chrissugar
Well-known member
OK, now that I have some real world info about the effects of DC servos in sound, I have some questions about this subject.
In my tests I used two different schematics. One circuit used for testing was based on the JLM hybrid schematic: http://www.jlmaudio.com/JLM%20Hybrid%20Opamp%20circuit.pdf and the other was based on Fred Forssell's circuits: http://www.forsselltech.com/schematics/Dual%20Amp%20PCB%20Schematic.pdf
The two circuits are very similar but there is one small difference. After looking to some other schematics that include DC servo, I concluded that most of the circuits take the DC offset voltage directly from the output of the opamp (gain block), and only Fred take the DC offset after the isolation resistor (the one used to isolate the capacitive load of the cable at the opamp output.
Question. What is the reasonig to do it one way or the other way, from a theoretical and practical point of view.
I was a bit intrigued by the fact that only in Fred's circuits I saw this way to extract the DC for the servo, but based on the fact that his tools are considered some of the cleanest sounding tools, I think he has some good reasons to do it this way.
chrissugar
In my tests I used two different schematics. One circuit used for testing was based on the JLM hybrid schematic: http://www.jlmaudio.com/JLM%20Hybrid%20Opamp%20circuit.pdf and the other was based on Fred Forssell's circuits: http://www.forsselltech.com/schematics/Dual%20Amp%20PCB%20Schematic.pdf
The two circuits are very similar but there is one small difference. After looking to some other schematics that include DC servo, I concluded that most of the circuits take the DC offset voltage directly from the output of the opamp (gain block), and only Fred take the DC offset after the isolation resistor (the one used to isolate the capacitive load of the cable at the opamp output.
Question. What is the reasonig to do it one way or the other way, from a theoretical and practical point of view.
I was a bit intrigued by the fact that only in Fred's circuits I saw this way to extract the DC for the servo, but based on the fact that his tools are considered some of the cleanest sounding tools, I think he has some good reasons to do it this way.
chrissugar