Topic: Matching Ohms

[spyder9]

I just purchased an AKG C568Eb shotgun mic to add to the one I've had.  Not realizing it until the mic arrived that each mic has a difference impedance.  1 is rated for 200 ohms and the other is rated for 600 ohms.  Obviously, the 200 ohm is the older one, though they look exactly the same.  I use a PS-2 to power them.  Will I have any issues with the different impedance?

I have done I test run with my stereo system cranked.  The mics seems to be off around 1 - 2 decibes from each other, which is very good.  Do you think its worth it to have it sent in so they have matching impedance?

Thank you.

   

[spyder9]

I posted this on AKG's website in their microphone forum.  I guess they came out w/ a change on these in 1988.  Specs on the 2 C568EB mics

C568EB (A) (circa 1987 or older)

200 ohms, 128db SPL, 8 mav/p sensitivity, and 1% distortion

C568EB (B) (circa 1988 or newer)

600 ohms, 128db SPL, 11 mav/p sensitivity, and .5% distortion

The C568EB (B) imcreased sensitivity and reduced distortion.  Chime in if this info helps.

[Chuck]

I posted this on AKG's website in their microphone forum.  I guess they came out w/ a change on these in 1988.  Specs on the 2 C568EB mics

C568EB (A) (circa 1987 or older)

200 ohms, 128db SPL, 8 mav/p sensitivity, and 1% distortion

C568EB (B) (circa 1988 or newer)

600 ohms, 128db SPL, 11 mav/p sensitivity, and .5% distortion

The C568EB (B) imcreased sensitivity and reduced distortion.  Chime in if this info helps.

They both have different output levels according to the sensitivity specs. I'd be willing to bet that they sound a bit different too.

[spyder9]

The output difference is about 2 decibels.  Which I can live with.  In terms of sounding different, I can't tell.  I've switched my canalphones from ear to ear.  And that's squinting.

Maybe a little bit distortion wise, but I think that was all in my mind.  I did my test w/ the Who 9/28/02 Toronto SBD.  Maybe that was a poor choice for the test.  The Who is all about distortion.

Another concern is will the different impedance suck my the battery dry on the PS-2.  I'm gonna find out that tomorrow night when I tape my friend's band.

They are sweet sounding mics.  The directivity is amazing on them.

[spyder9]

Got my answer from Mark Zucha AKG-USA.  Below are the emails for those interested.  Gonna give these mics are run tomorrow.  Can't wait.



Dan,

 I believe that the 200 ohm version is the original C568B made from 1980
 to 1984 and was superceded by the 600 ohm C568EB.  The slight difference
 in sensitivity should be the only difference in performance between them.
 
The current C568B replaced the -EB a couple years ago and only differs
in housing color.  It is now matte grey instead of black.
 
Mark Zucha
Technical Services Rep.
AKG, USA



From: Dan Nolan [mailto:dnolanjr@yahoo.com]
Sent: Friday, November 19, 2004 1:58 PM
To: Zucha, Mark
Subject: RE: C568EB shotgun

Hi Mark,

Thanks for the fast reply.

So I should be OK for using them as a tandem for
recording my friend's band?  I can always adjust the
decibels during mastering later.  I use Adobe Audition
1.5.

Also, will there be an abnormal power drain on my
Denecke PS-2 phantom power, because of the different
impedance when they are run tandem?


Thank you,

Dan



Dan,

You should be good to go.  The difference in current draw is negligible,
possibly as little as 0.5 mA. 

Just balance the levels at the mixer input or later during mixing and
you should have no problem using them as a pair.

Mark Zucha
AKG, USA
 

[jk labs]

I just purchased an AKG C568Eb shotgun mic to add to the one I've had.  Not realizing it until the mic arrived that each mic has a difference impedance.  1 is rated for 200 ohms and the other is rated for 600 ohms.  Obviously, the 200 ohm is the older one, though they look exactly the same.  I use a PS-2 to power them.  Will I have any issues with the different impedance?

I have done I test run with my stereo system cranked.  The mics seems to be off around 1 - 2 decibes from each other, which is very good.  Do you think its worth it to have it sent in so they have matching impedance?

Thank you.
   

One could speculate, from what you write, that the two mics differ in their electronics. Especially the part that forces the audio signal onto the mic cable. This will have no practical consequence for hookup and use.

The power drawn from the phantom supply is of the order 2 mA and so battery drain becomes a non-issue as well.  

It could very well be that most of the sonic signature of this family of mic lies in the acoustic properties of the tube and the diaphragm itself. I.e. there is no apriori reason to think the electronics impacts much of a sonic difference at all. (On the other hand the newer mic might be of a totally different design). Your testing so far seems to indicate the differences between the two versions are modest.

Regards
Jon

[spyder9]

Thanks Jon.  The physical design are exactly the same.  The only way I can tell any difference is the print on the bottom of each (200 ohms/600ohms).  Also, they seemed to have changed the switch on the bass roll off.  Newer one has a white switch on a red board.   And the older one has a black switch on a green board.  Another guy on the AKG Forum posted that the newer C568EB had its transformer tweeked.  That's it.  They didn't mess with anything else.  Both of my mics have the exact same bass rolloff, case design, xlr connector, and capsule.   Exact. 

[Chuck]

Thanks Jon.  The physical design are exactly the same.  The only way I can tell any difference is the print on the bottom of each (200 ohms/600ohms).  Also, they seemed to have changed the switch on the bass roll off.  Newer one has a white switch on a red board.   And the older one has a black switch on a green board.  Another guy on the AKG Forum posted that the newer C568EB had its transformer tweeked.  That's it.  They didn't mess with anything else.  Both of my mics have the exact same bass rolloff, case design, xlr connector, and capsule.   Exact. 

It sounds like you're good to go then...

[jk labs]

Thanks Jon.  The physical design are exactly the same.  The only way I can tell any difference is the print on the bottom of each (200 ohms/600ohms).  Also, they seemed to have changed the switch on the bass roll off.  Newer one has a white switch on a red board.   And the older one has a black switch on a green board.  Another guy on the AKG Forum posted that the newer C568EB had its transformer tweeked.  That's it.  They didn't mess with anything else.  Both of my mics have the exact same bass rolloff, case design, xlr connector, and capsule.   Exact. 

Interesting! So AKG might just have put some more windings on the secondary of the transformer:
This could explain the increase in dB (assuming it's in favor of the new mic  ) signal out from the mic
with the tradeoff that the new mic is less suited for delivering current into 200 ohms loads.  

[spyder9]

Exactly!  Ohms and sensitivity impacted only.  Like I said, I was squinting to tell the difference in sound.  If you were going to pick, the 200 or the 600, which one would you keep?  Like most of our fellow tapers, I'm anal and will eventually match the mics by Ohms.  In the mean time, I will be taping with these puppies until another one pops up. 

The 200 is complete, with original box, case, and instructions.,  I don't have the original mic clip, but I would include the H40 clip.  The 600 is mic only.  Not selling yet, but probably will later down the road. 

[spyder9]

It sounds like you're good to go then...

Yep, thanks calico.

[jk labs]

Exactly!  Ohms and sensitivity impacted only.  Like I said, I was squinting to tell the difference in sound.  If you were going to pick, the 200 or the 600, which one would you keep?  Like most of our fellow tapers, I'm anal and will eventually match the mics by Ohms.  In the mean time, I will be taping with these puppies until another one pops up. 

The 200 is complete, with original box, case, and instructions.,  I don't have the original mic clip, but I would include the H40 clip.  The 600 is mic only.  Not selling yet, but probably will later down the road. 

Personally I'd expect the physical properties of the two diaphragms (made a decade apart?) to differ way more than the electrical properties of the two transformers....

But I never speak of such issues as I don't want to cause anybody to loose sleep .... 

[johnw]

N ot sure how anal you are, but there is a new one on Ebay right now for $320 BIN or $250 with 0 bids. Ends in 3 days. Not affiliated, just trying to be helpful.

[spyder9]

T+ thanks!