Official 251 point to point on Acrylic build and support thread

[OPR]

Hey Lemon Elvis Welcome  to the forum.  if your after 251 boards you can contact me at [email protected].
Cheers
Mark

 

[tonycamp]

Hey Nelly,
I do have a few set left if you interested shoot me an email at [email protected]   
There's a great new release dare I say masterpiece album "Animus" by an Australian band Mayfair kytes that exclusively used the 251 clone for main vocal duties check it out!

https://mayfairkytes.bandcamp.com/album/animus

I'd like to hear some samples naked, and out of the context of these folks mixes, they are absurdly bright and sibby to my ears, i like the way you put that mic together, very cool!

 

[OPR]

Glad you like the Build Tony!
I think the brightness is a production choice thing particularly on the first track as these mics are as generally smooth as butter That particular mic had a Tim Campbell capsule from about 2 or so years ago and was the brightest capsule of the three I owned at the time but still a nice sounding capsule.

I'm now making my own multi-chambered Ck12 copy which I hope to offer the community at some point.I'll post some solo samples soon.

 

[micaddict]

I'm now making my own multi-chambered Ck12 copy which I hope to offer the community at some point.I'll post some solo samples soon.

... he said on the side ...

 

[OPR]

I guess you saw what I did there didn't you Micaddict 

 

[Lordward]

I know that not much has been going on here but I really like this build and have made a couple already.  They sound great!  I thought I would share my tube socket holder "invention" since I could not for the life of me find the "original" rubber mount anywhere out there.  I also think it falls apart too quickly.  So I was drinking a glass of Coca-Cola and came up with this idea:

 

[Potato Cakes]

Hello,

Where does R10 (100k) go? The 251 schematics I have been looking at have this resistor between C2 (100pF) and the plate voltage, but the layout (very helpful by the way!) does not show R10. Also, is there noticeable sonic benefit to using a 10nF film cap for C3 instead of the electrolytic?

Thanks!

Paul

 

[Potato Cakes]

Also, is the 3.3uF cap using in place of the zeners? I just wanted to be sure I was reading that correctly.

Thanks!

Paul

 

[OPR]

Hey Potato cakes,
The 3.3uf  runs parallel with the Zeners and R10 is a typo all fixed now!  Sorry for the confussion

 

[Potato Cakes]

Thanks! I scare easily...


Paul

 

[Potato Cakes]

Sorry, one more question if I may. I looked through the build photos you so graciously posted, but I didn't see you use zeners with the output cap. Did I miss it? I just want to make sure I have them oriented correctly. The 251E schematic shows them used with the relay polar pattern switching, so I didn't know how that would translate to this version without relays. I hope the answer isn't directly in front of me, making me look sillier than I am.

Thanks!

Paul

 

[OPR]

There are no zeners in the mic, This version uses 9 polar patterns like a C12, The zeners are in the stock PSU and the Film cap in parallel is to clean up the negative effects of Zener regulation.

 

[Potato Cakes]

Copy. I thought that they were located in the PSU, but I wasn't sure.

Thanks again!

Paul

 

[Potato Cakes]

Just built a point to point 251 using this layout, a Tim Campbell CT12, a Mundorf 2.2uF cap for C4, and the PSU from a D-251 PCB set. It worked perfectly the first time (except I did have the pattern connections in the PSU backwards) and it sounds very, very nice. The only down side is that I built it for someone else!

Thanks for your help and offering these resources.

Thanks!

Paul

 

[OPR]

Posted by: Potato Cakes

The only down side is that I built it for someone else!

Thanks for the feedback potato Cakes!
Glad you enjoyed the build!!

 

[Steve_musician]

I am building the d-251 and wondered if anyone could point me in the direction of some more specific instructions for the psu build. Mod is from an Alctron HT-11A. The photos are helpful but more detail would be useful for the wiring to xlr, pattern switch etc?

 

[micaddict]

I am building the d-251 and wondered if anyone could point me in the direction of some more specific instructions for the psu build. Mod is from an Alctron HT-11A. The photos are helpful but more detail would be useful for the wiring to xlr, pattern switch etc?

Welcome.

I think you're in the wrong thread.

Try this one:
https://groupdiy.com/index.php?topic=55010.0

 

[lyricalgeek]

On the layout it looks like C1 is connected in the center of the voltage divider node, attaching to R2, R3, and R4.  On the 251 Schematic it only attaches between R4 and the backplates.  Is this a mistake on the layout or am I missing something here?

 

[OPR]

Posted by: lyricalgeek

On the layout it looks like C1 is connected in the center of the voltage divider node, attaching to R2, R3, and R4.  On the 251 Schematic it only attaches between R4 and the backplates.  Is this a mistake on the layout or am I missing something here?

My schematic differs from the original and allows for 9 polar patterns instead of the three  on the original.
Hope this helps
Cheers
Mark

 

[lyricalgeek]

I do understand that your circuit uses the C12 polar pattern schema with the 251 circuit.

I'm still confused by 2 things:

1.  I can't see a reason why C1 is attached to the node that connects R2, R3, and R4 as (I believe I understand) this has nothing to do with the polarization of the Front Capsule.  On the original 251 schematic C1 is dropping to ground from the "back side" of R4 - after the for-mentioned node.

2.  While I see how you develop a voltage on the RC I don't see any signal path for that signal to add to the FC signal and pass to the grid.  On another implementation of this circuit (C12 polarization + ELAM 251) I've seen a DC blocking cap between the RC and FC to allow signal to sum together before going to the grid.

Sorry for the long winded questions.  Just trying to understand the design of this circuit and how it works.

thanks