Musical Fidelity A3.24 Nirvana

[PassiveO]

All,

After reading this thread a few weeks ago, I decided to buy an A3.24 DAC:

http://www.diyaudio.com/forums/showt...?postid=652574

I performed the mod, which took about four hours in two stages.

The first stage was removing resistors R108 and R208 and replacing them with these:

http://www.mouser.com/search/refine.aspx?Ntt=594-64Y502

Next, I removed the ouput coupling caps and replaced the ouput hookup wire with some soild silver I had left over from another project. Then , I powered up the unit and adjusted the trimmers until I had DC at the outputs fluctuating between 0 and 1.5mv.

The biggest issue in this stage of the mod was that the leads of the trimmer pots sourced from Mouser were too short. I had to cut some wire off of a few other resistors and splice the leads. No big deal, but I was sure to measure them after. You want them to be at 2.2K.

The results of this stage were much better bass resolution, much better detail and a huge soundstage. I felt that there was a touch of grain here and there and a somewhat lean midrange. Then I decided to go for stage two.

Stage two involved removal of the NE5532 opamps and replacing them with sockets. A word of caution, these are not easy to remove. Care is required. The technique I use is severing the leads leaving enough to grab on to with a pair of pliers or forceps. Then, heat the back side of the board and pull the leads out from the front. After that, you need a solder sucker and a needle soldering iron. Use the needle iron on one side to push through the holes and the sucker on the other for extraction of the solder. Having someone help you with this makes it easier, but I managed to do it myself.

The results of stage two built on stage one and were the key to best performance. I used four OPA627s in Brown Dog adapters:

http://www.cimarrontechnology.com/in...WPROD&ProdID=9

The soundstage grew more and any trace of grain was completely gone. The tonality of acoustic instruments was such that chills ran up my spine. The sound is so harmonically complete it's stunning.

Note that I feel AD825s are equal to OPA627s and I have prefered them in the past for phono stages and DAC mods (CIAudio VDA-1). I have a few but am out of adapters. The only issue with the 825s is that since they are SMDs they are difficult (for me) to solder on to the adapters.

If you are looking for a top-notch DAC, the modded A3.24 may be the ticket. It's the best I've heard, and they are relatively inexpensive used.

Cheers.

[PierreG]

Having an MF A3.2 CD, I wonder if I could do the same mod. I think the circuits are almost the same. Doesn'it?

[PassiveO]

Originally posted by PierreG
Having an MF A3.2 CD, I wonder if I could do the same mod. I think the circuits are almost the same. Doesn'it?

Someone else will chave to chime in on this, as I am not certain.