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Further to that comment, I took a look at Jules' dual OPA schematic here; https://content.instructables.com/ORIG/FTV/ESBC/KKV5OYHS/FTVESBCKKV5OYHS.pdf I think it should be possible to achieve what

Actually, once the capacitor is charged, there is no more current drawn, except the fraction of femtoAmpere due to residual resistance of the insulating materials, which is way higher than gigaohms.

I asked a similar question a while back and got some great resources. Here's the link to that discussion. /g/MicBuilders/message/32497 I did end up getting a few takstar capsules, a

Hello, I've read that ealier! Tho I completely did not understand what was going on in this article, now I know. Damn I think my mental breakdown just hit another level, trying different IC's,

https://audioimprov.com/AudioImprov/Mics/Entries/2016/7/4_Bias_Voltage_for_True_Condenser_Capsules.html This explains what you're seeing and how to measure with a cheap 1M meter.

That would actually cause what you are seeing. Big question: Does it work when providing bias voltage to the capsule? Remember those are literally a 50-100pF capacitor that we are charging up to

(off topic) We built one of those recently — invaluable for sanity-checking mics for output polarity. It’s also red. :) — matt.

Mix the signals at the output. Connect XLR pin 2 to pin 2 output from front side. XLR pin 3 is switched between front side pin 3 for cardioid, rear side pin 2 for fig-8, and rear side pin 3 for omni.

Hello The internal resistance of my meter appears to be 955kOhm so about 1MOhm. Best regards Wiktor Molak

If you have a 1M resistor, try this: measure a known voltage source 12V supply is good, even a 9V battery. Then put the 1M in series with the meter and measure again. You can calculate the internal

Full balanced signal is soooo overated... Balanced impedance is what matters. But why not?

Instinct tells me that trying to add switches around that kind of high impedance circuitry is asking for trouble! .. I may be proved wrong of course! :) I'm not sure why you're not keen on the single

You can't. Capsules need to see very high impedance, typically 1G (1 000 Megohm). You cannot operate a diff amp with such high values, noise would be enormous.

Actually, that's it! Removing U3 by making U4 a full differential means we can use that spare OpAmp after the U4 mixing stage as an inverting amplifier to produce the cold signal, thus giving us a

I did think about that Jerry, but decided that as the existing project PCB already has 2 x dual amps - each with one amp configured as a non inverting buffer and the other as an inverter - it might

Hi Arjay, Looks interesting! Thanks for the idea. I'm still quite keen on a balanced signal output though. How feasible is it to put switches on the high impedance side? If so, how about this... Still

There is also a possibility of using one less opamp, by omitting U3 and making U4 a full differential amp.

Hello, just a simple meter, it has few years now and I think I bought it for like 10 bucks. Best regards Wiktor Molak sob., 9 kwi 2022 o 18:35 Jules Ryckebusch <ryckebusch@...> napisa?(a):

I would ask the same. The first asset of voltages all seem good. The higher the stages the less current available thus the Meter can load it down. I have fluke 87 that has a 20M input impedance.

I live in the UK, so the shipping costs for Jules' PCBs are way too expensive for me!...... So I tried out my own experiments with the OPA1642 and OPA 1641 amps that Jules recommended.... Some project