Secrets of Home Theater and High Fidelity - John E. Johnson, Jr.

The ADE-24.1 Analog Digital Enhancer is an accessory that has been around for a long time. We reviewed the first version, the ADE-24, in 1999.

It works at low voltage (e.g., RCA analog output from CD player, iPod, etc.) and manipulates the harmonics, using DSP. I got one of these units at the California Audio Show and the demonstration definitely indicated that it could improve sound (make it sound more appealing, and widen the sound stage), so I decided to bench test it to see what it does.



  • Design: Manipulates Harmonic Distortion in Low Voltage Signals
  • Connections: 1 x RCA Stereo Analog In, 2 x RCA Stereo Analog Out
  • Dimensions: 2″ H x 10″ W x 5″ D
  • Weight: 3 pounds
  • MSRP: $275 USD
  • Margules Audio
  • Tags: Margules Audio, Audio Accessories, Harmonic Distortion


It is powered by 120 V from your wall socket (no wall wart). On the front is just the logo and the name of the product. The rear panel has one set of RCA stereo analog inputs, and two sets of RCA stereo analog outputs.


For the audio source, I used my iPod, with the stereo analog output jacks going directly to the Audio Precision, or passing through the ADE-24.1 before going to the Audio Precision.


Here is a spectrum measured directly from the iPod using a 1 kHz sine wave. I set the volume control on the iPod to maximum, which produced an output of 0.7 volts. The distortion was only 0.04%, and it was mostly second ordered.



Now, the spectrum when I passed the iPod signal through the ADE-24.1. The output of the ADE was slightly higher than the iPod, and the distortion rose to 0.2%, but again, it was mostly second ordered. Some of the information on the web implies that the ADE unit removes odd-ordered harmonics. These bench tests show that is not the case. It adds harmonics, namely second and third. The sound is much like one would hear with a triode tube amplifier, and the music from my iPod sounded more musical. The sound stage seemed to change as well, but it is difficult to say how, since I was using HiFiMAN HE-500 headphones with the accompanying EF5 headphone amplifier (so the sound stage change effect in the headphones may have just been part of the “more musical” effect that I heard – however, in the demonstration at the California Audio Show, they used speakers, and the sound stage seemed to widen). For those of you who use your iPod, iPhone, or iPad to play music through your audio system using the player’s analog outputs, this could transform your listening experience considerably.



So, what does the ADE-24.1 do by itself? Shown below are two graphs, one with a 0.4 volt input, and the other with a 1 volt input. The ADE-24.1 produces harmonic peaks like you might expect from a triode tube amplifier.




Bottom Line: The ADE-24.1 works by adding a significant amount of second and third ordered harmonics to the incoming signal. It does not eliminate harmonics in the source. Should you rush out and get one of these? If you play your iPod music through your audio system, I would suggest looking for one. I say this because Margules Audio sold out all the units they had at the California Audio Show, so you may have to find one on E-Bay, Audiogon, Amazon, etc. You can also contact Margules and ask them to make some more. It’s a very clever accessory.