|
|
Post by dejanm on Oct 1, 2009 18:37:30 GMT
Hi,
I bought a week ago one old MF X-ACT DAC on eBay. It was cheep. I thought that chip set will be similar to the chip set that is used for MF X-DAC V2, but I was wrong. Between these two DACs there is a huge differences.
This X-ACT has Sanyo receiver LC8900K. This chip is obsolete now and it has clock circuit integrated within the receiver. Therefore, there is no external clock, like in X-DAC V2. DAC chip is 18-bit Sanyo LC78835KM - which has integrated I/V conversion and 8-times oversampling circuit within DAC chip. For that reason the output stage is rather simple: it has only one OPA (NE5532AN) per channel.
Power supply is very similar (practically the same) as in X-DAC V2.
I will perform some standard upgrades, but it seems to me that X-DAC V2 is much better option. And X-DAC V3 is another league better than V2 ....
|
|
Deleted
Deleted Member
Posts: 0
|
Post by Deleted on Oct 1, 2009 20:36:21 GMT
dejanm
X-DAC V3 is in a league of it's own, but only after some serious modifications. A major area of improvement is the use of a dual reguated +-15V external PSU with a JLH fitted.
SandyK
|
|
|
|
Post by dejanm on Oct 2, 2009 4:17:15 GMT
SandyK,
I believe you've wrote it somewhere but I cann't recall all the details ... The question is: what happens if I plug into the 12V AC connector of MF X series unit, the DC regulated voltage ? I suppose that nothing really happens - only the drop on two diodes has to be calulated. Is it so ? Everything else should be working ok, actually even better than with AC supply ...
Is it a problem for diodes if they (two of them) will be always leading ?
|
|
Deleted
Deleted Member
Posts: 0
|
Post by Deleted on Oct 2, 2009 5:20:19 GMT
dejanm
I don't know about the others in the series, but with the X-DAC V3 the +-15V gets steered by the normal bridge rectifier diodes, and the other 2 rectifier diodes for the digital section voltage regulators.
It does of course work even better again if the bridge rectifier diodes are bypassed, but still works better than with the
12-0-12VAC wallwart, even with the diodes still in circuit. Surprisingly, with the X-DAC V3 there is no analogue section voltage regulation fitted, so this also helps stabilise the analogue section.
SandyK
|
|
|
|
Post by PinkFloyd on Oct 2, 2009 22:22:34 GMT
|
|
|
|
Post by dejanm on Oct 4, 2009 6:41:12 GMT
Sorry for missing that one. Although not much talking about X-ACT itself there ... I am just doing the similar mod of X-ACT as you did Pink but I am wondering if something more can be done ? Any ideas ? |
|
|
|
Post by dejanm on Oct 8, 2009 14:17:52 GMT
|
|
|
|
Post by dejanm on Dec 27, 2009 8:34:51 GMT
Maybe an assessment after a couple of months of using this DAC ...
First of all I had a problem with the receiver chip, which put the unit out of order. Finding Sanyo LC8900K happened to be an issue, because the chip is obsolete. I contacted several Chinese internet sellers but they couldn't help me. So I sent the question to Musical Fidelity and they were very kind in providing this IC (for some cash of course).
So it works again and there some positive and some negative things that could be reported.
First of all, the sound of this unit can be described as decent - having in mind very basic design, which is out of date compared to the designs of DACs in recent years. The used chips are actually oboslete and are certainly not state-of-the-art. Nevertheless, it sounds quite well, with no obvious faults in sound reproduction. I have though to say that nearly every passive and active part has been replaced with some very good parts, except resistors and chips.
I replaced N5532 OPA at the output first with 2604 and then with much more expencieve 2111. It is perhaps strange, but no obvious improvement has been achieved when I switched from 2604 to 2111. I have quite opposite experience in several other occasions with this switch, but that is here not the case.
Design of its internal PSU is very poor and correspondigly it is sensitive to the capacity and quality of the external transformer connected to it. Usage of stronger external power supply is therefore mandatory because it opens the sound considerably.
Still, I have a problem with one LED which blinks all the time when the unit is ON but not locked. This LEd (on the front it shows 33 MHz input frequency) is connected directly to the pin of the receiver chip and I couldn't figure out why it behaves like this. It doesn't though influence the functioning of the DAC but still it is not really optimal. I contacted one friend of mine who has this DAC for years and he told me that he has the same problem. This issue alone is strong recommendation not to go after this DAC. On the other hand, it can be bought quite cheap (for approx. 100 EUR on eBay) and it sounds decent. So for the people who are looking something that will bring some improvement for their DVDs or old CDPs, this may be an option. I am using this DAC connected with VdH optical cable to my DVD player - that means I am using it not very often. The sound improvement over the analogue outputs of my old Sony DVD is obvious and looking from that point of view, it was very good and cost effective upgrade.
|
|
|
|
Post by pwilson on May 16, 2013 19:42:09 GMT
HY ,IF YOU DONT MIND CAN YOU TELL ME FEW UPGRADE ICAN DO TO MY X ACT IJUST BOUGHT TIS UNDERATE PIECE OF HISTORY . SOME CAPS VALUES . I JUST WANT VERY SIMPLE AND BASIC LITLLE UPGRADE . THANKS IN ADVANCED. PWILSON
|
|
|
|
Post by eightdigitword on Jun 1, 2013 12:58:25 GMT
My Experience with this DAC is that your time and cash spent on it should be limited. Improvements through upgrades are restricted by poor design and use of massive nasty chips. Its easy to go crazy on stuff, i did, wish i hadn't, hope this helps.
as mentioned earlier get hold of an XDAC V3 or at the very least a X24K, both cheap on Ebay and have massive potential. All depends on the capabilities of the rest of your system, off course.
|
|
