Below you can find some sound samples with the modified ADA and other units. For the main project page, go here.    

    Please, observe that:

    - This is my first set of samples, all recorded with a digital Keyboard, the Roland JV-90, with no mixer in the path;
    - Other sources including analog synthesizers and sound capture with our own microphones and preamps will be included later;
    - Recordings always used the unit's local clock. I have no clock comparisons at this time;
    - Try listening with a good DAC, amp, monitors. We are comparing the ADC with expensive units, and improving over them.
    - I can easily hear the differences with my Macbook and an AKG K270, but I am already "trained" with higher quality monitoring;
    - If this is your first time trying to identify differences, be aware you have to learn to listen, spend some time doing it.
    - My MIDIs, even the sound selection, should be improved and completed, to focus on the most important aspects;
    - The Metric Halo unit is the ULN-2, from 2007, later expanded, input at the TRS plug, using input trim adjustment;
    - The modified ADA8000 had the preamps bypassed, LT1359 opamps, but with stock PSU and coupling caps;
    - The ADA8000 unit is the old model, with Wavefront converters. There is a new model (I have here) with AKM chips;
    - My custom AD converter uses my DC input buffers, my dedicated Power Supply Units and TI's flagship PCM4222;
    - All uncompressed stereo 48KHz/24bit AIF files, between 10MB and 20MB each;
    - Files could probably be compressed with a high bit-rate without loosing what we want to hear, but I wanted to start right;
    - Sound levels are about the same, not exactly. JV-90 level was the same, almost full output;
    - The DigRhodes patch has random panning, so each playback produces a slightly different result;

    PIANO (JV-90 Preset A11 - A. Piano 1)

    Piano ADA8000 Factory - PianoADAFactory.aif
    PIano MH TRS input - PianoMHTRS.aif
    Piano ADA Mod1 - PianoADAMod1.aif
    Piano DC PCM4222 - PianoPCM4222.aif

    DIGIRHODES (JV-90 Preset A26 - Dig Rhodes 2)

    DigiRhodes ADA8000 Factory - DigiRhodesADAFactory.aif
    DigiRhodes MH TRS input - DigiRhodesMHTRS.aif
    DigiRhodes ADA Mod1 - DigiRhodesADAMod1.aif
    DigiRhodes DC PCM4222 - DigiRhodesPCM4222.aif

    STRINGS (JV-90 Preset B31 - St Strings)

    Strings ADA8000 Factory - Strings31ADAFactory.aif
    Strings MH TRS input - Strings31MHTRS.aif
    Strings ADA Mod1 - Strings31ADAMod1.aif
    Strings DC PCM4222 - Strings31PCM4222.aif

    It surprises me how easily I can distinguish and perceive the superiority of our custom ADC even when recording a simple digital keyboard from the 90's, and listening everything with the AKG headphone on the Metric Halo ULN-2 (its DAC and Phone preamp). I already tested with modified and custom DACs, with good monitors before, and as expected, the less bottlenecks we have, the easier is to asses the quality of any of the components in the signal path. When I started modifying the ADA it took me some time to get used to the sound differences, because I was making one modification at a time, comparing opamps, and so on.

    In a short description I would say that the MH is a bit better than the factory ADA8000, and the modified ADA8000 improves a lot the clarity, the size of the soundstage, bass, treble, removing the major part of the "confusion" that small coupling capacitors and/or cheap opamps (TL074) bring to the sound. I still think, however, that the first modifications to the ADA make it sound too bright. Part comes from the LT opamps, but possibly also from the clock and PSU. While this might sound good for a keyboard, it can hurt vocals or other soft sounds. I did not include any sound sample with my new DC input buffers on the ADA, but they are at the PCM4222 ADC. Regarding this new custom ADC, it is far superior to all the others. The sound is thinner, in a good sense, it has exatly its size, is not enlarged ir difused as in the other units, it is precise, detailed, with a larger space around it, space between the notes. Sounds are richer, and very solid, and much more important, it inspires playing.

    I have to add a small warning. In some instruments, regions, or some notes, we may like the increased sound that the other units bring to the instrument, as if they are decorating the sound, including some chorus, something like this. This is indeed important, and may be desirable from an aesthetic point of view. I insist, however, that this is not the task for a converter. It has to be musical, but precise. We should employ preamps or other effects in the signal path to get exactly the sound that we are looking for, and the converter must capture this precisely, and not force its own color into the material. Keep this in mind when listening. Perhaps you like some of the sounds bigger, but they are not like that when they come out of the keyboard. The unit with the PCM4222 is the closest to the sound source, and I frequently check this by listening to the keyboard direct into the power amps (no mixer, no nothing).

    Here is a picture of the thing. It is big for a 2ch converter, with its separate Power Supply that has independent +15 -15 +5 +4 circuits. We are working to make a product out of this, and that should be smaller, hopefully!

   

    Porto Alegre, Brazil. johann at inf dot ufrgs dot br 
    Created on May 27, 2012.