iampoor1
Well-known member
Hi!
I have recently been attempting to further my knowledge of circuits, and I have found a great way to do that is by looking at them, and attempting to figure them out based on my (limited) knowledge. I know I am VERY wrong on some parts here (Hence this thread). I know some of this information might be redundant...but I would appreciate any recommendations for resources to read (Loving Dan Lancasters Active filter design, enough info, with enough math on the side..). Anyways Ill stop rambling and start posting. 8)
Here is the circuit. It is the transformer pre for Project 30 over at ESP
Okay so lets get started.
R7: Not sure what this does? Provides loading?
R8/C2: These form a zobel network, correct? Is there a simple formula for figuring this out? I dont totally understand zobel networks....
C1: I know this is the compensation cap. How is the value determined? It depends on the opamp and the high frequency damping which differs for each family of op-amps correct? I know that most audio grade op-amps are now internally compensated, but it can become important at super high frequency/high bandwidth applications to have control over this parameter. Is there any advantages for audio?
Vr1/R9/C3 control the feedback and set the voltage gain. The article says the preamp has a gain of 40db which is a voltage gain of 100. How the heck do you get a voltage gain of 100 from this circuit? Wouldnt a 1k resistor with a 100k pot provide that? What is the capacitor for and why is the voltage divider 1k/50k? I know I am missing something obvious!
C4 blocks DC at the output. WHat happens with a larger value here? More bass? (Or is this a dumb question?)
Also, is there any advantage to using say a small resistor on the output before C4? Say 100ohms?
Thanks for taking the time to read through all of this! Again...I know I am missing a ton of obvious things! If my searches have missed very obvious articles, please link me. I have finally decided to suck up my pride and just ask....
I have recently been attempting to further my knowledge of circuits, and I have found a great way to do that is by looking at them, and attempting to figure them out based on my (limited) knowledge. I know I am VERY wrong on some parts here (Hence this thread). I know some of this information might be redundant...but I would appreciate any recommendations for resources to read (Loving Dan Lancasters Active filter design, enough info, with enough math on the side..). Anyways Ill stop rambling and start posting. 8)
Here is the circuit. It is the transformer pre for Project 30 over at ESP
Okay so lets get started.
R7: Not sure what this does? Provides loading?
R8/C2: These form a zobel network, correct? Is there a simple formula for figuring this out? I dont totally understand zobel networks....
C1: I know this is the compensation cap. How is the value determined? It depends on the opamp and the high frequency damping which differs for each family of op-amps correct? I know that most audio grade op-amps are now internally compensated, but it can become important at super high frequency/high bandwidth applications to have control over this parameter. Is there any advantages for audio?
Vr1/R9/C3 control the feedback and set the voltage gain. The article says the preamp has a gain of 40db which is a voltage gain of 100. How the heck do you get a voltage gain of 100 from this circuit? Wouldnt a 1k resistor with a 100k pot provide that? What is the capacitor for and why is the voltage divider 1k/50k? I know I am missing something obvious!
C4 blocks DC at the output. WHat happens with a larger value here? More bass? (Or is this a dumb question?)
Also, is there any advantage to using say a small resistor on the output before C4? Say 100ohms?
Thanks for taking the time to read through all of this! Again...I know I am missing a ton of obvious things! If my searches have missed very obvious articles, please link me. I have finally decided to suck up my pride and just ask....