[sdiy] 10 x amp for line to modular level

mskala at northcoastsynthesis.com mskala at northcoastsynthesis.com
Fri Mar 1 04:13:15 CET 2024


On Thu, 29 Feb 2024, JoeF wrote:

> Hello, I've assembled a couple of video synths that can be audio reactive
> but they need a bigger signal than line level to work well. I want to build
> a 10x gain stage. Will any op-amp work if I am using a wall wart that is dc?

No, you need one that can accept the power voltage you're giving it.
Different op amps have different power ranges.  Some op amps accept a wide
range of power voltages but need at least a relatively high minimum.
Others are designed for just a single power voltage and will have trouble
with anything else, especially with an overvoltage.

Also to think about:

* If your "wall wart" is single-voltage (not a bipolar power supply) then
you may need to use AC coupling, and a voltage divider to create a
reference between the rails.

* Make sure that the op amp's output voltage swing, and your power
voltage, are big enough for your purposes.  "Line level" times 10 may be a
significant number of volts, and not every op amp can swing its output all
the way to its own power voltages, so the power voltage may need to be
higher still.

* If this is for video use, you may need to think about the op amp's
bandwidth.  Many op amps can comfortably pass video, but it's not a
gimmie.

-- 
Matthew Skala
North Coast Synthesis Ltd.


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