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 Post subject: A new large diaphragm mikes from MXL v67g
PostPosted: Fri Mar 18, 2011 7:38 pm 
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Шаман, типа...

Joined: Tue Feb 10, 2004 12:30 pm
Posts: 7312
Location: Pleasant Hill, California
Today I bought a pair of donors for my new microphones. Previous pair I made using MXL 770 donors.

This microphones look more elegant, have wider frequency response, and a transformer inside.

Image

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А женщина даже в мужской рубашке выглядит гораздо приличнее, чем мужчина в женских колготках! Be-be-be!


 
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 Post subject: Re: A new large diaphragm mikes from MXL v67g
PostPosted: Fri Mar 18, 2011 7:49 pm 
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Шаман, типа...

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It has 2 printed circuit boards inside. One for an amplifier, another for phantom power resistors and RF filter. God knows what is that filter for. I suspect, it was used in some previous model that had a voltage converter for capsule polarization.


Image


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А женщина даже в мужской рубашке выглядит гораздо приличнее, чем мужчина в женских колготках! Be-be-be!


 
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 Post subject: Re: A new large diaphragm mikes from MXL v67g
PostPosted: Fri Mar 18, 2011 7:50 pm 
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Шаман, типа...

Joined: Tue Feb 10, 2004 12:30 pm
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Location: Pleasant Hill, California
It has a transformer, 2:1


Image

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А женщина даже в мужской рубашке выглядит гораздо приличнее, чем мужчина в женских колготках! Be-be-be!


 
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 Post subject: Re: A new large diaphragm mikes from MXL v67g
PostPosted: Fri Mar 18, 2011 7:52 pm 
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Шаман, типа...

Joined: Tue Feb 10, 2004 12:30 pm
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Location: Pleasant Hill, California
Here is schematic available from online forums, I copied it from gearslutz.com


Attachments:
MXL-V67 (jpeg).JPG
MXL-V67 (jpeg).JPG [ 157.62 KB | Viewed 19619 times ]

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А женщина даже в мужской рубашке выглядит гораздо приличнее, чем мужчина в женских колготках! Be-be-be!
 
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 Post subject: Re: A new large diaphragm mikes from MXL v67g
PostPosted: Fri Mar 18, 2011 8:05 pm 
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Шаман, типа...

Joined: Tue Feb 10, 2004 12:30 pm
Posts: 7312
Location: Pleasant Hill, California
Wein bridge has poles on frequencies:

2162.4 Hz for 0.01 uF and 7.36k, and 723 Hz for 1 megaOhm and 220 pF. Looks weird...

For 10 nF and 1 megaOhm corner frequency is 15 Hz;
for 220 pF and 7.36kOhm it is 98 kHz.

Do you understand anything? I don't...

At least, it is a negative feedback in the whole audio frequency band, through voltage divider 1:136

I doubt that the JFET stage loaded on 20 kOhm, and with 5.7K in source has a voltage gain even close to this range. It can't be more than 20/5.7=3.5 only. That negative feedback is useless, at least. Wink

Wait, I forgot about phase shift of C5 and R17 (470 nF and 330 KOhm). It's corner frequency is 1 Hz. Too low to be considered as a part of an equalization network. It is just a capsule polarization voltage path with a negative feedback (useless one!) added.

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А женщина даже в мужской рубашке выглядит гораздо приличнее, чем мужчина в женских колготках! Be-be-be!


 
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 Post subject: Re: A new large diaphragm mikes from MXL v67g
PostPosted: Sat Mar 19, 2011 8:06 pm 
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Joined: Wed Oct 01, 2008 9:14 am
Posts: 41
Location: Denmark
Well, strange thing is you can sort of see what the designer was thinking (not that I am any kind of mic expert, mind. Wink )

If we temporarily 'forget' the second buffer stage, and R8 in particular, then it kind of makes sense. Then the gain would be roughly R17/R6, or 92 times. (R7 is bypassed by C4, so it doesn't contribute to the gain.) Then he added the second buffer, and forgot about the added load, killing the gain of the FET. Maybe the FB network, assuming it had done anything, was there to give some 'tube sound'...? Cool

Hope we get to see more details about this project as it progresses.


 
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 Post subject: Re: A new large diaphragm mikes from MXL v67g
PostPosted: Sat Mar 19, 2011 9:17 pm 
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Шаман, типа...

Joined: Tue Feb 10, 2004 12:30 pm
Posts: 7312
Location: Pleasant Hill, California
No, it can't be R17, since it is loaded on R8. R17 supplies polarization voltage to the condenser microphone capsule. Odd things looks like remains of some prototype that was gradually turned into another thing by people who did not understand what they were doing. No other logical explanation.

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А женщина даже в мужской рубашке выглядит гораздо приличнее, чем мужчина в женских колготках! Be-be-be!


 
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 Post subject: Re: A new large diaphragm mikes from MXL v67g
PostPosted: Mon Mar 21, 2011 9:16 am 
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Шаман, типа...

Joined: Tue Feb 10, 2004 12:30 pm
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Location: Pleasant Hill, California
By the way, I've found a source of this mystery R-C arrangement: in Neumann u87 it was used as a calibration signal input, for testing purpose. It was used as well as a kind of pop - filter when R2 is connected in parallel with R8: feedback in Neumann u87 is deeper, since R12 is 47K, and no source degradation like R6 in MXL.
So, it is odd here.

Even if to leave this calibration arrangement as is, MXL V67 does not have polarity switch, so R4 and C2 can be discarded: no DC on membrane. Another option is to discard that calibration input arrangement instead, to ground the stator and rearrange R4 to polarization voltage instead of to the ground: ground on stator would prevent dust and moisture attraction by it. Now it attracts dust and moisture because it has polarization voltage on it, that shortens life of the capsule.


Attachments:
u87sch.gif
u87sch.gif [ 158.47 KB | Viewed 18367 times ]

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А женщина даже в мужской рубашке выглядит гораздо приличнее, чем мужчина в женских колготках! Be-be-be!
 
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 Post subject: Re: A new large diaphragm mikes from MXL v67g
PostPosted: Tue Mar 22, 2011 8:58 pm 
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Шаман, типа...

Joined: Tue Feb 10, 2004 12:30 pm
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Location: Pleasant Hill, California
I tried to discuss this matter on Gearslutz forum and suddenly realized that I stepped on a religious territory hurting feelings of many people: microphone modders and proud owners of modded microphones, plus many of wannabees. It is not just a business, it is more like a religious sect... But since this particular forum is free from political and religious propaganda, I am going to continue this topic: my goal is to design what is capable to capture sounds clean and realistic, with minimum of audible distortions of any kind. And I want it to be optimal: good things not necessary have to require lots of resources to exist.

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А женщина даже в мужской рубашке выглядит гораздо приличнее, чем мужчина в женских колготках! Be-be-be!


 
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 Post subject: Re: A new large diaphragm mikes from MXL v67g
PostPosted: Wed Mar 23, 2011 3:26 am 
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Posts: 238
Smile

That's why I love to hang out here... now I wish I can learn more Russian.


 
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 Post subject: Re: A new large diaphragm mikes from MXL v67g
PostPosted: Thu Mar 24, 2011 12:20 pm 
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Joined: Wed Oct 01, 2008 9:14 am
Posts: 41
Location: Denmark
So basically the people you consulted were unhappy that you pointed out the MXL is an ignorant copy of a 40 year old Neumann design? Very Happy

Very much looking forward to your ministrations, Anatoliy. Always wanted to see how this is 'supposed to be done'. Will there by any chance be vacuum state technology from Russia involved? Pray

....

Coincidentally I just saw parts of a show on Discovery Channel called 'How It Is Made', where they showed how Neumann, Berlin made their modern microphones. Those people are certainly not fooling around, hard to put a finger on anything they do to make those...


 
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 Post subject: Re: A new large diaphragm mikes from MXL v67g
PostPosted: Thu Mar 24, 2011 12:41 pm 
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Шаман, типа...

Joined: Tue Feb 10, 2004 12:30 pm
Posts: 7312
Location: Pleasant Hill, California
Knarf wrote:
So basically the people you consulted were unhappy that you pointed out the MXL is an ignorant copy of a 40 year old Neumann design? Very Happy


Well put, Knarf, about ignorant copy! Applause

Quote:
Very much looking forward to your ministrations, Anatoliy. Always wanted to see how this is 'supposed to be done'. Will there by any chance be vacuum state technology from Russia involved? Pray


Vacuum state technology will be involved in the mike made of MXL-990. This one (v67g) will use FET input.


Quote:
Coincidentally I just saw parts of a show on Discovery Channel called 'How It Is Made', where they showed how Neumann, Berlin made their modern microphones. Those people are certainly not fooling around, hard to put a finger on anything they do to make those...


Germans are very thorough when working with precision instruments.

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А женщина даже в мужской рубашке выглядит гораздо приличнее, чем мужчина в женских колготках! Be-be-be!


 
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 Post subject: Re: A new large diaphragm mikes from MXL v67g
PostPosted: Tue Apr 05, 2011 2:52 am 
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Joined: Fri Mar 19, 2010 8:59 am
Posts: 21
Saw that chapter too... can provide a link for you to download if interested. (love How It's Made).

Funny how people take pragmatic approaches in search of clearing things out like personal/religious offense, specially given you're sharing that for all to improve!

I'm afraid lots of people in the audio world want to believe in "magic" as the reason for certain equipment sounding "special". That applies very specifically to musicians and I can understand them, but not in an AE.

I wonder if just like a SE circuit can be tweaked out to an specific OPT, in this case it can be tweaked for the cleanest, more natural response for this diapraghm. Guess you're looking for the most neutral response.

I was also taught in that school, one can always add "presence" or warmth later. Record it the cleanest and flattest, spice it up later. Keeps everything more controllable.


 
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 Post subject: Re: A new large diaphragm mikes from MXL v67g
PostPosted: Tue Apr 05, 2011 9:52 am 
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Шаман, типа...

Joined: Tue Feb 10, 2004 12:30 pm
Posts: 7312
Location: Pleasant Hill, California
Some people believe if they use microphones used by Frank Sinatra they would be populsr like Sinatra. Or, if they use guitar & amp like Richard Blackmore, they would be popular like him. That's why AEs ty to collect some specific gear, to attract customers.

_________________
А женщина даже в мужской рубашке выглядит гораздо приличнее, чем мужчина в женских колготках! Be-be-be!


 
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