katalog/detalji.php?ID=2677]), but even that's no longer available
In any case, everything has its field of application, so even Ceramic LF256/LF257 are useful for something. It really would have been much better and more honest if they had clearly stated that they installed original LF256/356 DIE chips in a ceramic casing and are selling them to us at an extra price. Hm, it seems that this was the option "LF156 MD8 -, DIESALE" sold as a package of 204 pieces... Hm, hm, LF156 is a much better option, now it's clear why it was better than TL072; ah, the mystery is solved ([https://www.ti.com/lit/ds/symlink/l...rl=https%3A%2F%2Fwww.ti.com%2Fproduct%2FLF256])
Great, so LF156 at -55..+125C with a lower noise level and operating at 40V, i.e., +/-20V, and also capable of driving a large capacitive loads up to 5nF.
To conclude, only purchase from verified and honest sellers who will sell you exactly what they specify, because with the others, you never know if you'll get a mouse, a cat, or a tiger in a sack.
Best regards,
A short story.
I look for a 2x22 tinned audio cable. RS have one. As there are no specs on website, I contacted them many times without answer. Manufacturer group belonging to my country, I asked commercial headquarter. Answer was : We can't help you as we stopped manufacturing audio cables since more then 10 years. Amazing !!!
Natural explanation would be old stock, but as they can't deliver datasheet, I have a doubt. I asked delay for an order bigger than available stock... and I got a "manufacturing delay" !!! I don't understand.
Who to trust today
I look for a 2x22 tinned audio cable. RS have one. As there are no specs on website, I contacted them many times without answer. Manufacturer group belonging to my country, I asked commercial headquarter. Answer was : We can't help you as we stopped manufacturing audio cables since more then 10 years. Amazing !!!
Natural explanation would be old stock, but as they can't deliver datasheet, I have a doubt. I asked delay for an order bigger than available stock... and I got a "manufacturing delay" !!! I don't understand.
Who to trust today