Fellow DIYers!
I have been looking for a nice, DIY friendly, inexpensive DAC to build, and although i have found quite a few ones, i would like to give my design to the community. It is a WM8740 based DAC with optical isolation, low noise power supply, and balanced outputs from the DAC chip itself.
My goals whit this DAC would be:
- inexpensive, yet great sound quality
- balanced outputs from the DAC chip, so that everybody can use whatever they want as a preamp (OPAMP, Tube, or any other based)
- should be easy to build with tools that are readily available to almost all DIYers
- EAGLE .sch and .brd files provided, so that everybody can customize it to their own taste
- small form factor
You can download the EAGLE files from here: LINK
Part recommendations, pictures from a completed unit, and measurements coming (hopefully) in the weekend. Stay tuned!
PS: please, if any of you have any kind of design advice, do not hesitate to share it!
I have been looking for a nice, DIY friendly, inexpensive DAC to build, and although i have found quite a few ones, i would like to give my design to the community. It is a WM8740 based DAC with optical isolation, low noise power supply, and balanced outputs from the DAC chip itself.
My goals whit this DAC would be:
- inexpensive, yet great sound quality
- balanced outputs from the DAC chip, so that everybody can use whatever they want as a preamp (OPAMP, Tube, or any other based)
- should be easy to build with tools that are readily available to almost all DIYers
- EAGLE .sch and .brd files provided, so that everybody can customize it to their own taste
- small form factor
You can download the EAGLE files from here: LINK
Part recommendations, pictures from a completed unit, and measurements coming (hopefully) in the weekend. Stay tuned!
PS: please, if any of you have any kind of design advice, do not hesitate to share 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.
Hi!
Thank you for your input. If i am correct, these chips are totally pin compatible with each other, so there is no need to change the layout of the PCB. Am i correct?
I would not call a 7805 "low noise"... otherwise, very interesting!
Also, you might take a look at this project using the WM8740:
DAC with WM8740
It converts the differential outputs to single-ended using buffers on the output.
I think retaining the option for a differential signal is better, but because you will sometimes find low-impedance loads to connect to you might want to buffer each of the four DAC outputs (+ and - of each channel) using a 5532 follower. Use a surface mount 5532 - it's pretty compact and can drive anything with quite low distortion. You would need a dual-rail power supply in that case, however.
Looking forward to your measurements.
Also, you might take a look at this project using the WM8740:
DAC with WM8740
It converts the differential outputs to single-ended using buffers on the output.
I think retaining the option for a differential signal is better, but because you will sometimes find low-impedance loads to connect to you might want to buffer each of the four DAC outputs (+ and - of each channel) using a 5532 follower. Use a surface mount 5532 - it's pretty compact and can drive anything with quite low distortion. You would need a dual-rail power supply in that case, however.
Looking forward to your measurements.
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Sorry, i did not really had the time to publish my part recommendations. I am slightly (maybe very) lazy when it comes to creating new devices in EAGLE. The regulator that i have used has a noise of about 50uV, and has the same pinout as the LM78XX series.
UPDATE: oh, thanks for pointing this out, the LM78XX has about 40uV of noise. Jeez, how did i miss this? If any of you can recommend an inexpensive, yet easy to implement linear regulator, i will replace my LF50CV with another (hopefully) better one.
Yes, i have seen PAVOUK's design, in fact, i took the WM8740 device from his site.
My idea for converting the signal from balanced to unbalanced, is to use a simple tube anode follower, with the - signal from the DAC wired to the cathode via a few kOhm resistor. I have bought a NOS Brimar 6SN7GT, and i am currently in the middle of winding the anode and filament transformer for it. The decoupling caps will be russian PIO MBGO-2 ones. Very cheap, quite a few ebay sellers from Ukraine have lots of them.
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They're pin compatible, but require a bit different control logic, if I'm reading the DSs correctly. The ak4490 variants give very little up to the 4497 except cost. Hard to recommend the 4497 nor the 9038 in any thread with the title "affordable". The Cirrus/Wolfson are quite good for the money though.
I like the tube idea, I'm not a fan of ne5532s the opa1612 will drop in in place of the 5532 and is far lower noise and a much nicer sound. But yes if you use tubes please include this in your circuit
The 5532 does not have any "sound" unless it has been implemented poorly in the circuit. As a voltage follower it has low noise and low distortion (I would not use it for implementing gain). I used multiple 5532 in a headphone amp (without gain, just as multiple output buffers in parallel) and the results were surprising. Sure, there are better op-amps nowadays but the 5532 is still very good, inexpensive, and can drive very low impedances.
Nothing wrong with the NE55532, but for an analog low-pass (antialiasing/HF hash) buffer for the WM4870, it might be best to look at an JFET-input opamp like the OPA164x series. Can choose to run some sort of esoteric buffer/composite within its feedback loop or simply daisy chain a unity-gain buffer on the end of it. Some of the weaknesses of the NE5532 become manifest with HF glitches that more modern opamps do not suffer from.
Speaking of hoping for devices price to drop -- of course! Although, really, audio-DACs and ADCs have flattened out performance-wise. One of the best features (sadly underused) in newer "32-bit" DACs is the integrated volume control, which is oftentimes more linear than a downstream potentiometer.
Speaking of hoping for devices price to drop -- of course! Although, really, audio-DACs and ADCs have flattened out performance-wise. One of the best features (sadly underused) in newer "32-bit" DACs is the integrated volume control, which is oftentimes more linear than a downstream potentiometer.
Hi fellas!
Just a little update. I took CharlieLaub's advice, and replaced the analog power supply secton's LF50CV with an LT1761-5. I has 20uV noise when a 10nF bypass cap is used across pin 4 and 5. I used a 100nF WIMA one. This IC is also inexpensive and has an SOT-23 package, making it suitable for DIY applications.
About the measurements: i will use an NI USB 5132 oscilloscope to measure the power supply noise, the I2S signals, and the outputs. I have made an early prototype that uses the LF50CV and has no optical isolation, it's measurements are coming tomorrow!
Just a little update. I took CharlieLaub's advice, and replaced the analog power supply secton's LF50CV with an LT1761-5. I has 20uV noise when a 10nF bypass cap is used across pin 4 and 5. I used a 100nF WIMA one. This IC is also inexpensive and has an SOT-23 package, making it suitable for DIY applications.
About the measurements: i will use an NI USB 5132 oscilloscope to measure the power supply noise, the I2S signals, and the outputs. I have made an early prototype that uses the LF50CV and has no optical isolation, it's measurements are coming tomorrow!
An externally hosted image should be here but it was not working when we last tested it.
Hi fellas!
A few pictures from my Hiraga Le Monstre amp, and from the DAC that has no optical isolation, and uses the old power supply. I am trying hard to make this little project useful, and i would also like to apologize for the delays. If anyone needs the PCB layout for the amplifier or its power supply, please leave a comment, and i will upload them here.
A few pictures from my Hiraga Le Monstre amp, and from the DAC that has no optical isolation, and uses the old power supply. I am trying hard to make this little project useful, and i would also like to apologize for the delays.
If anyone needs the PCB layout for the amplifier or its power supply, please leave a comment, and i will upload them here.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.
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.
Dear CharlieLaub!
I am very sorry for the delays, and i want all of you to know that this thread is still alive. I have bought some new PCBs, cut them to appropriate sizes, and i will try to build the new PCB in a few weeks. Also, i have removed the optoisolator from the PCB, and placed it on a small separate board. My measurements were not made because i still could not build the tube output buffer for this circuit. I still need to make the power transformer for them, but everything else is ready.
Hi Fellas!
I have redesigned the circuit to be compatible with the WM8741 and WM8742. I also included proper opto isolation, and an Atmega 8 for control. It is capable of driving an HD44780 display and handle a rotary encoder with a built in push button. I think these are totally enough for a DIY DAC. If any of you like the design, i will be more than happy to share the EAGLE files.
I have redesigned the circuit to be compatible with the WM8741 and WM8742. I also included proper opto isolation, and an Atmega 8 for control. It is capable of driving an HD44780 display and handle a rotary encoder with a built in push button. I think these are totally enough for a DIY DAC. If any of you like the design, i will be more than happy to share the EAGLE files.
An externally hosted image should be here but it was not working when we last tested it.
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