Admittedly, I have not done a dual delay v3205, so I haven't had to deal with this problem.
When you swapped R15, what value did you use?
The goal here is to bleed a little more signal to ground, so picking a low value for R15 will enable this to happen. A socket there and some experimentation might yield more positive results.
An increase in the Bias pot to 50k may further help this.
To raise the headroom, you could instead substitute a 7v or 8v regulator. I think I might have a 7v one. Or, you could use an 8.2v Zener in place of R19 which might be just enough to get it to operate in the correct range. I have some of those as well. I'd be happy to send the regulator and zener along to you.
Changing the preceding transistor will not have any noticeable effect since it's used as a buffer to make up signal lost from the filtering network.
When you swapped R15, what value did you use?
The goal here is to bleed a little more signal to ground, so picking a low value for R15 will enable this to happen. A socket there and some experimentation might yield more positive results.
An increase in the Bias pot to 50k may further help this.
To raise the headroom, you could instead substitute a 7v or 8v regulator. I think I might have a 7v one. Or, you could use an 8.2v Zener in place of R19 which might be just enough to get it to operate in the correct range. I have some of those as well. I'd be happy to send the regulator and zener along to you.
Changing the preceding transistor will not have any noticeable effect since it's used as a buffer to make up signal lost from the filtering network.