Hi all.
I am fairly new to DIY audio, so please bear with me!
I have decided to tackle a preamp as my first design/project. The idea is to have a ladder-type step attenuator going into an opamp buffer. The attenuator, which I already have, is 10k. I'm planning on using a LM4562 opamp in the buffer.
Hifi setup is:
Arcam Alpha 7 CDP (Zout = 150R) -> preamp -> Rotel RB-1070 (Zin = 33k)
All cables are 65 ohm, 67pF coaxial.
I'm posting the schematic I've done for the buffer (one channel shown). I wonder if I could prevail upon your collective wisdom to answer a few questions.
1. Does the 47k input resistor interact with the attenuator in terms of Zin for the preamp as a whole?
2. Is the 100R output resistor necessary? I've basically included it because other schematics I've seen have something similar. I'm assuming it's there for drive current reasons. Opamp Iout is rated at 26mA into 600 ohms.
3. Should I use coupling caps on the outputs? Opamp offset voltage is 100uV max.
4. Is the buffer even necessary with the 10k attenuator?
I am fairly new to DIY audio, so please bear with me!
I have decided to tackle a preamp as my first design/project. The idea is to have a ladder-type step attenuator going into an opamp buffer. The attenuator, which I already have, is 10k. I'm planning on using a LM4562 opamp in the buffer.
Hifi setup is:
Arcam Alpha 7 CDP (Zout = 150R) -> preamp -> Rotel RB-1070 (Zin = 33k)
All cables are 65 ohm, 67pF coaxial.
I'm posting the schematic I've done for the buffer (one channel shown). I wonder if I could prevail upon your collective wisdom to answer a few questions.
1. Does the 47k input resistor interact with the attenuator in terms of Zin for the preamp as a whole?
2. Is the 100R output resistor necessary? I've basically included it because other schematics I've seen have something similar. I'm assuming it's there for drive current reasons. Opamp Iout is rated at 26mA into 600 ohms.
3. Should I use coupling caps on the outputs? Opamp offset voltage is 100uV max.
4. Is the buffer even necessary with the 10k attenuator?