Rode NT1 and NT2A noise, low output, distortion

[12AX7]

Hi, everyone.

I have two Rode NT1 and three NT2A mics. They're basically brand new, they were bought new, were defective from the factory and were returned. No I got my hands on them.
They all have more or less the same issue - high self noise (wind like noise, pops, crackles, etc...), low output level, distortion, etc..
Are there any known common faults with these mics? Anybody have the schematics for either one?
I don't really even know where to begin troubleshooting.

Best regards
Joel

 

[Khron]

NT1 basically has the Schoeps circuit.

NT2-A's a bit more complicated, though. I can't quite remember where i came across this schematic - might actually be this exact subforum, just a month ago or so.

Noise can come from several sources. Although in these newer SMD circuits, the small ceramic caps can fail - either short, or "just" intermittent.

Last month i revived a Rode NT5 a friend got for dirt cheap at work as faulty, because it was really quiet. Replacing one of the ceramic caps in the capsule bias circuitry brought it back instantly.

A couple years ago, i got a couple of Shure KSM mics as faulty off eBay (a 27 and a 141), with noise symptoms. After replacing all the 68pF and 120pF caps with brand new TDK 120pF caps, all noise was gone.

https://groupdiy.com/index.php?topic=61079.msg773749#msg773749

 

[12AX7]

Thanks for the info!

Which Schoeps circuit does it use? Is it an exact copy or are some of the values changed?

Thanks for the NT2A circuit. Is there a possibility to find the values of the SMD components anywhere?

 

[Gus]

Are the microphones in a high humidity area?

What do you mean by "They're basically brand new"?

Did they work correctly at one time?

What NT1 model is it a NT1a or an older NT1?

 

[Khron]

"Which Schoeps circuit"? I'm only aware of the one. And anyway, not quite sure what it would matter.

At least in the case of the resistors, you could... i dunno... maybe look at the markings on them?
That won't help with the SMD ceramic capacitors in the NT2-A, but most of the values of those aren't all that critical / essential anyway.

 

[12AX7]

The mics were taken out of the box brand new by a customer, were found to be defective from the factory and were returned to the store. At least that's what I was told. Rode replaced them and told the store to bin the mics but I got them from a friend there.

The NT1 is the newest one, the black one with the SMD board.

I'm not sure if the mics were in a humid area. I did notice them forming condensation on the capsules more easily compared to a few others I had, they fogged up real easy with visible droplets and it took a while for them to dry. So I did try drying them. I put them in the oven with the "fan" setting at 50°C for 15min but it did not seem to do a whole lot. Should I leave them in for longer?

I didn't know there was only one Schoeps circuit, thanks for letting me know. I have a few Beag SDCs with Schoeps capsules but have never had any actual Schoeps mics.

The resistors are indeed easy to figure out but the caps were what I wanted to know about. I'll have a closer look at the PCB. The electrolytics in the NT2A are no name garbage, maybe I should check them.
I have a bunch of SMD caps in stock.
Did you measure them out or just replaced them all?

 

[12AX7]

Fixed them!

I've seen a lot of these "wind noise" problem posts about these mics around the internet.

My two NT1 and three NT2A all had the same problem.
The problem is the polarization filter caps, the silver SMD ones.

For the NT1, replace the silver SMD cap next to the yellow wire coming from the capsule. It's the biggest SMD cap in the mic, can't miss it.

For the NT2A, it's the two silver SMD caps right abobe the three wires coming from the capsule.

I'm not sure about the values, all the caps I desoldered measured different, anywhere from 2nf to 150nf since they were all failing anyway. Looking at the Schoeps circuit and other similar circuits I see caps anywhere from 10nf to 220nf used there. I went with 100nf and it seemed to work well.

Two NT2As still have one problem. One side of the capsule sounds duller, like there's a HF rolloff. Anyone familiar with this issue? On these two mics I replaced all the silver SMD caps but it made no difference.

 

[Khron]

Regarding those bigger silver caps - i'm pretty sure those are SMD film caps, so the wonky values may or may not be due to the desoldering process. Still, really interesting that they would fail...

Which side of the NT2-A capsule sounds duller, though?

 

[12AX7]

True, I did try my best to desolder them really quick and at a low temp but they were probably still affected.
Is 100n an okay value to use there?

On one mic it's the front and on the other it's the rear.

 

[charlygrand2013]

Fixed them!

I've seen a lot of these "wind noise" problem posts about these mics around the internet.

My two NT1 and three NT2A all had the same problem.
The problem is the polarization filter caps, the silver SMD ones.

For the NT1, replace the silver SMD cap next to the yellow wire coming from the capsule. It's the biggest SMD cap in the mic, can't miss it.

For the NT2A, it's the two silver SMD caps right abobe the three wires coming from the capsule.

I'm not sure about the values, all the caps I desoldered measured different, anywhere from 2nf to 150nf since they were all failing anyway. Looking at the Schoeps circuit and other similar circuits I see caps anywhere from 10nf to 220nf used there. I went with 100nf and it seemed to work well.

Two NT2As still have one problem. One side of the capsule sounds duller, like there's a HF rolloff. Anyone familiar with this issue? On these two mics I replaced all the silver SMD caps but it made no difference.

Hi.. 4 years later I revive this thread..
as other members know a few days ago I've removed 4 big silver caps from noisy rode nt2a.. cracking noise gone.. but the output now is much lower and there is a constant wind noise... as suggested from a very kind member I've replaced thats huges silver caps with 100nf ceramic ones, the output is lite better now ( not desired) but there still a wind noise (maybe cos I have to increase the imput level... ) and one side of the mic sound diferrent...like you wrote """one side of the capsule sounds duller""" I attach a picture of the original board.. the big ones silver caps tha I've had replaced are in red.. I've marked a silver one that still there's.. (yellow mark ) should I replaced it too ? is silver cap after the transitor...sorry about my English. I'm gonna upload today a pic with replaced ceramic ones.

 

[Khron]

The yellow-circled one is part of the high-pass filter.

 

[charlygrand2013]

UPDATE- solved !!!
Ok. just I got 4 film 100nf caps and replace the ceramic ones.. and voila!!! sound is almost perfect .. I cannot find out a dealer in my country of this film caps but i did take them out from and old unused board. Yes you right the value is 100nf x 100volts.. thanks for all !!!

 

[Khron]

In my NT2-A, one of the film caps failed, even though i would've rather expected the ceramic that's in parallel with it to have failed.