Voice Changer Project

FatPope

Hi guys,

I'm trying to put together a voice-changer setup to go along with a Halloween costume I'm making. I'm having some audio issues so I'm hoping that this might be the right place to get some advice on it.

Ok, so the idea is that whatever I speak will be fed in through a mic, modulated in a suitably interesting fashion, then output through speakers on my person in real-time, ideally loudly enough that only the modified voice is heard and not my actual voice.

To achieve this I bought a throat mic, this is then fed into my Nexus 4 android phone, the input is changed with an app I have, and then output through portable speakers. Both the input and the output have to go through the same 3.5mm socket on my phone. The mic has a 2.5mm Binatone jack. The layout therefore is


Microphone -> 3.5mm converter -> mic/speaker splitter cable -> phone -> mic/speaker splitter cable (same one) -> speakers


One of the issues with most throat mics though is that they are designed for walkie-talkies and not for standard 3.5mm jacks. The one I have uses a 2.5mm TRS Binatone jack, which is Microphone-Speaker-Ground. I can't post links unfortunately but the pinout of it can be found by looking for the binatone 550 headset in pinoutsguide.com

So, the first problem is, of course, converting from 2.5mm to 3.5mm for my phone. Most 2.5mm audio jacks are of the form Left Audio-Right Audio-Ground. This can again be found at pinoutsguide

I used a standard converter which does the job. Of course, as I'm going to be outputting the sound through the speakers, I have no need of the throat mic's speaker line, along with the single mono headphone that's attached to it. The mic signal itself though should come through on the left audio line and the speaker line should (I think?) do nothing.

The splitter cable has two TRS sockets and has a TRRS jack which goes into the phone. It's designed so that if you want to have entirely separate headphones and microphone for your phone you can do that. I've plugged in the signal from the throat mic into the mic socket of the splitter and the speakers are plugged into the headphone socket of the splitter.



It all works!! Kind of!
The problems are A.) the output volume is very quiet and low quality and B.) I have to hold the push-to-talk button on the mic as the VOX function doesn't work

I can see on my phone that the first problem is due to it only picking up a very low mic signal. I can use a microphone booster on my phone but then the sound quality becomes unusably bad.
The second problem I think is probably due to the unused speaker line on the mic. I'm not sure how VOX works but maybe the signal to turn transmit on/off comes along that line

I'm not hugely worried about the push-to-talk issue. At the very worst I can simply tape the button down. The volume issue though is critical and seems to be most likely caused by my unorthodox mic setup. As I understand it most basic mics use a TRS jack which can handle stereo, but simply use the same signal on the left and the right as there's only a mono source. I'm only supplying a left signal and nothing on the right, so am I correct in assuming that this would reduce the overall volume?

If I was to re-wire the jack, connecting the mic signal to both would that improve matters? Is there anything else I should be doing here or have I just gone for a totally stupid setup?

Anyway, the mic I'm using is the Comtechlogic CM-115TH which can be found on amazon

The splitter cable can also be found on amazon by searching for
"Startech.com 3.5mm 4 Pin to 2x 3 Pin 3.5mm Headset Splitter Adapter - M/F"

Hope you guys can be of some help and that this post isn't needlessly convoluted! Sorry about the lack of direct links. This feature on boards is really annoying!