[FEELER] Are you interested on Phantom powered Tube microphone kit?

Khron said:

How about something like the sE 2200A? I've just bought my 5th one (faulty) off eBay today ;D

Nice and roomy inside. I've actually started modding one to add a dc-dc converter inside and a pattern switch - still a work in progress though

Click to expand...

Sure, why not

Could you put pics of the inside and measure spacing for PCBs?

Gus said:

Years ago(2004?) at this forum there was a thread about a phantom powered tube DI mostly the same as a tube microphone circuit.
Think max power transfer not voltage.
I believe Thomas Holly was the thread starter.  I will try to find it.  IIRC different DC to DC converter chips were tried and other refinments.
EDIT found a thread http://groupdiy.com/index.php?topic=1195.0

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Thanks Gus for the link

Unfortunately links in this topic doesn't work anymore 
I can only imagine how this circuit looks but probably something similar with few exceptions

I'll do that tomorrow, i have another one here at home, but it's all in pieces

In the mean time, outside dimensions: http://recordinghacks.com/microphones/SE-Electronics/2200a

At least the replacement pcb's i've designed are shorter than the stock one (there's a blank one on the back side of the body rails, i'm guessing for structural purposes). The PCB width comes out at 36-37mm, with four 2mm holes - 29mm apart, side-to-side (with the mic standing up) and 35mm apart, along the length.

In case it helps until i can get mine back together:

https://www.flickr.com/photos/11328208@N00/8112015579

ln76d said:

Khron said:

How about something like the sE 2200A? I've just bought my 5th one (faulty) off eBay today ;D

Nice and roomy inside. I've actually started modding one to add a dc-dc converter inside and a pattern switch - still a work in progress though

Click to expand...

Sure, why not

Could you put pics of the inside and measure spacing for PCBs?

Click to expand...

Great!

So we have first candidate
Any others?

BTW. simple and effective mod for se 2200a original circuit is removing input cap and changing capsule connection

I mean, I think that the generic C12 bodies are the easiest choice, but you squeeze things down pretty well, why not put it in the generic FET mic body (the one that's used for the MXL V67g etc.)?

In the attachment is the schematic of  Holly's DI box. The biasing/heating isn't done correctly so be careful if you like to use it. It should be re-engineered IMO.
BTW, the maximum power available from the phantom is about 150mW.
If the efficiency of the converters is only 50%, still there is enough power to generate heater, +B and capsule biasing voltages.

"Been there, done that" If i remember correctly, in at least two of them, i also re-made the capsule biasing network, to get the (higher) voltage before the 20v zener. But that's off-topic already ;D

ln76d said:

Great!

So we have first candidate
Any others?

BTW. simple and effective mod for se 2200a original circuit is removing input cap and changing capsule connection

Click to expand...

MXL mics are more rare and more expensive on this side of the pond, than in the US, so...

midwayfair said:

I mean, I think that the generic C12 bodies are the easiest choice, but you squeeze things down pretty well, why not put it in the generic FET mic body (the one that's used for the MXL V67g etc.)?

Click to expand...

moamps said:

In the attachment is the schematic of  Holly's DI box. The biasing/heating isn't done correctly so be careful if you like to use it. It should be re-engineered IMO.
BTW, the maximum power available from the phantom is about 150mW.
If the efficiency of the converters is only 50%, still there is enough power to generate heater, +B and capsule biasing voltages.

Click to expand...

Thanks!
I have converter topology already, it's a little bit different and for the rest i need to make prototype and empirically choose some values.

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For the bodies!
I want to make PCBs which fit few donor bodies.
In many microphones 38mm width should fit.
I will measure mxl 2006 and alctron gt2b bodies (and maybe something else if i find).
Transformer need to be mounted outside PCB!
The biggest issue with universal pcb are mounting holes - many of these microphones have it in different positions.
If you have in mind any specific microphone, please measure internal frame and hole spacing (also from the top and bottom),

Oh, I see, you are going to use a converter for the heater rather than for the B+ and polarisation. Better make sure it is clean, or are you going to use HF AC?

Main idea is to use converter for Heaters and for polarisation. Then overall voltage drop will be sufficient for plate.
Good filtering definately will be needed

Considering the currents involved will be tiny, high value inductors should be small enough in physical size, and electrolytics are cheap

Rather there would be no need for many inductors. Caps of course, but where would be option there will be most film caps as possible

I strictly meant for the power supply (filtering)

Khron said:

I strictly meant for the power supply (filtering)

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Yes i know

Where low capacitances will be needed i will rather use film caps.
Why? More stable, lower ESR blah blah blah
These days film caps up to 4.7uF have pretty small packages, cost relatively cheap and we working on low voltage!

Here's basic concept of the circuit

Sometime around 2006-2007 I designed and built several versions of a p48 phantom powered tube condenser microphone.
A early version can be seen here:

http://goo.gl/EbgKck

I used several "tricks" (e.g. for level shifting and filament supply)

Cheers.

ZAPNSPARK

Zapnspark - really thanks for sharing

Exactly same heater converter
Even same pumps

Ok Guys!

Now you see how it can be made?

zapnspark said:

http://goo.gl/EbgKck

Click to expand...

Just curious about the function of R8 and C6 ( 330K and 1 uF)

Thank you Zap... looks great!

Question... did it work?

And if so, how did it sound? Was the tone different (wamer) than the  known FET mics (Alice or Occam3b)?

Thank you and regards!

HL

zapnspark said:

Sometime around 2006-2007 I designed and built several versions of a p48 phantom powered tube condenser microphone.
A early version can be seen here:

http://goo.gl/EbgKck

I used several "tricks" (e.g. for level shifting and filament supply)

Cheers.

ZAPNSPARK

Click to expand...

http://www.diystompboxes.com/smfforum/index.php?topic=42399.0
Also look for the EH one

Kinda makes you wonder if all the, for instance, FET mics that contain those discrete DC-DC converters for capsule bias, are all "legit"...

Gus said:

http://www.diystompboxes.com/smfforum/index.php?topic=42399.0
Also look for the EH one

Click to expand...