dukasound

C800G
« Reply #20 on: June 04, 2004, 04:35:45 PM »
Quote from: "gyraf"
Yes, original C800G uses tube rectifier in PSU.

No, I haven't had time to reverse it, sorry.

Jakob E.


I suppose 6X4 like on C37 ?????


gyraf

C800G
« Reply #21 on: June 04, 2004, 04:40:04 PM »
I haven't checked.

Here's a picture of the powersupply:

http://img56.photobucket.com/albums/v172/gyraf/Sony800G-PSU.jpg

Jakob E.
..note to self: don't let Harman run your company..

Gus

C800G
« Reply #22 on: June 04, 2004, 07:08:03 PM »
Just worked on the PS The resistor between the two cap areas is now 33K.  The zeners are now 3) 75V at 1 watt and a 4.7V at 1 watt for about 233V.

  Good news the microphone is quieter! at the lower voltage.  I might add a few more caps at the last stage of the HV.

  I was suprised the supercaps in the fil supply seem to lower noise.  It seems to me the person that designed the Sony C800G microphone did their homework.  I think they wanted the circuit part to "not be there".  Its a clean circuit with alot of headroom.


  If I was to build it again it would have tube or low switching noise diodes in the PS.  A switch to select the capsule voltage.   And I am thinking of a passive type cooling device.

  I think it is now very close to a DIY project.

  Gus

dukasound

C800G
« Reply #23 on: June 05, 2004, 06:01:57 AM »
Hi Gus
Where can I find supercaps?. On schematic are 0,22F (220000uF?)in series each paralel with 1M resistor?
Did you put supercaps in PSU or in mike?.
Duka

dukasound

C800G
« Reply #24 on: June 05, 2004, 07:15:12 AM »
Hi Gus
I forgot. What wattage is enought if I use one 110V and one 120V zener for 230VDC?.

Gus

C800G
« Reply #25 on: June 05, 2004, 11:47:32 AM »
Dukasound

  the wattage of the zener is a good question.  Zeners in the circuit are shunt regulators.  

  To do the math you need to know the tube circuits current.  Then you need to have a current in the zeners to have them regulate.  

  A simple case you know or guess the total B= current draw will be  say 2ma .002Amps.  I would have about 2 ma or more in the zeners if possable.

Power in watts = current X voltage.  This is only true with a DC circuit.  A tube microphone circuit is close enought for this.

so watt disapation of the zeners will be 110 V X .002Amps for the 110 one and 120V X.002Amps for the 120 one  So about a .25watts for each.

  I would use a 1 watt and leave leads long.  The leads are often copper and help as a heat sink.  I like to have an overbuilt supply.

  Not how do you get the current right?  I measure the last resistor between caps in the power supply voltage drop and calculate the current.
 
  the current = the voltage drop divided by the resistance In the above case you will be looking for about 4 ma.

I posted above some part numbers in mouser and digikey.  for you I would go to the web sites and get the part numbers spec and see if any of them are advailbe from you suppliers.  

PRR or anyone anything else to add?

dukasound

C800G
« Reply #26 on: June 05, 2004, 12:05:24 PM »
Hi Gus
Thanks for answer. I will use 1,4W. Here I can find 0,4W ZF series and 1,4W ZY series. All time I am thinking about tube rectifier. I make a couple amplifiers with tube rectifier. I ask my friend for 6X4 and maybe I will make it. Also I must find transformer with 250V-0-250V, I mean it is enought to have 230VDC.
Duka

Gus

C800G
« Reply #27 on: June 07, 2004, 11:38:28 AM »
I am checking the russian 6au6s I have I just noted something interesting.  One of them has a hexigon printed on the tube.  Is this a factory mark?  It looks like all the other ones.

  Who knows russian tube marks?

Flatpicker

C800G
« Reply #28 on: June 07, 2004, 11:54:58 AM »
Quote from: "Gus"
...Who knows russian tube marks?
Marik. I think he's still honey-mooning though.

Gus

C800G
« Reply #29 on: June 12, 2004, 02:43:16 PM »
I have 3 microphones set up in the basement.  Real VM1 it back together,  C800G type and a cap upgrades 2003.  I returned the U7 I fixed so I did not have it to test.  I have a 103 but the circuit in that seems to have a "grit" added to the sound IMHO so I did not use that.  All three of the microphones have good parts.

That VM1 capsule is like magic.  The next best sounding in the three is the 2003 capsule.  the c800g type now has a capsule from a MXL2001.

There seems to be something in the midrange that sounds more "real" with the vm1 capsule.  The 2003 sounds more like a neumann capsule.

2003 3 micron 797 audio neumann 103 capsule copy?
VM1 6 micron custom MBHO
2001 6 micron ?

  I have a CK12 clone from MBHO that I need to make a mount for, to try it in the sony circuit.

The russion tubes are interesting.  I made a burn in fixture that can run two tubes at a time.  I run the tubes for about 6 hours total at 6.3VDC, 140 V B+, 100K plate, 1K cathode.  After I do that I test them at about 5.5VDC  in the C800G type.  This semms to drop the noise.

  My VM1 and the c800g have about the same noise.

  Anyone have thoughts on why the russian 6au6 noise seems to drop after a "burn it"

  FWIW in a week or so I should have a Rode K2 in to look at and see if there are any inprovements that can be made.  I need to get my nt1000 back so I can take some picture of the part upgrades.


Marik

C800G
« Reply #30 on: June 12, 2004, 03:46:40 PM »
Quote from: "Gus"
I am checking the russian 6au6s I have I just noted something interesting.  One of them has a hexigon printed on the tube.  Is this a factory mark?  It looks like all the other ones.

  Who knows russian tube marks?


Yes Gus, you are right--these logos are factory marks, but I don't know hexigon one. Pentagon means it was made at Novosibirsk factory, FWIW. Try to PM IJR, he might know.
Samar Audio & Microphone Design

www.samaraudiodesign.com

The Art of Ribbon Microphones

ijr

C800G
« Reply #31 on: June 13, 2004, 02:45:23 AM »
Hello Marik!
Great to see you here!
"The ear is the only judge of tonal balance."
Radio Designer's Handbook, 1953, p.632.

Marik

C800G
« Reply #32 on: June 13, 2004, 03:31:39 PM »
Quote from: "ijr"
Hello Marik!
Great to see you here!


Salut Igor!

Yeah, vse dorogi vedut v... kruzhok "umelie ruki"  :grin:
Samar Audio & Microphone Design

www.samaraudiodesign.com

The Art of Ribbon Microphones

BR

C800G
« Reply #33 on: June 13, 2004, 08:38:09 PM »
Hey Guys,
I'm sorry if its a little off topic... but I came across this web site and i was wondering if this tube would be good for a mic body..  I'm thinking about tackling the G7, or maybe a C800.

http://www.kegworks.com/shoppingcart/customer/home.php?cat=324

I couldn't find the wire mesh.. does anybody have a link for that??? (USA)

I also noticed that SamAsh is selling some MXL for $99,  I was wondering if it would be worthed for the body.. I'm not familiar with the body size requirement for both G7 or C800G, but I think it would work.
I think this it is the MXLV67G...

any thoughts???
thanks
Gil

gyraf

C800G
« Reply #34 on: June 14, 2004, 05:53:04 AM »
Hi Gil,

Look in the "META - Microphones" thread for posts relating to DIY-mics:

http://www.groupdiy.com/index.php?topic=256

We try to collect info on a topic-basis like this..

Jakob E.
..note to self: don't let Harman run your company..

Gus

C800G
« Reply #35 on: June 19, 2004, 12:08:13 PM »
Latest news.

   I worked on the capsule.  My VM1 has a 67 type capsule however the backplate is rotated.  If you hold it up to the light you can see 10 spots of light in a 3 by 4 pattern.

  Now what I did to the MXL 1006 capsule I used in the clone.

  The screws at 12 and 6 o clock on the front side and the screws at 3 and 9 o clock on the backside hold the backplates together.

  4 screws hold the capsule to the platic yoke remove the two on the back side plate.

  Now if you rotate the backplate holding the capsule to the light you will see spots of light in different patterns.  I can get the same 10 spots but the screws don't line up.

  I found to MY EARS a pattern I like.  I rotate the backplate clockwise(this is looking at the backplate) 1 screw hole.  So now the backscrews are 1 down from the 3 oclock and one up fron the 9 o clock.

  Stewart has a picture of a taken apart MXL capsule at his site.

  Make sure your hands are clean and steady and the screwdriver fits.  I like to work on capsules on clean paper towels in a tray so I don't lose the screws.

  I debated posting this for a few days.  I think it is a big deal! Its easy to do and you can reverse it if you don't like it.

  I think Tim C understands what is going on.  I think it is mixing the M7 with the k67.

zebra50

C800G
« Reply #36 on: June 19, 2004, 01:00:32 PM »
Gus, this is a very exciting experiment. Are you talking about the single capsule or dual capsule type?
Ribbon microphone services
http://www.xaudia.com
Microphone blog

Gus

C800G
« Reply #37 on: June 19, 2004, 01:45:42 PM »
I have tried to take pictures did not work out.  I am going make a mask and use a backlight and try again.

I did this with the cardiod only capsule.  It should work fine with the multpattern.

This is the 18 screw brass ring china capsule from a MXL 1006.   k67 have less screws.  The soundkings might be the same.

Tim  I think it is different than the hyper cardiod.  I have microphones with pattern adjustment it "seems" to do something different.  It seems to sound different then just adjusting the pattern.

THIS  finding was from looking at the VM1.  I guess Dirk Brauner figured this out on his own.

I hope some people try this and report back.  I am aware that I might have made the capsule worse and am fooling myself because I did this.

Flatpicker

C800G
« Reply #38 on: June 19, 2004, 02:26:13 PM »
Quote from: "Gus"
...I hope some people try this and report back.  I am aware that I might have made the capsule worse and am fooling myself because I did this.
I have too many chores in front of me to get to it this weekend.  :sad:  

I told Marik about it and he said he had actually been considering the same thing - I told him you guys just think too much alike! Anyway, he was going to give it a try, so hopefully he?ll be jumping in shortly...

Marik

C800G
« Reply #39 on: June 20, 2004, 01:39:04 AM »
Quote from: "Flatpicker"
Quote from: "Gus"
...I hope some people try this and report back.  I am aware that I might have made the capsule worse and am fooling myself because I did this.
I have too many chores in front of me to get to it this weekend.  :sad:  

I told Marik about it and he said he had actually been considering the same thing - I told him you guys just think too much alike! Anyway, he was going to give it a try, so hopefully he?ll be jumping in shortly...


Hey guys, sorry couldn't come earlier--had terrible hangover after a bottle of Grey Goose last night--couldn't think whole day.  :cry:
Increase of acoustical resistance flattens the frequency responce of the capsule, but also, increases noise (as a result of acoustical resistance), and reduces sensitivity. The interesting thing is that decrease of acoustical resistance (like in Gus' case), due to less dampening, should boost midrange, and this might be a subjective reason (but also, might be not)why it sounds 'better'. Gus, did you make any frequency response measurements?
I gotta try it myself. I actually was thinking also of playing with different thikness of spacers here.
Samar Audio & Microphone Design

www.samaraudiodesign.com

The Art of Ribbon Microphones


 

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