Convert an old busted phone into a voice-altering prank machine


Have you ever wanted to be someone else, at least over the phone? Do you dream of turning the tables on telemarketers, making them hurry to get off the line instead of you? If so, [Brad] over at LucidScience has the project for you.

A bit of a prankster at heart, he walks through the conversion of a normal telephone into a Data Access Arrangement device (DAA), allowing you to interface it with either hardware or software-based audio mixers.

The process can be completed in a relatively short time period, and doesn’t require much more than an old telephone, a handful of tools, and some miscellaneous switches and jacks. He disassembled a telephone and trimmed off all of the unnecessary circuitry while retaining most of the original functionality. Line in and out jacks were then installed in place of the handset microphone and speakers, respectively. The final result is a compact box that relays altered audio from any kind of mixing device to person at the other end of the call. Since the majority of the phone remains intact, your calls still sound natural as they pass through the phone’s existing voice filter and preamp circuitry.

Once the DAA is complete, you can use any number of effects on your voice, limited only by your audio mixer. [Brad] says he has long-time friends that don’t even recognize his voice after he has run it through his effects machine, so get started on yours before April Fool’s day arrives!


  1. fred says:

    “and doesn’t require much more than an old telephone, a handful of tools, and some miscellaneous switches and jacks”. I guess the voice transformer effects box counts as “miscellaneous”.

  2. sidetabs says:

    Lol I think the dude meant the phone part not the whole thing. You can use free software too but you had to rtfa to know that.

  3. aggaz says:

    fred is rihgt, the title of this post is ambiguous.

  4. walt says:

    good luck finding a vt-1 for a reasonable price. ever since that To Catch a Chester show started using them to sound like young chicks, they got super pricey.

  5. seer says:

    well … why not using more hobbyist friendly chip such as HT8950 instead of the expensive and professional box?

  6. BobbySlay says:

    seer, oooooor the free software he mentions towards the end of his build log.

  7. Oneironaut says:

    Thanks for posting my project.

    To answer the above questions…

    – Yes, the build is about the mixer, not the actual effect, which can be either an external fx box or computer software (as explained in the writeup).

    – Indeed, the VT1 seems hard to find, but it is the best voice changer hands down.

    – The Holtek HT8950 is only good for a few funny chipmunk or devil voices. I have used them for gag voice changers in the past. The VT1 or even VCS software can pull of a voice disguise good enough to convince even your family on the phone.

    Check out the video I made of my voice and then search youtube for other voice changers to see the huge difference in quality. Those little black box units sound like cartoon characters!

    Ironically, some of these so called “Spy Stores” sell the VT1 with a few .01 uF caps soldered to an RJ-11 jack for well over $1000 and call it a custom designed voice changer.

    I just wanted to demonstrate how to mix audio to and from the phone system without needing to design or install a custom DAA solution.

    This was a fun project to make, and I enjoy talking to telemarketers with my satan voice. It’s amazing how long you can keep them on the line sometimes.

  8. Maave says:

    I’m fond of alligator clips on wires myself, a homemade adapter is really versatile.

    Try using the program VSTHost with some plugins for voice changing. The only problem will be latency which can be fixed with some ASIO drivers (like ASIO4All) instead of the default MME or DS drivers.
    I choose VSTHost over “voice changer” software because VSTHost is completely free and has a plethora of plugins. ckpitchshifter is a mandatory plugin for voice changing. X-Orcism is pretty good too.
    I had guides to setting up VSTHost but Google nuked my blog and never gave it back. Just screw around with VSTHost and you’ll get the hang of it.

  9. cns949 says:

    This wouldn’t get you a PH.D but it sounds like a lot of fun :)

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