I was pleased with the sound that the Metrum Quad Dac produced in stock form, as it had the fundamentals of music replay well organised. It exhibited good timing, timbre, sound staging, and sounded richer than the stock Altmann DAC. Although perhaps a little rough around the edges I could happily listen to the system with the Metrum installed, without fatigue, and enjoy the music it produced. I recognised similar traits with the Altmann Dac when I first listened to the system with this installed and it responded very well to upgrading the power supply.
I fitted one of my custom designed 250VA mains transformers a while back and this was a nice improvement over the mains transformers that Metrum use. The sound stage was bigger and more stable dynamically. The dynamic range expanded and the bass was more powerful and more natural. The high frequencies were better portrayed and I heard more heart and soul in the music. I did not post anything on the forum, as I wanted to finish the regulator upgrades first.
I installed a set of regulators in the DAC over a week ago and I have to say the result was more than I expected. The Stock DAC is very good and certainly punches above its weight in the performance stakes, but it really is a giant killer with a set of high performance shunt regulators and mains transformer installed even without much burn-in time.
The sound stage has expanded again and is now rock stable under all dynamic conditions and the image depth is much better with sound source locations well defined. The dynamic range is exceptional. Timbre and tempo are very good indeed. I have played musical instruments in the past and I am particularly sensitive to Timbre and Tempo. Most items of equipment damage these two parameters to a degree. The modified Metrum just excels here and it makes it so easy to understand the way the musicians are playing their instruments and the singers are presenting their songs. All the subtlety of the interplay shines through.
There are a couple of points to consider with this modified DAC.
Firstly with 6 shunt regulators fitted the operating temperature is elevated and the case gets quite warm to the touch. There are two options regarding this. One is to use the Dac with the top plate removed and the other is to transplant the metrum board to a larger case with good air ventilation.
Secondly, good recordings are very well presented but bad recordings are plainly obvious, as you can easily hear what is wrong with them. That said, my poorly recorded CDs were still listenable, even though compromised, as it was still possible to hear the musical message to a reasonable degree. There is no obvious digital glare with well-recorded music, but some edginess is apparent on some poorly recorded music. This is not the DACs fault.
CEES has done a very good job with his digital circuitry selection, and application, at his chosen market price level. Of course, at this price level he would not be able to apply such regulation and mains transformer upgrades. It is a credit to CEES that he achieved such good performance with LM317 type three terminal regulators in the stock form.
I have attached a photo to show the internal modifications.http://i700.photobucket.com/albums/ww7/paulhynes/210512download024.jpghttp://i700.photobucket.com/albums/ww7/paulhynes/210512download025.jpg
These modifications can be fitted to the Metrum Octave DAC too.
Regulator kit price
Quad DAC 6 regulators £198
Octave DAC 8 regulators £258
Insured carriage and packing to the UK will be £8, To Europe will be £12 and to the rest of the world will be £15.
Regulator fitting charge £100 plus return carriage for the DAC at cost.