I'm currently building a M2X which will be finished in a few weeks, and I have started thinking about a preamplifer.
I have the following requirements:
1. At least four inputs
2. Remote control
3. Motor volume control
4. Line outputs for headphone amp and tape recorder (in addition to output to the M2X power amplifier)
I already have the BA 2018 PCB and a solution for the power supply. I'm going to use a Muffsy Relay Input Selector (New Product: The Muffsy Relay Input Selector - Muffsy Phono Kits) and an ALPS motor controlled potentiometer for requirement 1, 2 and 3. The Muffsy input selector doesn't support a motor controlled potentiometer out of the box, but should be easy to add (I have some basic experience programming Arduino boards.)
But I'm unsure about the line outputs. Can it be as simple as wiring them directly from the inputs? That is split the signal from the Muffsy input selector to the BA 2018 linestage and two line outputs?
Thanks,
Trond
I have the following requirements:
1. At least four inputs
2. Remote control
3. Motor volume control
4. Line outputs for headphone amp and tape recorder (in addition to output to the M2X power amplifier)
I already have the BA 2018 PCB and a solution for the power supply. I'm going to use a Muffsy Relay Input Selector (New Product: The Muffsy Relay Input Selector - Muffsy Phono Kits) and an ALPS motor controlled potentiometer for requirement 1, 2 and 3. The Muffsy input selector doesn't support a motor controlled potentiometer out of the box, but should be easy to add (I have some basic experience programming Arduino boards.)
But I'm unsure about the line outputs. Can it be as simple as wiring them directly from the inputs? That is split the signal from the Muffsy input selector to the BA 2018 linestage and two line outputs?
Thanks,
Trond
Yes, unless you want to use buffers to avoid loading effects
from the source impedances and coupling capacitors.
Remember you can cause electrical feedback unless the "tape out" recording jacks
are disabled when selecting the "tape in" playback jacks.
from the source impedances and coupling capacitors.
Remember you can cause electrical feedback unless the "tape out" recording jacks
are disabled when selecting the "tape in" playback jacks.
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Thanks!
Pointers to a suitable buffer circuit I can use? An opamp and a few resistors sounds achievable!
Pointers to a suitable buffer circuit I can use? An opamp and a few resistors sounds achievable!
I've done some more reading, and I think I'm on the right track to something. Which opamp is recommended for this purpose?
Can I use something like this:
JFET input Cascoded Buffer Board Preamplifier assembled ! 699957464661 | eBay
or
Diamond buffer board bare PCB strong driving capability ! | eBay
?
JFET input Cascoded Buffer Board Preamplifier assembled ! 699957464661 | eBay
or
Diamond buffer board bare PCB strong driving capability ! | eBay
?
I'd try looking for something based on a trusty NE5532. Even if it has some gain, a modfication for unity gain is quite trivial. Just make sure they didn't skimp on an output series resistor.