G
Guest
Guest
I have been trying to build a modified version of the V76, thinking it would be a good thing for my son to use in his radio production studio. Well, it is kicking me butt badly.
First, the circuit has so much gain that it becomes easily unstable and oscillates in both low frequency (about 2-3Hz) and high frequency (about 200KHz). Grid stoppers helped the LF oscillstion and I can play with small caps across the feedback sections to stabalize the HF oscillation but it is still way too touchy.
I lost most of my hearing so I rely on oscilloscope readings for the general picture of how the circuit is working. I rely on my friend Ron, who runs a small recording studio, to actually hear what it sounds like. Well, after wrestling with oscillation for a while, I took it over to his studio for preliminary checks, hooked up a mike and found "highs rolled off, kind of midrangy with an emphisis on lows".
It appears the feedback gain circuit between the first and second stages is the main culprit in rolling off the high end. I am puzzled as to how it is doing this and have come here for some ideas. Also, as I'm sure you are aware, this circuit has so much gain that it ia nearly unusable without a really quiet stidio.
Here is a schematic of what I am trying. And and all help is appreciated.
http://users.adelphia.net/~thomasholley/Microphone/Modified%20V76.gif
First, the circuit has so much gain that it becomes easily unstable and oscillates in both low frequency (about 2-3Hz) and high frequency (about 200KHz). Grid stoppers helped the LF oscillstion and I can play with small caps across the feedback sections to stabalize the HF oscillation but it is still way too touchy.
I lost most of my hearing so I rely on oscilloscope readings for the general picture of how the circuit is working. I rely on my friend Ron, who runs a small recording studio, to actually hear what it sounds like. Well, after wrestling with oscillation for a while, I took it over to his studio for preliminary checks, hooked up a mike and found "highs rolled off, kind of midrangy with an emphisis on lows".
It appears the feedback gain circuit between the first and second stages is the main culprit in rolling off the high end. I am puzzled as to how it is doing this and have come here for some ideas. Also, as I'm sure you are aware, this circuit has so much gain that it ia nearly unusable without a really quiet stidio.
Here is a schematic of what I am trying. And and all help is appreciated.
http://users.adelphia.net/~thomasholley/Microphone/Modified%20V76.gif