IDX pro negative tension problem

[Tony60]

Good evening,
while waiting some parts to "dress" the TGSL I resumed IDX PRO that with the help of Nandor I put into operation. It works well but I realized that I do not have the negative voltage of -8 V (but -4 V). I saw that to connect the 2 tones Pcb you need this tension.
I kindly ask for your help.
Thank you in advance.
Tony60.

[Nandor]

Hi Tony

The IDX has split voltage supply, that means the +8 volt from the regulator becomes +4 and -4 by virtual ground that's why you have the LM358. It is normal, the op amps need negative voltage to operate but the oscillator still sees it as +8 because it does not use the virtual ground created by LM358.

All the best

[Tony60]

Ciao Nandor,
Thank you for the clarification. In fact IDX works well so I felt confortable. Now I have to think about how to power the two-tone generator. The schematic "audio 2 tones.lay" requires -8 and 8 volts;I'll build a small dual supply or I'll try with -4 and 4 volts.
Have a good day and thank you.
Tony.

[Nandor]

Yes it works with +4 and -4, its a nice addon for the detector.

regards

[Tony60]

Ok Nandor,
very very well; I go to build the two tones!!
Thank you.
Tony.