Hi, I have several questions for the connections between stages of a 'preamp':
1. Preamp out - xover in:
- Could i have it without dc capacitor and output impedance load (output to gnd, 10k)?
- Could I entirely omit the xover input bufer, and use the preamp output to feed the xover filters? Without coupling cap and output load resistor?
- What about the output resistor of opamp (470 ohms)? Would it mess the input network of the xover filters?
(C11.12, C11.13, R.11.12, R11.13 and so on)
2. Xover output to subsonic input
- omit the output cap and resistor to ground?
- the opamp output resistor (100 ohms), would it mess the input network of the subsonic (C21.1, R21.2, C21.2, e.t.c.) ?
3. Output of subsonic to allpass/ linkwitz input
- omit the output cap and resistor to ground?
- what about the current limiter in the opamp (100 ohms)? Would it mess the input network of the allpass (C31.1, R31.2)?
4. Xover/ linkwitz transform to digipot (toshiba TC9459)
- could i have it without load resistor (output of previous stage to ground, 10k)? The internal pot matrix of the digipot would set the impedance.
- I guess, it is good idea to keep the coupling cap here, to protect the digipot from DC peaks.
The purpose is to use minimum number of parts and omit coupling capacitors, wherever possible 🙂.
Regards - Emil
1. Preamp out - xover in:
- Could i have it without dc capacitor and output impedance load (output to gnd, 10k)?
- Could I entirely omit the xover input bufer, and use the preamp output to feed the xover filters? Without coupling cap and output load resistor?
- What about the output resistor of opamp (470 ohms)? Would it mess the input network of the xover filters?
(C11.12, C11.13, R.11.12, R11.13 and so on)
2. Xover output to subsonic input
- omit the output cap and resistor to ground?
- the opamp output resistor (100 ohms), would it mess the input network of the subsonic (C21.1, R21.2, C21.2, e.t.c.) ?
3. Output of subsonic to allpass/ linkwitz input
- omit the output cap and resistor to ground?
- what about the current limiter in the opamp (100 ohms)? Would it mess the input network of the allpass (C31.1, R31.2)?
4. Xover/ linkwitz transform to digipot (toshiba TC9459)
- could i have it without load resistor (output of previous stage to ground, 10k)? The internal pot matrix of the digipot would set the impedance.
- I guess, it is good idea to keep the coupling cap here, to protect the digipot from DC peaks.
The purpose is to use minimum number of parts and omit coupling capacitors, wherever possible 🙂.
Regards - Emil
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Top left picture... an NE5532 opamp will give a DC offset that varies with the setting of RV32. So whatever this feeds needs to be AC coupled.
Top right picture... the 4.7uF cap is almost certainly essential because the pin will be biased internally to some DC voltage.
Bottom left picture... if you are feeding the opamp output into the following circuit as shown by your line then you can omit the 10uF and 10k but must retain the circuit on the circuitry on the filter (Subsonic L) as shown.
Bottom right picture... again we are into DC offset and the 5532 is as bad as it gets in these type of circuits so yes, you should retain the AC coupled output of Subsonic L and also retain AC coupling at the output.
Top right picture... the 4.7uF cap is almost certainly essential because the pin will be biased internally to some DC voltage.
Bottom left picture... if you are feeding the opamp output into the following circuit as shown by your line then you can omit the 10uF and 10k but must retain the circuit on the circuitry on the filter (Subsonic L) as shown.
Bottom right picture... again we are into DC offset and the 5532 is as bad as it gets in these type of circuits so yes, you should retain the AC coupled output of Subsonic L and also retain AC coupling at the output.