Apex 460 mod with some Telefunken ELA M 251 influences

[Tim Campbell]

I don't know why you suspect the capsule. This capsule has no weird peak or resonance.
Here's a similar problem fixed from another customer who had a similar resonance:

"When I disassembled  the Tuchel connectors and such- on the night before I was to
send you the Capsule,

I was amazed to find a dislodged ground wire  -and a second wire that may have been
broken during the process

of testing.

After  re- soldering and raising your capsule high into the Basket, I was able to
truly hear your  CK12  for the first time.

And  as I suspected,...it is a - work of Love. The 'growling ' sound went away...as
did the big peak at 5300hz."

Perhaps a microphonic tube , the capsule mount being a little loose. A weird peak in the capsule would show up whenever you played notes in that range into the capsule.

You could try replacing the capsule with an 80pf capcitor and see if the resonance is still there.

 

[grantlack]

you can swap for a different tube in case the current one is microphonic.  to rule out mechanical, try wrapping the rails in weatherstripping or some such foam so that they're making constant contact with the body tube.  that should get you started on damping body resonance if that's your gremlin.

 

[david-p]

you can swap for a different tube in case the current one is microphonic.  to rule out mechanical, try wrapping the rails in weatherstripping or some such foam so that they're making constant contact with the body tube.  that should get you started on damping body resonance if that's your gremlin.

If the tube is microphonic, you will hear the resonance by tapping the mic body.

David

 

[saxmonster]

Ok so I replaced the nos tube with the original 12ax7b tube that came with it and the resonance went away.  I put back in the nos 6072 5 star and the resonance is still gone.  Something inside must have not been sitting right or out of alignment.  I now have the nos in and I removed one of the 1.0u wima caps.  I don't notice a difference but maybe that cap was putting stress on the mic casing and something to that effect.  Everything is great now and the mod is complete.  This thing sounds great.  Sorry Tim for thinking it might be the capsule but I had not other idea of what it could be.  The capsule is very delicate and I though I might have done something wrong with it even though I was very careful and doubled and tripled check my moves before I actually did anything.

Thanks guys for a great mod.   

 

[saxmonster]

How good is the 7 pin xlr mic cable that comes with the apex?  Should i build my own redco one or is their another company I should look at?  Is there a wire diagram for it, cause I can't get the ends off of the apex one cause the screws are in so tight and the flat heads are wearing the top of the screw out.  any idea?

Thanks
-Scott

 

[illacov]

Redco or Gotham FTW.

Peace
Illumination

 

[wave]

I got some Gotham from Redco for my MK47 and I must say, it's very nice cable. The internal wires are very nice and the external jacket is very supple. It's easy to work with too.

Dave

 

[saxmonster]

Thanks for the info guys,  should I make my own and save the $25+ or order everything separately and build myself?  I think i know the answer, ahahhah.  Anything I should look out for?  I have built a few mic cables over the years but not a 7 pin xlr.  I think I will go with the gotham.  Thanks again.

-Scott

 

[saxmonster]

Ok I got the redco cable, there are two thicker wires inside 20awg and the other 5 are 26awg.  I was thinking about attaching the 20awg to pins 1 and 3 of the 7 pin xlr connectors.  They would carry the higher vdc right?  What do you guys think I should do?

-Thanks
Scott

 

[HellfireStudios]

Yes, you would want the high voltage polarization leads to be the thicker ones. As far as the other leads go, if there are twisted pairs within the cable, one pair of them should be used for the transformer/signal out. The rest of the color-coding/wiring is up to you (just make sure you stay consistent at both ends of the cable).
Gotham cable is great. You will love it.

-James-

 

[dmp]

You would want the heavier gauge wires for high current, not high voltage.
I would suggest using the 20 awg pair for the heater voltage and ground.

The mogami tube mic cable, for instance, is shown to have the heavier gauge for heaters on the spec sheet:
http://www.mogamicable.com/category/bulk/microphone/tube/

I have used both the mogami and the gotham for tube mic cables. The Gotham is not as flexible - the mogami is terrific in use. But the mogami only has 6 conductors. If you want 7, the Gotham is needed.

 

[david-p]

You would want the heavier gauge wires for high current, not high voltage.
I would suggest using the 20 awg pair for the heater voltage and ground.

The mogami tube mic cable, for instance, is shown to have the heavier gauge for heaters on the spec sheet:
http://www.mogamicable.com/category/bulk/microphone/tube/

I have used both the mogami and the gotham for tube mic cables. The Gotham is not as flexible - the mogami is terrific in use. But the mogami only has 6 conductors. If you want 7, the Gotham is needed.

This is all true.  I was very disappointed, and still am, that the Gotham cable is so inflexible: it does not coil easily.  I got it for the 7 conductors, though I think I shall investigate the Mogami 6 conductor cable next time.

Having written that, I must record that the voltage drops in 30ft of the Gotham cable are really insignificant and the cable is quiet when moved.

David

 

[saxmonster]

Hi Guys,

I actually got the redco brand

REDCO TGS-M7

http://www.redco.com/shopexd.asp?id=3066&bc=no

Because it has the 7 wires. But turns out I can use 6 because pins 4 and 7 are both ground.  Live and learn.

As it is hooked up now the wire is very clean and crisp.  Coils up easily to but its only 15-feet.


As David said and after reading the mogami specs I will change it and use the thicker wires on the heater and grounds.  Pins 4 and 7 are grounds.  What is the best way to use the 2nd thicker wire for both pins? I guess I will attach it to pin 4 and jumper with a short piece to pin 7.  Does that work?

 

[david-p]

Hi Guys,

I actually got the redco brand

REDCO TGS-M7

http://www.redco.com/shopexd.asp?id=3066&bc=no

Because it has the 7 wires. But turns out I can use 6 because pins 4 and 7 are both ground.  Live and learn.

As it is hooked up now the wire is very clean and crisp.  Coils up easily to but its only 15-feet.


As David said and after reading the mogami specs I will change it and use the thicker wires on the heater and grounds.  Pins 4 and 7 are grounds.  What is the best way to use the 2nd thicker wire for both pins? I guess I will attach it to pin 4 and jumper with a short piece to pin 7.  Does that work?

I havent tried Redco, but the length is not the issue. The Gotham wire is just stiff in comparison with what Neumann and AKG supplied.

The thichker wires are intended for the high current supply.  I use both the thick wires for the heater current, coming and going.  Thus one of them is a duplicate ground, but the theory is that it isolates the dc and signal returns which have a separate ground return. Pin 7 in the Binder connector mates first, thus it should be the dc power ground.

David

 

[saxmonster]

Thanks Dave,
So pins 2 and 7 will have the thicker wires, now where is my de-soldering sucker, hahaha.

Thanks again
-Scott

 

[saxmonster]

Ok Guys,
I really didn't care for the mods I did on this mic.  I mean it just sounded ok, kinda lack luster so I wanted to step it up another notch.  I wanted a better mic.  So from reading other posts and forums I came across jjaudio.  I heard some demos of the dutch and was just wowed.  I heard the singer singing amazing grace and the tenor sax demos and was just like I have to get this done.  It was right up my alley.  I emailed jjaudio just to see if they would even do it since I had done so much to it already and I was in luck.  I sent it out and it was done and back to my house in no time.  I was expecting a huge wait period but man these folks rock..  All I can say is this mic is killing now.  I went with the Dutch 251 circuit and I am so glade I did.  I went with the works with vintage resistor and PIO caps, silver plated copper wire, etc.  Man it just looks vintage, ahhaha.  Its sounds so good.  Jim also redid the power supply as I was not going to do that myself.  I did learn a lot doing this project but it was just a bit over my head so I went and found help.  So I am just giving a shout-out to JJaudio for their great work and getting the mic sounding the best it can.  I try to get a demo of my sax up soon for you all to hear.  A big thanks to Langston and Jim for doing this.  ;D


-Scott

 

[saxmonster]

Other side

 

[dmp]

It looks like they used a plate out with a different transformer than the cathode follower, yes?
I'm guessing that is the big difference as it is a major circuit change, more so than magical components.
Thanks for sharing your experience.

 

[HellfireStudios]

Just out of curiousity, does the Dutch have the 100pF smoothing cap like the original 251? It would be between the plate and ground before the output capacitor. It also looks as though they used a Nichicon electrolytic for the output capacitor at C8. Why electrolytic? Maybe that was used "in place" of the aforementioned smoothing capacitor, who's existence is yet to be confirmed, to round off the highs. Looks good. I hope it sounds good as well.
FWIW, the Apex 460 is better suited to AKG C12 mods due to the capsule/headbasket acoustics being a closer match. The ELA M 251 had a bigger headbasket and, subsequently, a different sound. This might help to explain one of the reasons why you weren't happy with the self-modded results (the cathode follower wasn't helping this circuit either). Have fun with your new mic.

-James-

 

[saxmonster]

Yeppers,
They switched it to a plate follower based on the Telefunken Elam 251.  I know there are 3 more resistors and 1 more capacitor than what is on the original 251 schematic.  I guess this is how it has to be done in order to fit on the 460 pcbs.  This is where it got confusing for me.  But it sounds so great now. 

It is an AMI T14 transformer they used.  I don't know what the big capacitor is that the ami is attached to but I assume it is one of the PIO caps.  I will make a list shortly of what all was done to this mic now that it is complete.

Here are some demos.  Be kind, I had to do everything myself and running back and forth is annoying.  So my phrasing is crap but you get the idea.

-Scott

Dry Demo

http://www.ehornstudios.com/media/Dutch%20251%20Test.mp3

Wet Demo 

http://www.ehornstudios.com/media/Dutch%20251%20Test%20EFX.mp3