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I'm not sure there would be any significant difference in sound quality between Vgnd and Gnd as a reference for the transformer de-coupling? I think it would simply mea

Has anyone tried the TLE2071? https://www.ti.com/lit/ds/symlink/tle2071.pdf any insights into real world noise performance vs the 1641? I'm not expert enough in opamps to interpret the figures for

Yes when I first did this opamp tx circuit a couple of years ago, I had the experience that decoupling the transformer solved VG imbalance. I didn't need to refer it to actual ground IIRC. In this

Funny you should ask, I did exactly this (see pic here <https://lacinato.com/pub/electrets/instmic/mandomic.jpg>). I made a Primo EM-184 with Simplest P48 and built a clip-on mount to attach it to a

Hi all - I am interested in close-mic'ing some instruments that would normally be "professionally" mic'd with a DPA-4099. I am curious if anyone has done much of a shoot-out with regards to their

Well, for testing purposes - rather than actual final use? - then I've found the good old fashioned TL071? works quite well. It has many similar parameters, but it does make a lot more noise! As to

The guardring seems like a good idea, but I don't see how it could be done with one of these tiny opamps. it would have to be very fine, and if it were left free of solder mask, it would certainly

A friend of mine recently had exactly the same problem you described here and also solved it by thoroughly cleaning the PCBA with IPA. I gave him the advice to add a guardring. The guardring connects

if the virtual ground is high through the route you describe that suggests that: * isolating the transformer with a cap should help. It didn’t noticeably earlier but maybe now things are close and

Didn't notice that. I thought the schemo was the latest issue. This is good. Remember that, even with

It's not a 15v zener any more I increased it to 27v to give me headroom for the opamp gain. from my original post: "(possibly irrelevant aside - in my latest version I'm using a 7:1 transformer and

This is not normal, with a 15V zener the voltage should be less than 16V. The VG voltage should be pretty close to half of V+. OK OK. This shouldn't happen. It is a possibilit

Hello all, I don't normally post here much but @thet is there a specific reason why the transformer primary needs to use virtual ground versus "original recipe" ground at pin 1? I can guess we're able

I have put the board in a body for a more stable test situation. Though the cover is off of course. With a 100pF cap across the 1G resistor to simulate a capsule, I now have a very high virtual

How are you measuring it? What value are you measuring? What voltage are you measuring on pins 2, 3 and 6 of the 1641? Wrong assumption. That confirms it's not the origin of the problem.

If anyone sees a theoretical issue with my schem I'd be grateful for any enlightenment. If the schem is OK then I guess I'll find it through regular troubleshooting procedures. Actually I'm getting

How far off-center is the virtual ground voltage? I would try disconnecting stuff: 1) remove the opamp and measure voltages (all voltages) 2) restore the opamp, measure again 3) disconnect the

and here's the link direct to the schematic, which is what I meant to post: https://halfshavedyaks.xyz/pcb/images/schems/OPATX-sch.jpg

On my opamp mic with a transformer, my virtual ground is unbalanced, it is closer to actual ground than to V+ I thought it might be DC running through the transformer primary, I've tried with the

Thanks Jules, glad I checked.