Hi everyone, I was looking for some help with tweaking the gain reduction stage / preamp stage of the 1176.
I think I read on here some time ago, or maybe on Gearslutz some recommended ways of improving this stage.
The main improvement involved buffering the low side (Source) of the F.E.T. (BF245) with an invert of the top side (Drain)
this would mean that the F.E.T.'s Gate has DC on it only, instead of the the Gate voltage being modulated by some of the signal from the output of this stage, like it is at the moment.
It was also suggested that this inverting buffer have variable gain between 0.5 to 1.5 to minimize control feed through.
and also to Use a DC coupling around ground to avoid the need for a large value electrolytic capacitor (around 100uF in most designs)
I have based this new design on a op-amp based version of the 1176 I also found on here, just to make life easier.
at the moment I have not had any luck getting this to work, and I was wondering if somebody could point me in the right direction, or if any body else has tried a similar thing, or even if people have better improvements.
the last improvement i remember reading was to buffer the control voltage signal using a low-leakage JFET buffer in order to help stabilize it.
I am not sure where to begin with that.
any advice people can offer would be very much appreciated.
thanks.
I think I read on here some time ago, or maybe on Gearslutz some recommended ways of improving this stage.
The main improvement involved buffering the low side (Source) of the F.E.T. (BF245) with an invert of the top side (Drain)
this would mean that the F.E.T.'s Gate has DC on it only, instead of the the Gate voltage being modulated by some of the signal from the output of this stage, like it is at the moment.
It was also suggested that this inverting buffer have variable gain between 0.5 to 1.5 to minimize control feed through.
and also to Use a DC coupling around ground to avoid the need for a large value electrolytic capacitor (around 100uF in most designs)
I have based this new design on a op-amp based version of the 1176 I also found on here, just to make life easier.
at the moment I have not had any luck getting this to work, and I was wondering if somebody could point me in the right direction, or if any body else has tried a similar thing, or even if people have better improvements.
the last improvement i remember reading was to buffer the control voltage signal using a low-leakage JFET buffer in order to help stabilize it.
I am not sure where to begin with that.
any advice people can offer would be very much appreciated.
thanks.