SA2022 - Modular High End Analog Precision Preamp (with headphone amp, digital controlled relay volume, monitor output, IR remote, SE and bal. I/O)

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#161
I'm sure this is not pop corn noise - maybe just bad layout.😉
Testing the opamp on breadboard without close connected decoupling caps is just pure idiotic nonsense...
Decoupling is very important, also the 47R resistor at output of opamp (many circuits ignore the data sheet recommendations). If layout/decoupling is bad, you can't easily change to another opamp type without troubles. If e.g. a design is made for low impedance one cannot replace a LM4562 (easy drives 600R output) using an opamp which doesn't like output impedance below 2k.
Of course there exist badges with defective opamps. Glad that mine are all OK.
My MC preamp uses NE5534/LM4562 and the preamp tons of LM4562 and produces just random noise (with ultra low level!) if using full gain.

If the LM4562 and other high end opamp's would be so bad, why are the prices so high?

Have fun, Toni

P.S.: have also many LME49990 on Stock ... great parts
 
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#162
The LM4562 is renouned for having a significant fraction of devices with excess noise (which TI really don't like being mentioned!) Its also one of the worst for EMI pickup, alas. It also has more current noise than the good old NE553x devices. Basically its not a good choice for any kind of preamp.
But you are right about decoupling, you can't get away with sloppy decoupling on an LM4562, unlike some chips it needs decoupling from each rail to ground, not just between the rails. Distortion jumps 60dB or so if you get that wrong!

[ I got that wrong, once... ]
 
#163
SA2022 uses mostly all LM4562 in high current low gain circuits where popcorn noise is hard to measure and not even hear able. NE5534 is used in MM (high input impedance situation with high gain) and MC circuits (high gain).
Never had any LM4562 showing the popcorn noise problem. Maybe because I have bought most of my LM4562 in the year 2012 where National Semi produced them in 2012 or before 2012.
 
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#166
Pcb kit sold. After checking my lab I saw that one last kit is still available. Afterwards the kit price will grow like buying unobtanium because of uncertainty of supply chains risk and ambiguity depending on the destination country.

BR, Toni
 
#167
astx said:
SA2022 uses mostly all LM4562 in high current low gain circuits where popcorn noise is hard to measure and not even hear able. NE5534 is used in MM (high input impedance situation with high gain) and MC circuits (high gain).
Never had any LM4562 showing the popcorn noise problem. Maybe because I have bought most of my LM4562 in the year 2012 where National Semi produced them in 2012 or before 2012.
Click to expand...
Its not popcorn noise as I understand it, its excess 1/f noise in a small percentage of devices - enough that you can't economically manufacture a low noise circuit with one as you'd get lots of reject units on test. TI do not screen for this noise before the devices are packaged into pick-and-place reels... "Select on Test" isn't a thing any more...
 
#168
Using LM4562 in SA2022 is not a "must". If you are unsure: any good dual opamp in dip8 will work if it is capable to drive a 600R load. There are adapter pcb's available to use smd variants. If you have many NE5532A on stock the resulting performance of SA2022 will still be high end low noise.

Have fun, Toni
 
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