V-dac modifications

[FalseMetal666]

Finally got around to bypassing the output caps and there is a perceptible improvement in sound quality with no seeming downside. Leaving the DAC alone for now, I think I've put enough effort into a piece that's probably worth about $40 haha

 

[carlmart]

How does the V-DAC now compares in audio quality with other DACs?

 

[FalseMetal666]

Sorry to say, I've got nothing to compare it with. It definitely sounds better than stock and one of these days I'll get around to some A/B tests.

 

[PiotrekG]

Hello guys. Thanks for this superb thread and your willingnes to share the knowledge. I am about to upgrade my V-Dac too
But I am here to ask, if anyone knows how to run V-Dac on windows 10?

 

[les24preludes]

I just bought a V-DAC so will post when it's up and running. If anyone else wants to join the thread, so much the better.

 

[les24preludes]

I made a cable for my new V-DAC with V-PSU and now listening to it in my main system with my SE 2 stage valve amp. The sound is smooth and pleasant with good acoustic timbre and tonality. Easy to listen to but a bit dull. It's not as good as my other AK4490 DAC with currently a LT1364 or LM6172 op-amp in the output - that has more detail and the LT1364 has a very subtle and delicate treble.

The question for me now is whether to upgrade it. For it to move up a level at least 2 things would have to happen
1. Fit a 8 pin DIP socket so I could try other op-amps than the NE5532
2. Change the output cap to either a smaller polypropylene one or leave it out if the offset were tiny.

I can hear the makings of a better DAC in it. It's not expensive to experiment with. Around £60-75 on ebay.

 

[les24preludes]

I had a look at the PCB and measured the resistors on the output. The op-amp is JRC NE5532DD not OPA2132 as in schematic. I've added the resistor values to the schematic just for the output. Hoping to remove the 47uF cap and make any other changes to the resistors on the output accordingly.

 

[les24preludes]

I removed the 47uF output caps and the sound is a bit cleaner, rather than smooth and a little dull. But the quality isn't really there with the NE5532 chip. I don't know if I can be bothered to fit a DIP8 socket on the output so I'll probably just put the caps back and leave it at that. It showed some promise but it didn't really materialise.

 

[les24preludes]

Some progress. Out of my Mac Pro 2012 the sound is much smoother using the Toslink out. So that's staying unless I get better results with a USB converter like the V-Link which I have coming. The usual USB out has a layer of grunge on it, and the Toslink eliminates that.

I managed to fit a DIP8 socket on the output so I can swap op-amps. I'm not used to reworking PCBs and it took a while to work out how to remove the NE5532. First I cut the 8 legs off and removed the chip. Then I had to use my Engineer solder sucker and apply new blobs of solder to each pin to get the solder to flow so it would suck up. Anyway, it worked thank goodness. My first substitution is a LT1364. It's a good sound and I'll leave it in for a while. I also have OPA2132, OPA2134, LM6172, LM4562 and some NE5532s. In my AK4490 DAC I got the best results with LT1364 and LM6172 so we'll see.

 

[les24preludes]

I'm enjoying my modified V-DAC. I'm now using it with a V-Link for USB out of my Mac. Then SPDIF out into the V-DAC. I have the V-PSU at present but might make a 12V supply with a choke in it. The current consumption is 350mA at 12V DC, tip positive, barrel negative.

 

[les24preludes]

I've already outlined the modifications I made to my V-DAC, which is basically to cut out the NE5532 and replace it with a DIP8 socket, and also to remove the 47uF NP electrolytic output cap since the output is into a tube stage with cap coupling, all of which made it audibly cleaner and more detailed.

I just had a session comparing op-amps in the output stage, and my findings were as follows on a variety of classical, opera, jazz and modern gospel.
Top three:
LT1364 - best piano, good vocals, best high treble on cymbal sounds
LT1361 - good low level detail, a free relaxed sound, good piano and voices
LT1469 - almost identical to LT1361, very nice overall, smooth and involving

Fourth: LT6172 - good piano and voices, just below the top 3 because of a trifle more wooden sound overall
Fifth: LT1057 - neutral and good tone but less involving and didn't stand out like the top 3

I find it hard to choose between the top 3, and I enjoy all of them. They are available in DIP8 form from Farnell. With any of them the V-DAC goes up a level and becomes competitive with more mid-price DACs at a bargain used price. This is using the V-PSU, V-Link and SPDIF.

I have some further op-amps to try which require SOIC to DIP8 adapters which I haven't soldered yet. These are all well recommended:
OPA1642
OPA1612
AD8066
AD8599
AD8022