Hey Guys,
so I've bought a new pair of studio monitors and since I need a suitable amplifier for them I looked into the the different models of different manufacturers like Hypex, Anaview, B&O ICEPower, Sure etc. A lot of them have a few problems, in my eyes, that I want to address in one PCB:
1. Low input impedance,
2. Unbalanced input,
3. Lack of a power limiter.
What most of them have, though, is an auxilary power output between 14V and 17V, although with limitations concerning the capacitance connected to them (most of them have a limit of between 330-470uF), that I want to use in this project.
Now I designed a board in Eagle based on the design recommendations of the LM317/337 for the ps-section, the THAT design notes for the 1200 series balanced input receivers concerning rf-rejection etc. and the limiter based on Rod Elliotts project 53’s power amp limiter. So the circuit features adjustable on-board power regulation, THAT 1200 series balanced input receivers and an unbalanced opto based limiting section that is buffered by a dual opamp. The output of the buffer is unbalanced but can be impedance balanced out if the power amp has a balanced input (which some have).
Now I have a few questions:
1. Can you guys spot any major errors concerning the circuit or the layout of the pcb? (something like the power supply is to close to the the other components, input/outputs are too close together or the limiters detector circuit from the amps output is not isolated enough)?
2. I’m planning on pouring a ground plane on both sides of the pcb, does that make sense?
3. Rod Elliott talks about potential oscillation problems that may occur when using off-the-shelf optocouplers and states that „some precautions must be taken to ensure that the amplifier's output signal is not coupled back to the input“ (http://sound.whsites.net/project53.htm) but then doesn’t really continue discussing any precautions you can take, apart from straight up not using them. So my question is: are there any precautions I can take in the board layout that benefit the „input-to-output-isolation“ he is talking about.
I’m thankful for any input!
Cheers
Jannis
so I've bought a new pair of studio monitors and since I need a suitable amplifier for them I looked into the the different models of different manufacturers like Hypex, Anaview, B&O ICEPower, Sure etc. A lot of them have a few problems, in my eyes, that I want to address in one PCB:
1. Low input impedance,
2. Unbalanced input,
3. Lack of a power limiter.
What most of them have, though, is an auxilary power output between 14V and 17V, although with limitations concerning the capacitance connected to them (most of them have a limit of between 330-470uF), that I want to use in this project.
Now I designed a board in Eagle based on the design recommendations of the LM317/337 for the ps-section, the THAT design notes for the 1200 series balanced input receivers concerning rf-rejection etc. and the limiter based on Rod Elliotts project 53’s power amp limiter. So the circuit features adjustable on-board power regulation, THAT 1200 series balanced input receivers and an unbalanced opto based limiting section that is buffered by a dual opamp. The output of the buffer is unbalanced but can be impedance balanced out if the power amp has a balanced input (which some have).
Now I have a few questions:
1. Can you guys spot any major errors concerning the circuit or the layout of the pcb? (something like the power supply is to close to the the other components, input/outputs are too close together or the limiters detector circuit from the amps output is not isolated enough)?
2. I’m planning on pouring a ground plane on both sides of the pcb, does that make sense?
3. Rod Elliott talks about potential oscillation problems that may occur when using off-the-shelf optocouplers and states that „some precautions must be taken to ensure that the amplifier's output signal is not coupled back to the input“ (http://sound.whsites.net/project53.htm) but then doesn’t really continue discussing any precautions you can take, apart from straight up not using them. So my question is: are there any precautions I can take in the board layout that benefit the „input-to-output-isolation“ he is talking about.
I’m thankful for any input!
Cheers
Jannis