Real Mic from a Chinese Toy
« on: January 04, 2007, 03:43:31 AM »


The secret is in a good mic transformer...


In brief, I bought cheap mics well made mechanically. Unfortunately, electronics is toyish, for example, pad switch thast is needed to attenuate for less distortions/noises on loud sound sources actually changes bias of the FET increasing both distortions and noises; 80 Hz HPF switch adds 15 times less interstage capacitor rolling of 6 db / oct everything needed and unneeded; output stage is made of 2 emitter followers loaded through cables on 6.8K phantom powering resistors, also 22000 pF caps are connected to output of that emitter distorters that rectifies high end of spectrum and modulates by envelope the entire signal.

What I did,
I used a 15K:150 Ohm tranny, and asymmetrical A class amp with voltage gain=11. The amp consumes 2 mA only, so no noisy RF voltage converter to bias a capsule is needed, also resulting headroom is huge, and THD is very low, and the lower the lower is the signal. I don't need colorations from microphones, so it's internal amp has deep-deep-deep NFB and low gain for medically grade stirilly accurate power amplification with as widest as possible dynamic range.
No more phoney -10dB and 80Hz switches.


PimD

Real Mic from a Chinese Toy
« Reply #1 on: January 04, 2007, 05:09:11 AM »
:green:
Nice.
Just cut out the crap, and put in something good.  :thumb:
What mic is it, and which tranny did you use??

King_Cruiser

Real Mic from a Chinese Toy
« Reply #2 on: January 04, 2007, 05:31:34 AM »
Very nice indeed.

Gus

Real Mic from a Chinese Toy
« Reply #3 on: January 04, 2007, 09:32:29 AM »
I don't believe it if you have the stock SD capsule still in the microphone.

Careful  I believe People take stuff and redesign their products from this sites posts.

SSLtech

Real Mic from a Chinese Toy
« Reply #4 on: January 04, 2007, 10:26:57 AM »
Looks like the MXL 770, doesn't that one have the sub-1" diaphragm?

Of the ones that I've tried, those capsules are the limiting factor; I've given up on them. Tried transformer and transformerless approaches, but replacing the capsule made a VERY big positive improvement.

Metalwork and grille is indeed nice, but the capsule is the crippling handicap, from my experience. it's the massive 'ringing' centered aroung 10kHz which make it completely unusable to me.

If you found that the transformer improved things, just WAIT until you get something like a decent Peluso capsule in there...

Quote from: "Wavebourn"
22000 pF caps

..On your hand-sketch, you appear to show 220,000 pF caps, not 22,000pF...

Keith
"A waist is a terrible thing to mind"
Quote from: PRR
Ah, but that was 1999; we don't party like that any more.

Real Mic from a Chinese Toy
« Reply #5 on: January 04, 2007, 02:34:04 PM »
Quote from: "SSLtech"
Looks like the MXL 770, doesn't that one have the sub-1" diaphragm?


Yes, you are right. It could be bigger. :)
However, it has a peak around 10 kHz, but at least it is not distorted now! :grin:

Quote

Of the ones that I've tried, those capsules are the limiting factor; I've given up on them. Tried transformer and transformerless approaches, but replacing the capsule made a VERY big positive improvement.

Metalwork and grille is indeed nice, but the capsule is the crippling handicap, from my experience. it's the massive 'ringing' centered aroung 10kHz which make it completely unusable to me.

If you found that the transformer improved things, just WAIT until you get something like a decent Peluso capsule in there...


Why to WAIT? I want it now.  :grin:


Quote


Quote from: "Wavebourn"
22000 pF caps

..On your hand-sketch, you appear to show 220,000 pF caps, not 22,000pF...


What you mean is an interstage cap, that 22n are out of the picture, to the right on the sketch.  :wink:

Real Mic from a Chinese Toy
« Reply #6 on: January 04, 2007, 02:44:03 PM »
Quote from: "Gus"
I don't believe it if you have the stock SD capsule still in the microphone.

Careful  I believe People take stuff and redesign their products from this sites posts.


It could be better if they call me and ask to redesign their products. I don't mean the obvious redesign using expensive transformer like any beginner engineer can do, I mean something cheaper, tricky, and interesting.  :wink:

Real Mic from a Chinese Toy
« Reply #7 on: January 04, 2007, 04:14:32 PM »
Quote from: "buttachunk"
:thumb:

do you have a schemo to post ?


Here you go:


Gus

Real Mic from a Chinese Toy
« Reply #8 on: January 04, 2007, 04:48:45 PM »
The china transformerless are often a KIND of clone of a schoeps 1 fet 2 pnp with a DC to Dc converter section.
   Sometimes two 220k s source  to ground and the 1 gig from the junction to the gain instead of a 1 meg pot.  2k or 2.2 k drain and source Rs in the FET phase inverter then two PNP emitter followers with the 6.8K phantom Rs in the preamp as the emitter Rs.

SSLtech

Real Mic from a Chinese Toy
« Reply #9 on: January 04, 2007, 05:02:02 PM »
Quote from: "mediatechnology"
Would like to see what a cheap Chinese mic output topology looks like.

one or two here:

Keith
"A waist is a terrible thing to mind"
Quote from: PRR
Ah, but that was 1999; we don't party like that any more.


Gus

Real Mic from a Chinese Toy
« Reply #10 on: January 04, 2007, 06:04:43 PM »
some are like this
http://www.users.on.net/~effect/RodeNT2tl.pdf

If you look close at the Schoeps schematic  the outputs are matched and the B to C resistors are match and selected for the output pair.

Real Mic from a Chinese Toy
« Reply #11 on: January 04, 2007, 06:30:19 PM »
Quote from: "SSLtech"
Quote from: "mediatechnology"
Would like to see what a cheap Chinese mic output topology looks like.

one or two here:

Keith


Yep, instead of sourcing better transformers than they used before they seems decided to ever more cut costs implementing Shoep's toy.


Quote from: "mediatechnology"
Thanks Gus!

Yes I did notice the matching note. Probably the MXL not so matched.


Why do you think so?



Quote from: "mediatechnology"
Wavebourn: Ref to your picture. Is that a schemo of the previous output stage over the grill's left shoulder?

Do you have a diagram of the orginal? Would like to see what a cheap Chinese mic output topology looks like.


Here you go:


Real Mic from a Chinese Toy
« Reply #12 on: January 04, 2007, 06:57:14 PM »
Quote from: "mediatechnology"
So there are now three implementations of this same circuit. Do you suppose Rode tried to confuse us by drawing it from right to left?  :?


I dunno, but MXL's is indeed Shoep's toy with couple of additional whistles'n bells.

Kingston

Real Mic from a Chinese Toy
« Reply #13 on: January 04, 2007, 06:59:55 PM »
Quote from: "SSLtech"
Of the ones that I've tried, those capsules are the limiting factor; I've given up on them. Tried transformer and transformerless approaches, but replacing the capsule made a VERY big positive improvement.

[snip]

If you found that the transformer improved things, just WAIT until you get something like a decent Peluso capsule in there...


I have a few china mics just aching for a switch of capsules. I'm hesitant to use them anywhere because of the distinctive "china highs". I can tell the capsule is the one major factor in the sound. (a friend even bought me a t-shirt that says 'china sound'. haha...  :oops: )

who sells these peluso capsules? Google was elusive on the topic.

Seems like many people here buy these mics just for the metal work, and replace everything else.

Real Mic from a Chinese Toy
« Reply #14 on: January 04, 2007, 07:07:48 PM »
Quote from: "Kingston"

Seems like many people here buy these mics just for the metal work, and replace everything else.


I saw a decent mic body made from a fencing pole.  :grin:
Send me china capsules, I'll pay you for a shipment. :wink:

But "chinese highs" does not mean just a peak/ringing on highs, it means distorted highs which envelope modulates the rest of the signal. It is the type of distortions that are hard to catch up using ordinary THD measurements, but human ears catch them up well.

Sorr

Real Mic from a Chinese Toy
« Reply #15 on: January 05, 2007, 09:41:13 PM »
Doesnt anybody like 2SK30's anymore?

Real Mic from a Chinese Toy
« Reply #16 on: January 05, 2007, 09:51:01 PM »
Quote from: "Sorr"
Doesnt anybody like 2SK30's anymore?


I pulled up 2sk170 from the original.

Real Mic from a Chinese Toy
« Reply #17 on: February 06, 2007, 01:37:16 PM »
Here is the sample recorded by modified mics
http://wavebourn.com/male_sample.mp3

tablebeast

Real Mic from a Chinese Toy
« Reply #18 on: February 06, 2007, 06:49:48 PM »
Quote from: "Gus"
I don't believe it if you have the stock SD capsule still in the microphone.

Careful  I believe People take stuff and redesign their products from this sites posts.


Damn dude, shut up! Every single time someone tries to mod or tweak a mic that is currently in production you ***** and moan about how crappy the stock capsule is or how you were SOOO wronged by some horrible Chinese monster corporation that raped all your good ideas and left you with nothing. Poor baby. If you aren't going to be supportive or constructive then don't comment. I know this is off topic itself but you put the same off topic post on every single mic mod post and no one ever gives you sh*t about it, Gus. Well I AM! I know you have offered good advice and tips before but if you troll a site like this just waiting to 'warn' people about sharing their mods then you can just keep it to yourself. Why does everything need to be compensated with money? Doesn't it make you feel good that you possibly have improved these sh*tty mics into something more? Isn't the modding some kind of 'democracy in action'? Too much noise and not enough signal, GUS.

Gus

Real Mic from a Chinese Toy
« Reply #19 on: February 06, 2007, 07:03:25 PM »
tablebeast

  Did I say anything about the circuit Wavebourn posted?  I only posted about the capsule side.  Interesting circuit.

tablebeast

  you can think anything you want about me but read my posts carefully.  Did I ever post I was wronged?


 

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