hejsan

Help, I zapped my AKG D25 transformer (=D12)
« on: May 30, 2008, 02:11:23 PM »
Hi, I was recording the other day and was screwing with the bass response knob on my AKG D25 (which has the same guts as AKG D12)

Anyhoo, the grill fell of and it went zap, I saw a light in the transformer and now it is dead :sad:

I assume I killed the transformer somehow, so the question is how do I replace it?  Does anyone have a fitting transformer laying around?  or maybe a D12 with a dead capsule?

Where would I get a transformer for it?

Would it work if I bypass the transformer, like some sennheiser 421's?

Thanks,
hejsan
Just remember -- if the world didn't suck, we would all fall off.
Quote from: "Butterylicious"


rodabod

Help, I zapped my AKG D25 transformer (=D12)
« Reply #1 on: May 30, 2008, 02:43:03 PM »
Did you have phantom power on?

I'm surprised it has a transformer, but maybe you are right and it uses the same method as the MD421 (magnet next to transformer core).

I think I would try bypassing it if this is easy to see if the capsule still works.
Quote from: tv
punchy fat bastard chip

hejsan

Help, I zapped my AKG D25 transformer (=D12)
« Reply #2 on: May 30, 2008, 02:52:42 PM »
How did I know you would answer :green:  :guinness:
Quote from: "rodabod"
Did you have phantom power on?
Yes..I think..
Quote from: "rodabod"
I'm surprised it has a transformer, but maybe you are right and it uses the same method as the MD421 (magnet next to transformer core).

Well, the bass rolloff switch is a kind of "pull out and turn" thingy that moves pins around so it takes the signal out of different windings, or so it looks to me.

I'll try to take the signal straight out of the capsule. who uses that bass rollof anyway..
You want to know why I was screwing with it? Ok ok, I was on a portable recording session in a summer house and I wired the speakers out of phase :oops: No matter where I placed that mic, I couldn't get a decent oomph out of it so I started fiddling :evil:
I had all the other instruments panned hard left or right so they sounded just fine..
Then one of the guys said: "Wow, when I pan the guitar to the center it totally disapears" Doh!

Are dynamic mics usually just made out of a capsule and some kind of housing? Is there no other circuitry needed for them to work?

Thanks,
hejsan
Just remember -- if the world didn't suck, we would all fall off.
Quote from: "Butterylicious"

Rossi

Help, I zapped my AKG D25 transformer (=D12)
« Reply #3 on: May 31, 2008, 03:28:51 PM »
Some dynamic mics use transformer, others don't. Some use a very low Z capsule and a step up tranformer to get to the nominal 200 ohms setting. Shure SM57/58 comes to mind. Others have a 200-600 ohms capsule - most Beyer mics for instance. Then there are lots of older mics that have a 200ish ohms capsule and use a step up transformer for Hi-Z output. Many older mics  had switchable impedances. The Shure SD565 for instance can be configured hi-Z or lo-Z via a wire bridge.

AKG has service documents for many of their mics on their website. I'm pretty sure you can do just fine without the transformer. That mic was originally designed for singers. You don't need a the extra-gain from the transformer for a kick drum. In fact, you may get better bass response without the transformer. I'm just guessing; I don't have a D25 or D12 in my cabinet. Anyway, just try and see.
"I am not a number, I'm a free man!"
"Hahahahaaaaaa!!!!!"

hejsan

Help, I zapped my AKG D25 transformer (=D12)
« Reply #4 on: June 19, 2008, 12:18:56 PM »
Just an update to let you know that my mic lives again, I just bypassed the transformer.

Thanks for your help.

BTW: Do you recon it will be more sensitive to phantom power on its rails now that it has no transformer isolating it?
Just remember -- if the world didn't suck, we would all fall off.
Quote from: "Butterylicious"

rodabod

Help, I zapped my AKG D25 transformer (=D12)
« Reply #5 on: June 19, 2008, 03:04:36 PM »
Quote from: "hejsan"

BTW: Do you recon it will be more sensitive to phantom power on its rails now that it has no transformer isolating it?


No, not really. It's still just a coil of wire which should not see any DC potential across it. You should be ok. Just wire everything correctly and avoid hot-plugging.
Quote from: tv
punchy fat bastard chip

hejsan

Help, I zapped my AKG D25 transformer (=D12)
« Reply #6 on: June 19, 2008, 04:17:26 PM »
Quote from: "rodabod"
No, not really. It's still just a coil of wire which should not see any DC potential across it. You should be ok. Just wire everything correctly and avoid hot-plugging.

So you mean that it is bad for it to get phantom power? :?:

BTW: I think it sounds better after this "mod", it feels more responsive, but of course I don't have direct comparisons.
Just remember -- if the world didn't suck, we would all fall off.
Quote from: "Butterylicious"

rodabod

Help, I zapped my AKG D25 transformer (=D12)
« Reply #7 on: June 19, 2008, 04:41:33 PM »
Quote from: "hejsan"

So you mean that it is bad for it to get phantom power? :?:


No, it should be ok. As long as the phantom power is applied correctly. Same as with ribbon mics, or any other dynamic mic which doesn't use a transformer (most AKGs and Beyers).
Quote from: tv
punchy fat bastard chip

hejsan

Help, I zapped my AKG D25 transformer (=D12)
« Reply #8 on: June 19, 2008, 05:02:00 PM »
Ok cool, thanks a bunch.  :guinness: hic
Just remember -- if the world didn't suck, we would all fall off.
Quote from: "Butterylicious"

AJMAC

Help, I zapped my AKG D25 transformer (=D12)
« Reply #9 on: June 22, 2008, 02:40:19 AM »
Not to hijack, but this thread got me to thinking about something that has been in the back of my mind for a long time.  As an Intern I remember being told to never ever feed phantom power to an AKG D112.  I never really got a good reason why, other than they could be damaged, and I always wonder specifically why that was, if in fact that was the case at all.  Anybody have an explanation? or did the guy who told me that just not know what he was talking about?


rodabod

Help, I zapped my AKG D25 transformer (=D12)
« Reply #10 on: June 22, 2008, 05:57:07 AM »
Quote from: "AJMAC"
As an Intern I remember being told to never ever feed phantom power to an AKG D112.


If one leg of the phantom power goes to ground then the capsules diaphragm will shoot in one direction and potentially cause damage. Not a problem if things are wired correctly and you don't "hot-plug".
Quote from: tv
punchy fat bastard chip


 

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