[sjwong]

Quote:

Hm strange very strange. The hum of the headphone amp is mostly noticeable on the left side, there is also a crackling noise. All this with only the power connected, nothing else, no signal cable. Music plays fine when i connect that, but the hum and crackling overlays it completely. Also i exchanged the OPAs, problem stays Today I connected it again for the first time since a week, i didnt touch it otherwise. Interesting: When i turn the volume pot up completely the hum & crackling is almost gone What? faulty volume pot?

Definitely strange. I had a problem like this with my Little Dot when I originally bought it. I sent it back, and I think they just fixed one of the solder connections. Hopefully this isn't because of your DIY work!

 

[TigzStudio]

Darn, its seeming like Zhalou 2.0 is have more quality control issues then the 1.3, makes sense since it seems to be more complex.

 

[bizkid]

Yup i just checked the pics which i took on my first day with the Zhaolu. That cap was damaged from day 1:

It's the cap in line with the 6 wimas below the OPAs, though on the opposite side of the DAC chip. You can clearly see the dent. Well it still works though

sjwong: the headamp was far far away from any soldering action

But really i dont care since i dont use it anyway.

 

[ODG]

On my 1.3 there is hum and cracking noise if no digital signal is fed to it. Once there is signal to it, the red led lights up and noise no more.
This could be same case with the 2.0.

 

[Ori]

Quote:

Originally Posted by ODG On my 1.3 there is hum and cracking noise if no digital signal is fed to it. Once there is signal to it, the red led lights up and noise no more. This could be same case with the 2.0.

This is a known issue. The red light indicates a valid incoming digital stream. Some source equipment "fills in" the gaps with null data, so the light will remain on all the time and the PLL will maintain lock. Unfortunately, most source equipment will not do that.
The Zhaolu 2.0 added a mute circuit to circumvent this "problem". That circuit is not present on the 1.3.

 

[vmajor]

I had and am still having quality issues with the Zhaolu 2.0

I originally bought the A1852 version with LT and DY op-amps. It sounded great when fed through coaxial input from my M-Audio 2496 card. Unfortunately 3 days later the DAC started switching to Optical input without my intervention. I was finally unable to select Coaxial input at all.

I sent the PCB back to Eddie and also asked him to upgrade the PCB with the Black Gate option. The PCB came back upgraded but one of the Elna caps on the underside had a drop of solder shorting the legs. I used scissors to remove the short (now I see that many of Zhaolu enthusiasts purposefully bridge these contacts). This PCB I got back is also a later generation than the original one I sent back. This one includes some SMD components on the underside.

This new upgraded DAC had further four issues:
1. rampant clicking if a certain type of coaxial signal is being provided from my sound card
2. left channel going silent at random, but coming back to life after power cycle
3. very faint but audible whirring sound if optical input is selected,
4. what sounds like a ground loop on the left channel IF both my Alesis M1 Active Mk2 speakers AND my AT 900A headphones are connected.

The issue 1 is tolerable and there is no clicking when listening to music if I set my patch bay router on the sound card to S/PDIF (as it should be).

Issue 2 was I think related to a dodgy LT OPA. I replaced both with the original A2604 and fixed the problems as well as improved the sound tenfold.

3. Does not bother me as I do not use optical in, however I do find it annoying as it does limit my choices

4. Eddie suggest I disconnect the ground wire but I am not sure I want to do that - should I ever disconnect a ground wire and what are the potential detrimental effects? Zhaolu suggests I bridge the resistor that is located above the Zhaolu logo etching on the PCB.

I have to say Eddie is very helpful and understanding, however there is just one of him and yes I think that Zhaolu and Eddie QA/QC practices could be better.

Nonwithstanding all of the above, the DAC sounds absolutely amazing. I will be getting the upgraded headamp when stock becomes available.

Cheers,

Victor

 

[RogerWilco]

Sorry to hear that.I am glad eddie was helpfull.

 

[uzziah]

Quote:

Originally Posted by lan Yeah it looks pretty crazy underneath there. Well he is still getting sound isn't he? I recommend you practice soldering using an old piece of equipment before you getting back into the tighter areas of the zhaolu and maybe get another iron.

also, a little bottle of radioshack tape head cleaner and a toothbrush has done wonders for me to get things clean and nice before/after soldering. you can't see what's wrong if you can't see through a mess of flux.

 

[bizkid]

vmajor: Did you try the XLR outs for your active speakers? Did they improve things? I want to get some mogami starquad and neutriks to make 2 XLR cables, but i wonder if it's worth the trouble.

 

[eVITAERC]

Quote:

Originally Posted by vmajor I had and am still having quality issues with the Zhaolu 2.0 ..... 4. Eddie suggest I disconnect the ground wire but I am not sure I want to do that - should I ever disconnect a ground wire and what are the potential detrimental effects? Zhaolu suggests I bridge the resistor that is located above the Zhaolu logo etching on the PCB.

It's generally okay to disconnect the ground wire from the receptacle to the chassis, as it only serves as a place for electorn to drain should some massive amount of electricity somehow zapped the chassis. Audio techs disconnect ground wires all the time to break ground loops.

If you're still skittish about comepletely disconnecting the gorund wire, then you can connect the ground wire through a "ground loop breaker". Disconnect your ground wire form the chassis, then simply solder a 10 ohm (1-2W) resistor to the ground wire, and attach the other end of the resistor to the chassis. Then solder a 0.1uF capacitor in parallel with the resistor, but stricly speaking that's not necessay. The capacitor decouples high frequency noise induced on the chassis to the ground, meaning that your chassis can act as a RF shield, which might be important if you're near a computer or other RF device.

Of course if you have no soldering iron.... then just unplug the ground wire. It won't hurt, really.

 

[HumanMedia]

Quote:

Originally Posted by uzziah also, a little bottle of radioshack tape head cleaner and a toothbrush has done wonders for me to get things clean and nice before/after soldering. you can't see what's wrong if you can't see through a mess of flux.

Good idea (after as well). Note that a cleanup after for some types of solder is almost mandatory. eg. WBT solder uses a flux that conducts, not well, but it does. So if even if the solder job is precise, if there are traces of flux left which connect to adjoining traces, problems may occur.

 

[bizkid]

Cool i finally got my CS4398 board today

First impressions (using speakers): Room information is more precise and natural than the AD1852 which has an already mentioned more airy presentation, the change is very noticeable with classical music. Also blackness between instruments is better with the CS4398. Hard to judge if its "warmer" because my speakers already got great warm but resolving mids, not much to imrpove there

Besides warm vs airy the CS4398 is technically clearly the better DAC. It's soundstage information is more precise and it's easier to eg. locate different parts out of a drumkit. However that might not be noticeable at all on headphones. I do think that the CS4398 sounds airy too, but without overdoing it.

Btw i get the clicking sound on changing tracks too, even with upsampling to 96khz, but it doesnt bother me much.

EDIT: Just located the hum problem with my headphone amp.... it was a ground loop. Noticed it when i disconnect my speakers and turned the volume pot (without knob) when hum started while i touched it. Now i'll do some CS/AD comparisons with the K701

 

[udo]

Did anyone here get a reply from Zhaolu or a dealer about the clicking thet is reported?

Also: when does it occur?
When playing using CD/DVD/PC? What machine brand?
At what samplerates, bitdepths?

 

[vmajor]

bizkid: No did not try XLR yet. I will try to find some leads under 10m in lenght and try them out. The short leads are not that common... I may go to my local pro shop over the weekend and get some

eVITAERC: Thank you for the great explanation. I can use a soldering iron (badly) so I may attempt the "groud loop breaker" circuit. What power/voltage rating should I look for the cap?

Cheers,

Victor

 

[eVITAERC]

Quote:

Originally Posted by vmajor eVITAERC: Thank you for the great explanation. I can use a soldering iron (badly) so I may attempt the "groud loop breaker" circuit. What power/voltage rating should I look for the cap?

It should only have to pass RF noise, which is no a lot of volts. Something like 16v should give you plenty of headroom.

The 10 ohm resistor is the big thing that will stop ground loops. It's not uncommon to see a drop of 1-2V somewhere out of all the wires connected to ground. The low low resistance of wires (~0.5) will mean that somewhere from 2-4 amps flowing along the ground wires! with a 10 ohm resisto this drops to a much more sensible 0.1-0.2 amps, which should cure your ground loop problem. Unless, of course, your problem is not a ground loop to begin with.