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Anybody know the input impedance of the TPA3116? I'm having trouble getting sufficient volume using my Tortuga LDR passive pre.
It depends on the gain setting. See the table at the top of page 14 of the datasheet. That table is reproduced under the Gain Setting section of the tpa3116 wiki at DIYAudio.From my experience, most tpa3116 boards seem to default to 26 dB gain setting which corresponds to an input impedance of 30k Ohms.Hope that helps!
Thanks for that. That 's starting to get into the tall grass. I guess there would be a way to change the gain but too small scale for me. My tube amp worked with the Tortuga but it's out of commision. Time for a new amp.
Do you know what tpa3116 board you have? If you have the Yuan Jing Blue/Black board ("YJBlue", Danzz design, see wiki mentioned above), then it is very easy to increase the gain (and decrease input impedance) if you can do basic soldering. Increasing gain to 32db/15kohm requires only one resistor to be changed. Upping to 36db/9kohm requires two resistors to be changed.If this is something you think you might do, I'm happy to help with more detailed instructions. I will mention one caveat, though: I increased the gain to 32db on one of my YJBlue boards, and it caused a slight hiss to show up when no music was playing. It went away when any sounds were played, and was low enough that you had to be within inches of the speaker, but some folks may find this to be a deal-breaker. YMMV and all that.