CJ

CMV-563 Transformer
« on: August 10, 2005, 12:28:52 AM »
Props out to the Hitchhiker for flying this classisc out. It be a Neumann-Gefell mic x-former, the real deal Bv 551, yo.
We be takin a look under da hood to see wat makes er tick, no sayin?
It be fifty fingers old,    first try, bi-atch!
Major hi freaks, dig?
It goes like dis:

http://vacuumbrain.com/The_Lab/TA/Neumann/cmv563newm7s.JPG

and den dis:

http://vacuumbrain.com/The_Lab/TA/Neumann/cmv_563.jpg

Here goes the schematic:
(Gus probably has a mod, bet ten smacks)

http://vacuumbrain.com/The_Lab/TA/Neumann/lollipop_schemo.jpg

Parts is parts:

http://vacuumbrain.com/The_Lab/TA/Neumann/lollipop_parts.jpg

Questions?

Stay tuned, cus we gonna sweep it, freak it, B-H it, mag it, and bag it.
If I can't fix it, I can fix it so nobody else can!
Frank's Tube Page: www.mif.pg.gda.pl/homepages/frank/vs.html
Guitar Amps: http://bmamps.com/Tech_sch.html


CJ

CMV-563 Transformer
« Reply #1 on: August 10, 2005, 02:30:19 PM »
Doh, forgot to post a pic of the darn transformer! :oops:

Here ya go. I was messin with installing some Marinair lams  until I saw on the parts list that the core is made of mu metal. It looks dark, like silicon, so I didn't know what was going on. Never seen that lam shape before.



http://vacuumbrain.com/The_Lab/TA/Neumann/cmv_1.jpg

Plastic bobbins used, so this is probably a later model transformer. Nice granular lam stacking. You can almost see the winding struture thru the bobbins.

http://vacuumbrain.com/The_Lab/TA/Neumann/cmv_2.jpg
If I can't fix it, I can fix it so nobody else can!
Frank's Tube Page: www.mif.pg.gda.pl/homepages/frank/vs.html
Guitar Amps: http://bmamps.com/Tech_sch.html

hitchhiker

CMV-563 Transformer
« Reply #2 on: August 10, 2005, 03:05:27 PM »
nice pics cj,  

 the mic ser# this came out of is #8297. Maybe someone would know where to find out the vintage?

Lance

Gus

CMV-563 Transformer
« Reply #3 on: August 10, 2005, 04:45:03 PM »
CJ  

  I heard two cmvs(Daves) and they sounded different.  Both were back to back testing on the same equipment.  I think the sound difference had more to do with the transformers than the rest of the circuit.  We tried some simple things and it seemed to be the transformer more than than the other part of the sound.

  FWIW Dave tried one of my microphone builds and guessed/knew the transformer brand by its "sound" he did not know what was inside the microphone until I opened it.

  I woud like to know what the lam alloy is in a CMV transfomer.  It would be cool to find a DI DC 49% that might fit the coils.

CJ

CMV-563 Transformer
« Reply #4 on: August 10, 2005, 05:30:06 PM »
Hey Gus, can you check the clearance from the transformer to the mic body? I am wondering if some different lams will fit.
If I can't fix it, I can fix it so nobody else can!
Frank's Tube Page: www.mif.pg.gda.pl/homepages/frank/vs.html
Guitar Amps: http://bmamps.com/Tech_sch.html

Gus

CMV-563 Transformer
« Reply #5 on: August 10, 2005, 05:57:34 PM »
CJ that's a question for Dave about the fitting in the body.

  I don't think the lams sound like Mu in other microphone lams I have heard the lams kind of have the same china lam "sound" like less detail more "blur" to the sound.

  When we upped the gain a little the lams sounded better, like maybe operating at a better input signal level for the alloy? used.

soundguy

CMV-563 Transformer
« Reply #6 on: August 10, 2005, 06:44:02 PM »
you pretty much need to make a replacement that is exactly the same size.  The lams just barely touch the inside metal posts and the bobbin has in its smalles place .1" clearance to the outside body.

After screwing with that mic for a while I see no reason not to put a completely different transformer in there so long as it has the same ratio, etc.  I wouldnt put a lot of energy into upgrading the existing transformer design if its easier to just build something from scratch that has the same dimensions.

dave

chips are good with dip...

hitchhiker

CMV-563 Transformer
« Reply #7 on: August 10, 2005, 06:52:15 PM »
Gus,  
  I tested my two CMV's off the same pwr supply with the same M7 capsule and  I couldn't tell them apart. I could hear a small difference between the two power supplies (which read a few volts different).

Lance

Gus

CMV-563 Transformer
« Reply #8 on: August 11, 2005, 08:10:37 AM »
Lance

  I can believe they sounded close.   It might be that different transformers and/or alloy lams were used.  The two I heard on the same power supply and capsule sounded different.

  I could believe a cmv with a good capsule and transformer could sound good.

hitchhiker

CMV-563 Transformer
« Reply #9 on: August 11, 2005, 11:58:52 AM »
Gus,    right you are.  

 Some folks claim the original resistors and caps have lost their true value. I checked my mics and all seemed still correct.

Did you check the component values on Dave's mics?

The mic that I've changed to a Tab transformer is quite a bit better than it was. I think cj's tests will suggest the transformers are a problem.

Lance


CJ

CMV-563 Transformer
« Reply #10 on: August 12, 2005, 12:56:24 AM »
Boy, I don't know. This is one of the cleanest transformers I have tested. After I hooked it up right, that is. I got some bad curves by using the 50 ohm generator into the pri, which was wrong, because of the relatively low dcr/henries which would equate to a fairly low impedance input. After I switched the generator to the secondary and swept it, here is what I got:



Almost like a litz wound API or something.
Flat from 1 hz to 100k hz. Sorry about the small print. The graph goes from 1 hzto 1 meg hz.

Here is the phase angle chart:

http://vacuumbrain.com/The_Lab/TA/Neumann/cmv563_phase.jpg

and here is the current draw, some weird test I started doing:

http://vacuumbrain.com/The_Lab/TA/Neumann/cmv563_current.jpg

here are a couple of 1 khz ringers, no loading:

http://vacuumbrain.com/The_Lab/TA/Neumann/cmv563_1khz_sq.jpg




Here's a B-H:

k
If I can't fix it, I can fix it so nobody else can!
Frank's Tube Page: www.mif.pg.gda.pl/homepages/frank/vs.html
Guitar Amps: http://bmamps.com/Tech_sch.html

soundguy

CMV-563 Transformer
« Reply #11 on: August 12, 2005, 01:04:50 AM »
that picture definitely correlates to the sound of my mic, flat and clean.

dave

chips are good with dip...

CJ

CMV-563 Transformer
« Reply #12 on: August 12, 2005, 01:12:04 AM »
Yeah, I would feel kind of bad ripping this guy apart. You can't get those lams anymore, so even if you had the coil structure, you could not duplicate the core. I think I will try to get the turns via PRR method, and send it back to the Hitchhiker.

OK, I am going to revise the turns ratio to 1:9 after the sweep test.

I am guessing approx 900 turns on the pri and 8100 on the sec, which would mean 450 and 4050 on each bobbin.

Now where's that UTC!

:green:
If I can't fix it, I can fix it so nobody else can!
Frank's Tube Page: www.mif.pg.gda.pl/homepages/frank/vs.html
Guitar Amps: http://bmamps.com/Tech_sch.html

Gus

CMV-563 Transformer
« Reply #13 on: August 12, 2005, 07:50:09 AM »
CJ

   What alloy does the BH curve look like to you?

  Looking at the pictures, the traces that form the the BH curve look thicker than the traces for the other scope pictures, is this something that happens with other transformer BH curves?

   Again the two I heard one had better bass and low mids, and sounded better on male voice than the other.  The graphs and pictures still don't seem to show what I heard in the lows that changed between.

  I can believe the graph in the  highs because an older M7 capsule is not known for extended highs and the capsule might control that more than the transformer.

  This is an interesting mystery the transformers should sound better than I think they do.

hitchhiker

CMV-563 Transformer
« Reply #14 on: August 12, 2005, 12:41:15 PM »
:shock: well I'll be a .....

CJ

CMV-563 Transformer
« Reply #15 on: August 12, 2005, 01:19:55 PM »
Gus, I don't know what alloy, almost looks like straight steel, and took quite a hight level before saturating. I can compute the "A" number from the turns vs inductance to get a rough estimate.

These tests were done unloaded, so maybe when you plug it into something the transformer changes a bit. It looks like from the schamatic that the output connector comes right off the secondary. I doubt that Neumann/Gefell would have put out a POS x-former, considering how much work they put into the capsule, etc.

I can see how the leads could cause trouble, as these are pretty fragile, so maybe check your dcr with the specs that I got.

cj
If I can't fix it, I can fix it so nobody else can!
Frank's Tube Page: www.mif.pg.gda.pl/homepages/frank/vs.html
Guitar Amps: http://bmamps.com/Tech_sch.html

Gus

CMV-563 Transformer
« Reply #16 on: August 12, 2005, 01:36:53 PM »
CJ

The cores did not sound like Mu to me, Si steel would sound better with a higher level signal(cap bypassed cathode R).

Are the windings two or three layers in each bobbin?

did you try the chemical metal test?

soundguy

CMV-563 Transformer
« Reply #17 on: August 13, 2005, 06:34:40 PM »
Quote from: "CJ"
I doubt that Neumann/Gefell would have put out a POS x-former, considering how much work they put into the capsule, etc.


I agree.  I think my problem for my taste has been with the efficiency of that transformer.  Its a very clean sounding mic, that transformer is not adding tons of color and my guess is they worked hard to get it that way.  When you think about the other options available from neumann at the time it makes some sense logically that perhaps they designed this mic to be a the clean sounding model, not everyone at the time was probably hog wild about the blanket over the singer sound that a U47 could often provide.  We are all hog wild over distortion today, but look at fender's design history, in a time when everything you made was a distortion generator everyone it seems, worked hard to get more headroom out of their tube circuits.  This mic has all the plus sides of a U47 but without the blanket of distortion.  Maybe Im reading too much into it, but Id bet anything that the transformer was designed with at least some of that thinking in mind.  I personally would like to install a transformer with more color in there for my taste but I could see a dude recording a jazz record going positively hog wild over this mic stock especially on stuff like pianos and upright basses.  Its a neutral sounding mic.  I want a transformer with a ton of color on the output of mine.

dave

chips are good with dip...


 

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