Filmmaker75

Thank you all for your help. Now I would like some information on some things. - In headphones I always have a slight whistle that increases raising the volume. - The general volume is not very high and I am afraid that during a show it may not be enough. - The sidetone must always be kept at 0. If I raise it, a trigger whistle is generated. It's normal? - When I press the CALL button there is a loud noise in all the headphones. Can it be avoided in any way? - How can I make the sound be heard on both sides of the headphones? Do I simply parallel the cables? The current headphones have an impedance of 150ohm. These are the headphones I'm using: http://www.superlux.com.tw/upload/function.product.info/5e2a71e7-1b14-4924-a41b-0a795facd7e3/resource/ug_HMC660_HMD660_web_en.pdf Thanks in advance to anyone who will answer.

Thanks for the reply. I solved by changing the power supply. The one I used had the isolated output and even putting together 0v and grounding the electrical noise did not disappear. I purchased a notebook power supply that already has 0v and grounding in common. In this way there is no longer any noise. The shells I used are made of aluminum but have plastic fronts. I simply soldered a cable to each connector and carried it on the aluminum shell after scraping off some paint. Everything seems to work properly now. Thank you all.

in reference to the earth connection, looking at the wiring diagram I saw that the pins number 4 of SK1 and PL1 have the wording "chassis". Is this what I have to connect to earth? or directly the GND? Sorry for the non-technical question but I would not make mistakes and damage everything.

I use a headset for PC that has a common ground between the headphones and the microphone. I read that I don't have to connect HP- with GND. I have to wait for the headphones I ordered to arrive, they have separate GND headphones and microphone.

Thanks for the reply. I'm using this power supply to test the system: http://www.minoiailluminazione.com/16439-22636-large/arteleta-lb437-alimentatore-24v-100w.jpg Do I have to connect the -V with grounding? I searched for other 24 volts power supplies, even for notebooks, but I didn't find power supplies with a three-pin plug. In the picture below it is clear that there is no earth connection. I also have another question. I'm using a PC headset. I connected the microphone to the MIC and GND terminals and the headset to HP + and GND and so it works. The headphone has an impedance of 32ohm and I noticed that the two resistances R16 and R20 will heat up a lot. To avoid damage I try to turn on the beltpack only a few minutes at a time. I purchased Superlux headphones for Intercom that have 150ohm impedance that will arrive next week. Will they get better? Sorry for the long post but I'm not very experienced. I just bought the components and soldered them, I'm not very expert in electronics. Thanks for your help.

Hello everyone! I built two beltpacks and the PSU. All works but there is a strong background noise in the headphones. Hum. If I place a finger on the PSU's capacitors the buzz disappears. If I touch the metal of the potentiometer of the volume instead it increases a lot. I haven't put the PCBs in the boxes yet and I'm trying them on the desk. I'm using a PC headset. I measured with the tester the headphone output has about 9v ... By removing the headphones the voltage reaches 11v Any suggestions?