Noisy c414 eb p48

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gbruler

Member
Joined
Feb 14, 2015
Messages
24
Hey,
Our C414 has recently started making some weird noise, I'm not sure where to start looking for the source of it. The mic didn't function well for years, until last year my dad replaced most of the capacitors and we bought a capsule from Tim Campbell, and it is our go-to mic for a lot of stuff in our studio, especially on drums overheads and percussion, acoustic guitars and bass cabs. I always put the mic so that I know that the drummer won't hit it, though we did open the mic up and saw that the capsule is a bit dirty (my guess is wood chips from the drum sticks). We tried to replace the capsule with capacitors as Tim suggested in one of the other topics in here, and the noise was quieter, but was not gone completly, so I'm not sure if it really tells us that the capsule is bad. There is noise on all pickup patterns, and it doesn't seem to matter when I play with the switches so my guess here that the switches are fine.
Another thing, it is very hard to check which part causes the noises because the mic is making a lot of noise when it is open!
Here is a clip of the noise we are having, if it helps. Do notice that the gain on the preamp was pretty high so it really picks up the room too, and there is a loud noise somewhere in the middle that I'm pretty sure is not related to the mic.
https://drive.google.com/file/d/0ByyLGJW4qi4eU1pVc3VRLWNmZTg/view?usp=sharing

Thank you
 
Clean the capsule and change output capacitor - for MKT 2-3.3uF - C11 on schematic.
Test all the switches!
Put the pictures of the boards - here i will give you few tips for it.
 
Beyond blowing debris off the membrane with compressed air I would recommend you not try to clean the capsule yourself. If it is a capsule problem you'll most likely  exasperate it with additional moisture, contamination or damage, voiding any warranty.
Clean the PCB thoroughly with alcohol, clean the switches and make sure you connect the mic with a good cable to reliable phantom power.
Using a CK12 capsule to mic a bass/guitar cabinet is never a good idea if you are interested in the longevity of the capsule.
The air pressure slams the membrane against the backplate, damaging it over time.
The sound you posted could only be coming from a capsule because of contamination or moisture.
If it turns out to be the capsule please contact me.
 
Hey thank you guys very much for the advices.
We have tried to blow away the dirt out of the capsule with compressed air, but it didn't really help. It seems like it's all stuck there. My dad has a really gentle brush (for painting) which he suggested we can use but I stopped him to check with you guys if that's something we should do..
We are going to do the PCB cleaning on the weekend, and I hope that will solve it, though I'm starting to think it's the capsule as Tim said.
Tim you said that using a CK12 capsule to mic a bass or guitar cabinet is not a good idea, is it true for the k47 capsule too? (or in my case Thiersch's Blue line?)
Thanks guys
 
Don't use compressed air!!

Here you have my recipe for cleaning capsule from the other topic:

DON'T USE ALCOHOL!!!!!!!!!!
Even a tiny drop!

Clear distilled water only!

If the capsule is so dirty, with alcohol you will take off the gold layer.
No cotton wool also! It's easier to destroy the diaphragm and also it can left fibres which are hard to remove.
Buy cheap, very soft eyeshadow brush - works like a charm!
Prepare two containers of distilled water.
One with water to use for cleaning, second to wash the brush.
Gently moves, don't be afraid to put more water on the surface.
You will need repeat cleaning at least three times.
FIrst put more water on the diaphragm using brush. Wait 2 minutes and try gently to take off the dirt.
Round moves :)
Usual am using one brush for 5 capsules - then go to trash or using for something else.
 
As I said, do not try to clean this capsule if you have never cleaned a capsule before. The noise is most likely not the capsule.  No amount of dirt on a membrane will cause noise by itself, there would have to be dirt from the membrane to the backplate connections and it would have to be conductive (perhaps from salt water of your breath).
Clean everything else first.

As David Bock has posted many times 414 problems very often are caused by bad cables or poor phantom power.
My experience has been that 99% of problems with 414's come from dirty switches and pcb's. You could easily clean all the internals in less than an hour and not risk damaging the capsule.
 
i repaired a similar mic a few years ago
i cleaned the Hiz parts and the SNR improved a lot
you could even change the HiZ resistors if needed

however if the capsule is really the culprit (test with a capacitor in capsule's place), with careful hands, a brass CK12 can be cleaned as the membranes a glued on the peripheral rings.The dismantling is not too risky .After removing all the peripheral screws and removing both diaphragms , you can separate the backplates after noting the initial position.Take car of all the spacers.Then you can clean the membranes inside and outside with distilled water 50% and isopropyl alcohol 50% (don't brush unless needed, just dip).after that you can clean the backplates with the same liquid inside an ultrasonic cleaner (low power). Dry the parts carefully , suck the backplates intensively and  reassemble the capsule : first the diaphragms on the backplates and then the two backplates together .Be careful when you put the diaphrams on the backplates to avoid dust in between.Don't tighten the screw too much : risk to damage the backplates or the screw thread.Use non powdered gloves during all the process.

But if you hesitate, send the capsule to Tim with confidence.

 
I will just mention NEVER, NEVER use alcohol, even diluted on the acrylic parts of a CK12 type capsule. The surface evaporation of the alcohol can cause tensions from machining of the plastic to crack the acrylic. You may get lucky and not cause any problem but the likelyhood of damage is great
 
That's what i often saying also!
Not only CK12 but all the capsules!
Alcohol isn't needed.
Water is enough.
 
Dear Tim,
i never had crackling issues with perspex (red or transparent) and diluted isopropyl alcool ,on vintage AKG/Neumann material.
with only some water, it's hard to dilute the grease responsible for insulation loss.
I use another solvant (freon based) but still often diluted isopropyl alcohol , including with your CT12 .
However the material on your CT12 looks different, is different, and i will take care with it in the futur.
thanks for the information
regards
 
And i had with alcohol on both - Neumann and AKG - this was on the capsules which needed reskin anyway so i tried, because there was nothing left to lose. Also tried on few chinese capsules.
It wasn't even 50/50.
I had no issues with clean distilled water.
 
i've cleaned between 100 and 120 capsules , including a lot of chinese capsules
around 30 with diluted isopropyl alcohol
never had one issue with it
the only problem is the residual dirt after evaporation, but that  can't degrade significantly the capsule performance
that's why i use another solvant but i'd like to keep it for me ...
i hope you can understand
but what kind of issue are you experiencing with diluted alcohol ?
regards
Fred
 
Main problem was that with alcohol (i tried few different) i had little drops in the gold layer - which i never had with water only.
I remeber that one gefell M7 had done very matte - like the alcohol reacted with the whole surface - and it wasn't residual after evaporation.
It's not that i'm totaly against this method - everyone have own.
I had bad experiences with that, have good results with my own method and i think that if someone want to try cleaning for the first time and the capsule is worth more than few bucks - there's more risk to fail.
Before i started serious cleaning i tried many things to learn. Capsules which evidently weren't to repair by cleaning and many chinese capsules which i would not use anyway or were fault.
 
the moot point is to dilute the grease with or without brushing , only a solvent can do it without.
brushing is the most dangerous method on diaphragm , and probably the origin of your gold loss
never had a chemical reaction with pure gold, by definition , can't be oxydized. nor mylar, nor perspex.
your problem was probably a massive residual contamination dirt that reacted with the solvant.
chances that pure water could have clean it , in this case, are minimal.
thus reskin or another solvant...
 
There was no option for gold layer drops due to brushing - believe me.
Most of these capsules were in truly shitty condition - dirty as hell.
Some could have issue with the layer due to storage condition (like a damp basement) but i never had problem, even with these truly dirty bastards (yucky and sticky) using water only. I saved many of great capsules and they work all the time.
I would not say about oxidation  - other thing is that - do the gefell used always pure gold? Even in their hard times?
I don't know - but the capsules from different production years definately sometimes even looks little bit different.
 
Gefell probably used plasticizer for their membranes and you have made a prolonged exposure with alcohol...Perhaps you diluted it.
when i clean with isopropanol , i use very small amounts and short exposure...
 
I certainly second Tim's advise not to try cleaning the capsule.

About the ONLY thing you might try is the ln76d's soft makeup brush used DRY to gently remove loose dust from the diaphragm.

But this is only likely to help on the Neumann centre spot capsules.  It will not affect the noise on a CK12.

The danger with ANY liquid is that it will carry yucky stuff behind the diaphragm.  Then the only cure is to dismantle and clean everything in an ultrasonic bath and probably a new diaphragm.

Dismantling is NOT a trivial task.  David Bock points out that if you can't afford or have the parts to repair stuff when it all goes wrong, you shouldn't even think about doing this.

I suggest you listen to the advice of the commercial mike makers who have done this loadsa times and encountered all the disasters that WILL happen  :eek:

Cleaning the PCB and other bits you should do as a matter of course.  The advice on this so far is good.  Don't forget the connecting leads from capsule to PCB too.

.. $0.02 from dis ex-Calrec mike designer ...  ;)
 
Ln76d,
same for the perspex and alcohol ...no issue with isopropanol short exposure.
Don't know now for CT12 but i remember that Tim's material is thermo - sensible also, i had one time a deformation issue with one CT12 stored near a heat source.the diaphragms were stucked  at power on.
i had to rework the backplates to restore the sound but it can't really be at original specs now, but quite usable.
despite he offered me to change the parts , the result was good enough ...
i now think that his material is perhaps a bit delicate.

ricardo,
we're talking about mic capsules, not nuclear reactors , relax !  8)
Dry cleaning is perhaps more dangerous for the gold sputtering than wet...
if the liquid goes under the membrane with a CK12 (rare unless you cleaned the sides) , don't panic..
CK12 dismantle is not very complex, unless your hands are shaking , but it needs practice , use some chinese capsules first...
with a center terminated capsule, unless the membranes are glued (rare), then you're in trouble before you've even begun !
Neumann capsules K47/49 and K67/870 have a microscopic hole on one side or both , in the non sputtered zone , thus be careful !


 
Dear Fred!

You speculate too much :D
Of course I appreciate your expertise and valuable comments ;)
I used realy small amount of isopropyl - and i wouldn't even think too keep it longer at the surface.
Any kind of liquid except distilled water.
From what i remember it was instantaneously reaction.
Yes it was some kind of dilution - and it was a realy quick reaction.
With the water is different thing - it allows too keep a while on the surface when it's needed but even if - it's short time.
Similar result i had with some chinese k67 - i'm not sure that it wasn't early 797 audio version - it was long time ago.
Here the effect was not so tragic slightly tarnished ring outside center termination.
I fully agree that dry cleaning can be more dangerous.



 

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