Hi everyone hope everyone is doing great.
I acquired this DAC and looking for a popping solution.
The right channel will pop whenever audio starts playing. It can be replicated by either play/pause or turning volume up from 0.
There are a pair of CHAMP Modules (pictured, horizontal with many LEDs) which I assumed was the cause. After swapping the cards the popping did not swap so it could be up stream.
The three boards (vertical) are Decoder board, Digital Filter board, and DAC board.
The dac uses 4 PCM1704 chips.
No service manuals are available and information is sparse.
Aside from the popping and slightly higher noise floor compared to modern DACs, it sounds great. I use it for my tv as well so the pops between quiet passages doesn’t sound great.
Ps; this dac has a quirk of never turning off. When you press the front power button everything stays lit but the input/output relays are disengaged. I assume they’re subscribed to the idea of leaving your equipment turned on makes it sound better.
I acquired this DAC and looking for a popping solution.
The right channel will pop whenever audio starts playing. It can be replicated by either play/pause or turning volume up from 0.
There are a pair of CHAMP Modules (pictured, horizontal with many LEDs) which I assumed was the cause. After swapping the cards the popping did not swap so it could be up stream.
The three boards (vertical) are Decoder board, Digital Filter board, and DAC board.
The dac uses 4 PCM1704 chips.
No service manuals are available and information is sparse.
Aside from the popping and slightly higher noise floor compared to modern DACs, it sounds great. I use it for my tv as well so the pops between quiet passages doesn’t sound great.
Ps; this dac has a quirk of never turning off. When you press the front power button everything stays lit but the input/output relays are disengaged. I assume they’re subscribed to the idea of leaving your equipment turned on makes it sound better.
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Hi, I would suspect the 25 year old black electrolytic SMD caps and replace them for the newer version and preferably in a higher voltage rating like 16V. Since these don't even have a brand logo it will be difficult to know which brand and series but they look like tantalums or poscaps. They are also not all the same, some have an extra symbol after the voltag rating.
You could measure all and still find nothing or just replace them all 18 and see if the popping has gone. Make sure to choose the exact right casing!
You could measure all and still find nothing or just replace them all 18 and see if the popping has gone. Make sure to choose the exact right casing!
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They're manufactured between 2003-2006 so yes about 20 years old by now.
You're also correct that I measured them and they came out fine. Interesting, maybe what I can do is swap out the capacitors between left and right to verify.
You're also correct that I measured them and they came out fine. Interesting, maybe what I can do is swap out the capacitors between left and right to verify.
The PCB is made in 1999. Anyway, chances are that you will gain nothing but peeled off PCB tracks and then still have 20 year old caps and plops.
I would choose low leakage low ESR and reliable tantalum caps for this purpose. Not a cap connoisseur anymore but AVX TPS series are good.
I would choose low leakage low ESR and reliable tantalum caps for this purpose. Not a cap connoisseur anymore but AVX TPS series are good.
The board is quite forgiving to hot air soldering. I’ve already swapped the 2 middle DM74AS74M with no damage.
Do what you like. BTW it could very well be the PCMs that are EOL. Had that several times with PCM1702. You'll know that after the cap replacement.
20 Euro investment. Further suspects are the normal electrolytic TH caps and voltage regulators.
The distance in costs between repair and a new cheap but good DAC can be small. In fact needing to replace those PCMs will be ridiculously more expensive than a new upper class device. The meanwhile mystical properties of the chips (...La$t Of ThE R2r...) create deep emotions amongst the sensitive audiophiles that don't cry when they empty their wallets to obtain them. The TDA1541A syndrome 🙂
A switched power distributor would have solved the 24/7 service of a device probably used 1 or 2 hours in that 24 hours. Always on stuff is nice but it may fail after many years when power is cut a few times. Usually caps but DAC chip themselves also seem to die after many years. DAC chips were not designed for 20 years of 24/7 service. There will come a moment that even the nicest DAC wil be recycled as a toaster in China.
20 Euro investment. Further suspects are the normal electrolytic TH caps and voltage regulators.
The distance in costs between repair and a new cheap but good DAC can be small. In fact needing to replace those PCMs will be ridiculously more expensive than a new upper class device. The meanwhile mystical properties of the chips (...La$t Of ThE R2r...) create deep emotions amongst the sensitive audiophiles that don't cry when they empty their wallets to obtain them. The TDA1541A syndrome 🙂
A switched power distributor would have solved the 24/7 service of a device probably used 1 or 2 hours in that 24 hours. Always on stuff is nice but it may fail after many years when power is cut a few times. Usually caps but DAC chip themselves also seem to die after many years. DAC chips were not designed for 20 years of 24/7 service. There will come a moment that even the nicest DAC wil be recycled as a toaster in China.
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Wise words my friend. Yes I was surprised the dac never turns off too. It wasn’t until I opened it that I found out they stay on. I expected a standby circuit to keep the pilot light on but it turns out the whole thing stays energised. It also relies on the mains power to remember which input was last active as the logic NAND gates flipped when mains power is cut.
If the PCM chips are causing this pop I might just leave it as it is.
What was the common failure mode for your PCM1702?
If the PCM chips are causing this pop I might just leave it as it is.
What was the common failure mode for your PCM1702?
Hi except that the number is on my list of stuff I don’t want I forgot everything. Reasons to forget are normally premature failure or mediocre performance. Like PCM1710, PCM67, TDA1540 etc. I know I replaced them and this was long ago as it were the DIP versions. More recently I had it with ES9018K2M DAC chips in overheated Auralic Aries Mini devices. It happens. Consumer stuff that is replaceable so no big deal.
However your device has PCM1704 so I dirtied myself by doing association. So sorry, the La$t Of ThE R2r may be the best thing that happened to our planet.
However your device has PCM1704 so I dirtied myself by doing association. So sorry, the La$t Of ThE R2r may be the best thing that happened to our planet.
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