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Maybe the coil is picking up the 50Hz. Disconnect Q2 and scope IC2 output with coil connected and coil input jumpered.
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Very good idea! You are probably right. Wasn't a problem till now with de fake opamp having almost no gain.
Am I already at a point where I need coil shielding? Currently I just quickly wraped 20 turns of 0.5mm wire around a roughly 23cm plastic bucket to match dimensions mentioned on here.Comment
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try this one. maybe will be good for you.
https://www.ebay.com/itm/GOLD-MOUNTA...4383.l4275.c10Comment
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The 50Hz I'm seeing does not seem to come from the coil its also present with shorted coil.
Tried another opamp which seems to behave itself. It has a more reasonable 4Vpp output swing but lacks offset trim functionality.
Nevertheless, this one should allow me to continue building the integrator stage until I can get my hands on some genuine NE5534's.
Moving my iron test chunk over the coil I get the following response: https://daten-transport.de/ansicht.php?id=aCJhNF6PraMz
CH1: 555 output
CH2: NE5534 output
CH3: Sampling pulse
CH4: 1st LM358 output
Looks at least promising or what do you guys think?
Still need to wire up second integrator stage, a much better coil and lots of fine tuning I think though. But hey, we are in a kinda lockdown anyways.Comment
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