Preamp board, is this a good design to build?

[delverboy]

or choose a FET input opamp

So an opa2134 would be a better choice?

 

[Mark Tillotson]

That's got 8nV/√Hz, which might start to affect the overall noise performance a bit, the OPA1642 looks good to me and has a low 1/f voltage noise knee frequency.

 

[EUVL]

OPA1642

Great choice. 😊


Patrick

 

[delverboy]

the LM4562 is bipolar and getting its bias current through the wipers of the various pots, which can lead to catastrophic noise bursts once the pots start to get even a tiny bit scratchy and start interrupting the bias current... Either modify the circuit with capacitors on all pot wipers (and alternate DC bias current paths), or choose a FET input opamp where the input bias currents are small enough to mitigate the issue.

So with LM4562's installed it's been working great for about 6 mo's now. Almost dead silent. Will the pots get scratchy at some point, maybe?
I'm starting another one of these for a different project and am wondering if I should go with the 4562's again or try a FET input opamp. Rod mentions the opa2134 as an option. The recommended opa1642 isn't available in a DIP8. There are SMD DIP8 modules, but not from reputable sources, so what are the chances those are counterfeit?

 

[kgrlee]

So with LM4562's installed it's been working great for about 6 mo's now. Almost dead silent. Will the pots get scratchy at some point, maybe?

Yes