Upgrade the WM8740 to WM8741 you will have a hugh improvement on the details and bass.
Yeah, I sort of realized that it wasn't necessary because of the low voltages after asking the question and taking a closer look at the schematic. You say the mains transformer is the only thing that needs to be connected to earth, and that it has been done. I have an earlier version of the DAC similar to the one in the first post, where the mains pin on the power connector is not connected to anything. The mains transformer has two leads which are connected to the live and neutral wires. It appears that in the newer version of this DAC (seen here: DAC WM8740 4.0 balanced/unbalanced output 24bit/192KHz | eBay) there is a connection to the earth. How is it that the transformer in the early version is connected to the earth exactly?
Wolfson meets tubes
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.
http://flickr.com/gp/74943269@N02/62R6h7
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.
http://flickr.com/gp/74943269@N02/62R6h7
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Yes, 100% direct replacement.
This DAC is still available on ebay with addition balanced output. It also have an 8741 version but lot more expensive. Search WM8740 or WM8741, those units sold under raindrop_hui.
I purchased the unbalanced version of this DAC.
1.Modifications done OPA 134s replaced with OPA 627s all around.
2.Output Caps and bypasses removed Replaced with AMPOHM PIOs. 4.7uf (no bypass caps) I have had to mount these outside the box as they are Huge Caps
3.Bypass of muting circuit and output 10 ohm resistor.
4.All 47uf Electrolytics and .01 Polypropylene bypasses around OPAMPs have been removed and replaced with 10uf Metallized Polypropylene (again no bypasses)
5.Replaced stock fuse with HIFI Tuning Silver.
The sound with each step has improved greatly in the areas of musicality, timing and dimensionality and smoothness.
I am running through a homemade passive 10k attenuator with Vishay Nakeds directly to a 100k input tube amp so I have a couple of 6.8uf Mundorf Silver Oil coming to see if I can reach down a little lower than 30 HZ in the bass.
I am contemplating some improvements to the Power Supply. If any one has any suggestions please post.
Thank-you to all who have contributed to this posting, I have learned a great deal from all of you.
1.Modifications done OPA 134s replaced with OPA 627s all around.
2.Output Caps and bypasses removed Replaced with AMPOHM PIOs. 4.7uf (no bypass caps) I have had to mount these outside the box as they are Huge Caps
3.Bypass of muting circuit and output 10 ohm resistor.
4.All 47uf Electrolytics and .01 Polypropylene bypasses around OPAMPs have been removed and replaced with 10uf Metallized Polypropylene (again no bypasses)
5.Replaced stock fuse with HIFI Tuning Silver.
The sound with each step has improved greatly in the areas of musicality, timing and dimensionality and smoothness.
I am running through a homemade passive 10k attenuator with Vishay Nakeds directly to a 100k input tube amp so I have a couple of 6.8uf Mundorf Silver Oil coming to see if I can reach down a little lower than 30 HZ in the bass.
I am contemplating some improvements to the Power Supply. If any one has any suggestions please post.
Thank-you to all who have contributed to this posting, I have learned a great deal from all of you.
Could you post some photo of your DAC? For the power supply, you may try the Salas LV Shunt regulator. I am planning to replace all the capacitors with Nichicon Polymer Aluminum and MKS.
Unfortunately I don't have a digital camera that works at this time so I am unable to show pictures. Rather ugly anyway.
Thank-you for the suggestion on the Salas.
I was lucky and was able to pickup some physically small 10uf MKP caps to replace the Nichicon Electro's and chose to remove the .01 bypasses. I have found that bypasses are very good to use in power supply, however seem to smear sound when used in the signal path, even when using teflons.
I would suggest that you remove the original Nichicons and .01 bypasses, install just the Polymers and have a listen first.
I have been playing with 4.7uf Ampohm PIO and 6.8 uf Mundorf Silver Oils in the output (again without bypasses)and have had similiar results as JonL in his Capacitor Musings review.
These caps are physically too large to install inside the chassis so they are wired in with solid core silver and are mounted with 3M double sided rubber tape on the outside wall of the chassis. Ugly but functional.
Thanks again for the power supply suggestion.
How about replacing the 8740 with this:
1x WM8761GED 24-bit 192kHz Stereo DAC WM8761 | eBay
Any good?
1x WM8761GED 24-bit 192kHz Stereo DAC WM8761 | eBay
Any good?
Thanks Riddelsr for your detailed description and suggestion. Will try to remove the bypass cap.
I have replaced the 16 pieces of small Nichicon 47uf Electros with Elna Silmicll 50v. They have smoothed the sound out much more and tend to have more of a midrange focus. Perhaps I am imagining it but I think that the .01uf polypropylene bypasses that are in the Wolfson DAC Section are smearing the sound ever so much. To me it seems to be an ever so slight phase smear which seems to obscure air. Otherwise the Elnas are definitely superior to the original Nichicons in my unit and system.
As to the .01 bypasses I will wait until I have superior replacements before I experiment with snipping them out.
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