MK47 PCB tube mic kit - build thread

[The Frizzle]

Thank you for your answer pip!
I read a bit about tubes and the heater today and I think I did the heater measurements wrongly (I measured the heater pin against ground).
As far as I understood I'm supposed to measure between pin 3 and pin 4 of the tube since these are the heater pins.
I have 4 tubes, tested all and left the ones with the highest heater voltage in:
Tube 1 Heater: 16,48 V (Between pin 3 and 4)
Tube 2 Heater: 18,45 V (Between pin 3 and 4)
So the Voltage should be ideally 20V right? Is the 16,48 V too low for the tube to start working?
I ordered 10 new tubes here: https://www.tubezone.co.uk/product/6028-408a-philips-ecg-usa-tube/
Hope those are the right ones.
Would it be safe to raise the PSU Voltage to something like 110 volts to push tube 1 into working voltage? If not I'll just wait till the new tubes arrive.

 

[Category 5]

Roughly 18V at each tube is correct.  The 408a specifies 20V but the VF14 specified 36V.  Since the MKU47 uses the same original circuit design the two 408a tubes are wired in series so should each see half that voltage.  You should see about 36V at the output of the dropper resistor and about 18V on each tube. 

 

[Matt Nolan]

Thank you for your answer pip!
I read a bit about tubes and the heater today and I think I did the heater measurements wrongly (I measured the heater pin against ground).
As far as I understood I'm supposed to measure between pin 3 and pin 4 of the tube since these are the heater pins.
I have 4 tubes, tested all and left the ones with the highest heater voltage in:
Tube 1 Heater: 16,48 V (Between pin 3 and 4)
Tube 2 Heater: 18,45 V (Between pin 3 and 4)
So the Voltage should be ideally 20V right? Is the 16,48 V too low for the tube to start working?

Your tubes are working. The voltage at the output capacitor somewhere near half the supply rails tells you that. They're probably fine down to about 15V on each heater, but gain will fall off the lower you go.

As you are getting decent anode and backplate voltages and you are hearing tube microphonics at the output then I would suggest there is an issue somewhere in the capsule to grid circuit.

 

[The Frizzle]

Thanks alot Matt and Category 5!
I feel a bit dumb but I had the wrong 100M resistors in.
I think I had wrong measurements on the 100M and bought new wrong ones which measure like 100m
Hope this didn't destroy anything. I just found the ones from Max and soldering them in.

 

[The Frizzle]

Aaand it's working!!  ;D
Thanks alot guys!

 

[burglar]

- Referring to this diagram, will wiring terminal 7 & 3 (twisted together) of the connector inside the mic to B- be sufficient baring in mind that Audio ground and shield are strapped together in the psu?   

https://www.google.co.uk/search?q=mk47+psu&source=lnms&tbm=isch&sa=X&ved=0CAgQ_AUoAmoVChMIyuWRrcCLyQIVBb0aCh0-OwOJ&biw=1920&bih=916#imgrc=isDZ-zYrl7DzoM%3A

 

[burglar]

bump

- Referring to this diagram, will wiring terminal 7 & 3 (twisted together) of the connector inside the mic to B- be sufficient baring in mind that Audio ground and shield are strapped together in the psu?

https://www.google.co.uk/search?q=mk47+psu&source=lnms&tbm=isch&sa=X&ved=0CAgQ_AUoAmoVChMIyuWRrcCLyQIVBb0aCh0-OwOJ&biw=1920&bih=916#imgrc=isDZ-zYrl7DzoM%3A

 

[guisquil]

Hello,

This is my first post here, I'm very exited about building this mic, is there a store in the US like micandmod.com, Where they have the complete kit with out having to hunt over multiple places for all the necessary parts? I went to http://store.studio939.com but they don't have power supply kit.

Thanks

 

[Phrazemaster]

Hello,

This is my first post here, I'm very exited about building this mic, is there a store in the US like micandmod.com, Where they have the complete kit with out having to hunt over multiple places for all the necessary parts? I went to http://store.studio939.com but they don't have power supply kit.

Thanks

Welcome.

Half the fun (and difficulty) of this whole DIY thing is sourcing parts. Chunger has done a pretty decent job of putting most everything together in one place. What is it you think you are missing? Chunger lists it for you:

- capsule
- tube
- Alctron TPS-100 power supply
- SYT-5 of comparable microphone body
- 7 pin XLR microphone cable

No one is going to sell the whole shebang; you'll have to do some digging to get the capsule (how about a Thiersch?), tube (contact Bowie on this site, or google). The PSU, body, and cable, you can get from Chung.

The XLR connectors you may have to get from Mouser.

But it's pretty much done for you other than that. As far as difficulty sourcing things, this is one of the easier possible kits you could ever build. Let us know if you have trouble sourcing anything.

Mike

 

[guisquil]

Hi,

Thanks for the quick response, I read all 69 pages of this thread and then google "micandmod review" just because most people would do that before sending $800.00 to a store, and i think I have a good idea what the deal is between him and this community from reading the most relevant Google responses. I was hoping there was a place that I some how missed in the US.

What is the easiest power supply unit that you could built for this mic, maybe  case already drilled that included a pcb board etc?

Thanks,

 

[guisquil]

Thanks Mike,

Would the Alctron TPS-100 power supply work with this build?

- Alctron TPS-100 power supply

 

[Phrazemaster]

Hi Guisquil,

You could build a PSU using Zayance's board, available in the White market. But you'd still need to get a case and the parts, etc. Chunger has a fabled PSU in the offing but it's been cooking for a year or two; some kind of holdup.

I'm not sure if the TPS-100 would work; I haven't read this thread (I'm building the MKU47, a slightly different mic). But I do believe it can be modified.

Not to dampen your enthusiasm, but you might consider to work your way into this whole DIY thing with another kit - this is a lot to take on for a first time build. Might you consider building a preamp, with a kit by Hairball, or SoundSkulptor, or Seventh Circle Audio?

If it must be a mic, then I'm afraid you're going to have to roll up your sleeves and keep reading, googling, and asking questions and sourcing parts. But it's really not that bad.

For me personally, I have to build a PSU for my MKU47, and it's based off the same schematic. I'm going to build it PTP (point to point) just like Chunger did in a thread you can find here.

Otherwise go with Zayance's board but you'll have to drill a case, buy the parts individually, etc. But it's not that bad. Question is, do you want it bad enough? The planning part is half the fun!

Cheers mate.

Mike

EDIT: I forgot, there are some high quality all-in-one mic kits available. Such as:

• http://www.diyribbonmic.com
• http://www.diyrecordingequipment.com/products/rm5-ribbon-mic

 

[guisquil]

I WANT IT BAD!!!!!

--- Question is, do you want it bad enough?

Mike, I agree with you very good points. I have built tube stuff before so I think I can do this one.

In this case I'm trying to maximize my time, I want to have this mic as soon as possible as it is part of a bigger project that I'm doing, I don't want to make you cry because I assume you are a grown man so I'll skip the details but it is relate it to my health.

 

[Phrazemaster]

I WANT IT BAD!!!!!

--- Question is, do you want it bad enough?

Mike, I agree with you very good points. I have built tube stuff before so I think I can do this one.

In this case I'm trying to maximize my time, I want to have this mic as soon as possible as it is part of a bigger project that I'm doing, I don't want to make you cry because I assume you are a grown man so I'll skip the details but it is relate it to my health.

Well in that case...I would ask Chunger if he will be releasing the PSU very soon, or check the black market for someone just selling one...sounds like you just need a working mic for your secret health project...

 

[vinylwall]

These are the PSU cases I've been using.  Top notch work by Dan and he ships very quickly: http://collectivecases.com/?product=psu-cases

 

[guisquil]

Thanks those look great, I sent Zayance a email I can't open the PDFs file for the psu board ...

These are the PSU cases I've been using.  Top notch work by Dan and he ships very quickly: http://collectivecases.com/?product=psu-cases

 

[Phrazemaster]

+1 for Dan's cases - top notch!

 

[guisquil]

What capsules do you guys recommend for this build? What about  the Peluso P-K47 ?

Thanks

 

[Phrazemaster]

Dunno about the Peluso, but the Thiersche Blueline should be a fabulous choice.

 

[guisquil]

Thanks Phrazemaster

Any opinions on the Eric Heiserman HK47 capsule?

Can some one share trusted places where to buy tubes?

Has anybody used https://www.tubezone.co.uk/product/6028-408a-philips-ecg-usa-tube/ ? Or http://www.ebay.com/itm/6028-408A-Philips-ECG-USA-Tube-Lots-of-10-Pcs-/121241495506