开云体育

I have built quite a few of these with absolutely normal 1/4 w resistors from Amazon and they perform amazing. Compliments are really made to a high standard these days and most things will be just fine without fancy resistors.

On Sat, Jun 15, 2024, 10:12 AM Jules Ryckebusch via <ryckebusch=[email protected]> wrote:

Thanks for the positive feedback on my OPA mic instructable. I will look at the ".22nF" on the instructable schematic. I use metal film resistors and 1% for all of it except for the 1Gig, which is 5% or 10% (can't remember off the top of my head). As it is, the design?is already 40dB less distortion than the standard FET based Schoeps circuit and about 12dB of self noise. Component changes or use of .1% resistors are not going to provide measurable improvements. Even using Henry's output capacitors?wont drastically affect the output. You can measure the difference on the bench as he has.? Henry put the OPA mics through testing here:?

I love his quote at the end:?In short, these op-amp boards are the flattest and least distorted mic circuits I’ve ever tested. If you were to describe the “flavor” it would have to be something like “distilled water”. OTOH, like any mic, the main contribution to a “sound” is the capsule, and a good capsule will shine. A poor capsule will have no cover.

All my builds now are with SMD components with "normal" Mouser 1% thick film resistors. I still use the 22nF caps from the instructable as they are RF/EMI protection. Even if they are microphonic, the surrounding circuitry is so low impedance that they won't introduce?anything that the mic capsule isnt already picking up at orders of magnitude louder.?

Jules

On Sat, Jun 15, 2024 at 7:59?AM Lode Willems via <micbuilders=[email protected]> wrote:

Hi everyone.

I'm currently in the process of building an OPA Alice based microphone using a NW-700 body and TSB2555B capsule.

Jules instructable is an amazing guide that makes it trivial for anyone to build an OPA Alice using the linked supplies.
But one thing I find lacking is more information regarding the component selection.
As someone who's new to mic building and analog circuitry in general, I wonder how exactly the passive components got selected.
For this reason I've kept most components I plan to use for my mic the same as the provided BOM on PCBWay.

I did substitute some as I think they may perform better or because I already have them in stock.

If anyone could give me some feedback on these choices I would be more confident in my ability to finish this project.

For the 47, 2.2k and 47K resistors I went with 0.1% 25ppm/C 0603 resistors from the YAGEO RT series.
As I understand it matching the resistors on the XLR3 and XLR2 lines is important for good performance.

The 200 Ohm resistor is just a basic 1% thick film resistor as it doesn't really affect anything important in the circuit AFAIK.

I also plan on replacing the output capacitors with non-polar Panasonic ECE-A1HN4R7U caps.
This is based on the data from Henry at Audio Improv who showed that non-polar caps on the output reduced distortion.

Finally I replaced the 22nF EMI/RF suppression caps with TDK FG14C0G2A223JRT06 as these have a C0G dielectric making them non microphonic.

(BTW these are shown as 0.22nF on the instructables schematic which was super confusing)

I hope my modifications and my reasoning behind them make sense and thanks in advance for taking a look.

--

Best Regards,

Jules Ryckebusch

214 399 0931