I continue to struggle with this mono thing. I have decided not to mess with the preamp but to work at the phono-stage - less risky. RJM has helped me out with his PhonoClone but I have two other phono stages I need help with. I have run across two circuits that seem to be simple enough to implement. What do you think. I would mount the switch at the output of the phono stage. Advantages of one circuit over the other? What do those resistors do in the second circuit?
Thanks in advance.
Dave
Thanks in advance.
Dave
Most amplifiers have lo output resistance also called source resistance, the amplifier being the source in question. This resistance is too lo to shortcut the amplifier to ground or to another channel. Most amplifiers do not burn if output-shortcutted but distort much. In order to prevent these problems one mixes both channels to mono using big enuff resistors.
The two resistors stop you shorting left and right channel.
They act to mix the two channel signals together.
They act to mix the two channel signals together.
Two different (even just L and R) outputs, shorted together, will fight each other.
> How do you determine "big enuff"?
Most outputs are <1K, though may not be happiest with <2K load. Most inputs are >10K. Therefore 2K resistors (as shown) are a fine value. This is not very critical: 1K may be fine, 5K leads to a small loss if the load is as low as 10K.
> How do you determine "big enuff"?
Most outputs are <1K, though may not be happiest with <2K load. Most inputs are >10K. Therefore 2K resistors (as shown) are a fine value. This is not very critical: 1K may be fine, 5K leads to a small loss if the load is as low as 10K.
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