Hello all,
I've a big problem with a Ayon CD5 I had to replace twice a PCM1704K chip, and now it's the third time. In the past I could find without problem genuine TI PCM1704K, but it's seems to be a problem today. So I don't know what to do.
Is there a drop in replacement for this cheap ? I don't care too much if it's not as good as, it's a second system player, and I want to keep this race car because a lot of work has been done on it.
Ok that's not normal that one the 1704K break so often it's a weak point of this player, each time I connect or disconnect the XLR/RCA/Digital cables while the unit is switched on, I sooner of later know that a 1704 will die, it has been confirmed by a Ayon technician
So, any kind advice to help me ?
I'd short the "outgoing" ends of those monster capacitors to ground each time the player goes into STOP
What did the technician say? Why are the DAC's failing?
Hello Extreme_Boki,
Well, the technician from Ayon just told me that each time I would connect or disconnect any signal cable on the unit meanwhile it's powered on, I may have one the 1704 chip to stop working, sooner or later, without any technical explanation.
The first time a 1704 chip broke was with the original unit (not modified) I sent it for repair to Ayon and they told me the changed one of the 1704 chip.
The second time was far after the upgrade, one 1704 chip + one OPA627 broke. + one fuse (related to the OPA627).
This time again a 1704 chip, maybe two are broken and maybe an OPA627 This unit has always had ground problems depending of which amp was connected to, many users have the same problem.
The big output V-Caps TFTF have replaced initial Mundorf supreme with same value, the big supreme silver/gold/oil 3.3+0.33µF replaced a simple 3 µF Mundorf supreme. The blue vertical caps are an upgrade of the filtering capacity for the tube power supply.
This time I just stupidly unplugged an AES digital cable from the input of the Ayon to it's output, then the unit worked fine but after a few minutes the speakers started to emit a big low frequency noise (like a subwoofer at high volume) while playing music at the same time. I disconnected everything, checked inside an saw one of the fuse half blown (always the same), so I put an other one and checked again, but this time I had only crackling noise in the HP, no more music, typical of a PCM1704 broken. There's obviously something weak in this unit, I don't know what.
What I know it's I have to take care to never disconnect any cable behind while it's powered on, and it works.
Well, the technician from Ayon just told me that each time I would connect or disconnect any signal cable on the unit meanwhile it's powered on, I may have one the 1704 chip to stop working, sooner or later, without any technical explanation.
The first time a 1704 chip broke was with the original unit (not modified) I sent it for repair to Ayon and they told me the changed one of the 1704 chip.
The second time was far after the upgrade, one 1704 chip + one OPA627 broke. + one fuse (related to the OPA627).
This time again a 1704 chip, maybe two are broken and maybe an OPA627 This unit has always had ground problems depending of which amp was connected to, many users have the same problem.
The big output V-Caps TFTF have replaced initial Mundorf supreme with same value, the big supreme silver/gold/oil 3.3+0.33µF replaced a simple 3 µF Mundorf supreme. The blue vertical caps are an upgrade of the filtering capacity for the tube power supply.
This time I just stupidly unplugged an AES digital cable from the input of the Ayon to it's output, then the unit worked fine but after a few minutes the speakers started to emit a big low frequency noise (like a subwoofer at high volume) while playing music at the same time. I disconnected everything, checked inside an saw one of the fuse half blown (always the same), so I put an other one and checked again, but this time I had only crackling noise in the HP, no more music, typical of a PCM1704 broken. There's obviously something weak in this unit, I don't know what.
What I know it's I have to take care to never disconnect any cable behind while it's powered on, and it works.
Totally right, there's clearly a grounding problem in this unit. And yes, I should power off everything each time, but sometimes I forget it 
After replacing everything I'll be more carefull
This time the "funny" thing, is that before the big low frequency noise in the speakers, I noticed that one of the transfo was noisy, after removing and replacing the half blown fuse on the main board (the filament was just partially broken), the transfo noise disapeared, the player was ok and then 3 minutes later, big noise again and new fuse dead. I'm unfortunately not skilled enough to analyse the problem, I guess some expert would detect the weak point by analyzing the purpose of the sensitive fuse, so I'll just replace the 4x1704K + 4xOPA627 and be extremelly carefull in the future.
After replacing everything I'll be more carefull This time the "funny" thing, is that before the big low frequency noise in the speakers, I noticed that one of the transfo was noisy, after removing and replacing the half blown fuse on the main board (the filament was just partially broken), the transfo noise disapeared, the player was ok and then 3 minutes later, big noise again and new fuse dead. I'm unfortunately not skilled enough to analyse the problem, I guess some expert would detect the weak point by analyzing the purpose of the sensitive fuse, so I'll just replace the 4x1704K + 4xOPA627 and be extremelly carefull in the future.
+1 for unequalised ground potentials. Coupled with something marginal about the PS. Is the rail voltage for the 1704s close to the max?
I cannot see a mechanism other than a PS spike which kills the chips. Maybe a good start would be examining the ground potentials of your equipment when the boxes are not connected.
Thanks for these answers, unfortunately I'm not skilled enough in electronics to follow a hard discussion, but if you quickly sum up where I should measure the ground potentials it's something I should be able to do
What the guy who made the upgrade told me, it's that the zero potential of the signal and the zero potential of the frame were not the same because of a lot of resistors between both. Also a retailer of Ayon products told me that to remove the ground noise his customers had, he connected the ground of the XLR signal to the shell (on the cables), so basically it's like equalize both zero potentiel ?
I'll replace the PCM1704 and OPA627, but I'd like to understand
What the guy who made the upgrade told me, it's that the zero potential of the signal and the zero potential of the frame were not the same because of a lot of resistors between both. Also a retailer of Ayon products told me that to remove the ground noise his customers had, he connected the ground of the XLR signal to the shell (on the cables), so basically it's like equalize both zero potentiel ?
I'll replace the PCM1704 and OPA627, but I'd like to understand
Farnell, an authorized TI distributor, has several J-grade chips in stock.
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Thanks a lot, ordered
That's more than hundred bucks a piece! Are you going to try them without knowing what caused the failure?
Yes I know, that's expensive, but no other choice. Unfortunately I'm not skilled enough to determine what causes this failure, I just know that it's related to plugging or unplugging audio or digital cable while the unit is ON, so I'll take care in the future. If I can find some good technician closed to my home I'll ask to check what's wrong I ordered 4 PCM1704 so I'll change only the broken one(s) and have some spare parts.
Anyway I agree with you
I ordered 4 PCM1704 so I'll change only the broken one(s) and have some spare parts.Anyway I agree with you
Canvas, you were right !
Some news
After having replaced the 4xPCM1704 and 4xOPA627, I made some tests again. Everything worked well, but again one hour after, the music stopped. This time the right tube output stage was dead.
After investigation with my poor skills I found that the 9V was no supplied anymore from the transfo. So I brought the unit to a friend of mine, and he found that one of the thermal security in the transfo was broken, probably because of an exces of heat. So he fixed it and I came back home for a quick test. A the begining it was fine and again after one hour, the sound became like if it was an old radio. So I switched off and check inside, the fuse was OK, but the transfo was really hot with a typical smell. It's a small RCore transfo, 36W with a 9V(1,7A), 14V(0,5A) and 7,5V(0,5A) outputs with connectors, the 9V goes for the right output tube and the two others on the main board.
I found that it's the 14V output which generate a very quick increase of temperature in the transfo + buzz when connected to the main board. When disconnected, the unit still works (I mean there's sound but still "as an old radio"), no overheating of the transfo and no buzz.
So I don't know which part of the Ayon CD5 is powered with this 14V ? Not the DAC part, not the tube output, not the CD mechanic..Remain the digital input board ?
Some news
After having replaced the 4xPCM1704 and 4xOPA627, I made some tests again. Everything worked well, but again one hour after, the music stopped. This time the right tube output stage was dead.
After investigation with my poor skills I found that the 9V was no supplied anymore from the transfo. So I brought the unit to a friend of mine, and he found that one of the thermal security in the transfo was broken, probably because of an exces of heat. So he fixed it and I came back home for a quick test. A the begining it was fine and again after one hour, the sound became like if it was an old radio. So I switched off and check inside, the fuse was OK, but the transfo was really hot with a typical smell. It's a small RCore transfo, 36W with a 9V(1,7A), 14V(0,5A) and 7,5V(0,5A) outputs with connectors, the 9V goes for the right output tube and the two others on the main board.
I found that it's the 14V output which generate a very quick increase of temperature in the transfo + buzz when connected to the main board. When disconnected, the unit still works (I mean there's sound but still "as an old radio"), no overheating of the transfo and no buzz.
So I don't know which part of the Ayon CD5 is powered with this 14V ? Not the DAC part, not the tube output, not the CD mechanic..Remain the digital input board ?
Here's comes the truth !
With my poor skills I tried to understand what's the bug and found this :
The 4xOPA627 are powered with the 14V, throught :
- 4 xLM1086
- LM317T (+) + KA337(-) for left channel and same for the right channel
The strange thing is that only one KA337 is isolated (mica between the component and heatsink) all the 7 other regulators have no isolation. When I check with a multimeter, all the heatsink are connected between each other (LM1086, LM317T and KA337), excepted the isolated KA337.
I wonder in these conditions how this DAC has worked, I guess it can explain all the problems I had in the past (OPA 627 and PCM1704 died randomly) ?
With my poor skills I tried to understand what's the bug and found this :
The 4xOPA627 are powered with the 14V, throught :
- 4 xLM1086
- LM317T (+) + KA337(-) for left channel and same for the right channel
The strange thing is that only one KA337 is isolated (mica between the component and heatsink) all the 7 other regulators have no isolation. When I check with a multimeter, all the heatsink are connected between each other (LM1086, LM317T and KA337), excepted the isolated KA337.
I wonder in these conditions how this DAC has worked, I guess it can explain all the problems I had in the past (OPA 627 and PCM1704 died randomly) ?
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