For this matter of R2R vs. Delta Sigma or "math" DACs, there is more a dial than a switch. My experiences-informed preference lands on the R2R side of the fence. But The AKM chips, like the 4497, are admittedly unusually-organic-sounding delta-sigma chips. For example, the excellent m2tech Young Mk4 DAC using this AKM sounds unusually natural, and more so than their earlier, PCM1795-based Young MkII, which wasn't a slouch DAC in the grand scheme of things.
It's not so much that you want a "tube dac" as you might want a DAC with tubes in it in some useful way. Right now, I use an MHDT Pagoda Balanced R2R DAC built around the BB PCM1704. The 1704 chip is no longer produced and one of the reasons we are seeing discrete transistor ladder DACs from makers like Denafrips is that that his BB chip became too expensive to produce. It's more economical now to put hundreds or thousands of discrete matched transistors on a motherboard than to laser-trim microscopic resistors in a chip architecture.
Hence we have Denafrips, Holospring, etc. out of China. Not that that's a bad thing. It isn't. It's different.
What we care about is what sounds better. MHDT out of Taiwan builds to a consistent physical quality. They built their DACs around NOS vintage R2R chips. Some of the lower models drive I/V output stage from the chip itself. Others have separate, post-DAC-chip, discrete transistor I/V conversion, and some have op-amp post-DAC I/V conversion. Regardless, they all retain an organic, family sound.
The MHDT DACs respond nicely to tube-rolling. The stock GE 5670 triode is bland but not off-putting. Ranging through the family you might get snagged by the organic and dynamic boldness of a Bendix 2c51, for example. You have lots of direct replacement options. BUT, if you look beyond, via the world of socket adaptors, you can run MHDT DACs on 6922 family and 6sn7 tubes. This opens up significant further possibilities. For example, I run my Pagoda and Pagoda Balance DACs with NOS German CCa tubes, via adaptors, and have sample same with NOS Sylvania and RCA 6SN7 tubes. The basic lesson is there is a lot more to appreciate from digital if you are an organic analog aficionado than you probably think possible now. The soundstage, organic elasticity and range via NOS CCa, NOS 6922 tubes is more than palpable. Pushing on the 6sn7 conversions in my mind is more controversial but worth discussing.
All that said, after a 3 years project to perfect-bit rip 5500 CDs to inform a media server, plus incorporating Tidal HiFi/Masters in an analog-dominant domicile, I'll say that the most valuable addition I made was an Auralic G1 Ares streamer. There are two things this outstanding streamer does in addition to its basic attention to sonic excellence. First, it includes a 1gb SS RAM into which any input music is loaded, dejittered, and processed for output. It's a FIFO intermediary real-time system (you'll never recognize the delay). The dejitter and clocking effects relax all inputs without compromising resolution and details.Hate over-resolved, odd-distortion digital? The G1 won't be your reason.
MHDT DACs have tube buffers on the outputs. The tube you use has some sonic effects on the output voicing, vut fundamentally, MHDT DACs are not "tube DACs). Yet they sound more objective and organic at the same time as many more exalted DACs when tubed appropriately (i.e. not stock GE 5670) . I am looking at Lampizator.
Today, a Pagoda Balance costs almost $2600 US, which puts it in contention with Denafrips Venus II and some Holospring offerings. Is it worth it? I haven't done the side-by-side yet. But I'll say that one of the reasons we have discrete transistor Denafrips and Holospring out of Asia is because of how difficult and expensive it became to make the laser-trimmed-micro-resistors PCM1704 chip.
It's now much less expensive to make a discrete transistors ladder DAC in China than it is to make a laser-trimmed ladder dac chip routed into a production DAC, in the US or anywhere. else. To the point that the last and greatest BB PCM1704 has been irrevocably gone for a decade. I've heard many of these contending DACs but not enough to be conclusive. Early impressions are that in the $2000-$3000 BAL DAC category, MHDT Pagoda is still standing for any appropriate fight. The Yggdrasil isn't even a contender if you tube the Pagoda or Pagoda Balanced correctly. Even the supremely musical MHDT Atlantis 20bit DAC is a best friend when you need one. Just play with the buffer tube.
Phil
It's not so much that you want a "tube dac" as you might want a DAC with tubes in it in some useful way. Right now, I use an MHDT Pagoda Balanced R2R DAC built around the BB PCM1704. The 1704 chip is no longer produced and one of the reasons we are seeing discrete transistor ladder DACs from makers like Denafrips is that that his BB chip became too expensive to produce. It's more economical now to put hundreds or thousands of discrete matched transistors on a motherboard than to laser-trim microscopic resistors in a chip architecture.
Hence we have Denafrips, Holospring, etc. out of China. Not that that's a bad thing. It isn't. It's different.
What we care about is what sounds better. MHDT out of Taiwan builds to a consistent physical quality. They built their DACs around NOS vintage R2R chips. Some of the lower models drive I/V output stage from the chip itself. Others have separate, post-DAC-chip, discrete transistor I/V conversion, and some have op-amp post-DAC I/V conversion. Regardless, they all retain an organic, family sound.
The MHDT DACs respond nicely to tube-rolling. The stock GE 5670 triode is bland but not off-putting. Ranging through the family you might get snagged by the organic and dynamic boldness of a Bendix 2c51, for example. You have lots of direct replacement options. BUT, if you look beyond, via the world of socket adaptors, you can run MHDT DACs on 6922 family and 6sn7 tubes. This opens up significant further possibilities. For example, I run my Pagoda and Pagoda Balance DACs with NOS German CCa tubes, via adaptors, and have sample same with NOS Sylvania and RCA 6SN7 tubes. The basic lesson is there is a lot more to appreciate from digital if you are an organic analog aficionado than you probably think possible now. The soundstage, organic elasticity and range via NOS CCa, NOS 6922 tubes is more than palpable. Pushing on the 6sn7 conversions in my mind is more controversial but worth discussing.
All that said, after a 3 years project to perfect-bit rip 5500 CDs to inform a media server, plus incorporating Tidal HiFi/Masters in an analog-dominant domicile, I'll say that the most valuable addition I made was an Auralic G1 Ares streamer. There are two things this outstanding streamer does in addition to its basic attention to sonic excellence. First, it includes a 1gb SS RAM into which any input music is loaded, dejittered, and processed for output. It's a FIFO intermediary real-time system (you'll never recognize the delay). The dejitter and clocking effects relax all inputs without compromising resolution and details.Hate over-resolved, odd-distortion digital? The G1 won't be your reason.
MHDT DACs have tube buffers on the outputs. The tube you use has some sonic effects on the output voicing, vut fundamentally, MHDT DACs are not "tube DACs). Yet they sound more objective and organic at the same time as many more exalted DACs when tubed appropriately (i.e. not stock GE 5670) . I am looking at Lampizator.
Today, a Pagoda Balance costs almost $2600 US, which puts it in contention with Denafrips Venus II and some Holospring offerings. Is it worth it? I haven't done the side-by-side yet. But I'll say that one of the reasons we have discrete transistor Denafrips and Holospring out of Asia is because of how difficult and expensive it became to make the laser-trimmed-micro-resistors PCM1704 chip.
It's now much less expensive to make a discrete transistors ladder DAC in China than it is to make a laser-trimmed ladder dac chip routed into a production DAC, in the US or anywhere. else. To the point that the last and greatest BB PCM1704 has been irrevocably gone for a decade. I've heard many of these contending DACs but not enough to be conclusive. Early impressions are that in the $2000-$3000 BAL DAC category, MHDT Pagoda is still standing for any appropriate fight. The Yggdrasil isn't even a contender if you tube the Pagoda or Pagoda Balanced correctly. Even the supremely musical MHDT Atlantis 20bit DAC is a best friend when you need one. Just play with the buffer tube.
Phil