Official C12 Clone - Build and Support Thread

[Category 5]

No after it settles in figure 8 both side sound very different

In headphones this is normal because the phase of the rear capsule is reversed.  Are you compensating by inverting the phase on the preamp or in the DAW?

 

[Matador]

No after it settles in figure 8 both side sound very different

You you listening in headphones?

 

[saxmonster]

Hi Guys,
Got my new AMIT14 today and here are my readings.

For the Red Wires I get 20.1R Where Chunger had 20.4R

For the Blue Wires I get 915R Where Chunger had 930R

Should I be worried or are these within spec?

Thanks
-Scott

 

[ciscan.81]

Are you saying that the sounds/noise only happen during the transition between patterns, and that the mike sounds normal after it settles?

The RC time constant on the pattern supply is quite long:  20-30 seconds if memory serves.

Yep, that's the case for me...

Mic is otherwise quiet, sounds good and operates normally. If I crank the gain through the roof there is the tiniest bit if tube noise but nothing to worry about.

I'm away from home at the moment and so I'm unable to check,  but the duration of the noise may well be 20-30 seconds as you mentioned.

To be honest, I haven't actually checked tone difference between front and back in fig. 8, I don't use that pattern often...maybe I'll check it when I return home in a few weeks.

I'll butt out until then and let Mr.GrinschSD sort out his bugs.

Thanks

 

[Matador]

Hi Guys,
Got my new AMIT14 today and here are my readings.

For the Red Wires I get 20.1R Where Chunger had 20.4R

For the Blue Wires I get 915R Where Chunger had 930R

Should I be worried or are these within spec?

Thanks
-Scott

Those all look fine to me: perhaps a short bit of winding difference but shouldn't impact anything.

 

[Mr.GrinchSD]

HAHA ok im not gonna be home for a couple go day's but I'm gonna run the mic powered on and let that tube burn in for a couple of hour's I think some of the hum is from the electro harmonic tube, probably should have got something a little nice for this build 

I post some update's when I'm back home and can play around with it more. And as always

THANKS FOR THE HELP EVERYONE!!! Hope to get this thing working flawless SOON

 

[saxmonster]

Its alive and sounds fantastic, here is a clip from a test recording tonight.

http://www.ehornstudios.com/media/C12.aif

I do have one issue and that is this ring but it makes it with out the shell on too.  I think its the post on the frame vibrating.

check it out.  Just taping on the outside of the body and lightly on the head basket.  The sound doesn't change.

http://www.ehornstudios.com/media/C12issue.aif

maybe my zip ties are too tight?  Don't think you can hear it when its in the microphone holder.

 

[andyfromdenver]

Sounds lovely saxmonster!  Nice saxamaphone
Don't know about the ringing, I guess just never  ever play or sing anything that resonates that frequency (j/k). 
Hope you sort it out, or it's a non issue in use.

 

[MicDaddy]

Lots and lots of my mics have funny resonance when doing the microphonic ping test.

If it's an issue you can try some kind of potting or damping.  Hot glue, epoxy, fiberglass. 

I'd try in front of sources that move a lot of air, kick drum, bass cab, or other sources that have fundamentals near that resonance and see if you can excite it.  If not maybe non issue?

 

[Matador]

Yeah good advice MicDaddy.

There are a few things at play:
1) Single layer headbaskets can do this:  if you read in the thread, adding mass around the inside bottom (with JB Weld, etc) can help this a lot
2) Tube microphonics:  what you are hearing is mechanical coupling of the heavy-massed body to the tube internals, causing the ringing to be converted to output signal.  Even guitar amps do this.  You can mitigate it by selecting tubes for microphonics by either a) testing your stash with the pencil eraser test (rap on the side of the tube with the eraser end of a pencil, and pick the tube with the quietest "thunk"), or b) pay someone to screen the tube for you.
3) Mass of the body:  the more body mass, the lower in frequency the resonance occurs.

One of my mikes has a resonance around 640Hz, however it hasn't been noticeable in any recording I've done with it so far.

 

[saxmonster]

Are the GE 5 star HQ tubes any good.  Never saw the HQ in red on them before.  Anyone seen or heard these before?

 

[saxmonster]

Well I took the shell off as well as the head basket and the ping sound was still there when I tapped on the frame and on the tube and on the 7pin connector and the pcb.  So it didn't matter when I tapped the sound stayed the same so some how I need to dampen the frame so the vibrations don't make that sound.  I think it is just inherent in this microphones frame.  I wonder how I can insulate the bottom part from the rails and the rails from the top part that the capsule mount screws into. 

 

[chunger]

Well I took the shell off as well as the head basket and the ping sound was still there when I tapped on the frame and on the tube and on the 7pin connector and the pcb.  So it didn't matter when I tapped the sound stayed the same so some how I need to dampen the frame so the vibrations don't make that sound.  I think it is just inherent in this microphones frame.  I wonder how I can insulate the bottom part from the rails and the rails from the top part that the capsule mount screws into.

I may not now exactly what I am talking about but if you want to change the resonant frequency of the frame rails, one possible method is to add mass.  There is ample room to add  self-adhesive lead tire balancing weights to one or both of the rails.

http://www.amazon.com/JEGS-Performance-Products-Standard-Lead-Free/dp/B007VR8BXS/ref=pd_sbs_auto_3?ie=UTF8&refRID=0BW51METTYJN76YHTJB9

Another way would be to dampen the rails perhaps with something like this applied to rails and top plate.

http://www.amazon.com/3M-08840-500-Sound-Deadening/dp/B005RNGRMU/ref=sr_1_10?s=automotive&ie=UTF8&qid=1421040514&sr=1-10&keywords=automotive+sound+deadening

 

[saxmonster]

Thanks Chunger,
I am going to do some more test tonight and unmount the pcb and see if the noise is there if I pencil eraser tap the pcb lightly.  Im thinking it might be just the rails transferring to the top mount where the capsule stand and head basket screw too.  Maybe rubber washers between the metal joints would stop it.

Anyone else every have this problem with the mic.  I don't notice it when its in the mic stand just when handling the microphone.  Maybe I shouldn't worry about it and just let well enough alone.

 

[Matador]

I will give the "retap the screws" advice again.

Many of the 2mm internal screws don't hold well IMHO, partly due to the thread depth and partly due to the material of the body.  I've found that stainless steel 2-56 screws tap very well into the existing holes, and have much deeper thread depth and hold the body together much better/tighter.  The 2-56 doesn't remove a lot of new material and it pretty/easy quick to do.

The tighter the individual pieces, the more total mass and the lower the resonant frequency (at least in theory).

 

[saxmonster]

Matador,
That sounds like a great idea.  Do you do it for all the screws that make the up the chassis?

What about the screws that go into the ring at the bottom where the 7 pin connector is. 

So I will look for 2mm 2-56 thread stainless steel screws.  What size thread do the original 2mm screws in the chassis have?

 

[Matador]

That sounds like a great idea.  Do you do it for all the screws that make the up the chassis?

Yes, if memory serves:

1) 4 screws hold the two side rails to the base
2) 2 screws, one in each side rail, to the top plate
3) 2 screws to hold the capsule mount to the top plate
4) 4 screws to hold the PCB to the side rails
5) 4 screws to hold the transformer shield to the side rails
6) 2 screws to hold the headbasket to the top plate 

 

[chunger]

Matador,
That sounds like a great idea.  Do you do it for all the screws that make the up the chassis?

What about the screws that go into the ring at the bottom where the 7 pin connector is. 

So I will look for 2mm 2-56 thread stainless steel screws.  What size thread do the original 2mm screws in the chassis have?

The original threads are metric M2.  I typically tap to 2-56 when I strip a screw and need to repair it.  Matador prefers to just do them all from the get-go  ;D

 

[saxmonster]

So we are leaving metric and going to standard right?  So I wanna get 2-56 stainless steel machine screws with a round top and I have to measure how long the old ones are. 

Does metric have different thread counts per inch or all they all the same thread count.

 

[originalmusician]

Not much was said about the mic comparisons posted by TheJames on page 81 other than mic A is fuller down low, which I agree with. In addition, mic A appears to have more self noise, and I prefer the tonal quality and cleanliness of mic B for this particular application.

Since it appears no one else is going to weigh in, which is which or did I miss this somewhere? OK, don't be mad at me if I picked the wrong mic.  :'(

I also have stock capsule and a beesneez, so I'll do some of my own comparisons and see if I feel the same way.