MK47 PCB tube mic kit - build thread

[Studio Mollan]

Thanks for the comparison.

Im using the Skylar body with Thiersch red mylar capsule. My Flea has a Thiersch blue PVC and EF12.

The thicker (heavier) and more flexible (for now) PVC alone would make that one less fast and less modern sounding.
Likely smoother/less "harsh", too.

Then there's the tranny, coupling cap etc.

In that order, I guess.



Henk

Hi and thanks for your answer. You're right. That's what I've heard from the PVC as well and now also experienced. Any idea of what type of coupling cap for a darker sound?
/
Emil

 

[micaddict]

Purely by coincidence I stumbled upon a Gearslutz thread where someone (buzzjoe) compared a Flea U47 with a Voxorama U47.
The latter is made by Andreas Grosser and is currently the U47 clone that people rave about. I t seems it has surpassed The Wagner in that regard.

Here's the quote:

Neither the Flea47 nor the Voxorama sounded like I expected. Both sound very good (and virtually noise free) but also very different: the Flea47 sounds VERY smooth, soft and warm while the Voxorama sounds much more forward, open and "modern". The Flea47 sonds very warm and pleasant but I expected a little more "edge" and presence in the upper mids while the Voxorama does have that presence but lacks some "warmth" and low end (compared to the Flea47).

 

[micaddict]

Any idea of what type of coupling cap for a darker sound?

I'd have to leave that one to others. Max first, probably.

It already has a paper-in-oil, no?



Henk

 

[ioaudio]

Hi Emil,

that's likely the capsule as stated before, hence my suggestion towards the blue line - i had more than a few builders changing from red to blue after the fact.

The 10nF is specified by the original schematics - 0.01µf = 10nF

-Max

 

[Studio Mollan]

Hi Emil,

that's likely the capsule as stated before, hence my suggestion towards the blue line - i had more than a few builders changing from red to blue after the fact.

The 10nF is specified by the original schematics - 0.01µf = 10nF

-Max

Hi Max and thanks for your input!
Ok I will get a couple of blue ones then.
Will keep you posted on my findings.

Am I crazy or does not the original schem say 0,001uf? Maybe different revisions?

 

[ioaudio]

Am I crazy or does not the original schem say 0,001uf? Maybe different revisions?

Never heard about that, do you have a link with the 0,001?

http://www.gyraf.dk/gy_pd/g7/u47.gif

 

[Studio Mollan]

Am I crazy or does not the original schem say 0,001uf? Maybe different revisions?

Never heard about that, do you have a link with the 0,001?

http://www.gyraf.dk/gy_pd/g7/u47.gif

You know what, i probably am crazy. I spent last night (very late) comparing my microphones and I could have sworn it was 1nf. I trust you more than myself in the middle of the night though. I ant check my notes now as I'm in the middle of a session.

 

[Studio Mollan]

Am I crazy or does not the original schem say 0,001uf? Maybe different revisions?

Never heard about that, do you have a link with the 0,001?

http://www.gyraf.dk/gy_pd/g7/u47.gif

Actually I just found my reference. The U47 book by Oliver of AMI.

 

[ioaudio]

Must be a typo.

 

[Sorr]

Have a microphone with a Thierch Blue capsule in for repairs (the person who built it is uncontactable ). It has a noise floor problem.

The top resistor of the capsule divider is 3M instead of 2M, which gives a lower polarizing voltage.
The rear capsule is connected to the relay via a 1nF cap and there is resistor divider from the B+ to it.
With a ~ 10nF cap decoupling cap to ground part way down it.

Just wondering if anybody knows about these mods to the microphone?

 

[ioaudio]

What kind of noise?
The mod might be a U48 conversion? Shouldn't be difficult to revise it to normal.

 

[Melodeath00]

Actually I just found my reference. The U47 book by Oliver of AMI.

The U47 Book? Why have I never heard of this, and still can't find it when I google it?

 

[Studio Mollan]

Actually I just found my reference. The U47 book by Oliver of AMI.

The U47 Book? Why have I never heard of this, and still can't find it when I google it?

Well its a really small book. A couple of printed pages. I thing Oliver used to sell them cos my tech bought it a few years back. A bit strange now in the digital age. Pay for a couple of printed pages. I wont post it cos i don't know if oliver is stiull charging for it. NOTHING new though. Its well covered here in this forum. A few Schematis and conversions for 5841, Ef12, ef14 etc.

 

[Sorr]

"What kind of noise?
The mod might be a U48 conversion? Shouldn't be difficult to revise it to normal. "

General noise, signal to noise ratio is too high for recording quite vocals.
The new owner had previously changed valves, no difference.

But you are correct, it  was converted to a U48.
Just changed it back, will see about the noise floor.

 

[Sorr]

Can anyone post the link to the connectors and cable BOM?
I cant seem to find it.
Thanks.

 

[Aleks]

Hi everyone,

Finished my MK47 mic today, fired up nicely no pops or crackles. I have left it to burn in with the stock capsule for now and need to buy a quality capsule for future use. Sounds good even with the cheap chinese one supplied.

Thanks to Tony Camp for giving me the inspiration to build the power supply in an ammunition box. I think it looks cool left as is.

Donor mic was a T-Bone SCT-700, these are very cheap from Thomann in Europe and come with shock-mount and carry case.

Need to research my next project now. Thanks to all the people who make this site what it is.

Cheers, Aleks

 

[micaddict]

Congrats!

Cool PSU case BTW.



Henk

 

[l.e.d]

Hi, does anyone know thw wattage of the 100K carbon comp resistor in the mic?
Thanks

 

[tonycamp]

Hi guys!
I've been using my pair of Mk47's for about two now and they sound very good indeed!
I'm comparing them to my Flea47 and although they are similar sounding the top end is a lot smoother in the flea. Also the flea sounds overal more polished and more flattering, it saturates more and better than the MK47's do, but i guess thats to be expected from a 5000USD microphone. The mk47 is "faster" more modern sounding i guess and compared to the Flea a bit harsh in the hi end. Its not harsh sounding at all though, just comparing to the Flea.   
Im using the Skylar body with Thiersch red mylar capsule. My Flea has a Thiersch blue PVC and EF12.

Any ideas on how to stretch the MK47 towards the flea? I know its a different cirquit but maybee you can get a bit closer with different types/values of caps?
If anyone experimented on this id be very happy for your thoughts!

Also: Howecome the polystyrene cap is 10nf instead of the original U47 spec 1nf? I tried replacing it with a 1nf SilverMica. Hard to tell the difference, at least on this source. 
/
Emil

I've tried a bunch of the usual suspect capsules in my mk47, i can tell you, IMO the blueline is the runaway winner in that regard, smoooooth is the top end, and has that chocolatey M7/u47 vibe(as i understand it), not a bright mic at all, just pretty as heck. I'm also on my 6th set of western tubes, i have hit paydirt with this last pair. I will get the aluminum 10k resistor to throw in here, as i've had the crackling on the first sets of tubes, but i attributed that to bad tubes? remember, DIY requires YOU to dial in/polish up your creations, i simply wouldn't trade my MK47 for a single clone out there.

 

[Studio Mollan]

Hi guys!
I've been using my pair of Mk47's for about two now and they sound very good indeed!
I'm comparing them to my Flea47 and although they are similar sounding the top end is a lot smoother in the flea. Also the flea sounds overal more polished and more flattering, it saturates more and better than the MK47's do, but i guess thats to be expected from a 5000USD microphone. The mk47 is "faster" more modern sounding i guess and compared to the Flea a bit harsh in the hi end. Its not harsh sounding at all though, just comparing to the Flea.   
Im using the Skylar body with Thiersch red mylar capsule. My Flea has a Thiersch blue PVC and EF12.

Any ideas on how to stretch the MK47 towards the flea? I know its a different cirquit but maybee you can get a bit closer with different types/values of caps?
If anyone experimented on this id be very happy for your thoughts!

Also: Howecome the polystyrene cap is 10nf instead of the original U47 spec 1nf? I tried replacing it with a 1nf SilverMica. Hard to tell the difference, at least on this source. 
/
Emil

I've tried a bunch of the usual suspect capsules in my mk47, i can tell you, IMO the blueline is the runaway winner in that regard, smoooooth is the top end, and has that chocolatey M7/u47 vibe(as i understand it), not a bright mic at all, just pretty as heck. I'm also on my 6th set of western tubes, i have hit paydirt with this last pair. I will get the aluminum 10k resistor to throw in here, as i've had the crackling on the first sets of tubes, but i attributed that to bad tubes? remember, DIY requires YOU to dial in/polish up your creations, i simply wouldn't trade my MK47 for a single clone out there.

I have orderd a pair of blue lines and expect that to be the final touch to my mk47s. If I can find time for it I'll try the u48 mod later this summer. It looks like a fast and easy mod (well... I've said that before...) but anyone with tips on that would be nice.
Indeed a beautiful sounding circuit/kit and knowing the full potential of this build I probably wouldn't have bought my Flea 47. Super cheap and a fairy easy build. Apart from the possible danger of high voltages I would consider this one of the simplest microphone builds on this forum. If you haven't built one yet, do it!! I've built mk47, u67 and u87. This one worked right away. No bad tubes, no noise. I had pops and crackles once caused by a loose 1k5 resistor. I reattached it to the base, did not change the tubes, and it has probably seen 200 hours of quiet studio time since.
Great job Max and all contributing forum members!