[BobM]

I have a Zhaolu 2.5C that I have modded with some help from Paul/Occam (thanks) and it sounds pretty darn good. I have noticed that it sounds significantly better using the TOSLINK digital input from my transport rather than the RCA jack input (yes, I did upgrade the cheap RCA jack to a gold connector).

Another modder of the Zhaolu (Oritek) uses a torroidal on the RCA digital input and claims a much better signal than through the stock components. Anyone know the value of this torroidal and other information on where to get one and how to install it (i.e. what gets removed and what gets connected where - it seems fairly straightforward based on the picture)? Here's a picture:



Thanks,
Bob

[BobM]

I got an answer over at www.diyaudio.com. Check out page 10 of this thread: http://www.diyaudio.com/forums/showthread.php?s=&postid=1432607#post1432607

There's also some other interesting information on a better grounding scheme for the power supply board, but it's a lilttle hard to follow without a picture.

Anyone else care to comment?

Bob

[art]

Trying hard to be nice............

If your TOSLINK sounds better than the coax input, then it is a really bad design. I don't know of any other way to put it.

As for that transformer.......without having one to measure, I can only be 99% certain that it is not a good one. I would bet that the cheap Pulse Engineering one that Mouser sells is better than that one. They only cost a few $, give one a try before you waste money on that one.

Sorry if that was not the kind of comment you were expecting.

Pat

[BobM]

Pat,

That is a perfectly acceptable comment, and EXACTLY what I was looking for. I also feel that a digital RCA connection should surpass a TOSLINK one. Which is why I'm looking for ways to improve on it.

Thanks for the recommendation at Mouser. There's lots listed for Pulse though - do you have a parts # perhaps?

Bob

[art]

Yep........PE-65612. I think around $3-4. I would suggest that the Newava.......uh, I think 22083 is the right one.......from Digi-key is the best I have found.

On page 7 or so of The Lab index, there is a long thread about pulse transformers. I made measurements of both the Newava and PE ones.

Of course, wiring is critical for SPDIF. I believe in the SB3 mod thread, I show where bog-standard audio wire doesn't cut it.

The next step would be to stick a video op-amp in front of the RX chip, but I bet that is beyond your plans and/or skill level. Layout becomes critical for those.

Pat

[BobM]

Thanks Pat. If it wasn't for Digikey's $5 charge for orders below $25 I would definitely order from them more.

Damn this hobby and the incremental costs.

Bob

[randytsuch]

Trying hard to be nice............

If your TOSLINK sounds better than the coax input, then it is a really bad design. I don't know of any other way to put it.

As for that transformer.......without having one to measure, I can only be 99% certain that it is not a good one. I would bet that the cheap Pulse Engineering one that Mouser sells is better than that one. They only cost a few $, give one a try before you waste money on that one.

Sorry if that was not the kind of comment you were expecting.

Pat

I was sure you were going to say to lose the RCA jack, and change it to a 75 ohm BNC.  Of course, you should do this on the transport end too.

Randy

[art]

Yeah, but.........

It will cost him $9 for the BNC jack that I use. He will have to spend $8-12 to get a BNC for the cable. Double that if he does the same to the transport......

I dunno how much he wants to spend. That is why I suggested a $4 transformer.

He can always change it later! Once it is working.

Pat

[BobM]

I made some mods to the grounding scheme on my 2.5C based on some posts at DIY-Audio by kevinkr. This dropped the noise floor very noticeably. There is definitely some problems with the original layout, using common ground planes (both top and bottom) to connect components - not a good design overall.

I also made significant changes to the audio output board, effectively using one part of the dual op-amp to regulate the DC servo for the first op-amp. A rather dramatic reduction in parts on this board and significant re-routing. I also bypassed the relay. All of this is on the DIY-Audio thread as well, here:

http://www.diyaudio.com/forums/showthread.php?s=&postid=1444927#post1444927

The change in the sound of this DAC to the better is pretty dramatic. A nice improvement, for sure. Real weight, body and punch while maintaining the great extension and soundstaging that this DAC was known for.

Bob