This project started when I noticed one of my cheap Samson C02 mics had more noise (hiss, very evident at high gain levels) than the other in the pair . I had not really used the mics very much so I don't know if this is something that developed over time or if it was like this when they were purchased new. And yes, I knew these mics did not have very good specs anyway with regards to self noise.
After reading this message here in GroupDIY, I decided to first try the mentioned mod to see if that might offer overall improvement and solve the hiss at the same time. It didn't. I know the suggested mod was more about addressing the low sensitivity of these mics so I wasn't that surprised that the hiss was still there after the mod. In any case, see the attached schematic for the mod I implemented. NOTE: This diagram was drawn from observation of my actual mic and I make no guarantee of accuracy or suitability for use in your situation or with your sample of the mic. I applied the mod to both of my C02's.
I'm still evaluating, but overall the mod may have very slightly improved mid-range presence. It did not seem to change sensitivity at all; the mics still require the same amount of gain to get usable signal. Noise level (on either mic) was also not changed. In retrospect, I don't think the mod was worth the time.
After doing the mods, I continued on to see if I could reduce the noticeably higher hiss on the problem C02. By the time I stopped, I had replaced every component on the PCB, and the hiss was still there
. I know the problem is NOT the capsule; when I switch capsules with the quieter C02 in the pair, the hiss remains.
There is only one change I made that resulted in an audible difference: When I replaced R4 (see attached diagram) with a new 5.1K 1%, I noticed the hiss was even more pronounced. Thinking that maybe I had purchased a bad resistor, I did some measurements: The removed R4 was 5099 ohms, and the new R4 (measured out of the circuit) was 5076 ohms (still within the 1% spec). I re-installed the original R4 and the hiss seems to have dropped back to the original level. This has me a bit stumped and I'd be interested in any comments on why this small difference in this part of the circuit would result in a noticeable change in the hiss level.
Thanks for any comments.
After reading this message here in GroupDIY, I decided to first try the mentioned mod to see if that might offer overall improvement and solve the hiss at the same time. It didn't. I know the suggested mod was more about addressing the low sensitivity of these mics so I wasn't that surprised that the hiss was still there after the mod. In any case, see the attached schematic for the mod I implemented. NOTE: This diagram was drawn from observation of my actual mic and I make no guarantee of accuracy or suitability for use in your situation or with your sample of the mic. I applied the mod to both of my C02's.
I'm still evaluating, but overall the mod may have very slightly improved mid-range presence. It did not seem to change sensitivity at all; the mics still require the same amount of gain to get usable signal. Noise level (on either mic) was also not changed. In retrospect, I don't think the mod was worth the time.
After doing the mods, I continued on to see if I could reduce the noticeably higher hiss on the problem C02. By the time I stopped, I had replaced every component on the PCB, and the hiss was still there
. I know the problem is NOT the capsule; when I switch capsules with the quieter C02 in the pair, the hiss remains.There is only one change I made that resulted in an audible difference: When I replaced R4 (see attached diagram) with a new 5.1K 1%, I noticed the hiss was even more pronounced. Thinking that maybe I had purchased a bad resistor, I did some measurements: The removed R4 was 5099 ohms, and the new R4 (measured out of the circuit) was 5076 ohms (still within the 1% spec). I re-installed the original R4 and the hiss seems to have dropped back to the original level. This has me a bit stumped and I'd be interested in any comments on why this small difference in this part of the circuit would result in a noticeable change in the hiss level.
Thanks for any comments.
