Help me fix my AKG 414 EB

[Silvas]

Hello,

I´m checking this mic...it´s working ok, sounds great, all polar patterns OK, sadly, the capsule is a "teflon" CK12....which i succesfully cleaned and the sound improved quite alot.  I also flipped the capsule. The problem with this mic is the HPF. When off, no problem, but in the 75 and 150 Hz position, the mic hums quite loud...looking at the schemo, it looks like it´s something related to transistor "tr3", which i checked and it was fine, i even changed it...Any ideas?

Thanks so much !

 

[Biasrocks]

It could be a faulty switch. Check C2 and C3 and make sure they are properly grounded, when the switch is engaged.

C2 & C3 increase capacitance to the capsule to provide the -10/-20 pad.

Mark

 

[Rossi]

Faulty switches are frequent with the C414. AFAIK no replacements are available anymore.

To me it looks like a problem with C5 and/or C6. In the off position, the signal goes directly to C7 and the transformer; with the low cut engaged, the signal passes through C5 and C6. Those caps are probably tantals and may have failed by now. In fact, it may be a good idea to exchange all tantals, while you're at it. At least check them all for capacitance and resistance, if you like to keep it as original as possible. Those C414s are a bitch to take apart (I have a C414 EB P48).

 

[maxwall]

Check the tantalum caps out of circuit, all of them. Look for shorts.

 

[Biasrocks]

Faulty switches are frequent with the C414. AFAIK no replacements are available anymore.

To me it looks like a problem with C5 and/or C6. In the off position, the signal goes directly to C7 and the transformer; with the low cut engaged, the signal passes through C5 and C6.

Whoops, should have read the post slower.

C2/C3 control the pad not the bass roll off.

Sorry.

Mark

 

[Silvas]

Thanks so much guys, apparently the tants aren't shorted but it is indeed a good idea to replace them anyway. The switch seems to be working ok, i ohm'd it in every position. I'll keep looking and post my findings.

 

[Silvas]

Solved

it was indeed the damn tantalums...C5 and/or C6, i replaced all tantalums but one. Thanks !

 

[maxwall]

Silvas,

Good to hear that.

Those things give me problems all the time with older gear.

I found the same issue with one KM84 and 414EB mic as well, had the hum.

I have had tants sometimes not short but increase in ESR resistance that sometimes
creates the hum issue. In other words, The bad tant cap's ESR would be higher than one in good condition.
In can go either way with tants, shorts or higher than normal ESR. Both cause problems.

I been told that the tants can fail under operating conditions with voltages applied and be fine when tested out of circuit no voltages applied, but this is seldom the case.

When Tants fail they tend to find paths to ground. Or ground hums

 

[Silvas]

In fact, the tants ohm´d out OK, but obviously they were defective...this was a quick fix, i love old silver 414´s !

 

[maxwall]

Those old silver 414EB CK12 paired with the right tube mic pre eq will yield a very C12 like sound. I've done A/B comparisons and it is very close with a good CK12 of course.

 

[Silvas]

One of my favorite vocal sounds is a silver 414 i have in the studio, coupled with my hamptone style pre with peerless input trafo...pure magic. Mixing engineers love the sound, they´re always like "which mic and pre did you used? sounds gorgeous ! the black 414B-ULS doesn´t come even close IMHO.

 

[Rossi]

Those old silver 414EB CK12 paired with the right tube mic pre eq will yield a very C12 like sound. I've done A/B comparisons and it is very close with a good CK12 of course.

You're talking about the brass capsule version I suppose? I have a black C414EB P48, the one that came between the silver EB and the BULS, and while it sounds good, it doesn't sound particularly exciting on vocals. More like an honest flat type of sound. I do like the pattern consistency and the good off axis response (for an LD mic). I like it as an instrument mic.

Many of the silver EBs have the teflon capsule; the later ones were originally equipped with the (flat response) teflon capsule, and a lot of earlier ones were retrofitted with a teflon capsule if the original brass one had gone bad. Most, if not all, of the black EB P48s had the flat teflon capsule. The BULS, I think, was the first generation that came either with the flat teflon or the HF-boost teflon capsule that was to mimick the brass capsule response.

I never had a silver EB to compare with, but my black EB should sound pretty similar to the later silver EBs with the teflon capsule. What I find a little weird, though, is that the silver EB has a DC converter while the later EB P48 uses a simpler circuit without a DC converter. Yet, despite the lower polarization voltage (about 44V versus 60V), the black EB has better noise specs.

 

[Silvas]

all the silver 414EB i´ve ever used unfortunately were equipped with the teflon capsule...but as long as the sound is satisfying to my ears...who cares? of course i would like to have a brass CK12 equipped mic. Maybe it´s this particular 414EB i like and use, but i love it so much.

 

[maxwall]

Yes,  definitely referring to the brass CK12. P48's have a flatter character but not disappointing at all. The Silver 414EB with brass Ck12 are really colored in a pleasant way.

 

[Rossi]

all the silver 414EB i´ve ever used unfortunately were equipped with the teflon capsule...but as long as the sound is satisfying to my ears...who cares? of course i would like to have a brass CK12 equipped mic. Maybe it´s this particular 414EB i like and use, but i love it so much.

As I said, I like my black EB, too. I just don't use it on vocals much. Most people think of the EB as the best 414 generation. What's interesting is that the (flat) capsule remained the same, so the only thing that really makes a difference is the higher circuit complexity from the BULS onward. The EB has a fairly simple circuit apart from the DC converter. The EB P48 is just a little more complex in the audio circuit (but dropping the DC converter which probably was an economic decision). After that the audio circuit became more and more complex and probably more linear. But linear, it seems, is not what people want.

I also have a C422, which is a stereo C414 EB, but I haven't fully restored it yet. I bought it used without the remote control and built a remote control that kind of works but not as well as it should. The problem is that this particular C422 was modified with a different plug, so the normal S42 remote wouldn't work even if I could find one. So, while it doesn't work fully to its original specs, first impressions are very favorable. I didn't  think a LD mic could have such even patterns. The stereo image is very dimensional. Which is to say, the flat response teflon capsule is not so bad at all, it's just very different from the brass capsule sound. I'm not so sure about the later HF-boost teflon capsule variation. That one doesn't appeal to me much as it is neither as tasty as the brass capsule nor as linear as the flat response teflon capsule. But who knows, maybe it would sound nice with a simpler circuit?

 

[e.oelberg]

I have two black EB with a Teflon capsule, I swaped one of the teflons for a Campbell CK12, was quite interesting.
I found the teflon to be more close to the source, but also a bit boring. The brass CK12 is strong colored and  there are situation I'd prefer the flat teflon, In the mix though the brass ck12 wins, it's also much easier to EQ.

nicholas

 

[Trosky]

Hi, I have a Akg C414eb P48. I would like to use it with the slate VMS emulation. So there is a EQ correction that could I apply for one of the pattern and get a complete flat response?. And which pattern is the more flat on this mic.

Thank you

Regards!

 

[gyraf]

Copy of an old GS post.

Trosky, are you real or Bot?

/Jakob E.