Quick DIY dual output LDC

[Gus]

Something I simmed.
Basic cut and paste circuit.
Added LPF for 67 like capsules
You should match parts between the amps

 

[kingkorg]

Great stuff as always Gus. Thanks for sharing!

 

[Winston OBoogie]

Great stuff as always Gus. Thanks for sharing!

+1

 

[dab0815]

Hope that makes sense.

A little bit
Im still unsure about the grounding. You say i connect the backplate to shortest grounding spot on one pcb. I dont know where that is is a grounding spot anywhere where i can possibly soldier the ground to?
I use the same boards and mic body as you did it seems you connected both backplate ground and capsule to the same spot on the pcb is that right? See attatched picture where on the above board there are two leads seem to be soldiered to the same spot.. can you confirm that?

Next is the grounding to and from xlr. So if i got this right ill take the ground from both pcbs (from the 3 bottom cables that go to the xlr) and connect them to the xlr ground pin.
Then i go from the ground from the xlr pin to the chassis of the mic like screw or soldier it to the metal part where i screwed the pcbs to.

Could you confirm this or let me know if im wrong? Then i could finish my build later today hopefully finally

 

[kingkorg]

Your mic should have one common ground. That would say all the ground points would be the same. It doesn't matter where you connect capsule ground to. It's one and the same ground, on the xlr, any ground point of the pcb, body, etc.

As for the red wire, i have no idea, i made that mic a while ago, i don't remember how exactly i wired it. The mic is in another country in my studio, so i can't check

 

[mhelin]

Now this could be the motivation for building a separate PSU for a solid state mic (and maybe experimenting with different head amp circuits), the hanging cables just look ugly...

 

[kingkorg]

This was really a quick build, just a proof of concept. I don't believe i used more than an hour or two on it. Latest one i built uses 5 pin XLR like the Sphere.

 

[dab0815]

Your mic should have one common ground.

ok so i pulled everything from the st51 out of the manley type body and installed the sphere clone innards in that body to see what that would sound.. got the same humming..
so here is what ive done..

i connected ground points from each of the two pcbs to xlr pin 1 (ground)

pin1 to the pin where the screw is. checked with multimeter that pin 1 is connected to mic body.

i checked with multimeter to find a ground point on one of the pcbs (checked of that spot connects with pin 1 of xlr) and connected capsule backplate to that pcb ground point.

i tested with multimeter that backplate is now connected to xlr pin 1 and mic body so it should be grounded correct right?

i connected capasule lead to the spots of each of the two pcb where they were the old capsules were wired to and where you have showed me.

i connected xlr 2 to xlr pin 2 and xlr 3 to xlr pin 3 of one pcb. and xlr 2 output to pin 4 and xlr 3 to pin 5 on the second pcb..
capsule is working as intended btw..

so i thought because how the body came they had a second ground on the capsule going to the headbasket so i connected a second wire from capule backplate to headbasket and connected headbasket to top basket because they didnt connect when i checked with multimeter.. still humming..

i discovered that the humming and ground noise goes away when i touch the mic body and at the same time with the other hand push very hard down on the top of the microphone (when i didnt connect second wire to headbasket).. dont know if that help anything...

right now im really out of ideas what i can do to the the ground issues away.. maybe i got a faulty body or so.. or im just too stupid to understand..

btw the mic body (the tube i mean) itself does not conduct.. at least i tested with multimeter..

 

[kingkorg]

You have to make sure that the top of the grille, that cap is also grounded. Not just the ring, but mesh too. Maybe use some aluminum kitchen foil to make everything sit snug. It could also be that the mesh is not properly grounded at all.

 

[dab0815]

You have to make sure that the top of the grille, that cap is also grounded. Not just the ring, but mesh too. Maybe use some aluminum kitchen foil to make everything sit snug. It could also be that the mesh is not properly grounded at all.

yes i had connected a wire from capsule backplate to mesh of the headbasket and then a wire from headbasket mesh to top of the grill mesh.. and as the backplate was grounded so the mesh should be too.. but it didnt change anything..

 

[dab0815]

damn me! i put in aluminiumfoil touching the capsule backplate and mic body and both mesh of the grill. and it is dead quiet now! i dont know why it didnt work with the wires tho? but i will try connecting a wire
this stupid mic body did cost me about 3 days and 3 nights.. man.. i did learn a thing or two tho

but why this mesh has to be connected to the mic body or capsule backplate (i mean the metal frame inside not the mic tube..) and none of my other mics have too?

and a big THANKS for all the help @kingkorg!

and some other little thing. how come you didnt have to extend the capsule leads? although the capsule leads on the b2 pro capsule were longer than the one on the st51 i STILL had to extend them with this manley body. it needs like crazy long wires? (i mean that for your manley ref c clone build..)

time to take this mic to a test..

 

[kingkorg]

The body itself should be grounded already at xlr, so there was probably bad contact from the body to the mesh. So just connect it to whatever ground you like. Remember, that paint coat doesn't conduct, so if they didn't scrape off some paint and connected mesh properly, there was no continuity.

I can't answer all the details regarding my builds, as i really go through a lot of mics, and other gear. I can't remember what i did yesterday.

Don't expect to save money or time on DIY builds, you do it to learn. My latest 1:1 Sphere replica costed easily double that of the original mic if you count in time, wages in Norway, and design/manufacturing of pcb.

 

[dab0815]

its more for the fun. and when i started i became obsessed lol. im self employed and if i count in the money i lost from letting some slide for this i could easily afford the original sphere too

i tested a little bit more with the aluminium foil and the problem for all the 3 days was only that the mesh was not connected. they didnt scrape paint on the inside so nothing touched the mesh. thats why the original had an extra wire to connect the capsule ground to the mesh. i did try to replicate that but i dont why it didnt work. i guess my connection to the capsule backplate (i just attached the wire with sticky tape to test) didnt work.. should have screwed it to some screw of the capsule ring..

the foil is now touching the side of the capsule and the headbasket mesh on the side and also connects top mesh..

But learned a lot so i guess my next build will be alot easier. for example that mic bodys dont conduct most of the time..

anyway: thanks again to you (or maybe curse you for getting me addicted to this haha) for helping me! couldnt have done this without you!

for the future i might put the sphere clone in that ali u47 clone body and the st51 back in the ref c clone body.. but i dont know which shockmount works with the u47 ali body yet..

And also i have to check if the capsule lead extension did introduce hearable noise but right now my background noise is too loud anyway.

 

[ccaudle]

the original had an extra wire to connect the capsule ground to the mesh

That sounds like a good way to get RFI injected into your circuitry.
The shield should be the shield, and the circuit reference should be separate, and they should connect together at one point.
AES48-2019 (most recent version of Audio Engineering Society standard for cable and enclosure shielding and grounding connections) illustrates it like this:



The "SHIELD" label is pin one from the XLR connector, it should connect directly to the case (meaning reliable conductive connection, depending on type of metal and finish it might take some extra work like scraping paint, and possibly putting some solder to prevent corrosion).
The "REF" label is what is often colloquially called circuit ground. The circuit "ground" should connect to the case near that same point. There should be no other connections between the circuit and the case, you do not want there to be a path for circulating RF currents flowing on the case to be able to divert and flow through the circuit board.

 

[dab0815]

That sounds like a good way to get RFI injected into your circuitry.
The shield should be the shield, and the circuit reference should be separate, and they should connect together at one point.
AES48-2019 (most recent version of Audio Engineering Society standard for cable and enclosure shielding and grounding connections) illustrates it like this:

View attachment 81126

The "SHIELD" label is pin one from the XLR connector, it should connect directly to the case (meaning reliable conductive connection, depending on type of metal and finish it might take some extra work like scraping paint, and possibly putting some solder to prevent corrosion).
The "REF" label is what is often colloquially called circuit ground. The circuit "ground" should connect to the case near that same point. There should be no other connections between the circuit and the case, you do not want there to be a path for circulating RF currents flowing on the case to be able to divert and flow through the circuit board.

Ok than the body i used (chinese manley ref c clone from alibaba) is a very bad design. because the mesh and outer body (the tube of the mic body) cannot be grounded from xlr because the mic tube itself is not conductive and the bottom part of the mic where the xlr connects with the screw is also not conductive. So there is no possibility to shield or groind the mesh from the headbasket other than connect it with a wire or aluminium foil from either the capsule or the inner mic body (the metal parts where the circuit board is screwed to..

 

[dab0815]

I will try by scratching off some paint on some non visible areas where i think that it then should ground or shield properly..

 

[dab0815]

but why is it different if the capsule backplate is connected to pcb ground and from there to xlr and then the mic body and mesh is connected from xlr to mic body and mesh..
or is it because ground then is like running from capsule to mesh through pcb and body. and other wise ground connects from capsule to pcb and mesh likewise and it is going two ways instead of one way.. sorry i think im not really using the right lingo and explain myself cumbersome..

so then it might be better (if i cant get it right by scratching some paint from certain places) to connect the aluminium foil from the inner metal frame body to the mesh and not from the capule backplate directly right?

 

[ccaudle]

why is it different if the capsule backplate is connected to pcb ground and from there to xlr

If you draw out the "true" schematic it becomes more obvious. Every connection has resistance, inductance, and capacitance associated with the connection, so the "true" schematic shows resistors and inductors everywhere there is a connection between two elements. All the circuit elements are shown connecting to a single node, but in reality the resistance and inductance between the capsule backplate and the rest of the ciruit board is pretty low when connected directly to the circuit board, but will be higher resistance when connected to the mic body. Any current flowing through a resistance or inductance generates a voltage proportional to the impedance, or the converse, any voltage presented to a point will generate a current proportional to the impedance if it has a return path to the voltage source.
When you touch the microphone, or when high RF signals are near the microphone (such as from the cell phone in your pocket) any difference in potential across the microphone body will now be across the top and bottom of the circuit as well, causing noise current to flow through the circuit reference connection (aka circuit "ground"). You only want signal currents flowing through your circuit, otherwise the noise current becomes part of the signal current and is irreversibly part of the signal from that point on. Since current always flows in loops it requires at least two connections for current to flow, which is why you want just one connection between the circuit and the shielding enclosure, that way no noise currents on the enclosure have a way to flow through the circuit.

 

[mihi_fuchs]

Hi everyone,

here's my approach on the dual output mic and also some soundsamples are in the dropbox folder. Just in case someone is interested in playing around. I also tried it out with the townsend plugin and the polar pattern designer of Austrian Audio (see the sound samples in the thread).

Dual Output Microphone: 2x Schoeps Circuit + K87 capsule BM-800 Donor Body)



Cheers
Michael

 

[mateus]

Wow, this sounds tasty!
@kingkorg Could you point me out in the right direction?
So, I need to buy a couple Sterling ST51 and what else? Any PCB in specific?

Cheers!