mic modifications

Andybot

Member
Hi,
I was interested in finding out more about mic modification to improve the quality of the mics I have.( cheaper condensers) There seems to be alot of post on this in here but im looking for something that will go through and explain whats going on and what im doing so I can aquire some knowledge on this subject.

Are there any articles or links that are worth reading.
Thx
 
microphone modifying

Hi Marik, thx for replying.
I have two apex mics, the 180 and 435, which im sure can be improved upon.
An oktava mc012 which i might mod for a friend, but ill buy specific mics if i know i can improve then.

It seems to me that i need more 600 dollar mics on a 100 dollar budget so im looking into modifying as a way of having higher quality mics at a lower cost.

Just so you know i do have soldering/tech experience but do not know where or on what to start.

I like tha apex mics, to be honest, and here in canada they are so cheap but
if I could improve the clarity/noise floor then id be very happy with them.


Thx
 
Oktava 012 mods were discussed here a few times. Make a search for 'Oktava mod', or 'Oktava mods', etc.

I have modified quite a few mics, but unfortunately never had chance to work on Apexes. I would think they have very similar schematics to MXLs, or other Chinese stuff. Are yours transformer coupled, or transformerless? Any chance you could "reverse" schematics? If you could post big and clear pics of both sides of PCB, I could do it, when I have time.

As a rule of thumb, the main thing to upgrade is to change cheap caps in signal path, including this from capsule, with good film (I like polypropilene) caps. From capsule you could use polystyrene.

If it is transformer coupled, besides of cap changing, I would suggest relam the trafo with Nickel core. I did it in MXL2001 and Nady, and the sound has improved considerably.
 
Hi Marik,
I will try to track down shematics for either of the apexes. I have the 135 open and it looks transformerless, having said that my cam will yield useless pics for you to get a schematic from, and mine would be my first try at reversing.

So ill look to see if someone else did it .
Thx for the help, A
 
mic modification

Hi,
i did my best to draw out the board.
The red lines are the traces running underneath the board.
Ask for any of the values of the components and ill post them.

Any input on what may be worth upgrading on this apex 180 mic
is appreciatted.
Thx, A
 

Attachments

  • apex180schematic.jpg
    apex180schematic.jpg
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I'm no pro, but I would say start by upgrading C1, C2, C13 to higher-quality caps.
It looks like the circuit may be doing some EQing. You may be able to "shape" the tone to taste by playing slightly with the values of the inductors and caps in the middle section.
Don't do anything until someone more knowlegable says so, though :)
 
mic mods

Thx Bleyrad,
ill wait for more posts before i decide what to do.
I did notice a mistake in my schematic,
the RHS of R6 joins to the LHS of R14 and not to R9 as shown.

I have asked apex for the official schematic but have not heard back yet.

While im here has anyone released any books about mics, how they work and can be modded.
Thx, A
 
Andy,

Could you please check a couple things. Pin 1 (Black wire) should be grounded. I am still not sure about resistors R9, R13, and R14. R9 (it is a HiZ) may be whether grounded, or connected to R13-14 to provide additional bias for an input FET. One of them may be a trim pot (is it square?)

As I suspected, this is a very common schematics, based on Schoeps circuit, and can be found in many microphones, such as MXL603, 990, 991, 1006, 2003, SPA-1, Rode NT2, etc.

Sorry Bleyrad, there is no EQ section, but there is an oscillator to raise capsule bias on transistor T4, and the caps to replace are C13, C3 and C4. Instead of C13 use 820--1000pf polystyrene. I suspect C3 and C4 are 0.22Mf cheap ceramics--use polypropilene 1Mf, instead. If there is room, try even 2.2Mf for better bass performance. If you don't have RF problems, you could try to remove C1 and C2, and put jumpers instead of resistors R1 and R2. Also you can try to replace D1 and D2 with 100K resistors and see if you like it.

These very simple modifications should give you considerable sound improvement. Please report your impressions.

Good luck.
 
Hi Marik,
thx for your reply.

First, yes pin 1 is grounded its just sneaky.

Resistor R9 is large brown oblong with 1 km writen on it. Not a trim pot in sight.

I did mess up the drawing a little around this area and will repost the correction when my scanners working again.

I will post my observations as soon as i can.
Thx again
 
MC012 mods

Andybot:

There is a detailed mMC012 mod article by Scott Dorsey in the September 2003 issue of Recording Magazine. The article addresses mods for noise and frequency response improvements. You can get a legal copy by calling: 303-516-9118.

Paj
8^)
 
mic mods

Hi,
i updated the schematic I did, thx to everyone that replied.

I was wondering about the caps that need replacing, c3, 4 and 13... they look like they were sealed by dipping them in a yellow plastic, is it possible to identify them from this?

Also they have the numbers 224, written on c3 and 4, and 102, written on c13, i know that these are the uF values but could someone explain how tha system works.
Thx
 

Attachments

  • apex180schematic.jpg
    apex180schematic.jpg
    61.6 KB · Views: 365
Andy,

These are very cheap ceramics and SHOULD BE REPLACED. Once again, use 2.2Mf instead of C3-C4.
 
mic mods

Thx Marik,
i normally buy from digi-key but are there other good suppliers of caps for this kind of modification.

Replacing c3 and 4 with a higher value cap, it seems theres a 0.22uF in there rightnow, will have what effect. Im just curious.

Finally, is there any special cap thats good for this and what voltage rating should I be going for.

Thx
 
Andybot said:
Thx Marik,
i normally buy from digi-key but are there other good suppliers of caps for this kind of modification.

Replacing c3 and 4 with a higher value cap, it seems theres a 0.22uF in there rightnow, will have what effect. Im just curious.

Finally, is there any special cap thats good for this and what voltage rating should I be going for.

Thx

Andy,

The 2.2Mf value will improve bass response, lowering the low frequency one oktave down. I like Solen caps, which have very good value for money and are not terribly big. I got them from Antique Electronic Supply (when I lived in Tempe). Google and you will find many suppliers for them. They come in 250V and 630V rating. Use 250V. First, check if they fit, though. Also, I like Kimber Caps a lot, but they are more expensive.
 
mic mods

Thx Marik, I was just driving myself insane searching for suppliers for caps, but now I can relax.
Solens are made up here in canada I think.
Thx for you time, A
 
mic mods

Hi,
im having trouble finding the caps i need in a size that will fit. The mic is oktava size just to give you an idea.

I need 1000pF polystyrene and 1-2.2 uF polypropylene, does anyone have an idea where I may find these in a smaller size.

What type do people use for the oktava mods?

Thx for any replies.
A
 
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