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.)

 

[SamsaGregor]

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.)

I have tried it now. I think I did it right. I soldered a 100nf ceramic capacitor between this component's right leg and left leg, which I suspect is the JFET. Keep in mind that I'm a rookie at this. The noise was pretty similar; if anything, it became more intense. It's hard to tell because the noise sometimes changes. But I was expecting a bigger difference. I took a screenshot of the eq before and after.

 

[RuudNL]

I'm afraid you have to dig deeper...

 

[SamsaGregor]

I'm afraid you have to dig deeper...

Yes, it looks like that. My next course of action is to replace the output transistors then.

 

[Somkereki]

For decades, I was a service engineer for the audio equipment of Hungarian theaters. (Today I am retired, but active, because my hobby is electronics and sound technology.) I repair hi-fi devices of my wide circle of friends in my own well-equipped laboratory. I have encountered many noisy components during my work so far. The fastest way to find the noisy part is to briefly touch them with the soldering iron. You have to wait a few seconds, because it takes time for the heat to reach the right part inside the component. You have to be careful with metal encased parts, I did it by inserting a small piece of silicone rubber. With my left hand, I held a sheet of a few tenths of a millimeter with tweezers, practically a silicon washer plate for power transistors. There is also freezing spray available in electronics stores, but it does not always help, heating is better. If there is a tantalum capacitor in the circuit, that is always my first suspect! Then the transistors. Since it is a microphone, in many cases the noise of many megaohm resistors is also common. I listened to the sound, it could be anything. A funny story: I was still young and my colleagues and I were handling the microphone amplifier at a state ceremony. It was a cool morning, maybe 10-15 Celsius. The amplifier started to crackle loudly. It was still built with discrete transistors. I recognized a serial error, quickly removed the cover and found the crackling transistor with the warmth of my hand. The crackling went away, but I kept my fingers warm until the end of the ceremony. . The ceremony was long, as politicians spoke. By the end, my hands were cramping from the immobility.