MK47 PCB tube mic kit - build thread

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Anyone else build the mic with the Beez Neez capsule? I like the sound of my mic a lot, but it really doesn't produce a lot of bass. Is this how it's supposed to sound? I shot it out against a Gefell M71, and the latter has a little more low mids and less high end (and doesn't sound quite as smooth and silky and tube-y), but otherwise is pretty similar in frequency response. This is using the mic in cardioid mode, of course.
 
sorry for the mix-up udo/erich!

living, do you use a capsule from the group-buy?  Maybe try connecting the Gefell capsule with the MK47 amplifier for a direct comparison?
 
ioaudio said:
sorry for the mix-up udo/erich!

living, do you use a capsule from the group-buy?  Maybe try connecting the Gefell capsule with the MK47 amplifier for a direct comparison?

I won't risk that, but if someone I send a capsule two years ago for reskinning finally returns it to me I will check it with that capsule. :)

But there should be other people who build it with the Beez Neez capsule, how much bass do you get out of the mic?
 
Sory to hijack  :-[

redrawn the board to fit bigger resistors as well (on p.19), better to have some Choices on the resistors side also, so will fit most 5W to 7W resistors, as well as some of the 10W, depends on their pitch of course, but it's always good to have those resistors a little over the PCB, so possible to bend the legs anyway....
Waiting for the power transformer and will test drive, but i"m sure it will work as suppose to anyway....


 
Anyone else using the Tube Town transformer having an issue with in-rush current?
I keep blowing T125mA fuses... If i stick a 250mA fuse in its fine.

Pretty sure its not my wiring, every thing seems fine.
I'm using a much bigger choke than necessary  could that cause the psu to draw more current?

What are the little gadgets that you can add before a transformer to suppress in-rush currents?

edit: The quiescent current while on measures 60mA so it must just be in-rush, my DMM doesn't catch the current peak. (or the fuses i bought are faulty?)
 
mrclunk said:
Anyone else using the Tube Town transformer having an issue with in-rush current?
I keep blowing T125mA fuses... If i stick a 250mA fuse in its fine.

Are you using slow-blow fuses?  That's what I used in mine to accommodate the inrush current.

Cheers,
--
Don
 
Yeah, i used slow blows, think the fuses must be marked wrong seeing as that's the point of slow blows...
I noticed a current spike of 160mA a minute ago when i turned on btw.
 
I cannot get rid of popping a cracking sounds on this mic.....Ive re built it re wired it  tried all sorts but I cant find the problem......only thing I can think of is a or both tubes.......anyone have problems with the  tubes ?....

Thanks
 
Success! :)

Turned on this morning and it didn't go bang. Sounds nice, certainly full bodied.

Omni's not 100%, sounds like the back is slightly louder than the front, but need to test further.

Lots of very intermittent pops but i'm hoping this is just the tubes burning in. Apart from that, very quiet.
Like others have said its pretty microphonic but maybe with a decent shock mount this will be ok.
Anyone noticed how the elastic strings in new shock mounts are always way too tight to absorb much. Give me a perished oldie anyday.
I'll get some some pics up soon.
thanks
paul
 
mrclunk said:
Like others have said its pretty microphonic but maybe with a decent shock mount this will be ok.

This is caused by the tubes.  These tubes are dead cheap so stock up on some and change them out until you find a nice quiet pair.  My mic is dead quiet and isn't microphonic at all.  Remember, all the major mic mfgs. back in the day (Neumann, etc.) screened the tubes for microphone usage and only the best/quietest ended up in their mics.  My guess is they rejected a lot even then.  There's no reason to have a microphonic problem in a mic of this caliber.

Cheers,
--
Don
 
This thing is driving me insane it wont stop popping cracking farting......trying allsorts to find the cause ....A weired thing happend, I sprayed some switch cleaner on the around the board & tubes sockets & now there is purple liquid coming from a tube socket....its like ink,  the switch cleaner is clear.......

My 1uf capacitor that goes to the O/P tran is getting quite warm......I have 45 volts on the tube side of it......is that ok ?
 
Think Im having some bad luck.......reading back on other DIYers problems I seem to have them all.....the pops & cracks wont go away.....the only thing I can think is its the tubes, il have to try n get some others to try.....I lost full response turned out to be my 10 nf capacitor went dead I replaced it with same value got full sound back.....the large 1 uf cap was getting quite warm I have 45V on the plates , I read back in this thread that should be ok......mine gets warm tho .....does anyone else notice this ? on inspection the terminals are dis colouring, i think its been leaking.....it also stinks a nasty smell.....I thought this must be the cause of the pops n crackles.......NOOooo sadly but have stuck a 1uf 250V poly there which stays cool....inbetween all this the mic sounds good..........
 
Just finished building up one of these, but the output level seems really low.  Any ideas?  What mic should I compare it to as far as output level?
Thanks in advance!
Best,
Bruno2000
 
Finished mine, all works - except pattern switch which I haven't wired up yet due to lack of a 14k resistor - and sounds very nice (LOADS of bass, this thing is big all the way down in a way I've not experienced with my cheap mics). 

For the moment, while I try to source a 5W trimmer for the PSU, I just tried to get as close as I could with fixed resistors that i had, it is currently running at around 102V with the mic plugged in but it seems to work fine, I can only presume of course that 105V is where you will be getting optimum performance, but I have nothing to compare the sound with.

What effects should running it at 3%-ish below specced voltage have? Will it affect the sound much? I plan to finish the psu to spec when i can, but it would be good to know.
 
bruno2000 said:
...but the output level seems really low. 

reading what you posted on the capsule thread i think your problem is solved now?

>>Finished building mine today.  Sounds incredible! Thanks Max for providing such an accessible route to DIY mic heaven.

great, congrats and thanks for the nice words!

>>What effects should running it at 3%-ish below specced voltage have?
thants no problem at all.

-max
 
I have now been using my mic pretty extensively over the past couple of weeks and an issue has come up. 

I am getting loud steady pops in the audio path.  The sound resembled when I first was burning in the tubes.  The problem seems to happen at random times.  I have used the mic for hours flawlessly and then all of a sudden the popping starts.  Sometimes it starts popping within 10 minutes of being turned on.

I have tried swapping the tubes out without success.  All of the tubes have been sufficiently burned in.

Things I have tried:

-Steady PSU Voltage at 105.1v
-Visually inspected all solder joints and components for cracks.
-Swapped tubes

I have the feeling that the popping has to do with the mic warming up.  The only thing is that after the popping starts it usually goes away after a while.  Could this be an issue with the capsule?

Thanks,
Andy
 
Sounds like tube issues.

You can however replace the capsule with a capacitor and test to confirm (I think maybe 40-60pF?) that it's not the capsule. I have also heard of people overheating the tube for a short period of time to refresh and tube. I guess this probably "cleans" the cathode or something. I don't know too much about that procedure but some searches might lend some more detailed info.

Hope that helps!

Cheers,
Jonathan

 
Andy I have same problems a few posts back on this page .....I havent solved it still....I have just about given up.....had one bad capacitor & I think my oil capacitor is leaking oil  buts its not the cause of my noises.....only thing I can think is a tube or both are bad..... I havent got others to try sadly harder to get in UK.......good luck with yours Andy let us know if you find the cause...
 
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