The "mod your Zhalou" Thread

[Ruach]

I got a set of the D2 (AD1852) from Eddie last week. The performance of the stock D2 is not exactly impressive.

I started some mods on the D2 and it became a winner.

Changed the RCA connectors, biased the opamps to Class A, changed the power filter capacitors to better grade caps, bypassed the LM1117 with tatalums.

The mod that made the most impact is the addition of 3 cheap EI core transformers (one for the digital receiver, one for the digital supply of the DAC and another for the analog supply of the DAC).

There are other mods that I put on hold for the moment and this includes removing the 4 pieces of the DC blocking caps (just behind the opamps) as the datasheet for the AD1852 shows that these caps are not necessary.

Have fun guys

 

[Ori]

Quote:

Originally Posted by Ruach addition of 3 cheap EI core transformers

Love that pic!!!
Quote:

Originally Posted by Ruach removing the 4 pieces of the DC blocking caps (just behind the opamps) as the datasheet for the AD1852 shows that these caps are not necessary.

The DC offset between the outputs of the AD1852 is high (I measured 200mV), so don't do that mod without something to tweak the DC offset on the outputs.

 

[lan]

Quote:

Originally Posted by Ruach I got a set of the D2 (AD1852) from Eddie last week. The performance of the stock D2 is not exactly impressive. I started some mods on the D2 and it became a winner. Changed the RCA connectors, biased the opamps to Class A, changed the power filter capacitors to better grade caps, bypassed the LM1117 with tatalums. The mod that made the most impact is the addition of 3 cheap EI core transformers (one for the digital receiver, one for the digital supply of the DAC and another for the analog supply of the DAC).

Nice. I just have to say that performance is relative. People reading "not impressive" might scare some people away and it shouldn't. Most pieces of equipment don't use multiple transformers but just one or 2 with multiple secondaries. Separate ones is a trait of only the uber high end units. If you mod things, most stock things aren't impressive IMO.

The transformer mod is possible and easy on the zhaolu d2 because it has multiple rectifiers and voltage regulators which is beyond the normal you see around. Ideally you would want those and multiple transformers but you hardly ever see that.

I havn't had a chance to take a look inside one of these unit. I'd have to find small EI transformers for this.

 

[TigzStudio]

Rauch,

do you mind taking a higher resolution picture of your mods?

Just so I can see in detail =) =)



I notice tha tmost likely if you want the headphone amp upgrade that is coming out, you probably wont be able to fit the EI transformer.

 

[Ori]

Quote:

Originally Posted by TigzStudio I notice tha tmost likely if you want the headphone amp upgrade that is coming out, you probably wont be able to fit the EI transformer.

Here is a simple math...

A good DAC with a compromised headamp would give you a good DAC and a compromised headamp... Now, a Compromised DAC with a good headamp would give you a compromised DAC and a compromised sound through the headamp...

So, which is better?!

 

[lan]

Quote:

Originally Posted by Ori Here is a simple math... A good DAC with a compromised headamp would give you a good DAC and a compromised headamp... Now, a Compromised DAC with a good headamp would give you a compromised DAC and a compromised sound through the headamp... So, which is better?!

The answer is move it into a larger case so you can have it all

 

[hyamaiata]

Hey, do you guys know if the American dealer, iFi Audio, is going to offer the blackgates upgrade? How much is the blackgates upgrade from Eddie?

 

[Ruach]

I have yet to measure the DC offset. 200mV is considered high. The datasheet for the AD1852 specified an offset of 50mV. If it is convenient, can you take another measurement? The D2 which I modded is back with a friend who owns it.

Page 14 of the AD1852 datasheet also shows an application schematic of the AD1852 without the use of the DC blocking caps.


Quote:

Originally Posted by Ori Love that pic!!! The DC offset between the outputs of the AD1852 is high (I measured 200mV), so don't do that mod without something to tweak the DC offset on the outputs.

 

[uzziah]

Quote:

Originally Posted by Ruach I got a set of the D2 (AD1852) from Eddie last week. The performance of the stock D2 is not exactly impressive. I started some mods on the D2 and it became a winner. Changed the RCA connectors, biased the opamps to Class A, changed the power filter capacitors to better grade caps, bypassed the LM1117 with tatalums. The mod that made the most impact is the addition of 3 cheap EI core transformers (one for the digital receiver, one for the digital supply of the DAC and another for the analog supply of the DAC). There are other mods that I put on hold for the moment and this includes removing the 4 pieces of the DC blocking caps (just behind the opamps) as the datasheet for the AD1852 shows that these caps are not necessary. Have fun guys

really excellent work

 

[Ruach]

You are right Ian. The transformer mod is easy as there are 6 sets of rectifiers on board the D2.

One set (18V, 0V, 18V) for the opamps, one set for the microprocessor which controls the optical, coaxial toggles, and mute function. Two sets for the receiver and the buffer and two sets for the AD1852 chip.

Having independent transformer for each rectifier isolates the power supply and the improvements raise the performance to another level. Anyway, the EIs cost me US$3 each and for a US$9 mod, I am getting most bang for the buck.

The IC rectifiers on board the D2 looks sleezy. They can be rebuilt using discrete diodes (fast recovery or schottky). This should reduce the high frequency switching noises in the power supply.

 

[Cyrilix]

Seems like people don't have good impressions with the AD1852 chip...just something I've noticed so far when compared to the CS4398.

 

[Ori]

Quote:

Originally Posted by Ian The answer is move it into a larger case so you can have it all

Or better yet - two separate cases...

Quote:

Originally Posted by Ruach I have yet to measure the DC offset. 200mV is considered high. The datasheet for the AD1852 specified an offset of 50mV.

That's 50mV typical... My unit measures 102 and 207 mV, so do I have a lemon or is that spec just optimistic?!

I also wanted to comment about the usage of your extra trannies. The circuit most sensitive to noise should be the PLL, fed from the AVDD pin of the receiver chip. The next most sensitive is the analog part of the 1852.
If you can, then give each of these a seperate source transformer and use the third tranny for all the digital supplies.
Refer to the section of PCB layout of the CS8416 chip spec for some real good advice. I don't have a 2.0 in my hands (yet...), so I can't tell you a more specific advice.

 

[Borat]

Quote:

Originally Posted by uzziah you'd line up to carry that box around? not me.

I think Jon L. is referring to the advantages of clean battery power for sound performance, not portability. Similar to the Storm and Ack! dAck! which both run on battery power with good results.

 

[Ruach]

Hi TigzStudio,

Just drop me a PM. I have a 2mb file for the same photo that you see in my previous posting.


I have just check with Eddie and he saie that it is ok to remove the DC blocking caps. However, he did state that one has to be careful about the orientation of the opamps when you swap them around.


Quote:

Originally Posted by TigzStudio Rauch, do you mind taking a higher resolution picture of your mods? Just so I can see in detail =) =) I notice tha tmost likely if you want the headphone amp upgrade that is coming out, you probably wont be able to fit the EI transformer.

 

[fkclo]

Quote:

Originally Posted by Jon L Oh, yeah, Battery-powered Zhaolu, if available, will definitely mean my buying it. When you see him again, could you tell Eddie people are lining up to buy the battery version, so please make it happen? (People will line up after this post). While you are there, could you also encourage him to make USB input available? (another long line will form).

Just have another face-to-face chat with Eddie yesterday. I handed him some ERS cloth tape to try out if it provides better EMI/RF shielding inside the Zhaolu. My unit won't be ready until after the first week of June.

Some update: While the trial battery setup provides remarkable performance, there is currently no plan to make it a commercial offering. Time (all Eddie got is 24 hours a day) aside, the cost of putting together a nice package (a box, charger, batteries, voltage distribution....etc) may render the offering unattractive for most. This reveals part of Eddie's modification philosophy - he does not seem to support the idea of spending more on modification than the base unit itself. In another words, when the pure battery unit is going to cost comparable to the DAC itself, Eddie feels there will be a lack of commercial incentive. That aside, I do believe he can come up with a few to entertain real die hard Zhaolu fans.....

Regarding USB, Eddie seems to have his own approach towards modifying a Zhaolu. He wanted to rely on the topology that is built into the Zhaolu, rather than making a different DAC out of Zhaolu. So, whatever Eddie is doing with a Zhaolu, it will still be a Zhaolu.

For those who are after a transportable DAC with USB, I do believe the Stello DA-100 is a good choice. Out of my limited experience, I think the Stello has the best execution of USB in an audio DAC.

F. Lo