SENNHEISER MD421 - Converting to XLR - HELP!

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khstudio

Well-known member
Joined
Dec 27, 2005
Messages
2,116
Location
New Jersey, USA
OK, I have 3 421's, 2 are black = MD421U & the other is an older White/cream colored MD421HL.

Years ago I had a guy convert the old style (small 3 pin/2 position switch = M/S) to an XLR (5 position switch M/S) he ordered it from SENNHEISER.

I just recently noticed it's out of phase. I don't understand what's going on.
There is BLACK, RED & GREEN wires going from the mic to the Jack/Switch...
I found what I thought to be the GND - Black, conected to pin 1 & the plugs case (used ohm meter)

The RED wire was connected to pin 3
The GREEN to pin 2

So I flipped pin 2 & 3/Green & Red & it DIDN'T flip the Phase :shock:
What is happening here :?:

Also, I've read that the HL versions have HI & LOW impedence... Is the impedence tranny built inside the old plug :?:

Here are some pics of what I've got.

Mic-plugs.jpg


Plugs.jpg


Please HELP!

Kevin
 
In the HL / HN models you don't have earth on any of the pins - you had to earth it via the barrel of the Tuchel connector.

The three conductors provided two impedances - high and low. One wire was common, the other two provided either high or low impedance.

I'd attach a multimeter and read what resistances you have amongst these three wires. Write them down, but be careful maybe not to keep the multimeter on too long (I'm nor sure if it is very good for the voice-coil / diaphragm).

I can't see your photos for some reason.

Roddy
 
Rob,
Your exactly the guy I needed :thumb:

I know you know about these things...
Your right about holding the meter on there... I can hear crackling when I test those (also on my newer versions)

Pins 2 & 3 on the old & new ones = aprox 220ohms.

I'm thinking the Tranny for Hi/Low impedence is in the old barrel... not sure though.

I'm about to try flipping them again, I may have put them back in there original spot by mistake. I mean, the mic sounds as good if not better than my newer ones when I flip the phase in my pre's & all that's doing is flipping pins 2 & 3 so it should have worked.

I still would like to learn about these mics a little more if you have any info you can share :wink: PDF, Manual, schemetics (in english) I can't read the damn german ones.

Thanks,
Kevin
 
[quote author="khstudio"]
Pins 2 & 3 on the old & new ones = aprox 220ohms.[/quote]

Sounds good.

I still would like to learn about these mics a little more if you have any info you can share :wink: PDF, Manual, schemetics (in english) I can't read the damn german ones.

Ok, PM me your email address, or I can send them to the GroupDIY Gmail account. The German ones are more fun! :razz:

By the way, I think your website may be down. I can't get those photos, nor your homepage to work.

Roddy
 
Well, I must have been on crack the 1st time I thought I swaped them:roll:

I swaped the wires & it works = in phase. :green:

Rob, The old jack assembly says 421 HL on it. is the tranny in there?

I read somewhere that the newer XLR models (I have a U) don't use the tranny :? ?

Also, my newer "U" models have 3 wires connected to the XLR - Blue, Red & Bare sheild to pin 1... so am I right by connecting the Black to pin 1 on the old one (HL). It sound almost exactly like my new one... actually better.

TRY: www.khstudio.net
 
[quote author="khstudio"]
Rob, The old jack assembly says 421 HL on it. is the tranny in there?

I read somewhere that the newer XLR models (I have a U) don't use the tranny :? ? [/quote]

Well, I heard that Sennheiser got complaints that it wasn't fair to keep the trannys in such confined spaces:

trannygc6.jpg


Seriously though, I think the transformer is inside the barrel.


Also, my newer "U" models have 3 wires connected to the XLR - Blue, Red & Bare sheild to pin 1... so am I right by connecting the Black to pin 1 on the old one (HL). It sound almost exactly like my new one... actually better.

Yes, but make sure that the black wire is just earth - there should be good continuity between this wire and the mesh grill.

The older MD421s cost a lot more to make. Sennheiser changed the design to reduce production costs. The older models used an aluminium voice-coil, whereas the current models use copper. I wonder if the older models have a better transient response?.......


I get this:

There is no website configured at this address.

You are seeing this page because there is nothing configured for the site you have requested. If you think you are seeing this page in error, please contact the site administrator or datacenter responsible for this site.

Roddy
 
[quote author="khstudio"]Thats strange... Can anyone else see my website :?:

Thanks,
Kevin[/quote]

Yep - "site is under construction"

Jakob E.
 
Very strange... some of you can see it & some not.
I don't know.

Thanks for helping out :thumb:

The mic is working fine after flipping pins 2 & 3. I must have soldered them right back to their original spot by mistake... go figure. :mad:

BTW,
For future reference:

OLD SENNHEISER MD421HL (inside wires to XLR)

BLACK - Pin 1 (and mesh grill)
GREEN - Pin 2
RED - Pin 3

Wiring for correct polarity when converting the old SENNHEISER MD421HL (Tuchel - with 2 position switch with HI/LO impedence transformer built in)

- TO -

The newer, XLR - with 5 position switch (NO Transformer)

NOTE: Use an ohm meter to check pins.
Also, the Green & Red wire should show around 220ohms of resistance.
BE CAREFUL NOTE TO LEAVE THE OHM METER CONNECTED TO THE RED & GREEN MIC WIRE TOO LONG - COULD DAMAGE THE MIC.


Kevin
 
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