Microphone design tutorial

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chrissugar

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Joined
Jun 4, 2004
Messages
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Location
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Here are a complete disection of the cheapest microphone made by the famous B company [not the B company that make those crapy things, the other B]
Although it is a "cheap" fet microphone I think it is a nice one.
I always like to disect because you can find some interesting mechanical or electrical design ideas.
Here is the mike:
DSCF6969X.jpg

DSCF6973X.jpg

DSCF6976X.jpg

DSCF6977X.jpg


chrissugar
 
It looks like some holes align from the front to the back on this capsule. Sounds like some mods people were doing on another thread here (I think it was the C800 thread). The remainder of the circuit looks pretty basic.
 
Note the 5 thur holes in the capsule. The VM1 has 10. I have not taken my capsule apart to see what the spacer thickness is. The thur holes and backplate spacer adjust the prox effect nd pattern.

Parts look junker(for the price of this microphone) than the parts used in my VM1. The video of the phantom in a link I posted show a different transformer. That transformer looks small!!



Thats alot of money for a microphone with a transformer that size. The u87 is tiny IMO


Did you get to trace it yet is it a U87 without a feedback filter network and a lower gain fet like a mpsa30. 24 or 33V zener reg like a u87 3.9k source R bypassed with a cap and a 47K in the drain. I am guessing this because the VM1 is basicly a u67 circuit changed to cathode bias without the feedback network and feedback windings on the transformer.

The more I learn about microphones the harder I am on "pro designers" I am less impressed with Brauner as time passes My VM1 sounds good but have you looked at the price? The Soundelux stuff looks cool and the E49 looks like it should take away all of neumanns M149 sales If people have ears. I need to hear one of the E49s i think thats what the M149 should have been like. The M149 recordings I have heard sound good but it is harder to mess up a good capsule grill microphone design with ? circuits IMO.

The fence pipe microphone I built should sound killer when I get my real u87 capsule in the next week or two. Look at the fence post microphone the yellow wires are single point ground and the microphone uses the min parts.

Someone should design a PCB for the pipe microphone Maybe I will hand draw one to fit the china microphone bodys fit a good capsule remove a layer or two of grill mesh in a MXL V67, joemeek 1636 transformer etc.............................................................................
 
Wing c tube in my vm1

I am beginng to think the twist of the k87/67 backplates could be done a little better with a standard not twisted backplates u87 capsule but with bigger bore holes and or a spacer change.

Now I think I understand why SPA posted things about Brauner microphones and neumann in the past. I wonder what microphone manufacters realy understand a condeser microphone. I don't understand all of a condenser yet but I am working on it.

I am not a fan of Rode microphones but I like the ntk electronics 120V lots of headroom etc. (still needs a little help) better than any of the new tube transformerless circuits I have seen of other companys.
 
The board looks like one made with, say, an MG chemical presensitized kit. The board's geometry and manufacturing look fine, but no solder mask or anything like that.

Gus: that sounds pretty serious. Are you planning to get into the mic business?

I thought I was crazy but now I know... :razz: My evap machine should be done in about three weeks. It cost me about $1200. I can load four diaphragms at once. When it's assembled (and if it works) I'll post photos in the appropriate thread.

-Dale
 
Hi Gus

The capacitors are Panasonic FC and Jamicon.
You are right the transformer is small but think about the AKG C12. It is not too big, so it can be done even with small ones.
Here are some pictures of my C12s, look at that transformer:
DSCF6881X.jpg

DSCF6891X.jpg

DSCF6890X.jpg


chrissugar
 
I believe the microphone sounds good.

I have a problem with the price of the unit and some of the parts used. In the USA Brauner stuff goes for alot of money to much for some parts used IMO What was that old Billy Crystal line "It is better to look good than to feel good".

Even if the jamecons are in the power supply section they can affect the sound( all the jamecons I have measured there was not one I liked the measurement of on a lc102). The power supply is part of the circuit. It also looks like some of the high Z connections are on the board for this kind of money whats up with that.

If you want be be considered one of the best microphone company(brauner) you should use the best stuff no matter what Image counts on the inside of your microphone because of the web.

The PCB looks like it does not have plate thurs. The board also looks like you heat it once and the trace lifts, FWIW the traces in my VM1 look like they will lift if I look at them sideways.

The AKG get away with the transformer being small because the circuit use rolls off the lows before you hit the transformer. I have not heard a small transformer I liked as much as a big one. The 1636 is still to small for me but it is what I had the fit in the fence microphone.

To my ears the lower you can go with the capsule circuit high pass freg the More real the microphone can sound, I don't care as much about the highs as I do about the lows.

The the PBC and build inside that microphone is not even up to the build and PCB design of alot of people here.

Its hard to mess up a capsule you have made for you by MBHO.
 
I started to trace the pcb from the pictures. It looks like the transformer to fet? connection is via an electro cap! I don't see any zener it look like this microphone wants exactly 48V and the voltage is divided via resistors! not a good Idea.

I am a apalled by the PCB build It looks like two transistors could this be like a v67,2001 circuit? Is the electro to the transformer 4.7uf?

A good modern mass produced microphone should have a DC to DC converter of some type for the capsule voltage and a regulated supply for the gain stage. this allows one to get some current drive out of the gain stage.

It llooks like you pay alot of money for a body and a capsule made by another company.
 
[quote author="chrissugar"]Hi Gus

You are right the transformer is small but think about the AKG C12. It is not too big, so it can be done even with small ones.
[/quote]

This particular mic is an enigma for me as well as C12A. These both guys (esp. C12) were built against of any ideas about microphone designes. Still they are very fine mics. The only explanation I can find is good grill, good tube, and most of all, good capsule. The last is probably the most important, although it did not help in U47FET...
 
Y'know I keep looking at that mic and thinking how cool the shockmount is... :roll:

Thanks for the inside shots of the C12. I like the build, especially the use of perspex for mounting the components.
 
By the way, if you microphone guys would like to see more disection just give me a sign because I have also Neumann U67, UM57, CMV563, Rode Classic Tube and Bruel&Kjaer mics and capsules.
Also can make macro pics from the C12 if you need detailed pictures.

chrissugar
 
[quote author="chrissugar"]By the way, if you microphone guys would like to see more disection just give me a sign...[/quote]Does this qualify as a sign?
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