MK47 PCB tube mic kit - build thread

Looking good!

Is that a Skylar headbasket?

micaddict said:

Is that a Skylar headbasket?

Click to expand...

Yep, it's an EQU47 body by Skylar (Equinox Systems).

It looks smoother/rounder than any other Equinox I've seen (including the improved ones on the site).
Too round ain't good, either (early Fleas are plain ugly IMO), but some of the EQ47 almost look trapezium-like. (Perhaps more so in the first batch.)
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/  \

Yours looks just right to my eyes. 

If Skylar has one left like that, I'm bait.

Skylar, you there?

Hey drgrateful,

Nice work!

How does it sound with the Thiersch capsule?
Do you made a comparaison with another mics? Brand/Model? 

I'm on my MK47 too but it not finished yet.
I sent you a PM and asked about the PSU case that is in your pictures.

It's exactly the style of PSU case that I'm looking for.

I have spent a lot of time searching on the web but I have found it.

Can you tell where you buyed it? Please.

Thanks in advance for sharing infos , links & opinions

Jam

drgrateful said:

zayance said:

Use Thiersch Plastic cover, perfect for that....

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Yes, but I have already attached the capsule to the support...

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The Thiersch plastic cover trick works with the capsule attached to its holder
Axel

daddymac said:

How does it sound with the Thiersch capsule?
Do you made a comparaison with another mics? Brand/Model? 

Click to expand...

Well, I am using it thorugh a Seventh Circle Audio N72 pre and, to me, it sounds wonderful. To be honest, I am not the most qualified person to make comparisons with other high end mics: for example, I never heard an original U47. There are people in this group much, much, more qualified to give you an answer. I can only say that it promises to give extremely good results in my home studio. Anyway, in the end, I have learned that questions like yours can hardly get definitive answers.

daddymac said:

It's exactly the style of PSU case that I'm looking for.
I have spent a lot of time searching on the web but I have found it.
Can you tell where you buyed it? Please.

Click to expand...

You can find it here:
http://www.groupdiy.com/index.php?topic=47865.0

mad.ax said:

The Thiersch plastic cover trick works with the capsule attached to its holder

Click to expand...

Thanks, I'm sure your suggestion will be very useful!

micaddict said:

It looks smoother/rounder than any other Equinox I've seen (including the improved ones on the site).
Too round ain't good, either (early Fleas are plain ugly IMO), but some of the EQ47 almost look trapezium-like. (Perhaps more so in the first batch.)
__
/  \

Yours looks just right to my eyes. 

If Skylar has one left like that, I'm bait.

Skylar, you there?

Click to expand...

I would be willing to bet that his headbasket isn't as rounded as it appears in the photos.

I wonder if drgrateful has a picture of this headbasket from a high vantage point above the unit looking down from 12+ inches away? Sometimes when you photograph headbaskets (wow, I've done my fair share of that!), they look more curved than they should depending on camera/lens/vantage point/closeness to subject...you start getting a fisheye effect the closer you are to the subject with some cameras.

Anyway, I bet the headbasket wouldn't look so rounded from further away looking down slightly...like this:



In any case, if you want to add more rounding to the top mesh, you can shape it by hand or make a wooden punch to help you shape it (personally, I wouldn't do this, but it can be done).

Hi Skylar,

here are a couple more pictures, taken from about 30-40cm away (and zooming in):

Thanks. That's what I expected it to look like. Looks like all our other headbaskets.
I knew there was no way a rounded top could have passed through QA (5 individuals, including myself, inspect every unit).

Skylar and drgrateful, thanks for elaborating.
The camera lens explanation seems plausible.

OK, before people get the wrong impression here, I hate the round look of the older "bowler hat" Fleas (new Fleas look fine though) and I like the Equinox, especially the improved versions.
And by "trapezium" I mean not only flat on top but also at the angled bit, if that makes sense, with a relatively sudden kink. But if at all (I didn't see them in the flesh) those were likely from the first batch.
It's just that the one in drgrateful's earlier picture looked extra nice and smooth, for some reason. That's all.

Also, I personally thanked Skylar for the great work and for starting all this.

Oh, and the kits were sold out anyway.

BTW here's a pic of ten originals and yes, they did vary:

Now let's get back to the electronics kit, please. 

Hi all.  Please forgive me if this is a stupid question, just thought it was better to ask than not.  I was in on the TNC group buy a while ago and bought one the tube mics, the ACM1200, a C12 "style" mic with one 12AX tube in it..  It came with a power supply.  Can I use this power supply to power the MK47? 

Thanks.

David R. said:

Hi all.  Please forgive me if this is a stupid question, just thought it was better to ask than not.  I was in on the TNC group buy a while ago and bought one the tube mics, the ACM1200, a C12 "style" mic with one 12AX tube in it..  It came with a power supply.  Can I use this power supply to power the MK47? 

Thanks.

Click to expand...

No you can't use that PSU without mods...

I also have those mic's and have started an m49 conversion here:
http://www.groupdiy.com/index.php?topic=44667.0

I traced the PCB and came up with this schematic of the acm1200 psu:
http://www.groupdiy.com/index.php?action=dlattach;topic=44667.0;attach=12049;image

Interestingly, it does have a 200V PT and very similar layout to the MK47 PSU... As a matter of fact if you compare the two schematics you could quite easily mod the acm1200 PSU by changing some resistors, adding a pot, etc...

I don't think max's transformer/PCB/tubes will fit into one of these apex460 style bodies.

Best Luck!
-jb

I haven't start building this PSU yet. I have ordered all parts and now I just want to make sure I am on the right track.

Is this right? I have never drawn this types of things before, so excuse me if it's smeared and maybe hard to see every part. I've read this thread like 10 times, to figure out every detail. But my PSU skills are limited...

The part I'm most lost in is the wiring between Mains - on/off switch - fuse - torodial

If someone have a couple of minutes, I would really appreciate some help.

Best regards
John

Monoklang said:

Is this right? I have never drawn this types of things before, so excuse me if it's smeared and maybe hard to see every part. I've read this thread like 10 times, to figure out every detail. But my PSU skills are limited...

The part I'm most lost in is the wiring between Mains - on/off switch - fuse - torodial

Click to expand...

In what way are you lost, please, John?  I dont see a problem with the switch/fuse/transformer connections.  As I recall it, the 1k resistor is an alternative to the choke. Is the lamp grounded by its body to chassis? It will need a return

Also, assuming you are using the same Binder connector that I am (Skylar body), I advise you to connect pin 7 to your B- pin 3 (at both ends).  This gives a lower resistance for the ground connection and, just as importantly, pin 7 connects first and it is good that this be the ground.

David

Yes, it´s either the choke or the 1k resistor, not both in parallell.

The 680R/330R (200R+130R) combo is for adjustment to 105V (together with the pot), just add or take them out until the voltage is correct.

So I have done a lot right

Ok, so I:
- remove the first 1k 5W. So it's just the choke.
- Connect pin 3 & 7 in all Binder connectors (PSU, cable connectors and mic)

About the lamp, I'm not sure how to connect it. I've ordered a  Fender Jewel light, a 6,3V bulb and a fender lamp holder from Tube-Town:
http://www.tube-town.net/ttstore/product_info.php/info/p465_Fender-Lamp-Holder.html

And I know the the Torodials sec is 6,3V

But about that return, do I take the 0V from the torodial (as in link it from the IEC's neutral?)

I'm really happy that I pulled this off by reading that PSU scheme and by looking at this threads pictures.

..or well I haven't built the thing yet...

Thank you all

Monoklang said:

So I have done a lot right

Click to expand...

YES

Ok, so I:

Click to expand...

- remove the first 1k 5W. So it's just the choke.  YES!

- Connect pin 3 & 7 in all Binder connectors (PSU, cable connectors and mic)

Thinking about it, it is not clear how many separate wires you have in your cable.  I was assuming that you have 7, but if you only have 6 core cable, I advise using pin 7 instead of pin 3 for the reason I stated.

About the lamp, I'm not sure how to connect it. I've ordered a  Fender Jewel light, a 6,3V bulb and a fender lamp holder from Tube-Town:
http://www.tube-town.net/ttstore/product_info.php/info/p465_Fender-Lamp-Holder.html

Click to expand...

OK.  I can see two terminals on this.
 

But about that return, do I take the 0V from the torodial (as in link it from the IEC's neutral?)

Click to expand...

To advise on where the return goes I would need to know the model of transformer you are using.

And I know the the Torodials sec is 6,3V

Click to expand...

The light you have chosen is likely to be much brighter than you want.  I would have advised an LED with a resistor in series to reduce the brightness: 390 ohms would be a good start with a red LED. This can be increased in value to lessen the brightness.

David

Hi guys, I just finished my mk47 build with skylers u47 style body and q47 capsule. Lucky for me it fired up on the first try and it sounds unbelievable to my ears. This is by far the best quality mic I own so far. My only concerns are my voltage readings. I just want to double check with you guys to see if everything seems to be standard.

Test switch in omni I get 112vdc at b+ and 112vdc at the pattern point
Test switch in cardioid I get 105vdc at b+ and 48.5vdc after the 14k resistor

Mic connected in omni I get 98.6vdc at b+ and  45.3vdc at the pattern point
Mic connected in cardioid I get 98.5vdc at b+ and 45vdc after the 14k resistor

45.3vdc at the pattern point seems low to me, but my knowledge can't tell me for sure. Should it match the b+ voltage?

Big thanks to Max, Skyler, and everyone contributing on this forum.