From Oakley Sound via analogue Sent Mon, Jun 18th 2018, 09:49
From Oakley Sound via analogue Sent Mon, Jun 18th 2018, 09:49
Noise in reverse biased transistor junctions can be surprisingly variable in quality. One of my designs, the 5U Oakley Noise/Filter module, requires selection of the noise transistor which is a BC547. Originally I had thought that the process of selecting the best noise transistor was to find the loudest one. But oddly, the loudest ones actually didn't sound as good as the quieter ones. The loud ones were often prone to random bursts of noise while the quieter ones produced a more even and wide band noise. The BC547 sounded better than the BC550 too. On another note, I have found that noise transistors and noise diodes often become quieter with age. The amount of Pro Ones I saw in my later years as a repair engineer that had really quiet noise. I'm pretty sure they weren't that quiet when they were new. I wonder too if the noise spectrum changes over time. Tony www.oakleysound.com