Ladder Schumann R2R DAC Review

[Curupira]

I recently purchased a LCD-X and i am looking into making it sound wider in my head with an R2R like Hiby RS2 or anything that comes out next year,

Peace APO has a nice variety of DSP options as mentioned.

Furthermore, If you really like crossfeed, I'd recommend you try the ifi xspace, 3dspace or whatever they are calling it these days (each product has its own name variant), it's the best rendition of crossfeed that I've tried so far: it not only mix the channels to about 60% (from what I could measure with a dBmeter using a puretone), but delays one ever so slightly and, from what I suspect, also tilts the FR ever so slightly anticlockwise. This latter change is what made me like it, as I feel normal crossfeed has a tendency of muddying down our (my) perception of tonal balance. It works really well with darker/warmer headphones like the Audezes.

On topic: I really hope that someday Amirm can get his hands on Holo Audio stuff, as it's R2R and other unconventional topologies can even compete with Shenzen stuff. This DAC in particular really seems like a Denafrips in disguise, even the casing is the same...

 

[Steven Holt]

Interesting that they even machined a branded lid for the transformer!

Amir, may I ask you (or one of our technical experts) for a 'teaching moment'? That large transformer in the front, is that used for the power supply only, or does it play a part in signal conversion? I'm used to seeing one of these in an amp, but not in a DAC. In short, just what does it do? Thank you!

 

[JayGilb]

Amir, may I ask you (or one of our technical experts) for a 'teaching moment'? That large transformer in the front, is that used for the power supply only, or does it play a part in signal conversion? I'm used to seeing one of these in an amp, but not in a DAC. In short, just what does it do? Thank you!

It's a toroidal transformer and it converts standard 120 vac to lower level ac voltages that are then rectified into dc voltage to power the circuitry. It plays no direct role in signal conversion.

 

[Billy Budapest]

It is possible to construct a well-measuring R2R DAC, but the resistors you would need would have to be of such high precision that they would be cost prohibitive not to mention extremely hard to source.

 

[Veri]

Shenzhenaudio also distributes Geshelli gear, doesn't it? Same kind of thing, isn't it.

AFAIK, no. They don't ....?

 

[DonH56]

It is possible to construct a well-measuring R2R DAC, but the resistors you would need would have to be of such high precision that they would be cost prohibitive not to mention extremely hard to source.

Most if not all R2R DACs are actually segmented designs, with the MSBs split into multiple unit (unary) cells so lower precision is required, then trimmed. The trade is complexity and component count, among other things.

For example, a 16-bit DAC would need resistors matching to about 1/65,536 or 0.0015%, not terribly reasonable. If instead you split the top 4 MSBs (most significant bits) into 16 (actually 15) unit resistors the matching is reduced by a factor of ~16 to 0.024%. Still pretty ugly, but you can at least buy 0.01% resistors. The trade is now you need 16 extra resistor cells in the DAC. Going to 6 unary bits adds 64 resistor cells but the required matching is ~0.1%, much more realizable (though still hard). The unary MSBs also reduce matching requirements for the lower cells. You can extend the number of unary bits, increasing the size and complexity of the DAC, but further reducing matching requirements to make it (perhaps) more manufacturable.

There are other schemes, of course, but a segmented DAC is fairly straightforward to design and implement. My guess is all those resistors arrayed on the left side of the picture are part of a segmented DAC design.

 

[Veri]

Will a 95+ SINAD tube amp be next?! Wouldn't that be something....

I wouldn't hold my breath. But if we see even 75dB that would be nice.

Umm. The liquid platinum amp can achieve this with its balanced output. Given the right gain/knob level, it can get up to around ~0.005-0.001% distortion levels :

 

[fpitas]

Umm. The liquid platinum amp can achieve this with its balanced output. Given the right gain/knob level, it can get up to around ~0.005-0.001% distortion levels :

Impressive, although 3.5W is a bit limiting.

 

[PatentLawyer]

Impressive, although 3.5W is a bit limiting.

Yeah and to clarify to the extent it matters, I was referring to speaker amp, not a headphone amp.

 

[fpitas]

Yeah and to clarify to the extent it matters, I was referring to speaker amp, not a headphone amp.

3.5W could be a horn amp. Mine only need 20mW for 85dB

 

[Multicore]

It's not. You're clearly over-interpreting it.

Well, yes but that's my specialty.

:P

 

[TNT]

Filter FFT... "Slow"... what does it mean.... - please use audio_science terms to describe what you think about the filter.

//

 

[staticV3]

Filter FFT... "Slow"... what does it mean.... - please use audio_science terms to describe what you think about the filter.

Gentle slope, low dB/Oct

 

[Prana Ferox]

Impressive, although 3.5W is a bit limiting.

Somewhere a Nelson Pass fan just read this and got the vapours

 

[phoenixdogfan]

Ticks all the tweako audiophile boxes: R2R ladder dac implemented via FPGA. And it does about as well as expected which is to say not nearly as well as a 9038 Deta Sigma based offering which costs considerably less to build as well.

Some people just gotta do it their way, never mind what the data is telling them.

 

[JanesJr1]

https://www.foobar2000.org/components/view/foo_dsp_meiercf
https://sourceforge.net/projects/equalizerapo/

One guy really likes it:

https://www.reddit.com/r/headphones/comments/qhqraz

Best of all, it's free.

I don't get it.

I've spent many hours tinkering with things to extract the natural (i.e. recording venue) spatial cues.

But I just don't get crossfeed. I try it with EAPO and it just contracts the spatial image. The Meier and Chu filters just seem to add capricious artifacts to the FR (e.g. boomy bass). It never sounds natural or spatially expanded at all to me.

This is probably off-topic, but if there is someone who can point me toward a good reference on cross-feed, thanks in advance....I do seek good soundstage, but have never heard artificial spatial cues that worked for me without seeming to degrade fidelity. (Other than stereo, which is not perfect, but works for the most part...)

 

[okok]

technically the best r2r is PCM1704, best resistors inside...

 

[phoenixdogfan]

I don't get it.

I've spent many hours tinkering with things to extract the natural (i.e. recording venue) spatial cues.

But I just don't get crossfeed. I try it with EAPO and it just contracts the spatial image. The Meier and Chu filters just seem to add capricious artifacts to the FR (e.g. boomy bass). It never sounds natural or spatially expanded at all to me.

This is probably off-topic, but if there is someone who can point me toward a good reference on cross-feed, thanks in advance....I do seek good soundstage, but have never heard artificial spatial cues that worked for me without seeming to degrade fidelity. (Other than stereo, which is not perfect, but works for the most part...)

Everyone is different. Specifically, everyone has a different head shape, technically known as an HRTF, which means adjustments like adding cross feed through EAPO will be heard differently. For you, it contracts the sound stage, for someone elese it expands it. That's simply the way it is when using headphones.

Not only that, everyone hears the same headphone differently because of shape of their ear canal produces resonances which are idiosyncratic to them, so there really is no one universally correct headphone FR because said FR will be altered by each individual person's ear canal resonant frequency (-ies).

Of course that can be fixed by doing a personal headphone on ears EQ by running a sine wave through individual frequency bands and adjusting to create subjectively equal loudness for each band. Doing so that will compensate for the ear canal resonances.

 

[amirm]

But I just don't get crossfeed. I try it with EAPO and it just contracts the spatial image.

I have the exact experience. It is hard for me to fathom that others like it but I am told some people are like you and I.

 

[okok]

I've spent many hours tinkering

maybe save your time and uninstall it, the magic is no magic