How Good is ES9018 in Voltage Mode? (Part II)

Another data point (by Andrea Ciuffoli and QuangHao) showing that voltage mode output of the Sabre DAC is quite good [link]

This evening I have tested the following configurations with a my friend with lot of experience on audio reproduction and recording.

1. Actual op-amp module (balanced with passive IV 10ohm)
2. Satri design (balanced not suggested because it does not work good on balanced circuit)
3. Raleigh Audio Line Stage clone with K & K Audio Basic CCS modules (balanced current mode with passive IV 10ohm)
4. Un-balanced direct connection in voltage mode with only 2.2uF Z-Cap capacitor (0.1uF bypass MKP1837 as option)
5. Lundahl LL1684 (balanced in voltage mode with OS-CON)

The last is the best.

(Transformer 1:1 configuration with center 10K // 2.2 – 22uF Sanyo OS-CON as described in the old Glass Audio article of Stefano Perugini: http://digilander.libero.it/paeng/a_24_bit_dac_full_article.htm)

Perhaps using the Lundahl transformer to convert balanced to single ended beats the unbalanced v-out mode (#4 and #5 above) because the balanced to unbalanced conversion gives you twice the voltage swing.

Seems that straight balanced output should be the same or even better than unbalanced output through a transformer because in the first case there is nothing in the signal path that can color the signal. I use the DAC in balanced voltage-out mode since my amp (UCD180HG) has balanced inputs.

Same author makes this claim in his blog [link]

It is possible to use the voltage output and after some listening tests with my friends I consider this configuration as the best.

In this case the output stage can be a transformer.

The last firmware allow to get an un-balanced signal output but you get only 1Vrms at 0dB.

You can read the previous post on this subject here: [link]

Both of my operating ES9018 DACs are used in voltage mode differential outputs to UCD180HG amp modules (connected with Cat5E patch cables)

MORE REPORTS COMING IN

To my knowledge, QuangHao and Andrea are the first “manufacturers” that have given a serious look at voltage mode output. As people start receiving their DAC, some are starting to compare V-out vs I-out modes. Here is one that praises the sonics of the V-out mode: [link]

FYI – I finally assembled my unit this weekend, and I must say that anyone who has not tried running the op-amps modules in voltage mode is doing themselves a rather large disservice. It seems to sound much livelier in voltage mode to me.

The Bass is the best that I have ever heard on my system. The soundstage is very large. Both Voltage and Current modes sound great. But I find that in voltage mode, the sound is just subjectively more “alive” sounding. I haven’t performed any measurements yet, so I don’t know if this is simply the result of possibly preferring higher distortion by running in voltage mode or not.

I just find that there is more of an emotional connection to the music in voltage mode using my op-amp modules. Plus there is amazing impact on transients such as bass drum.

Another V-out report [link]

I haven’t tried the opamp output stages yet but the LL1684 sounds so good that I wonder if I ever will get to it
Especially with high resolution recordings it’s remarkable, it’s the first DAC that I hear pianos playing like real pianos.

I use Foobar configured as here.

The Smashing Pumpkins have a reissue of “Mellon Collie And The Infinite Sadness” that’s available in 24bit/96kHz and some songs are very good

TUBE SOUND?

According to Dustin Forman, the designer of the ES9018 DAC,

… The current mode is simply when the current going in and out the pin of the chip is being sensed. This mode has the benefit of cancelling 2nd and 3rd harmonics of some of the internal analog circuitry.

The “voltage mode” is when the pin of the chip has a voltage that is being sensed. While this has the 2nd and 3rd harmonics (at the -100dB level or so), some people have even claimed this mode is more “tube-like”. It is all personal preference. [link]

Is it really just “personal preference”?

HIGH FREQUENCY (Out of Band) NOISE

The only concern with voltage out is the filtering of high frequency noise. This can be mitigated in several ways:

Passive filtering First order RC filter

This is what I’ve been using. The attenuation is “minimal” but I cannot detect whether the high frequency noise causes a problem or not (since I have no other filter to compare). However, according to TI [link], using a fist order RC filter is a feasible solution for removing out of band noise and actual measurements comparing a second order low pass vs a passive RC low pass shows no degradation in performance.

Passive Filtering High order LC filter

Abraxalito has been sharing a lot of work on high order passive filtering for DACs. You can check his blog here [link], and here is an example of a balanced mode 7th order LC filter

I have not have a chance to build/try one of these filters…

DAC settings to reduce HF noise

High frequency noise can be reduced by adjusting the quantizer setting in the DAC. According to ESS [785],

The HF noise coming out of the DAC in 6bit mode is noticeably more than it is in 9 bit mode. DAC output seems to require less filtering. Running the analog section with a less aggressive filter has some nice benefits (better slew rate etc) to the final audio

In addition, a higher value quantizer setting seems to give better sonics [link]

Sonic difference, 9-bit vs 8-bit true differential (only register settings were changed)

Under 9-bit quantizer mode, the sound is less bold, and attacks are more solid, noises contained in recordings are more audible. Although those difference are very small amount and It required me repetitive comparison over and over.

BEST CONFIGURATION?

Thus it seems that a pretty optimal configuration for the ESS DAC is:

• Vout mode with a simple RC low pass
• 9-bit quantizer setting
• Higher sample rate input [link]