OPEN SOURCE DIY Mic Project - ORS 87 - Stripped Down u87

[Juan Vargas]

Then it's okay.
But do you know that these 2 resistors must be matched, with a precision of < 0.4%?
I bought a lot so I could make matched pairs.

yes I know I should buy more to match them, or getting 0.1% ones

 

[nyystero]

Can someone help me with wiring the Neutrik NTE10/3 on Khron's plus board?
From the thread i understood it needs to be wired in reverse which makes it a bit more confusing to me, and it's a little different from homero's board so i have a hard time finding an image i could use as reference.

 

[Juan Vargas]

on the NTE10/3 the yellow wire and white I got about 43 ohms and the red and black wire I got about 1.7K ohms I see P+and P- the higher resistance goes towards the circuit and the lower resistance to the S1+ and S2- I think it goes like that I see option for center taped transformers on the ORS Plus is not clear to me I want to try Khron's PCB design later, about that connection he can explain better he got more knowledge than me I just star to learn last year I usually build class AB audio amplifier and also PCB designs

 

[Khron]

on the NTE10/3 the yellow wire and white I got about 43 ohms and the red and black wire I got about 1.7K ohms I see P+and P- the higher resistance goes towards the circuit and the lower resistance to the S1+ and S2-

That sums it up pretty well. Worst case you might need to swap the S1+ and S2- wires, in case it ends up reverse-polarity.

I see option for center taped transformers on the ORS Plus is not clear to me I want to try Khron's PCB design later, about that connection he can explain better

The option is there - if one has a transformer with a center-tapped secondary, then R4/5 are not needed.

Sadly i still haven't managed to find the time to write up a build guide, but i haven't given up on that thought!

 

[nyystero]

Gentlemen, we have sound!!

Need to backtrack and fix some loose ends and read up on biasing the fet but at least it seems to be working
View attachment PXL_20250305_151630912.jpg

View attachment PXL_20250305_151725166.jpg

 

[Khron]

Gentlemen, we have sound!!

Need to backtrack and fix some loose ends and read up on biasing the fet but at least it seems to be working

View attachment 147184

View attachment 147186

Well damn, did none of the mounting holes line up with the chassis rails in that?

 

[nyystero]

Well damn, did none of the mounting holes line up with the chassis rails in that?

The lower ones did, but the capsule wires were quite short so had to improvise for now

 

[Juan Vargas]

nyystero thanks for the photos nice build indeed

 

[nyystero]

That sums it up pretty well. Worst case you might need to swap the S1+ and S2- wires, in case it ends up reverse-polarity.



The option is there - if one has a transformer with a center-tapped secondary, then R4/5 are not needed.

Sadly i still haven't managed to find the time to write up a build guide, but i haven't given up on that thought!

Might be a silly question but what would happen if s1+ and s2- was wrong?
Would it be a phase issue or it just simply not working?
I half quessed it but it seemed to work

Now trying to figure out REW to use my audio interface as a scope, i set the drain to around 11v with a multimeter to start with.
Do i have desolder capsule wires for this?

 

[Khron]

Would it be a phase issue

Just this, yeah.

Do i have desolder capsule wires for this?

No, that's what the "Cal" input is for.

 

[mrchapp]

No, that's what the "Cal" input is for.

How do you guys do that? I mean, how do you inject a signal there without noise wrecking the analysis in a mic with its body open? I find myself measuring, opening, adjusting pot, closing, and repeating. Surely there must be a better way.

 

[Khron]

How do you guys do that? I mean, how do you inject a signal there without noise wrecking the analysis in a mic with its body open?

Try to ignore the mains frequency and its harmonics? They'll be rolling off by 500-1000Hz anyway.

Plus the signal you're feeding into the cal input WILL swamp out the mains interference, even before approaching circuit clipping, so... Yeah