Hi all
I’m using 16 stages of allpass filters to create a 0.8ms delay in order to compensate de distance between a bass speaker and a horn mounted driver. A LM1876 is used for amplification.
Allpass filters are all the same, R1 then C1 on the + input, R2 on the – input, R3//C3 on the feedback. R1=23.7k, C1=1nF, R2=R3=22k, C3=22pF. OpAmps are LM837
At the end, the signal has a lot of distortion, I can see it with the scope !!
I tried with TL074 opamps and suppressed the 22pF caps.
Distortion is lower but not enough, noise is very higher than with LM837………
I saw at Linkwitz website that he uses an R and C filter, the next one is a C and R filter and so on…
Is there a reason for that ?
What could I do (staying with analog delays, no BBD, no digital) to get low distortion and low noise, without risk of instability of the opamps ?
Thanks for your help
Best Regards
I’m using 16 stages of allpass filters to create a 0.8ms delay in order to compensate de distance between a bass speaker and a horn mounted driver. A LM1876 is used for amplification.
Allpass filters are all the same, R1 then C1 on the + input, R2 on the – input, R3//C3 on the feedback. R1=23.7k, C1=1nF, R2=R3=22k, C3=22pF. OpAmps are LM837
At the end, the signal has a lot of distortion, I can see it with the scope !!
I tried with TL074 opamps and suppressed the 22pF caps.
Distortion is lower but not enough, noise is very higher than with LM837………
I saw at Linkwitz website that he uses an R and C filter, the next one is a C and R filter and so on…
Is there a reason for that ?
What could I do (staying with analog delays, no BBD, no digital) to get low distortion and low noise, without risk of instability of the opamps ?
Thanks for your help
Best Regards