[Seba]

Just finished installing my Zapfilter. I use only RCA's for now with wires coming straight out from the case. I have to make holes for XLR connectors to the back panel and finish everything up then.

First impressions are that bass is noticeably bigger and treble gain new sparkle (might also be harshness because the lack of burn in). Oh, and those 56Ohm/5W resistors smell a little and get hot.

 

[C37]

If your zap filter shipped with the very small toroid for the psu, a cheap and good upgrade is to replace with something beefier. I replaced mine with one of the 15V 2x 0.5 A from twisted pear (Avel lindberg) just for the sake of trying and am not going back. It's also a dead quiet (my zap toroid was buzzing) Be warned it's bigger than stock one so your zhaolu will be crammed as an egg. Maybe mount all the psu outboard ...

 

[reemixx]

I received my Zhaolu D2.5A with discrete headphone amp upgrade a couple of days ago. It's also been modded a bit, straight from Coem Audio in Australia. I've been listening to it and just letting it burn-in for most of that time. Overall, I'm very happy with the sound compared to my previous DAC/amp (Lexicon Omega). Most noticeably, the soundstage is much wider, there's a lot more detail, the sound is very airy, and music sounds better when played at a lower volume than it did with the Omega. All good things, and what I was hoping for. But there's also a few things that are bugging me.

When listening through my AD700's, there's a fair bit of sibilance, especially with female vocals, and cymbals sound a little strange like the upper highs are being rolled off, so I end up with a lot of hissy hi-hats, etc, and it's a bit fatiguing especially with heavier rock music. There's also a lack of bass extension, which is probably what's bugging me the most, since the lack of bass to round out the sound just makes the sibilance stand out even more.

I figure these issues are probably due to one or more of the following:

1) Burn-in: I haven't properly burnt in the unit yet. It's had (roughly) 20 hours. Is this a probable cause? Will the extreme highs and lows become more evident over time? I've noticed some very slight changes already, so I'm hoping so.

2) Headphones: The AD700's are quite bright to begin with, and tend to be light on bass. That said, I get a lot more bass through the Lexicon Omega (but obviously with a detriment to detail) using the same headphones. Is it possible the AD700's are just a bad pairing with the Zhaolu?

3) Opamps: The unit came with the LT1057's in the DAC section. I thought these were supposed to be pretty decent, but maybe they're causing the sibilance? I remember reading that someone swapped them out for the LM4562's instead, and noticed the sibilance went away. I think that was with a CS DAC though. Would it be worthwhile to try it anyway?

4) Ears: Maybe I'm just really used to the sound of the Omega that the Zhaolu sounds strange to me now, but I'm kind of skeptical of that. I'm not a bass-head at all, yet still noticing a lack of bass. My ears are also pretty sensitive to treble, so obviously this is a problem. The same issues come through when using my Audioengine 2 speakers as well, though obviously not as much since the speakers are pretty bass-heavy and resonate a bit on my desk.

Soooo... any ideas? In the meantime, I'll just keep on letting it burn-in and try to figure out exactly what I'm hearing. I've also ordered some LM4562's anyway, so will probably give those a go when they arrive.

 

[Ori]

Bass will improve with bypassing the four coupling caps on the analog PCB. The LT1057 do not sound good in this circuit. Replacing them is mandatory.
Then give the unit more than 20 hours...

 

[reemixx]

Cheers Ori.

I read somewhere that it was more the CS DAC that needed bass improving with bypassing the coupling caps, and that the AD was pretty good? Either way, I'm not a DIY person, so that's not something I'll be doing myself.

Fair enough about the opamps. I'll pop in the LM4562's when I get them. I also have OPA2134's as spares, but I'm guessing they'll sound worse than the LT's?

Still burning in, too.

 

[Ori]

Quote:

Originally Posted by reemixx /img/forum/go_quote.gif Cheers Ori. I read somewhere that it was more the CS DAC that needed bass improving with bypassing the coupling caps, and that the AD was pretty good? Either way, I'm not a DIY person, so that's not something I'll be doing myself.

Actually, this is the easiest first-time mod. The boards use sockets to connect between them so they come apart easily. You just solder four wires and no need to remove any components.
If you don't feel comfortable doing it yourself then take the board with the exact instructions to any audio-video technician. They'll do it in minutes and not likely to charge much.

 

[Bleemv1]

hey reemix,

I got my zhaolu from coemaudio too. Was the mod only the discrete headphone amp? or did they others as well? When I got mine done, I got them to do the cap bypass, upgrade some of the other caps, and some better rca jacks. Although I don't have the discrete headphone amp, the built in one wasn't so bad. More burn in will improve it too I think

 

[reemixx]

Ori: Fair enough. Maybe I'll look into it, after I've tried rolling opamps and burning in a little more. Where can I find more info about the mod?

Bleemv1: The info I got from Coem when I asked what mods they do with the Zhaolu was:

Quote:

There are upgraded capacitors and Op-Amps, capacitor upgrades are present in the power supply and DAC circuits.

So I guess they just switched out the capacitors for better ones. I didn't ask them to do any mods, that was just what it came with.

 

[Ori]

Quote:

Originally Posted by reemixx /img/forum/go_quote.gif Ori: Fair enough. Maybe I'll look into it, after I've tried rolling opamps and burning in a little more. Where can I find more info about the mod?

Read my post with pics on page 130 of this thread.

 

[Bleemv1]

Just wondering if it's worth replacing things like Caps, resistors to better quality parts? I don't really know anything about electronics but I'm comfortable with soldering in replacement components. Does anyone know if this has been discussed in this uber thread? I'd look through it but it's 137 pages long so if someone remembers around about where cap replacements were discussed that would be great.

Any recommendations on what parts (like Blackgates etc.) would be good too, and where I can order them from (I Live in Australia )

Thanks guys

 

[reemixx]

Quote:

Originally Posted by Ori /img/forum/go_quote.gif Read my post with pics on page 130 of this thread.

Thanks a bunch.

 

[Bleemv1]

I just found out that my zhaolu has already been upgraded with ELNA caps, so I guess upgrading them won't really achieve that much.

What's the transformer thing that can be added to the coax input? I think you do them Ori?

maybe a clock upgrade could benefit the DAC (but I've heard it's more beneficial if the clock on the transport is upgraded rather than at the DAC)

 

[BobMcN]

Quote:

Originally Posted by Bleemv1 /img/forum/go_quote.gif What's the transformer thing that can be added to the coax input? I think you do them Ori?

That's probably Ori's implementation of a pulse transformer. Yes, it should improve the smoothness of the digital signal immensely, but you need to know the right part. Here's the part # I used from Mouser: 673-PE-65612

There are 4 connections on it. I simply connected the + of the RCA to one and the through side of the pulse transformer to the board, and the - side of the RCA to the orher with the through to the board. A little hot glue stuck it to the board itself (it's fairly tiny). There's a good empty spot to the side of the RCA jack where it shouldn't interfere with anything else.

Quote:

Originally Posted by Bleemv1 /img/forum/go_quote.gif maybe a clock upgrade could benefit the DAC (but I've heard it's more beneficial if the clock on the transport is upgraded rather than at the DAC)

That's mostly true. The best bang for the buck on a clock would be in the transport.

Bob

 

[Bleemv1]

Hi Bob,

thanks for that. I'll look into getting that part

I think I can follow your instructions. What is the "through side" of the transformer? is it just one of the connections?

Thanks

 

[BobMcN]

There are 2 connectors on each side of the transformer. Using a meter you will need to identify which ones pair off (go "through" to the other side). Otherwise you could potentially wind up crossing the + and - of the signal.

Bob