MK47 PCB tube mic kit - build thread

[gurkan75]

Hi, I have got a question: what is the correct way to determine capsule polarization voltage? Seems to me that measuring before the 100M resistor gives me about 5V less than what theoretically should be at the voltage divider..

It was mentioned earlier that the Beezneez capsule likes to see 60V, trying to make sure that is what I am supplying.

 

[Volume11]

Need opinions of mounting the 1k5 resistor 'heater' from MK47 kit.


Thanks

Jason

Here is a pic of my mounting I've used it twice now worked great

Anyone have a part number for this resistor?

Thanks

I think it would be this one.

http://fr.mouser.com/ProductDetail/Arcol/HS10-1K5-1/?qs=sGAEpiMZZMtlubZbdhIBIKR5oQtBrv7qwqZcsowM%252bXM%3d

Or RS 252-2530

Be sure to fit the treated bolt that locks the Male binder in place before poiting where to drill holes for it. Never know.

Thanks for the heads up. I just went to check the q47 page with Skylers bodies and capsules. I remember the link for the correct 7 pin binder connector is in there. For some reason I can't get into the thread. It says that it no longer exists or I don't have permission. Anyone have the part number for this piece? Sorry for all of the ridiculous questions, I'm just having a hard time finding it online.

Thanks

Chad

 

[LHS]

The binder part # is 09 0042 00 07 (just ordered mine yesterday). It's sold at binder-usa.com or binder-connector.de if you're in Europe.

 

[david-p]

Hi, I have got a question: what is the correct way to determine capsule polarization voltage? Seems to me that measuring before the 100M resistor gives me about 5V less than what theoretically should be at the voltage divider..

It was mentioned earlier that the Beezneez capsule likes to see 60V, trying to make sure that is what I am supplying.

60v is the usual polarizing voltage for nearly all mike capsules.

David

 

[Volume11]

The binder part # is 09 0042 00 07 (just ordered mine yesterday). It's sold at binder-usa.com or binder-connector.de if you're in Europe.

Thanks, but that looks like a female connector. Is that correct ( if it really matters), or is this one more ideal.. http://www.binder-usa.com/psearch_detail.php?pid=5203

 

[LHS]

Not sure which part of the cable you were asking about. The part number I mentioned attaches to the mic. The part you listed attaches to the power supply. And then there's the panel mount on the PSU.

Binder series 691

Female cable-mount (available in my webstore) : 09 0042 00 07

Male cable-mount : 09 0041 00 07

Female panel-mount : 09 0044 00 07

Also:

You can use Binder connectors on the PSU end. The ones I am using are the 691-Series 7-pin.
What I would actually recommend is to use Amphenol-Tuchel connectors on the PSU end.
Why? Because they're less expensive & more readily available.

So you could build a cable that has:
Binder 7-pin Female cable-mount connector on one side (this connects to the mic),
Amphenol T 3475 002 or T 3475 001 Male cable-mount on the other end.
Then at the PSU use an Amphenol Female panel-mount T 3478 000.

Now the $25,000 question...why not just use Amphenol all around in the first place?
a) because I wouldn't have been able to integrate it into the end-cap as well the Binder
b) the binder is larger in size which looks better and is slightly easier to solder/assemble.

 

[drgrateful]

Hi, I was about to solder the capsule termination wires when I noticed that they are a bit too short to be soldered after the glass tubes (I am using a Thiersch blue line capsule). I don't know if this has been asked before, but is it ok to solder the wires before the glass tubes (i.e. on the side with written "front", "rear" and "back-plate")? If yes, is there any particular spot where it is preferable to solder the termination wires (e.g. closer to the glass tubes or closer to the grid and relay pins)? Or maybe any point connected to the appropriate lead will be fine? Thanks, Matteo

 

[micaddict]

mrvision wrote:

My next build I will probably experiment a mod to use 6AK5 tubes (same electrical properties/different heater). There are more options and brands to try than the 6028.

Anyone else like to comment on this?

 

[david-p]

Hi, I was about to solder the capsule termination wires when I noticed that they are a bit too short to be soldered after the glass tubes (I am using a Thiersch blue line capsule). I don't know if this has been asked before, but is it ok to solder the wires before the glass tubes (i.e. on the side with written "front", "rear" and "back-plate")? If yes, is there any particular spot where it is preferable to solder the termination wires (e.g. closer to the glass tubes or closer to the grid and relay pins)? Or maybe any point connected to the appropriate lead will be fine? Thanks, Matteo

No problem in soldering extra wire to the capsule leads, but try to leave the original leads as long as possible, and make sure the joint cant short on anything.  Also, and this is VERY important, cover the capsule with cardboard or something to prevent any solder or hot flux from getting on the diaphragm.

David

 

[zayance]

Hi, I was about to solder the capsule termination wires when I noticed that they are a bit too short to be soldered after the glass tubes (I am using a Thiersch blue line capsule). I don't know if this has been asked before, but is it ok to solder the wires before the glass tubes (i.e. on the side with written "front", "rear" and "back-plate")? If yes, is there any particular spot where it is preferable to solder the termination wires (e.g. closer to the glass tubes or closer to the grid and relay pins)? Or maybe any point connected to the appropriate lead will be fine? Thanks, Matteo

No problem in soldering extra wire to the capsule leads, but try to leave the original leads as long as possible, and make sure the joint cant short on anything.  Also, and this is VERY important, cover the capsule with cardboard or something to prevent any solder or hot flux from getting on the diaphragm.

David

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

 

[drgrateful]

No problem in soldering extra wire to the capsule leads, but try to leave the original leads as long as possible, and make sure the joint cant short on anything.  Also, and this is VERY important, cover the capsule with cardboard or something to prevent any solder or hot flux from getting on the diaphragm.

David

OK, thanks. Then I will go to plan B and use some wire stripped from the pair inside a mic cable and solder it to the capsule leads, then isolating it with some heat-shrink tubing.

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

Yes, but I have already attached the capsule to the support... I think I will go with something like this:

 

[zayance]

hmmm, well maybe, but it could also be risky like this also? i said the plastic given with Thiersh because it's a thick one,
and won't melt of flux spread on it, well not as fast as your plastic.... And it's for the same reason people said cardboard or so...
Anyway do as you like... I would take out the capsule, protect with Thiersch box and do the cable jobby....
A couple of minutes to take it out and do it carefully is better than sending it back for reskining imho, well that's in the worst case scenario...
Anyway be carefull.

 

[drgrateful]

OK, I soldered some extra wire taken from a Gotham GAC-3 cable. Everything seems to have gone fine (at least as far as I can see now).

 

[micaddict]

Quote from: grantlack on November 13, 2011, 06:58:52 pm
as i look at the u48 schematic, it appears that the fig8 pattern was accomplished by simply switching a 1nF cap into the signal path between the membranes.  any reason the same approach couldn't be taken in the mk47?  the execution would be simple enough, it's just a matter of whether it would behave the same.  i tend to find omni to be less useful in my day-to-day work.

If your plan is to make a MK48 (sacrifice the omni patern to favor a figure 8 ) it's doable.
Pay attention to the U48 schematic. It's not just a matter of adding a cap and a resistor, you also need to modify the voltage divider.
In the U47 the 2M/3M extract 60V from the 105V PSU in order to polarize the front of the capsule. If you'd polarize the back with 105V, you wouldn't get a real figure 8 pattern (cause you'd need 120V). So for the U48 they changed the voltage divider  to 3M/3M. That gives 52.5V to the front, and then 105V at the back is right.
You can do the same with the MK47. Just keep in mind that, just like with a real U48, you'll loose a bit of sensitivity because of the lower polarization voltage.

Axel

"If you'd polarize the back with 105V, you wouldn't get a real figure 8 pattern (cause you'd need 120V)."

Does this mean that without the voltage divider modification you'd get either cardioid or hypercardioid?

 

[Monoklang]

Hi, I'm gathering all parts needed for the MK47 PSU, I've read this thread 3 times but still have a newbie question left:

I want 3 toggle switches (card-omni, power on/off and the test switch)

What kind of switches do I need. There are like a 2000 to choose from and I just want to be sure that choose the right ones. I'm at mouser.

Contact form SPDT or DPDT?
Should it be "on-off" or "on-on", I mean should all three switches be 2 positions switches?
And what voltage should they be able to handle? (230V in my country) does that even matter?

That's it. Thank you all for all information!

 

[wave]

Hi, I'm gathering all parts needed for the MK47 PSU, I've read this thread 3 times but still have a newbie question left:

I want 3 toggle switches (card-omni, power on/off and the test switch)

What kind of switches do I need. There are like a 2000 to choose from and I just want to be sure that choose the right ones. I'm at mouser.

Contact form SPDT or DPDT?
Should it be "on-off" or "on-on", I mean should all three switches be 2 positions switches?
And what voltage should they be able to handle? (230V in my country) does that even matter?

That's it. Thank you all for all information!

Power and test can be SPST. Pattern switch is SPDT

Dave

 

[david-p]

And what voltage should they be able to handle? (230V in my country) does that even matter?

It doesn't matter.

David

 

[Monoklang]

Thanks!

And what about the On-off-on, on-none-off and on-none-on ... thing?

There's a lot of options, and I have never bought those before.

Regards
John

 

[wave]

Thanks!

And what about the On-off-on, on-none-off and on-none-on ... thing?

There's a lot of options, and I have never bought those before.

Regards
John

For the SPDT I get on-none-on

Dave

 

[drgrateful]

Here are some pictures for my build:

http://s1071.photobucket.com/albums/u507/drgrateful/U47%20clone/

It's been working wonderfully since when I first connected it four hours ago.