21er - 22er - 23er Board 1,7Veff. Output
The simplest variant of a serial device to increase with or without the exchange of the coupling capacitors, the output voltage is the exchange of only two resistors. To obtain an output voltage of 1.7 V rms. Due to the low supply voltage of the op.-amp. of only 5 volts is not possible to further increase. Unless you work with DC / DC converter and replace the Op.Amp. as already described on the previous page.
just replace the yellow marked 18kohm resistors with 27kOhm SMD size 805, and done!