I just received my Wolfson 4.0 BIY DAC :)

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riddellsr

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Joined 2010
bigpandahk said:
Dear Riddellsr

Where are the output caps you mentioned?
[The output caps are the Nichicon 47uf Electros closest to the output rca's. The bypasses are small 104J or .01 bypass caps. I understand that some models have 22uf and even some have 10uf. The Ellectrolytic are all noisy . The bypasses are either MKP or Mylar and are meant to smooth out the Electros. Since I am using a better quality Film Cap for this position I have chosen to remove the .01 bypass because I find that they muddy the sound. The V Cap site in its Tech Room section has an excellent how to with formulas to decide on what value is best for replacing with. For my purposes I need about 5uf and up to have extension below 30 HZ. As the better quality caps are much larger I have had to mount the caps outside of the chassis. Now I have experimented with 4.7uf Ampohm PIO, 4.7uf Russian K75-10, 5.6uf Russian Polystyrene and 6.8uf Mundorf Silver in Oil both standalone and with a Teflon .1uf bypass. For my rig the best balance has come with the Mundorfs standing alone. As I am running directly from the DAC to a 10K Passive to a tube amp I require a larger value cap. If I was running a Preamp with an input impedance of say 47K-50K I would install a much smaller value cap.
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riddellsr

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Joined 2010
bigpandahk said:
Dear Riddellsr

Where are the output caps you mentioned?
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In proper response to your question the .01 bypass caps are the smaller red or reddish brown caps with 104j printed on them. They are used all over this DAC. The ones in question are the ones that are installed right next to the Electroytic 47uf Nichicons at output..
These are an inexpensive MKP or maybe even Polyester with can be improved upon throughout this DAC. I have replaced in the Power Supply with a same value MKP with excellent results.
 
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bigpandahk

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Joined 2009
riddellsr said:
In proper response to your question the .01 bypass caps are the smaller red or reddish brown caps with 104j printed on them. They are used all over this DAC. The ones in question are the ones that are installed right next to the Electroytic 47uf Nichicons at output..
These are an inexpensive MKP or maybe even Polyester with can be improved upon throughout this DAC. I have replaced in the Power Supply with a same value MKP with excellent results.
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Thanks Riddellsr. The output cap and relay were not shown on the circuit diagram given by Hui. I further checked the circuit, the caps near the output terminals are not connected to the output. They are caps for the power bypass.
 
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avbuilder

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Joined 2009
thanks bigpandahk

Got to know about chinese colors from here

Chinese Vocabulary: Colors in Chinese

which confirmed the connections for the power from the burnt toroid as already stated by bigpandahk the front ones are 0-9, 0-9 while the other two are 0-15, 0-15 however on brief power up there was a wisp of smoke means there is a short circuit. Checked with multimeter which confirmed that some of the rectifier diodes are bad will replace are 16 diodes (IN4007). Could someone suggest a better one in its place.
 
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bigpandahk

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Joined 2009
avbuilder said:
thanks bigpandahk

Got to know about chinese colors from here

Chinese Vocabulary: Colors in Chinese

which confirmed the connections for the power from the burnt toroid as already stated by bigpandahk the front ones are 0-9, 0-9 while the other two are 0-15, 0-15 however on brief power up there was a wisp of smoke means there is a short circuit. Checked with multimeter which confirmed that some of the rectifier diodes are bad will replace are 16 diodes (IN4007). Could someone suggest a better one in its place.
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I will replace those 1N4007 with UF5404, a fast switching diode. Regarding the transformer, please note that the second 9V output should have 1 Amp current.
 
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avbuilder

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Joined 2009
Unfortunately I have already ordered the transformer 0-9v lines being 0.6 ampere. Replaced all rectifiers and the DAC is up and running. There are many suggestion to tweak this DAC what should be the most effective mods which can be easily apparent on listening. Not interested in minor improvements.
 
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aptsys

Member
Joined 2010
avbuilder said:
thanks bigpandahk

Got to know about chinese colors from here

Chinese Vocabulary: Colors in Chinese

which confirmed the connections for the power from the burnt toroid as already stated by bigpandahk the front ones are 0-9, 0-9 while the other two are 0-15, 0-15 however on brief power up there was a wisp of smoke means there is a short circuit. Checked with multimeter which confirmed that some of the rectifier diodes are bad will replace are 16 diodes (IN4007). Could someone suggest a better one in its place.
Click to expand...

There should be no problem replacing the damaged diodes with the same 1N400x. The AC frequency is no where near needing any kind of fast switching diode.
 
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avbuilder

Member
Joined 2009
As already posted the DAC is up an running. Few of the rectifiers had malfunctioned leading to a short circuit in one of the secondary windings leading to heating and short circuiting of the rest of the primary and secondary windings turning into an inferno before the fuse blew.

All it took was a change in all rectifiers, toroid and a voltage regulator.
 
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bigpandahk

Member
Joined 2009
avbuilder said:
Unfortunately I have already ordered the transformer 0-9v lines being 0.6 ampere. Replaced all rectifiers and the DAC is up and running. There are many suggestion to tweak this DAC what should be the most effective mods which can be easily apparent on listening. Not interested in minor improvements.
Click to expand...

Replace the 8740 with 8741 will give you great improvement on details and bass.
 
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rotzooi

Member
Joined 2008
google.nl
rotzooi said:
Last week I did a few mods : removed filter and amplifier stage, replaced all caps round wolfsons, used Oscons, placed tube buffer including tube rectifier and extra power supply.

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


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


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


A few pictures of the inside of the Wolfson DAC. You can see the oscons round the Wolfons, the oscons in the power supply, the new tube buffer stage with riken resistors, russian pio's for output and Jensen pio's as couple caps.

It is the best DAC I ever made with wonderful open sound!
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kroyin

Member
Joined 2012
Hi have this DAC (wm8740 replaced with 8741).

A couple of days back I found that one channel was playing louder in my chain (dac->b1->aleph j).

After a bit of investigation with a 1khz 0db test tone I found that the left dac outputs .1v less than right (1.5v on left 1.6v on right). This translates to 1V difference at aleph amp o/p

Do anyone have a circuit diagram with expected voltages written down. I have till now swapped the opa627 ,tried both the usb & opt inputaround but the problem is always with left
Thanks guys
 
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K

kroyin

Member
Joined 2012
kroyin said:
Hi have this DAC (wm8740 replaced with 8741).

A couple of days back I found that one channel was playing louder in my chain (dac->b1->aleph j).

After a bit of investigation with a 1khz 0db test tone I found that the left dac outputs .1v less than right (1.5v on left 1.6v on right). This translates to 1V difference at aleph amp o/p

Do anyone have a circuit diagram with expected voltages written down. I have till now swapped the opa627 ,tried both the usb & opt inputaround but the problem is always with left
Thanks guys
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Few more data points (for someone to help me :)..don't even know if the info is useful)

The DC voltage across the lower 4 opa-627 (across pin 6 vout & RCA gnd) is consistent at at 1.47x V but the AC across the upper 2 opa's (pin 6 & RCA gnd) has the .1v diff
 
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