It is about last year I finished this tube DAC AD1865 using high-performance USB input from JLsound USB receiver module, but somehow, this project was burry in my photo archive, so, I think I will reveal it now.
This project starting after my previous DAC project using the same 6DJ8 tube in SRPP configuration as gain-amplifier at the DAC output stage. This SRPP circuit is proven to work best with DAC as gain stage and I've made the best sounding tube DAC here, at that time with PCM1704 high-performance 24-bit multibit DAC. Although in this project I will use different DAC IC, but one lesson for the key success for good sound is the components selection and individual component upgrade that most of the time will cost more than the whole initial DAC build itself.
Fast forward to this DAC build, I will build almost the same DAC but with few different approach.
Please continue reading.
In this DAC build, the digital receiver use here is more advanced. It using USB receiver module from JLsound I2s-over-USB that specialized making this module for DIY community. This module also makes this DAC build simple but great. You can search their official websites and find this module for EUR 75 each.
Why this module better than my previous PCM2706 USB receiver? Because this JLsound using newer XMOS XU208 processor, up to 32-bit resolution and 768 kHz sampling frequency. Which those number is no meaning for me actually, but good to know for their compatibility. What makes me thrilled with this module is the option for the user to configure the power supply feed to this module between BUS voltage from the USB host to all this module, or split it between the digital section using the BUS voltage and the analog section using external power supply, or both of them are completely use separate power supply. This to make sure the power supply in this digital section is uninterrupted with the dirty BUS power supply from the USB host.
The separation for this power supply section also meaning that the I2S digital signal output is isolated from the BUS USB section, making the I2S output cleaner.
The others capability for this JLsound USB receiver is the option for the module to set the output exactly to the DAC we want to feed in. Let's say I want to use AD1865 DAC in this project and configure in non-oversampling, using the guideline in their manual, I setting the output using the jumper and a resistor to flag this module to output right-justified 18-bit MSB first as require by the AD1865 DAC itself.
Done and easy.
So, the next step I just focus my build to the AD1865 DAC along with the regulated power supply required for it, together with the SRPP tube module.
This tube DAC build is not using solid-state diodes and FET in the power supply section, instead it will use 5U4 tube rectifier that mostly found in the tube power amplifier. This high current rectifier for DAC is to make sure no current drop at the analog section.
Because this DAC will use 5U4 rectifier, so there will be choke (inductor) in it to bring-down the ripple to inaudible band noise. Together with the power transformer, in this DAC project is using Hasimoto high quality transformers. They are PT-100R power transformer and C-30-40 choke coil.
This is the reason why this DAC special.
Because the transformer cost more than the DAC:)
The casing for this DAC is typical wooden box style with steel metal on bottom and top. It is to suit the appearance of the vintage DAC unit itself. Not too special, but once all component is put inside this case, this makes the DAC shines its mantra to become seductive, mystic and at the same time tempting.
I hope you're agree with me about this.
I test this DAC by connecting the USB OTG cable to my tablet, using UAPP bit-perfect music player playing my WAV music files on it. The analog output from this DAC goes to my audio system as usual.
Tube DAC when it implement correctly like this DAC will always sound best. The sound is engaging with great micro detail and spectacular depth and width of the sound-stage presenting with this DAC will never fail the listener to enjoy the music more and more. The warm and energetic sound of tube cannot be replaced with solid-state or op-amps. No wonder using tube as DAC output like this still become the best choice to bring the music lively and emotionally.
Disclaimer: Any statement and photos in this article are not allowed to copy or publish without written permission from the writer. Any injury or loss from following tips in this article is not under writer responsibility.
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