MK-U47 - build thread

[georgerarnold]

Before my NOS 408a tubes was noiseless, I put them in my Mic and burned them in for 3 Days nonstop.

Interesting. What sort of noise did you get?

 

[emrr]

Thank you that's a good and cheap place to start. I'll try it first thing.
The noise is a scratchy static noise, not constant it never stops for longer than a second or two.

There should be plenty of comments about the 1K5 type in this thread. 

If it doesn't go away or change with different tubes, then it sounds next most likely to be a carbon resistor, there are a few in there. 

 

[georgerarnold]

There should be plenty of comments about the 1K5 type in this thread. 

If it doesn't go away or change with different tubes, then it sounds next most likely to be a carbon resistor, there are a few in there.

Thank you. the 1.5k resistor didn't make any difference but I've been with a tech today and we have ordered other resistors to replace.
One thing I was wondering and perhaps someone here can help me with; why are some resistors metal film other carbon etc? The tech guy wanted to replace the carbon ones with metal ones and he thought I was crazy for wanting to keep them the same type in case it changes the sound in some way.
Thanks again.

 

[Gus]

The following has been posted about over the years

Sub in a 50pf to 100pf cap for the capsule. install the body and grill.
Let the microphone run and test for noise.

If no noise most likely the capsule or connection to the PCB board


If you still have noise

Can be the tubes I see GREEN paint in some pictures are they the 1980s run?

Something I would try but only do if you know what you are doing is to build a tube test burn in circuit to check the tubes for noise outside of the microphone

 

[georgerarnold]

Can anyone tell me what the wattage is for the carbon comp resistors in this mic? The 100k and 30k.
I replaced the other resistors and now the noise seems better but not totally gone.
Do you think it's necessary for them to be carbon comp for the sound?
I'm just going to replace all the cheaper components and if the noise continues then look towards the pricier ones.
Cheers

 

[Delta Sigma]

Can anyone tell me what the wattage is for the carbon comp resistors in this mic? The 100k and 30k.
I replaced the other resistors and now the noise seems better but not totally gone.
Do you think it's necessary for them to be carbon comp for the sound?
I'm just going to replace all the cheaper components and if the noise continues then look towards the pricier ones.
Cheers

Whatever you have on hand should be fine. 1/4W. I'm assuming you're talking about R5 and R6 in the Neumann schematic.

Your tech probably wants to replace carbon comp because they're less reliable, noisier and change more with temp than metal film. The reason why they're used in vintage mic designs is because they can slightly colour the signal. That's why they're used in the audio portion of the mic like the load resistor.

You probably shouldn't continue replacing random components until you've burned in your tubes and replaced your capsule with a cap as Gus and Moby suggested. It's better to know what your problem is before you fix it.

 

[georgerarnold]

Whatever you have on hand should be fine. 1/4W. I'm assuming you're talking about R5 and R6 in the Neumann schematic.

Your tech probably wants to replace carbon comp because they're less reliable, noisier and change more with temp than metal film. The reason why they're used in vintage mic designs is because they can slightly colour the signal. That's why they're used in the audio portion of the mic like the load resistor.

You probably shouldn't continue replacing random components until you've burned in your tubes and replaced your capsule with a cap as Gus and Moby suggested. It's better to know what your problem is before you fix it.

Thank you for your reply. You're right, I will order the cap first.
Cheers.

 

[Delta Sigma]

Thank you for your reply. You're right, I will order the cap first.
Cheers.

It doesn't have to be anything special. If you can get a cap locally in the 50-100pF range, that's good enough. The idea is to eliminate the capsule and is leads in your troubleshooting. Keep in mind, you can still have noise from your Hi-z section if the guy who built it touched it without gloves. Clean it as best as possible. Do not get alcohol on acrylic boards or styroflex caps if there are any; use distilled water.

 

[georgerarnold]

It doesn't have to be anything special. If you can get a cap locally in the 50-100pF range, that's good enough. The idea is to eliminate the capsule and is leads in your troubleshooting. Keep in mind, you can still have noise from your Hi-z section if the guy who built it touched it without gloves. Clean it as best as possible. Do not get alcohol on acrylic boards or styroflex caps if there are any; use distilled water.

Hi, sorry to bother you again. There are three cables coming off the capsule, one off the base and one from either face of the capsule. Can you tell me, do I need to disconnect all three of the cables and then put the cap between where the two cables from the face of the capsules were? Or how would you do it?
Thanks.

 

[Delta Sigma]

Hi, sorry to bother you again. There are three cables coming off the capsule, one off the base and one from either face of the capsule. Can you tell me, do I need to disconnect all three of the cables and then put the cap between where the two cables from the face of the capsules were? Or how would you do it?
Thanks.

I haven't built this mic but there should be a backplate wire, a front diaphragm wire and a rear diaphragm wire. I'm gonna guess that the rear diaphragm wire goes to the omni switch. Leave your switch in cardioid, remove the capsule, put your cap from the front diaphragm connection (tube grid and 60M-1G resistor) to the backplate connection (10nF cap and 100M-1G resistor). Don't remove the wires from the capsule, leave them connected at the capsule and disconnect them from the mic.

DO NOT touch the capsule or any high impedance component without gloves. Even a little oil or contaminent from your fingers can cause noise. DO NOT let anything touch the membranes on the capsule. Make sure you have a plan forwhere you will store tha capsule while it's out of the mic.

 

[JMc]

Hi folks. I need some help here. I purchased two MK-47 kits from IOAUDIO years ago - the earlier version with the green PCB, not black. I built the first one in 2011 using Max's build thread in an Equinox body with a Thiersch redline M7 PVC capsule. I thought I had saved the instructions with photos, as a PDF, but I can no longer find it. I'd like to build the other kit, but I could really use those instructions. I see another member re-posted the instructions for the MK-U47 on page 35 of this thread with most of the photos, but some are still MIA. I also found a link to dropbox with all the photos, so I could be able to reconstruct the instructions with all of the photos intact, but that's not the build I need. Does anyone have an intact build instruction for the earlier MK-47 complete with photos? Also, is Thiersh still selling capsules? I might try a blueline mylar M7 if they still are. If anyone could assist either with a link to the complete build instructions with all photos intact, or can send me a PDF of same, I'd sure appreciate it. Thank you.

 

[Delta Sigma]

Do you still have the other one you built? Could you fill in the blanks from it?

You could read other similar threads as well Check out Dany's EF47 thread and look at his layouts from his mic body solution page.

Chunger posted some nice build threads, search the entire forum for posts from chunger with the word "newbie". In his MK47 build thread, he has a link to the PSU wiring diagram.

If you already have a Thiersch, why not try a different capsule manufacturer for something completely different? Beesneez makes a great K47. If you're set on an M7, people rave about Dany's and I just heard someone raving about Eric H's M7, saying it's the best thing out there.

 

[JMc]

Yes, I still have my original build. Been using it continuously for the past 10 years! I just hate to open it back up, but that may be my only option, I guess. I guess i could try a different capsule. I think I want to stick with M7's. I'll have to do a search about Dany and Eric's M7's. I haven't been on here for several years and have a lot of catching up to do. Thanks, Neil. Cheers.

 

[innercityman]

Hi folks. I need some help here. I purchased two MK-47 kits from IOAUDIO years ago - the earlier version with the green PCB, not black. I built the first one in 2011 using Max's build thread in an Equinox body with a Thiersch redline M7 PVC capsule. I thought I had saved the instructions with photos, as a PDF, but I can no longer find it. I'd like to build the other kit, but I could really use those instructions. I see another member re-posted the instructions for the MK-U47 on page 35 of this thread with most of the photos, but some are still MIA. I also found a link to dropbox with all the photos, so I could be able to reconstruct the instructions with all of the photos intact, but that's not the build I need. Does anyone have an intact build instruction for the earlier MK-47 complete with photos? Also, is Thiersh still selling capsules? I might try a blueline mylar M7 if they still are. If anyone could assist either with a link to the complete build instructions with all photos intact, or can send me a PDF of same, I'd sure appreciate it. Thank you.

If you decided to sell your kit, I'd be interested.

 

[Whoops]

Max (ioaudio) is not around this forum anylonger so could please someone explain what was the difference between ioaudio MK47 project and this ioaudio MK-U47 project?

Thank you so much

 

[EvLoutonian]

Hi folks. I need some help here. I purchased two MK-47 kits from IOAUDIO years ago - the earlier version with the green PCB, not black. I built the first one in 2011 using Max's build thread in an Equinox body with a Thiersch redline M7 PVC capsule. I thought I had saved the instructions with photos, as a PDF, but I can no longer find it. I'd like to build the other kit, but I could really use those instructions. I see another member re-posted the instructions for the MK-U47 on page 35 of this thread with most of the photos, but some are still MIA. I also found a link to dropbox with all the photos, so I could be able to reconstruct the instructions with all of the photos intact, but that's not the build I need. Does anyone have an intact build instruction for the earlier MK-47 complete with photos? Also, is Thiersh still selling capsules? I might try a blueline mylar M7 if they still are. If anyone could assist either with a link to the complete build instructions with all photos intact, or can send me a PDF of same, I'd sure appreciate it. Thank you.View attachment 85692

Hi. I think (hope) that I saved out that step-by-step build guide at some point . . . .
Lemme check for you.
Is there somewhere I can upload it on the forum?
(otherwise, just post me your email, and if I find it I'll forward it to you)

Cheers!
Evan

 

[martthie_08]

for anyone reading this, I have all the missing images from page 35 back on my server.
Since it is now all https I would have to edit the post for the images to show,
unfortunately I can't do that because in the meantime there is a limit of 30 images per post.

 

[innercityman]

Max (ioaudio) is not around this forum anylonger so could please someone explain what was the difference between ioaudio MK47 project and this ioaudio MK-U47 project?

Thank you so much

What I know is that MK-47 is very close to Oliver Archut's design D-47 as I've built an MK-47 last year... Same 2 x 408A tubes versions, so I guess the MK-U47 should be close to the D-EF47 which uses an EF800 tube. I could be wrong

 

[Whoops]

What I know is that MK-47 is very close to Oliver Archut's design D-47 as I've built an MK-47 last year... Same 2 x 408A tubes versions, so I guess the MK-U47 should be close to the D-EF47 which uses an EF800 tube. I could be wrong

Thank you so much for your reply mate. That's great to know.

Anyone has more info regarding the differences between ioaudio MK47 and MK-U47?

Thanks you

 

[martthie_08]

MK-U47 has 2x 408 tubes..
See schematic on the top of the previous page..