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Experience in Modifying Audio Alchemy Dac

Posted by Mpoes (A) on February 1, 2007 at 12:03:11

I have been playing around with an Oppo dvd player and surround processor as my only source of digital music, and found myself increasingly unhappy. Previously I had used a Pioneer Elite I didn't like, and a Sony I wasn't so happy with. I modifed the Oppo with better capacitors like Elna Silmics and Cerafines, upgraded some film caps, opamps, etc. I still found myself much preferring my vinyl collection. The digital music just lacked any emotion, the soundstage was very flat, everything was too sterile, bass sounded thin, and the top end sounded brittle and harsh at times. Overall, I wasn't happy, and I found myself listening to less and less cd's.

Finaly I started upgrading a bunch of things, and have a bunch of left over Silmic and Cerafine caps laying around, along with a bunch of Wima Film and Foil caps. I decided I should take another listen to my Audio Alchemy Dac from the mid 90's, and see if some mods could fix some of its problems. I always liked it's sound in that it was very natural, coherent, and somewhat warm. Always had great bass weight and extension. HOwever, it couls also sound wooly, be overly diffused in the stage area, lacked resolution, and appeared to lack good extension.

I replaced all of the power supply caps with Elna Silmic's, and half of the decoupling caps on the boards with those, and half with the Cerafines. I replaced the .1uf cap on the coaxial input, which was blue and very small, so I think it was some sort of ceramic, but of a style I had never seen. I used an AVX .1uf for that location, and extended the leads slightly to make it fit. I checked the capacitance afterwords to make sure that didn't chance, and it was within spec even with the longer leads. Inductance I can't speak of, but just that mod seemed to improve things a bit. I replaced the .1 and .01mf film caps around the fets and opamps as well, which also had a slight but perceivable differnence. The last thing I did to the board was replace the opamps OP267 I believe, with Burson Discrete opamps.

Currently I am running this on the stock power supply and love the sound. It has retained a similar overall warmish tonality, while offering far greater percieved resolution, extension, and much better soundstage precision. It also has quite a bit of depth now, which it never seemed to have before. I also am finding that the speakers do a better disappearing act than they did with the other digital sources, and even this one in stock form. I'm really impressed what 150 dollars or so was able to do with this dac. I can't say its a giant killer, or that a more modern dac wouldn't better it, but it sounds, to my ears, better than any of the modified samsung, toshiba, or oppo digital players I have messed with. Oh I forgot another important mod, I shortened the digital out on the Oppo, added a digital transformer, and I am using a Burson clock with it all as well.

My last mod will be to build a jung regulated dual 14 volt power supply. I have some boards I need to finish, and a few transformers perfect for the job, as they are around 50 va and one is 12 volts, the other is 16 I believe. I think the 16-0-16 at 50va would work perfect in making a regulated power supply for the dac, and should offer a further improvement I would imagine. The difference it made for my phonostage was very noticable, especially in background noise/blackness. Another idea is battery supply, which I'm just starting to mess with. Easy to impliment, and possibly even quieter.

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