midwayfair
Well-known member
I should have specified, I was having the problem in Figure 8, NOT in Cardiod or Omni.
I got it up to about 70 before a very loud sound would cause it to stick to the backplate. Speaking voice I could get up to almost 80 but I wouldn't trust that to be stable even for speaking. I might do a future simple build with only cardi and omni (no figure 8) and put it at 120V. I also noticed last night that I didn't actually end up with a K12 from the group buy ... I guess experimenting with that will be further down the road.
I went back in and made some further refinements to the mic after soldering it up ... decreased the current consumption of the emitter follower to give the FET a bit more to work with, added a big 220nF at the diaphragms to ground, and now I'm pretty happy with 55-60V. Less self noise but as much output as my build with the 2:1 transformer even though I'm using a 4:1.
No Zeners in sight (the 33V reg at the mic input was causing noticeable hiss in the dry path and I was losing too much current to use the emitter follower). I do still think it might be worth using 62V zeners to regulate the rectified output, but since I don't use any unusual phantom power setups I think I'm good.
I'll post a schematic and layout when I get that far, but I'm impressed enough with the simple oscillator with additional filtering that I don't think the 2-transistor one will offer enough of a benefit to warrant the extra parts.
I got it up to about 70 before a very loud sound would cause it to stick to the backplate. Speaking voice I could get up to almost 80 but I wouldn't trust that to be stable even for speaking. I might do a future simple build with only cardi and omni (no figure 8) and put it at 120V. I also noticed last night that I didn't actually end up with a K12 from the group buy ... I guess experimenting with that will be further down the road.
I went back in and made some further refinements to the mic after soldering it up ... decreased the current consumption of the emitter follower to give the FET a bit more to work with, added a big 220nF at the diaphragms to ground, and now I'm pretty happy with 55-60V. Less self noise but as much output as my build with the 2:1 transformer even though I'm using a 4:1.
No Zeners in sight (the 33V reg at the mic input was causing noticeable hiss in the dry path and I was losing too much current to use the emitter follower). I do still think it might be worth using 62V zeners to regulate the rectified output, but since I don't use any unusual phantom power setups I think I'm good.
I'll post a schematic and layout when I get that far, but I'm impressed enough with the simple oscillator with additional filtering that I don't think the 2-transistor one will offer enough of a benefit to warrant the extra parts.
