Official C12 Clone - Build and Support Thread

[saxmonster]

Matador,

Would this tap work ok?

http://www.ebay.com/itm/200815447593?_trksid=p2055119.m1438.l2649&ssPageName=STRK%3AMEBIDX%3AIT

and would these screws work ok?

http://www.ebay.com/itm/Stainless-Steel-Phillips-Pan-Head-Machine-Screw-2-56-x-3-8-Qty-250-/400702569221?pt=LH_DefaultDomain_0&hash=item5d4bbbfb05

Thanks
-Scott

 

[Matador]

Tap is fine.

I used 1/4" length (not 3/8"), but I'm guessing if worst came to worst you could trim long ones down.

 

[saxmonster]

Ok, I think he has 1/4 too.  They are all the same size for the construction of the mic frame right, all 18 screws are the same size except for the one on the pcb to the rail that has to go to the other side to catch the threads of what was the old tube holder.  I might just leave that one alone.

 

[saxmonster]

So I did more testing on the pinging sound and I took out the screws holding the pcb down.  I pulled the pcb away from the rails and then tapped the rails and got just a thunk type sound but no ringing or pinging.  I can live with that.  When I tapped the pcb I heard the actual ringing pinging sustain type of resonance.  I know this is a highly sensitive area but it seems that the pcb is acting like a microphone capsule and as if the pcb is like a diving board that resonates after someone jumps off it.  Like the pencil tap is someone diving of the board. hahhahaha

I tried it with both the GE 5 star I have an the China 12ax7b I have and both tubes didn't' effect the pinging.  When I put the china one in the elam there is no pinging either 

Again when I just tapped the rails or a body part I just got a thunk not a sustained note or ring.

 

[saxmonster]

tube

 

[Banzai]

If it's not a microphonic tube, don't be afraid to tap each component individually until you find the offender. Focus on the caps and wiring.

To cure a ringing component simply glue it to the pcb (always glue all caps anyway), and for wires just make them longer.

Again when I just tapped the rails or a body part I just got a thunk not a sustained note or ring.

 

[Category 5]

It very likely could be the polystyrene cap on the front side of the board.  They are prone to microphonics.  Careful trying to glue it with hot glue.  The insulating foam will melt easily.  I usually just bend the leads until I get a less resonant position.  A little piece of cut sponge foam underneath can work too.  Try to contact the body of the cap only and not the leads. 

 

[Category 5]

It very likely could be the polystyrene cap on the front side of the board.  They are prone to microphonics.  Careful trying to glue it with hot glue.  The insulating foam will melt easily.  I usually just bend the leads until I get a less resonant position.  A little piece of cut sponge foam underneath can work too.  Try to contact the body of the cap only and not the leads. 

 

[saxmonster]

Category5  You are the freakin MAN!!!!!!!!!!!!


It was the polystyrene on the back side on the left when looking at the back.  Holy crap as soon as I put my finger on it the ringing stopped.  DAM your good as is everyone on this list that has helped me in the past.

I am gonna try messing with the leads or the sponge trick first and see if I can get it to stop.

I have tapped everything on this pcb but never did the ones in the back, dam it dam it dam it.

Thanks again.

 

[Winetree]

I use the Loctite GO2 Glue alot. It dries clear and doesn't get hard. Great for securing components. 
I've also used it to deaden Mic bodies and head baskets from ringing. You can get it at Home Depot.

 

[Banzai]

Yeah, always glue all your caps down. Use E-6000 as it's non-conductive.

If you don't have any, buy it today and you'll wonder how you lived without it (you'll see what I mean when it dries).

 

[Matador]

To be honest, I've never liked grounding the PCB through the mounting screws.  It can mean that noise current can flow through the tube body and then through the ground layer of the PCB, which could couple as noise due to the common impedance.  In principle, it would be better to leverage the fact that the 7-pin XLR in the bottom of the mike could connect the mike shell and circuit ground together and there wouldn't be any common impedances (or this could even be done inside the PSU, and cable shield and circuit ground could be separate all the way up until that point).  Thus one could rubber isolate the PCB and perhaps mitigate some of these problems.

However I couldn't get much noise difference between the two methods, and a solid ground is better than an intermittent one, so having the PCB set screws solidly bond to PCB ground seemed like the lesser of two evils (e.g. favor low ground impedance vs. mechanical isolation).  However with rubber isolation mechanical coupling from the body to the circuit would be reduced. 

I'll have to run some more experiments when I finish my next two samples.

 

[tonzauber]

Hm i just destroyed my Lorlin in the attempt of putting the knob on. No wonder, the shaft of the switch measures 6,3mm, whereas the knob allows only for 6,1mm.

Or am I just too heavy handed and stupid? Or have I been missing something?

 

[Nyquist]

My knob went straight on no problems. Seems your knob may have been different. I would have drilled the knob out a bit. Any way the switch is stuffed now. You can however use the original switch that came fitted in the stock power supply to get you up and going.

 

[Winetree]

Gee, and the original switch was suppose to be crap. They look Heavy duty compared to the plastic junk.
I still have the originals just in case.

 

[Nyquist]

The main difference between the stock PSU switch and the switch supplied in the kit is the switch Chunger supplies is sealed where the stock switches contacts are open so is more susceptible to dirt,dust and corrosion due to moisture.

 

[saxmonster]

Can it be snapped back together?  I have my old original one that came with the PSU if you need it, its still assembled.

 

[Nyquist]

IF some clips are broken try some small dabs of glue to get it back to together.

 

[MicGeek]

Gee, and the original switch was suppose to be crap. They look Heavy duty compared to the plastic junk.
I still have the originals just in case.

I used the original in my builds.  The resistors were easy to replace.  Sure, the switch is open, but it just seems so much sturdier than the one in the kit.  I'm sure a heavier duty version of the closed switch would be quite pricey, though.  I have a couple extra of each if anyone needs them. 

 

[Nyquist]

True and the switch with open contacts can be cleaned and would be part of the microphones maintenance.