First time - Schoeps CMC5 schematics

[Karl-0_0-]

Re-translate it back before posting

My mail notice was translated, but not the actual reply here.

How and where does the capsule connect to the circuit? And what's that polystyrene cap supposed to achieve?

Pogopin in nosecone to terminal 1, DC from terminal 2 and cap between the terminals to adjust the current maybe?

I don't know what I'm doing and don't know how to connect the capsule correctly, so I tried to apply the same design as certain DIY company hoping one of you guys would correct my mistake.

 

[micolas]

@Khron thanks for the heads up!
My smartphone has a bug when I edit a post, if I'm not careful to do the translation.

So @Karl-0_0-
BC416 is PNP, in your schematic it is drawn NPN
T2's emitter must go to DR3 -> pin 3

 

[Karl-0_0-]

BC416 este PNP, în schema ta este desenat NPN
Emițătorul lui T2 trebuie să meargă la DR3 -> pinul 3

Better?

 

[micolas]

Better?

Now you need to clarify the capsule connection and the presence of that C14 capacitor as @Khron pointed out

 

[Khron]

I tried to apply the same design as certain DIY company

And what company might that be?

Pogopin in nosecone to terminal 1, DC from terminal 2 and cap between the terminals to adjust the current maybe?

I promise I mean no offense, but... you might wanna consider possibly going back to study some electronics basics?

https://sound-au.com/articles/index.htm#begl

 

[Karl-0_0-]

And what company might that be?

MP, but their PCB design is altered.

I promise I mean no offense, but... you might wanna consider possibly going back to study some electronics basics?

https://sound-au.com/articles/index.htm#begl

No offense taken. Exactly what I need. Thanks for the link.

 

[Karl-0_0-]

Now you need to clarify the capsule connection and the presence of that C14 capacitor as @Khron pointed out

I'm going back to school. So for now let's pretend that thing never happened.

 

[micolas]

@Karl-0_0-
Maybe this diagram will help you.
Use the values of the components you want, adapt some details from Shoeps.

 

[rogs]

Better?

You need to reverse the values of DR1 and DR2, and C8 is 6.8pF not 68pf

 

[Karl-0_0-]

You need to reverse the values of DR1 and DR2, and C8 is 6.8pF not 68pf

Thanks for pointing out the mistakes.

 

[Karl-0_0-]

@Karl-0_0-
Maybe this diagram will help you.
Use the values of the components you want, adapt some details from Shoeps.

Thank you for the diagram.

My struggle is I want to be able to use the nosecone/pogo pin design like in the MicParts Schoeps style and jp8s KM84+ version, where there is only one connection to the PCB. But every diagram I stumble upon there are two connections from the capsule to the PCB, and where I'm at right now I don't have the skills to adapt any diagram to fit the one connection design really.

So if there are readily available files for that type of CMC5 style PCB I'd just drop everything and order a couple of those.

 

[jp8]

Better?

Better!

What kind of output connector will your circuit have? On your schematic, you chose the Tuchel connector wiring scheme. Assuming you want XLR instead, then from top to bottom the pinout should read 3, 2, 1 (1 = Ground). At least, this is how it's depicted in the original Schoeps circuit diagram, which I assume is right. The circuit from @micolas ' post #28 shows pins 2 and 3 swapped.

If your capsule has the membrane connected to the shell (= Ground) instead of being "floating" as in Schoeps capsules, you'll want a 1nF coupling capacitor between capsule and JFEzt Gate and feed the polarization voltage to the backplate (center pin of the capsule) through a 1G or higher resistor. In this configuration, and assuming a positive polarization voltage, pins 2 and 3 should be connected as depicted in post #28.

Jan

 

[jp8]

So if there are readily available files for that type of CMC5 style PCB I'd just drop everything and order a couple of those.

For which mic body?

Many chinese SDC mics already have a Schoeps-style circuit. Some better than others, but they can be easily modded and improved to the same quality level as the CMC 5 circuit. Takstar CM-60 and CM-63 are popular SDCs to that end. Alctron T-02A is another good candidate. All these mics fit the excellent 3U Audio capsules.

Jan

 

[micolas]

Better!

The circuit from @micolas ' post #28 shows pins 2 and 3 swapped.

In the Shoeps scheme, the capsule is connected directly to the gate of the jFET.
In the other scheme, the capsule is coupled through C3=1nF to the jFET, which will produce phase inversion. That's why XLR 2 and 3 are reversed.

 

[Karl-0_0-]

Better!

What kind of output connector will your circuit have? On your schematic, you chose the Tuchel connector wiring scheme. Assuming you want XLR instead, then from top to bottom the pinout should read 3, 2, 1 (1 = Ground). At least, this is how it's depicted in the original Schoeps circuit diagram, which I assume is right. The circuit from @micolas ' post #28 shows pins 2 and 3 swapped.

Hi Jan, thanks for sharing your knowledge.
You are right in your assumption. I chose the Tuchel by mistake. XLR is what I want.

If your capsule has the membrane connected to the shell (= Ground) instead of being "floating" as in Schoeps capsules, you'll want a 1nF coupling capacitor between capsule and JFEzt Gate and feed the polarization voltage to the backplate (center pin of the capsule) through a 1G or higher resistor. In this configuration, and assuming a positive polarization voltage, pins 2 and 3 should be connected as depicted in post #28.

Jan

Something like this? I looked at the Takstar scheme on your website just now and added the "capsule ground" path, but that might not be needed?

I'll also reply to your other post here. I haven't thought about microphone body yet, since I don't know how big the footprint will be. But Takstar is indeed a good option. The reason I'm giving this design an attempt is because I want the satisfaction of soldering a PCB from scratch. But it doesn't have to be "my own" design.

PS. I'm currently waiting for a delivery from PCBway and your KM84+ board.

 

[jp8]

In the other scheme, the capsule is coupled through C3=1nF to the jFET, which will produce phase inversion. That's why XLR 2 and 3 are reversed.

Sorry, but I have to disagree with your statement. A capacitor can not and will not invert the signal. It's the capsule polarization direction that determines the polarity of the capsule sign: the original Schoeps circuit and the circuit you posted both have positive polarization on the membrane. In this configuration, C3 an R3 can be omitted in your circuit.

With XLR pins 2 and 3 as depicted in your circuit, the circuit should be redrawn as follows:

• Bottom side of capsule (membrane) connects to Ground, not to R11 and C8.
• Bottom side of R3 connects to R11 and C8, not to Ground.

Jan

 

[micolas]

With XLR pins 2 and 3 as depicted in your circuit, the circuit should be redrawn as follows:

• Bottom side of capsule (membrane) connects to Ground, not to R11 and C8.
• Bottom side of R3 connects to R11 and C8, not to Ground.

Jan

The scheme is not mine.

I posted it quickly without careful analysis, for some reference.
Now I looked more carefully. You are right.For Karl, this is how it should be changed

 

[jp8]

Something like this? I looked at the Takstar scheme on your website just now and added the "capsule ground" path, but that might not be needed?

Yes, indeed, like that. The capsule ground connection, back to the signal ground on the PCBA is through the mic body and XLR ground connection. As such, it is not part of the circuit on the PCBA and can be left away if the circuit diagram is used to design a PCB layout from. As current always flows in a closed loop, the ground connection can be added, just for a better understanding of the circuit.

PS. I'm currently waiting for a delivery from PCBway and your KM84+ board.

Enjoy building the KM84+! And of course, enjoy using it. If you need any help, don't hesitate to post your questions!

Jan

 

[Karl-0_0-]

Yes, indeed, like that. The capsule ground connection, back to the signal ground on the PCBA is through the mic body and XLR ground connection. As such, it is not part of the circuit on the PCBA and can be left away if the circuit diagram is used to design a PCB layout from. As current always flows in a closed loop, the ground connection can be added, just for a better understanding of the circuit.

If I understand you right I can remove C14 and GND, and it won't make a difference if I design a PCB from the scheme?

But for claritys sake it can be added to scheme to get a better understanding of the circuit.

On another note. In the original scheme Dr5 is labeled "Ferrite bead", so I'm guessing it's an inductor. But I wonder at what value.

Enjoy building the KM84+! And of course, enjoy using it. If you need any help, don't hesitate to post your questions

Thanks, I'll keep that in mind.