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PostPosted: November 8th, 2019, 3:24 pm 
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Joined: June 4th, 2013, 2:39 pm
Posts: 176
I know some you guys have experience building DACs so I'm looking for suggestions.

My friend there in DC, Jim, and I both ordered the Doge 7 DAC about two months ago. They are supposedly redesigning them and they were selling the old model at a steep discount. Jim's works fine, but mine developed distortion in the right channel after about a week. There are two boards in the case, one for the DAC circuitry and one for the tubed output stage. The headphone output bypasses the tube stage and the distortion shows up there so I'm pretty sure the tube stage is not the problem.

The chip is an ES9038. I contacted the sales rep about the problem and after some back and forth he said they would just send me a new DAC board to drop in. That was three weeks ago and I am not getting any response now. ;-( For the moment I've got a $1000 doorstop. I'm keeping my fingers crossed that I'll hear back from them, but if I don't I was trying to figure out how to salvage the unit. Is there an ES9038 DIY DAC I could drop in and connect to the tube output stage, or maybe something using a different chip? The DAC board doesn't employ opamps but goes directly to the 6-tube output stage.

Could I send the board to someone to diagnose without shipping the whole unit? (It's very well-built and heavy.) The board has two harness clips for the outputs to the tube stage so it's easy to disconnect. Or does anyone know a good repair person who could take a look at the whole unit, if it comes to that?

I'm going to poke around some more and see if there's anything obvious, like a loose solder joint or something.

If I don't hear back soon I'll open a PayPal dispute and see what happens, but in the meantime I was just trying to think of what to do with this lovely, not-working thing. It sure sounded nice while it worked.


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PostPosted: November 8th, 2019, 3:36 pm 
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Joined: July 24th, 2015, 4:17 pm
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Location: Parkville, Maryland
Grover Gardner wrote:
I know some you guys have experience building DACs so I'm looking for suggestions.

My friend there in DC, Jim, and I both ordered the Doge 7 DAC about two months ago. They are supposedly redesigning them and they were selling the old model at a steep discount. Jim's works fine, but mine developed distortion in the right channel after about a week. There are two boards in the case, one for the DAC circuitry and one for the tubed output stage. The headphone output bypasses the tube stage and the distortion shows up there so I'm pretty sure the tube stage is not the problem.

The chip is an ES9038. I contacted the sales rep about the problem and after some back and forth he said they would just send me a new DAC board to drop in. That was three weeks ago and I am not getting any response now. ;-( For the moment I've got a $1000 doorstop. I'm keeping my fingers crossed that I'll hear back from them, but if I don't I was trying to figure out how to salvage the unit. Is there an ES9038 DIY DAC I could drop in and connect to the tube output stage, or maybe something using a different chip? The DAC board doesn't employ opamps but goes directly to the 6-tube output stage.

Could I send the board to someone to diagnose without shipping the whole unit? (It's very well-built and heavy.) The board has two harness clips for the outputs to the tube stage so it's easy to disconnect. Or does anyone know a good repair person who could take a look at the whole unit, if it comes to that?

I'm going to poke around some more and see if there's anything obvious, like a loose solder joint or something.

If I don't hear back soon I'll open a PayPal dispute and see what happens, but in the meantime I was just trying to think of what to do with this lovely, not-working thing. It sure sounded nice while it worked.



The issue here is if -- and that is a big if -- you can find someone that can trouble-shoot at a board level. And only if they the have entire unit to run diagnostics. They would need a 100-mHz. scope (at least) and the various chips' application information (and/or handbook) to determine the fault. if you find that person we would all like to know who it is.

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Walt


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PostPosted: November 8th, 2019, 4:05 pm 
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Joined: February 28th, 2013, 1:19 pm
Posts: 331
Grover,

Not sure if the board could be evaluated apart from the unit due to interface with power supply and display/control logic circuits. Unless there is clear indication of these interfaces, voltage, polarities, etc., you could easily destroy the board trying to save it. Unless it was your intent to test it on Jim's unit via a board swap. Anyway, I did look at the Warranty section on the DOGE website, and they did indicate as much as 5 weeks for shipping out parts. I would be nervous as you are on the silence, but maybe continue to wait and try to contact the company again for an update. It may be on a "slow boat from China".

Sorry I cannot be much help, I have a couple broken DACs of my own.

David


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PostPosted: November 8th, 2019, 4:14 pm 
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Joined: June 4th, 2013, 2:39 pm
Posts: 176
Thanks, both. Good points. I'll wait and see what happens, and if all else fails try to get a refund if possible. Meantime I got a Topping DX7s that I like quite a lot, so I'm not at a loss for good sound. ;-)


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PostPosted: November 8th, 2019, 11:10 pm 
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Joined: June 4th, 2013, 2:39 pm
Posts: 176
Okay, I had a thought and did another test. It's NOT the DAC board, which is good news, I guess. It's something on the output board. There must be an opamp for the headphones or something between the DAC board and the input of the tube gain stages. Either they'll get back to me and arrange for repair, or I'll file a dispute with PayPal and see if I can get some of my money back. It's possible that my tech buddy at work could troubleshoot it--he's pretty good. But I'll just have to wait and see which option presents itself. Thanks for the suggestions, folks, it at least pointed me toward some more poking around.


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