MK47 PCB tube mic kit - build thread

[teacat]

Finally got a body(thanks to chunger) to put my mk47 guts into(ok, that sounds.... eww) and she's alive!
What really impressed me was from the first moment turning it on- dead quiet. No hiss, no crackle, no hum. Suddenly I now have in my paws one serious mic and after less than an hour into the burn-in I was off recording a living-room acoustic jam. I used a chassis-mount resistor with some thermal compound and boy does this thing get warm.

Thanks ioaudio!
Thanks chunger!
Thanks zayance!

If I'm ever in Austria, France or the east bay, I'll buy you guys a beer.
I'll post some clips soon.

 

[ioaudio]

Thanks teacat 

 

[Pip]

So here is my tail sad but true. I have gone through 3 sets of 408a Western Electric tubes. What happens is the mic will sound fine for weeks at a time and then all of a sudden start making popping or crackling noises. Replacing the tubes with new to me NOS tubes has done the trick twice but here we are again. I don't mean taking them out and reseating them that has not worked. I tried that first of course but had to change tubes. I Know that tubes are a crap shoot. But was just wondering if anyone else has had this reoccuring problem as well?

As a side note I started out with JAN Phillips tubes but they sounded not good at all.

 

[baol]

Hi Pip, I had the same problem: after a few hours every pair of tubes started to pop and crack, last try was to change the 1500 resistor with a wirewound chassis-mount. Now it's completely noiseless.
In the same "repair session" I revised all the solders too, but I'm sure the solution came with the new resistor.

 

[gary o]

I also had the resistor problem others diyer had our same problem I guess its under some strain & as its connected to the cathode.

 

[teacat]

So I finally got to do a real recording with the mk47 as mid in a m/s capturing violin/vox last night. Sounded fantastic but I had one issue where when both the mic and the laptop were plugged into AC there was a horrible static noise. I haven't experienced this problem with this setup until now. I saved my ass by unplugging the laptop while doing takes.  Seems like a grounding issue? It was only when I had the mk47 and matachung c12 plugged in to the AC, with just the other mics it was fine.

 

[ioaudio]

Sounds like a ground loop, happens often with laptops and external psu's and preamps depending on the locations mains.

 

[etiefenthaler]

For all interested:

here's a live recording to watch and listen on YouTube.
http://www.youtube.com/watch?v=xvKaHNFycj4

No cut, no additional reverb or processing or eq. Only rendering to mp3

Recording chain:
Musician - guitar - church - 2 mk47 - mindprint an/di pro - spdif to maudio microtrackII.
Would have got better results with my mytek 8x192 converter. But for YouTube my small mobile-rig converter is more than o.k.

enjoy

Erich

 

[micaddict]

For all interested:

here's a live recording to watch and listen on YouTube.
http://www.youtube.com/watch?v=xvKaHNFycj4

No cut, no additional reverb or processing or eq. Only rendering to mp3

Recording chain:
Musician - guitar - church - 2 mk47 - mindprint an/di pro - spdif to maudio microtrackII.
Would have got better results with my mytek 8x192 converter. But for YouTube my small mobile-rig converter is more than o.k.

enjoy

Erich

Many would pick the usual suspects, i.e. SDCs like Schoeps, DPA et al. But this sounds just great! Warm, smooth and organic, but not lacking too much detail IMO.
Not too noisy, either. LDCs do have an advantage in this regard, but I only mention it because these are tube mics and some have found their MK47 noisy.

I'm not so much into classical guitar, but to this I could listen for hours.

Thanks for posting.
We need more of this.

 

[sliebers]

So here is my tail sad but true. I have gone through 3 sets of 408a Western Electric tubes. What happens is the mic will sound fine for weeks at a time and then all of a sudden start making popping or crackling noises. Replacing the tubes with new to me NOS tubes has done the trick twice but here we are again. I don't mean taking them out and reseating them that has not worked. I tried that first of course but had to change tubes. I Know that tubes are a crap shoot. But was just wondering if anyone else has had this reoccuring problem as well?

As a side note I started out with JAN Phillips tubes but they sounded not good at all.

I'm having the same issue with my build.  I've gone through about 10 sets of JAN Phillips and thought I found 2 pairs that were quiet after about 60 hours of burn-in.  My mic is quiet for about and hour and then starts spitting and crackling.  I'm bummed because it sounds amazing until the noises start.  I really can't use it for anything serious because the noise pops up at critical moments.  I read about changing the 1500 sand bar resistor, but didn't think that was the cause as I heat sank it to the brass base with heat sink compound and a metal strap bolted into the base. 
I'm going to get a wire-wound chassis mount 1K5 and see if that stops the noise.  I hope so, otherwise I'm going to gut the innards and use a different tube.

 

[ioaudio]

The problem with the 1,5kOhm resistor popped (pun...) up a couple of times now - often caused by thermal extension through the mounting - using a aluminium housed resistors solved this.

 

[dandeurloo]

Hey Max and others, I have built 4 of these mics for me and friends.  They all show the same noise as being described.  I have the suggested resistors inside my mics.  It doesn't make a difference, they are still noisy. 

I mounted the resistors to the base of the body (skylar's) and I have thermal paste on them to help the heat transfer.  Has anyone tried a regulated PSU?  Would that make a difference. 

It would be AMAZING to get to the bottom of this, like others have said the mics sound amazing, other then the inconsistent crackle and pops.

Any suggestions would be great.

 

[gary o]

Hey Max and others, I have built 4 of these mics for me and friends.  They all show the same noise as being described.  I have the suggested resistors inside my mics.  It doesn't make a difference, they are still noisy. 

I mounted the resistors to the base of the body (skylar's) and I have thermal paste on them to help the heat transfer.  Has anyone tried a regulated PSU?  Would that make a difference. 

It would be AMAZING to get to the bottom of this, like others have said the mics sound amazing, other then the inconsistent crackle and pops.

Any suggestions would be great.

I had this problem was a right pain changed every part finally I swapped the 1K5 didnt have correct value & wattage one laying around so I made 1K5 out of a few values to test ..... silence it was gorgeous to hear, well not hear..... ordered a metal mount one , tried before mounting worked lovely  cant remember the wattage but Im guessing the higher power rating the less strain the resistor is under .

 

[ioaudio]

Hey Max and others, I have built 4 of these mics for me and friends.  They all show the same noise as being described.  I have the suggested resistors inside my mics.  It doesn't make a difference, they are still noisy. 

I mounted the resistors to the base of the body (skylar's) and I have thermal paste on them to help the heat transfer.  Has anyone tried a regulated PSU?  Would that make a difference. 

It would be AMAZING to get to the bottom of this, like others have said the mics sound amazing, other then the inconsistent crackle and pops.

Any suggestions would be great.

Hi Dan,

probably the thermal paste makes cracking noises? Other than the that the usual suspects (besides tubes) are the 10nF styroflex when soldered too hot/long.

 

[dandeurloo]

Hey Max and others, I have built 4 of these mics for me and friends.  They all show the same noise as being described.  I have the suggested resistors inside my mics.  It doesn't make a difference, they are still noisy. 

I mounted the resistors to the base of the body (skylar's) and I have thermal paste on them to help the heat transfer.  Has anyone tried a regulated PSU?  Would that make a difference. 

It would be AMAZING to get to the bottom of this, like others have said the mics sound amazing, other then the inconsistent crackle and pops.

Any suggestions would be great.

Hi Dan,

probably the thermal paste makes cracking noises? Other than the that the usual suspects (besides tubes) are the 10nF styroflex when soldered too hot/long.

OK, I will try both of these options.  I have been very quick with soldeirng in the Styroflex but still could be that.  I have rewired and cleaned and cleaned the boards.  So hopefully it is one of these two options.  I am surprised that it would be the same on all four mics however.

Could it be the tubes don't love unregulated supplies? 

 

[ioaudio]

Yes, since it occours on all four mics i bet it's the 1,5k / mounting. For a short test you don't have to mount the new resistor.
The passive PSU is fine and used by the large majority - just a couple of posts above Erich presented a lovely guitar recording inside a church.

-max

 

[scott_humphrey]

For all interested:

here's a live recording to watch and listen on YouTube.
http://www.youtube.com/watch?v=xvKaHNFycj4

No cut, no additional reverb or processing or eq. Only rendering to mp3

Recording chain:
Musician - guitar - church - 2 mk47 - mindprint an/di pro - spdif to maudio microtrackII.
Would have got better results with my mytek 8x192 converter. But for YouTube my small mobile-rig converter is more than o.k.

enjoy

Erich

FANTASTIC!

 

[micaddict]

Yup, this is something special.
Great performance.
Great instrument.
Great room.
Great recording.
Made my day.

 

[Winetree]

Should I switch out the 1500-10 watt ceramic resistor I'm using with this?
I've got it zip tied to the side rail. Haven't run the mics long enough for trouble but I'm placing a Mouser order.

http://www.mouser.com/Search/ProductDetail.aspx?R=805F1K5Evirtualkey58810000virtualkey588-805F1K5E
It's only 5 watts but any larger wattage would be too big sizewise.

 

[gary o]

Thats what I have in my mic & works greay for me