New Audio-gd R-7, R-7HE R-8, R-27, R-27HE, R-28 Flagship Resistor Ladder DACs and DAC/amps

[Mix80]

I hope it's clear what is missing in the scheme?
Dots connected by yellow line traced by multimeter

 

[Mix80]

About the quality of AGD products,

Here's another example:

The board simply did not fit into the case and was cut with a hand tool.
And again, AGD makes excellent products in terms of engineering solutions.

 

[Currawong]

I hope it's clear what is missing in the scheme?
Dots connected by yellow line traced by multimeter

Do you have a soldering iron? If so, just bridge the connection and see if it works. I expect that the impedance will wrong, but at least you'll know if that was where the fault lies.

 

[tumpux]

Amos, I think the problem here is this Mix80 guy didn’t get a proper support from the brand. He asked for the schematics to AGD so he can check whether there is any missing component on his AES port, but he didn’t get satisfactory response from the manufacturer. Otherwise we would not have him posted it in this forum.

I can understand if something missed in the QC process, but the least a brand would do is helping the customer to resolve the problem.

 

[FredA]

Just wanna add that based on my experience sometimes the AGD quality control is not the best for a company that sells directly to the consumer. I have a Master 9 preamplifier that has a female 4 pin XLR connector in the right ACSS output channel instead of a male 4 pin XLR. Just in the right ACSS output channel, the left ACSS output channel is using the correct male 4 pin XLR.

Anyway the issue was resolved with AGD sending me the correct XLR connector so I can replace it myself instead of sending the unit back to China, but the point is it shows that their quality control procedure was not including checking that all the functionality is working before sending the unit out. In my case, you don’t even need to check the ACSS output connection to find the problem. You can see it visually that the right ACSS channel has a different connector from the left channel.

I can see why the AES input connection issue like this could pass their QC process. It’s not part of their QC process at all. I believe the majority of AGD consumers never use the AES input in their DAC or use the ACSS output in their preamp.

There are issues once in a while but most of the time, it is minor. And upon receiving the gear, the customer is supposed try the gear to make sure everything is fine. One good reason is transport-caused damage. So in case some issue is found, the unit can be returned to audio-gd and replaced for free. So far, it happened to me once out of 15 or so, twice if i count a transport-induced cosmetic damage (i repaired myself). Otherwise, a very minor issue occured with a friend's unit, which i repaired. I am fine with all this because audio-gd is an artisanal shop and because of their high-value offerings.

At this stage, @Mix80 should also test that his aes/ebu output is fine and that his unit is properly configured (clock mutiplier must not be too high).

 

[FredA]

Also, the unit does not look clean in this area. @Mix80 Was it bought used? There are marks there and things do not look as good as usual...

 

[tumpux]

I don’t subscribe to that logic. Just because it’s cheap does it mean it’s ok to not do the QC process properly? When you put an AES input in your box, you have to make sure that it works before the unit is being shipped. Otherwise these 300 hours of burning in claim is just a joke. I know that we’re not talking about established brands like Pass Labs or Audio Research here, but public should have an idea of what kind of trade off that they get when buying from home industry brand in a far away land like AGD.
Calling it an artisanal shop sounds so much as shilling to me. Don’t do that.

Again, the real issue here is he didn’t get a proper support to decide whether his problem is due to the unit defect or due to other compatibility.

And Fred, I am sure that you have one of the AGD DAC with the AES input. Why don’t you open it up and share the picture with us so we can confirm that there is nothing unusual about his unit?

 

[FredA]

I don’t subscribe to that logic. Just because it’s cheap does it mean it’s ok to not do the QC process properly? When you put an AES input in your box, you have to make sure that it works before the unit is being shipped. Otherwise these 300 hours of burning in claim is just a joke. I know that we’re not talking about established brands like Pass Labs or Audio Research here, but public should have an idea of what kind of trade off that they get when buying from home industry brand in a far away land like AGD.
Calling it an artisanal shop sounds so much as shilling to me. Don’t do that.

Again, the real issue here is he didn’t get a proper support to decide whether his problem is due to the unit defect or due to other compatibility.

And Fred, I am sure that you have one of the AGD DAC with the AES input. Why don’t you open it up and share the picture with us so we can confirm that there is nothing unusual about his unit?

I think that audio-gd has ok quality control but they can drop one once in a while, like most cies. And if there is a communicarion issue with Kingwa, it is not 100% his fault. I always am able to get what he says eventually. And i remain polite and friendly whatever happens. I have always had excellent support from Kingwa. I trust Kingwa and that he does the stated burn-in on his gears. Finally, the overall build quality is excellent, much above your average maintream cie. We don't have to agree.

I wrote Kingwa to ask if something is missing. Should get an answer within the next 12h.

 

[Mix80]

I will not quote the correspondence with Kingwa here, for ethical reasons, but every time I encounter a problem or just want to ask something, I repeat the same request several times and simplify my question as much as possible to such a state that even child. Since the answers from Kingwa often do not even correspond to the topic of my questions. But these are all solvable problems and it was always possible to agree with Kingwa, before this case with the AES port. Here I spent a week trying to find out and understand something, and I received the closest answer to the topic only after the discussion started here: send the DAC back to the manufacturer at my own expense, if anyone knows how much it costs - can compare the costs of installing one SMD resistor and shipping 20kg to China and back.
While before that, Kingwa trusted me with a much more complex repair. I'm already worried, maybe it's not he who answers me, but some kind of bot ... (

 

[FredA]

I will not quote the correspondence with Kingwa here, for ethical reasons, but every time I encounter a problem or just want to ask something, I repeat the same request several times and simplify my question as much as possible to such a state that even child. Since the answers from Kingwa often do not even correspond to the topic of my questions. But these are all solvable problems and it was always possible to agree with Kingwa, before this case with the AES port. Here I spent a week trying to find out and understand something, and I received the closest answer to the topic only after the discussion started here: send the DAC back to the manufacturer at my own expense, if anyone knows how much it costs - can compare the costs of installing one SMD resistor and shipping 20kg to China and back.
While before that, Kingwa trusted me with a much more complex repair. I'm already worried, maybe it's not he who answers me, but some kind of bot ... (

Got the answer from Kingwa. No part is missing. That spot you have identified is only used when a cheaper version of transformer is installed. In your case and in all cases, Kingwa chose to install the best transformer. Missing part occurences are nearly impossible as the boards are soldered automatically.

If I were you, I would try to borrow another aes/ebu source. The fact that the contact is not made with the connector could be due to the possibility that a cap is used in series to block dc. Just a guess, not sure it is commonly done. Also, ensure that oversampling is not cranked up on your mutec. Finally, try to see if pin2 contacts with its pad.

 

[DACLadder]

Greetings dear community, Please help me with a problem. AES EBU input is not working for me in my DAC R7HE MK2. I discovered this recently, although I have owned the device for a long time.
When the port is activated, crackling and noise are heard, connecting a signal source does not help, no sound is played from the source.
I decided to check what could be the problem.
Opened the cover, and checked the signal circuits in the AES port.
As a result, I found out that in my DAC, pin 1 of the AES port is not connected anywhere.
Pin 2 is tracked to an empty resistor space on the board. Next, the signal should go to the transformer, but my DAC does not have a series resistor in this circuit.
And only Pin 3 is traced to the transformer.

I have a question. Do any of you have any information on the resistor value on your DAC board at the AES EBU input for Pin2? I indicated this place in the photo.

Does your R7HE mk2 have the 110 ohm terminator across the transformer input. See pictures of my HE7 mk2 below? I think it is 110 ohm resistors as you can't measure across the transformer windings in circuit.

Not sure what resistor that is with '001'. The red caps are in series with the AES/EBU signal pairs to block DC on the signal line. Large DC offsets would fry the tiny transformers wires.

Do you also have Pin 1 not tracked and not connected to chassis ground?
Thanks in advance for your replies and help.

Pin 1 - cable shield (chassis ground) is not connected on my HE7 mk2. Likely the cable shield is only connected on the source side to avoid ground loops. The little transformer provides galvanic isolation of the signal pair.

 

[FredA]

Does your R7HE mk2 have the 110 ohm terminator across the transformer output. See pictures of my HE7 mk2 below? I think it is 110 ohm resistors as you can't measure across the transformer windings in circuit.

Not sure what resistor that is with '001'. The red caps are in series with the AES/EBU signal pairs to block DC on the signal line. Large DC offsets would fry the tiny transformers wires.



Pin 1 - cable shield (chassis ground) is not connected on my HE7 mk2. Likely the cable shield is only connected on the source side to avoid ground loops. The little transformer provides galvanic isolation of the signal pair.

See my post.

 

[Mix80]

DACLadder
Thanks for the first really helpful answer.

I don't have a terminating resistor on the transformer.

As I wrote earlier, Pin 2 is accurately connected to the board, since I can trace it to an empty resistor pad, then the signal does not pass, I.e. none of the transformer pins are connected to pin 2 of the AES/EBU connector.
Please tell me. In your DAC, pins 2 and 3 from the AES connector are traced to the transformer?

 

[FredA]

DACLadder
Thanks for the first really helpful answer.

I don't have a terminating resistor on the transformer.

As I wrote earlier, Pin 2 is accurately connected to the board, since I can trace it to an empty resistor pad, then the signal does not pass, I.e. none of the transformer pins are connected to pin 2 of the AES/EBU connector.
Please tell me. In your DAC, pins 2 and 3 from the AES connector are traced to the transformer?

He said a cap is in between pin 2 and the transformer. So the tester won't show continuity. It's normal. On the other hand, you seem to be missing the 110 ohm resistor to the right. Could be hidden by the transformer.

Your dac looks like it's been worked on by someone with limited skills (marks on the pcb, so so soldering on the transformer, possibly missing 110 resistor). Has it?

 

[DACLadder]

Correct… on pins 2 & 3 you can’t measure anything with an ohmmeter as the two red coupling caps block current. Best way to debug and know for sure is to use a scope.

I would ask Kingwa about the 110 ohm resistor termination. He could have changed procedure during production.