“Walking up a road at night, I have seen a lamp and a lighted window and a cloud make together a most complete and unmistakable face. If anyone in heaven has that face I shall know him again.”― G. K. (Gilbert Keith) Chesterton
For all those aspiring paranormal engineers, this is probably one of the more in depth examinations of the Raudive Diode detector that you’ll find on the web.
If you’re not familiar with the device or Raudive himself, you can check out my earlier post here.
I spent some considerable time building and testing different designs of this EVP recording device and wanted to share my results.
Here’s the TL;DR: There are many different schematics on the internet, the components are similar and I don’t think the specifics matter much. This is definitely a “set it and forget it” type of device. Recording through the diode is different than a microphone as no ambient noise is captured. That plus the metal shielding means there’s not much of an opportunity for a stray signal to get through. You’ll need to record for a long time.
I didn’t get particularly startling results when testing any of the devices, but I only recorded a few minutes for each. Perhaps your mileage may vary.
I tested four different designs: three of my own builds using schematics found on the web and one commercial version. The challenge is that there are several different circuits available (Raudive himself had three different designs) and no clear examples of what successful output should sound like.
I used a Sony PX370 voice recorder for the experiments. This is a great little recorder in that you can adjust the mic sensitivity and it has built in USB for file transfers to PC.
The only modifications I made to the recorded audio was amplification. I’ve heard a lot of clips from other sites that have been heavily processed – with obvious effects like noise reduction and voice isolation. If you do enough post-processing you can make audio sound like anything, so I thought it would be be better to just present as is.
Let’s start with Raudive. To the right are the three circuits that he describes in his book. Here’s an excerpt that describes the diode detector:
“A short (6-10cm long) arial is used to give a more or less broad-banded signal, which is rectified by a diode and fed directly by cable to the radio or microphone input of the tape-recorder.”
Raudive states that diagram #1 was used in his earliest experiments, success was had with Circuit #3, but Circuit #2 was only a blueprint.
Here’s a short clip of one of Raudive’s recorded sessions. He had four different methods for capturing “spirit voices”, it’s unclear if this one was from his diode detector. I’m including this as a comparison to the output from my home-built devices.
To the right is the commercial device that I tested. (I pried it open to see the circuit and what components were included.)
Out of respect for the seller I’m not going to post the schematic, but the circuit is probably closest to Raudive’s third design as there’s no inductor present.
Here’s an audio clip below from a recorded session done from this device. Essentially white noise as expected.
This device below uses a slightly modified schematic from paranormal research site jimsdestinations.com. Many designs are similar with a common ground to a metal box as shielding. There’s much debate as to the usefulness of the shielding which effectively acts like a faraday cage. It blocks electromagnetic interference, but some say it’s useful to have some noise with the signal.
The design below calls for a 500uH inductor, but for this particular build I substituted a 470uH shielded inductor and added a 1.6K resistor between the mic and ground connections of the TRRS connector. The resistor is needed for a mobile phone to detect an external mic is connected. All other components are as specified.
Here’s an audio clip of a recording session done in a field while using this device. Again, not too exciting, just white noise for the length of the clip.
For this device below, I used the same circuit but substituted a 500uH unshielded inductor.
Here’s a clip from a test using this device. As with the others, I tested outside in a field to avoid interference. The results are the same as well, just white noise for the duration of the recording.
The next one below uses a schematic similar to a commercial device as depicted here by Tangram Studios.
At this point I realized I was going to be testing several different circuits and improved my build a bit. I found a larger enclosure, a terminal block and added a prototyping board so I could more quickly swap components in and out. There are two inductors in the case, but the actual parts used were the 470uH inductor and 2nF capacitor below.
Here’s the recording done with this one. You can hear from the clip that the device almost certainly picked up interference my phone, which was interesting considering it was a good 3-4ft away from the device during the recording. Other than that, my results were consistent with the others – a lot of white noise.
Konstantin Raudive’s “Breakthrough” book included a vinyl with some amazing audio captured from his devices.
Some of the interpretations are no doubt examples of pareidolia, but there are sessions where the “voices” captured are amazingly clear.
Unfortunately none of the circuits that I’ve built and tested so far have produced anything remotely close to the audio that he demonstrated. My recordings were very short in length, so perhaps longer sessions might be more productive.
I’m going to continue to test different designs, and as I do I’ll continue to update this page with the results. What’s great about this project is that the circuit is really straight forward with very few components so not a crazy time investment to try things out.
At the bottom of this post I’ve listed some resources for a deeper dive on this topic. If you decide to build one of these, drop me a line and let me know your results!