I received my STRYKER SR-76NC microphone by STRYKER US this week.
I'd like to share my experiences to give room for optimizations. I really don't like to criticize as I'm happy that there's one manufacturer, who picked the design of the Palomar SL41 and who did a new production following with it.
Nevertheless there are weaknesses and room for optimization.
I drawed the schematic by reverse engineering.
The values of the SMD capacitors have been developed by my capacitance measurement device. That might be not 100% accurate while testing the soldered capacitors within the complete circuit, but I'm sure I got the correct values.
Unfortunately there's no schematic printed on the packaging.
There is a 2 paper sheet within a rough description of the 2 variable resistors.
But in my opinion this is not enough to describe it correctly. As both variable resistors interact. It only gets clear if you have a look to the schematic, I guess.
Cause first of all you need to adjust RV2 for the bass attenuating characteristics you'd like to have. As RV2 does not only change the sound characteristics,
but it changes also the audio level! The higher the attenuation of basses (resistance of RV2 needs to get smaller), the less on resulting audio level.
The weakness of the design is the value of C4 with 1,5µF. Meaning
it's needed to decrease RV2 massively (and automatically the AF level as well)
until you might recognize any change in audio characteristics. Now I'm not wondering anymore why people told here, that they do not recognize any significant change in audio characteristics.
After setting RV2 to you desired sound characteristics, you can continue with RV1 to get the needed audio level.
But RV1 will not only work as a volume attenuator,
it interacts with its parallel C6 as a dynamic changing AF highpass filter too. The higher the resistance of RV1, the less volume - but also the less attenuation of the basses. These are 2 effects in parallel. You might hear these results more or less on-air.
I just like to say, people need to know that to adjust both VRs in the correct order. Otherwise you might go around in circles on adjusting for modulation level and quality.
Optimizations:
First of all
C4 needs to be changed from 1,5µF to
100nF, which acts as an AF highpass filter on about 160 Hz,
even if RV2 is on its top position of full 10k (= least AF level attenuation). On setting RV2 to 5k, AF highpass rises up to 320 Hz which is a crisp sound. And still does not attenuate the AF level too much.
That's a simple modification which will solve the problem and make the SR-76NC even better, I guess.
Hope you enjoy.
vy 73,
Jochen, DG2IAQ, 13OP25