A NOS 192/24 DAC with the PCM1794 (and WaveIO USB input)

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Almeg69

Member
Joined 2009
Bones13 said:
I am having an issue with my 5 volt PSU section. I have the power supply boards from Doede. The 12 volt one works fine.

When I power up, the LED next to the TP122 is dim, there is some current, but its not lit correctly. At this point, I get an output voltage of 1.2v or so.

Now, if I touch any metal object to the TP122 heatsink, the LED becomes very bright (brighter than the other one, and brighter than both the ones on the 12 volt board) and the voltage is 5.5 or so. I had carefully calibrated it to 5v before this foolishness started. Of course, when I power on the unit, the Wave I/O does not initialize with 1.2v.

I reflowed all the joints twice, and remeasured all the parts that I could. I confirmed all the capacitors face the same way as the 12 volt board, which is working correctly.

Bad TP122? I don't recall having to use an insulator against the heat sink.

Ideas? I might just use the USB power for a bit, until I can debug this PSU.
Click to expand...

Have you checked that the BC550 and BC560 are in the correct place ? If not one of the transistors will get hot ...
 
Bones13

Bones13

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Joined 2006
Paid Member
DDDAC is up and running. I found a mis connected out lead (connected to common, not neg) and noticed noise with the CT from the transformer touching metal.

Getting a fair bit of distortion though. My power voltages are 5.1 to the Wave I/O board, and 11.2 to the DDDAC (blue board).
 
dddac

dddac

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Joined 2003
blog.dddac.com
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The swapped transistor is the most common fault so far. Seems to be tricky somehow.

On the distortion, Harmonic or digital? Did you check output voltages? Also, did you connect the transformers to the common and POS when live? Your transformers might have been magnetized... This could lead to distortion. But it could be other things, like wrong bias. Without transformers connected, do you measure 2.7 volt between pos- com and neg- com ?
 
Bones13

Bones13

Member
Joined 2006
Paid Member
dddac said:
The swapped transistor is the most common fault so far. Seems to be tricky somehow.

On the distortion, Harmonic or digital? Did you check output voltages? Also, did you connect the transformers to the common and POS when live? Your transformers might have been magnetized... This could lead to distortion. But it could be other things, like wrong bias. Without transformers connected, do you measure 2.7 volt between pos- com and neg- com ?
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The sound was more of an unstability, another vibration mixed into the music. I will have to see of its only on one side or not.

Only one of the transformers was hooked up wrong, and it was for a short while. The first time I turned on the DDDAC the PSU worked for awhile. At that point I noticed one of the channels was lower than the other. No doubt due to the transformer mis-wiring.

I did get out of sorts with it yesterday, and put it up for awhile. I will get it out in a while and test those things: test the voltages, and test each channel separately.

Thanks Deode!
 
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Almeg69

Member
Joined 2009
dddac said:
You can do two parallel as long as they are thermally connected. Both need a resistor after emitter to make sure they balance

Tip 142 is also fine no problem use big heat sinks
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Last night I swapped the TIP122 for the TIP142. It will fit if you squeeze the leads with a pair of pliers to make them square.

Also fitted were 2 off Mundorf 10000uf 40v AG`s instead of the 4700uf and 2 off Vishay 470uf 40v to replace the Nichicon`s.

2A ceramic fuse now used instead of 1a.

I done a quick no load test and all is OK so far.

I will work on the heatsink later, it is BIG ...
 
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billyboyk

Member
Joined 2008
Hum...

Hi everybody !

I have finished my DDDAC :D, sounds great ! :eek:

I have just a little problem of humming when the pot is going to high level, hum is coming.

I need to connect the cinemags to stereo pot for manage my two mono blocks but the issue is still there with any other amplifier. I see that if I connect ground to Cinch plug, it is OK but I think it is not a good solution:

An externally hosted image should be here but it was not working when we last tested it.


Each components of the DAC are isolated from the metal case.

Any idea ?

Thank Doede for the great job, expect this litte issue, I am very happy ! :)
 
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Almeg69

Member
Joined 2009
I have finished the uprated power supply using a larger TIP142 transistor with huge heatsink as I leave the dac switched on permanently.

Next up is soldering the 5 stacks to my existing 11 stacks to create a 16 stack ....
 

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A

Almeg69

Member
Joined 2009
All working OK so far .... Now for the bedding in time 1 - 2 months.

The power supply heatsink runs at 35ºC which is fine by me as I leave the Dac on permanently.

Now I know 16 decks work OK, I want to make a double 16 stack one for left, one for right with dual power supplies using Lundhal chokes ... I like to think big :)

16 stacks is so July 2015
 

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Extreme_Boky

Extreme_Boky

Member
Joined 2003
dddac said:
I think there is no need to start claiming credits throug PayPal etc. just take this on with audio creative. the tax rules are complicated but very clear. so this need to cleared administratively. I will check this as well.

please do not forget I always send my kits as private person, so there was never vat on it, it is not to compare with the official way of doing business.
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Hi Doede,

Just to inform you that I ordered the DDDAC kit with two power supplies and a 4-stacker- DAC broads. I expected VAT to be automatically deducted from the total price, once I selected Australian shipping address - but this did not happen... So, it seems that Audio Creative has done nothing, and it’s been a year since people initially complained about this issue.

I have contacted your distributor by e-mail and asked for a refund; however, may I make suggestion to you, to ask your distributor Audio Creative to AUTOMATICALLY deduct the VAT portion from the total cost, at the time when the order is placed? This will improve the overall buying experience.

Thank you,
Nick
 
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Almeg69

Member
Joined 2009
Chanh said:
Very nice!
What sort of improvement(s) jumping from 11 to 16, were you noticed?
Unfortunately my enthusiasm for PCM DAC has damping down greatly after hearing a very good native DSD DAC. Will reroute the investments/energies to the DSD DAC here on! :)
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The bass content and slam along with the transient reproduction. The soundstage gets deeper with better ambient clues and the treble and mid range get more lifelike.
I will have a longer listening session later but the improvements are not subtle :)
 
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