Aston Origin crackling noise troubleshoot

[SamsaGregor]

Hi!

I want some advice. I bought myself a little project to learn more about microphones. It's a broken Aston origin and has a crackling noise, which sometimes does weird sizzles and small pops. I'll attach a recording of it. The capsule had a tiny tear or hole, so I replaced it with a new one of the same style. But the exact same noise is still there.

Visually, the circuit looks fine, and I can't find anything abnormal. There are no swelled capacitors, nothing. Other mics work as they should with my current setup, so it shouldn't be an issue. I have obviously tried different interfaces and cables, but the issue persists.

How should I go about troubleshooting it?

All the best,

Sam

 

[RuudNL]

I can't open the .wav file.

 

[Khron]

Looks like a pretty standard Schoeps affair, minus the capsule bias oscillator.

Thing is, it could be anything. In my sE X1, it turned out to be some resistor(s), of all things It wasn't the semiconductors, it wasn't any of the capacitors...

https://khronscave.blogspot.com/2017/05/se-electronics-se-x1-rebuild.html

 

[SamsaGregor]

Hmm, I tried to upload it again, but I do get the error, too. Here is a Google Drive link instead.

 

[elskardio]

a bad FET?...

 

[SamsaGregor]

Looks like a pretty standard Schoeps affair, minus the capsule bias oscillator.

Thing is, it could be anything. In my sE X1, it turned out to be some resistor(s), of all things It wasn't the semiconductors, it wasn't any of the capacitors...

https://khronscave.blogspot.com/2017/05/se-electronics-se-x1-rebuild.html

Oh, I read your blog. It's very informative and gives me some clues on how to start troubleshooting. I really hope it's not one of those small components.

a bad FET?...

Maybe the FETs could be a good place to start with replacing? So, I guess I'll order all the reasonably large components and try replacing them starting with the FETs. I don't trust my abilities to replace any of the smaller stuff. Or is there any other direction I could take in the troubleshooting to make more informed decisions?

 

[pasarski]

What effect does the switches have? Does the pad make the signal and the noise go down or just the signal? Does the low cut work?

 

[SamsaGregor]

What effect does the switches have? Does the pad make the signal and the noise go down or just the signal? Does the low cut work?

Thanks for your reply. I didn't think of this beforehand, but it might give you some clues. The pad and lowcut function as they should, but they only affect the signal going into the mic, not the crackling noise. The noise stays the same, but I can hear clear differences in the rest of the signal. I even checked with an EQ to confirm that the low cut works since it's hard to hear behind all the noise.

 

[pasarski]

Thanks for your reply. I didn't think of this beforehand, but it might give you some clues. The pad and lowcut function as they should, but they only affect the signal going into the mic, not the crackling noise. The noise stays the same, but I can hear clear differences in the rest of the signal. I even checked with an EQ to confirm that the low cut works since it's hard to hear behind all the noise.

Yes there's a clue. It's something after the switches, not something between them and the capsules diaphragm. Still lots of possibilities left unfortunately.

 

[RuudNL]

Solder a 100 nF capacitor between the drain and the source of the FET.
If the noise becomes less 'bright', the FET causes the problem.
If the noise stays the same, one of the output transistors could be defect.
(But it can also be anything else. Anyway: in that case you can eliminate the FET.)