Hi,
I've built the synthacon vcf as per the rev.1. schematic, but am having trouble getting it to work. admittedly i've built it on vero board, but i was careful, and have thoroughly checked my wiring. Strangely when i run audio in the Low pass i get no out put, on the band pass i get a muffled signal, as if the cut off were set down low, and on the high pass i get the complete unfiltered signal. Neither the cut off pot nor the res pot make any difference except for a slight noise shift when i turn the resonance one, but no self oscillation. I used half a tl072 instead of a tl071, but that part seems to be working, since i can vary the gain of the signal with the 250k pot i have across the op amp feedback. I also measured the control voltage from the freq pot which is sweeping correctly through the voltages. I have replaced all the transistors and some of the electrolitic caps. I'm kind of stumped, if anyone can offer any advice or points in the circuit i can measure for known volatges that would be really very appreciated, having spent several days on this with no results im not sure what else to try. I am running it on +/- 12v. From what i've read this filter sounds really interesting so I'd love to get it to work!
thanks a lot,
Gus
[Non-text portions of this message have been removed]
I've built the synthacon vcf as per the rev.1. schematic, but am having trouble getting it to work. admittedly i've built it on vero board, but i was careful, and have thoroughly checked my wiring. Strangely when i run audio in the Low pass i get no out put, on the band pass i get a muffled signal, as if the cut off were set down low, and on the high pass i get the complete unfiltered signal. Neither the cut off pot nor the res pot make any difference except for a slight noise shift when i turn the resonance one, but no self oscillation. I used half a tl072 instead of a tl071, but that part seems to be working, since i can vary the gain of the signal with the 250k pot i have across the op amp feedback. I also measured the control voltage from the freq pot which is sweeping correctly through the voltages. I have replaced all the transistors and some of the electrolitic caps. I'm kind of stumped, if anyone can offer any advice or points in the circuit i can measure for known volatges that would be really very appreciated, having spent several days on this with no results im not sure what else to try. I am running it on +/- 12v. From what i've read this filter sounds really interesting so I'd love to get it to work!
thanks a lot,
Gus
[Non-text portions of this message have been removed]