Modified my Pavane to give it more of a
Darth Vader feel.
The small white accents goes perfectly well.
The RCA connectors on the Pavane is incredibly loose. I've never had a DAC that had this issue before. It plugs in without any force and slides off with me slightly pulling with my pinky finger.. I will be replacing it with a rhodium plated
(Rh) one on the next update. Mainly doing this so my cables won't fall out. But who knows. Maybe the improve material
(tellurium copper > brass) and upgraded wire will open the sound up a little. One can only hope.
When I first received my Pavane, the input i used was coaxial RCA. After opening my unit and noticing that both the BNC and RCA is connected to the mainboard by a wire, i feared impedance match could become a problem and that could induce jitter. Shortly after I switched over to AES/EBU and to my ears, it was much better.
For a long time coming I've had this dream of hearing music as close to being real as possible though a digital source which, before the Pavane, lead me to the Holo Audio Spring. The Spring was a great piece of equipment that offered R2R ladder technology as well as the removal of filter hardware giving it the ability to do NOS (no-oversampling). To my surprise, It went above and beyond by offering I2S! For me that checked all three boxes.
I2S + R2R Ladder + NOS
For me, these three provide the best possible transmission, conversion, and playback. This lead to impeccable realism in sound quality. Totally rid of digital artifacts.
After owning this device for a few months, I soon stumbled upon what I now own, the Metrum Pavane. To my surprise, it sounded better than the Holo Audio Spring even though it did not offer the I2S input. I instantly bought it and made haste of my Spring. Goodbye Spring. Maybe I'll see you again next year.
As an audiophile among many others, I began to have this itch. Cream didn't help. I wanted what the Spring offered but the Pavane couldn't do. I wanted to see if what already sounded lifelike, could get any better. I wanted to push the envelope of what I thought was best. I wanted.. I2S.
As an owner of the Singxer SU-1, I wanted to make most of my transport AND source. Using the AES/EBU connection on it just didn't satisfy me. Seeing the HDMI connector open to the world didn't let me sleep soundly at night. In that moment I hated the audiophile hobby. Wanting something that can't be done, yet open to knowing how good it would feel if that need was satisfied. I jumped the gun...
The next day I contacted Metrum Acoustics and to my surprise, they had an I2S input board available. Downfall? It had to sacrifice the USB board. Even more of a downfall? It didn't have the HDMI connector, but an RJ45 Ethernet port. Cool beans... Just what I needed... NOT.
Being the cable maker that I am, I just went with it. Waited patiently I told myself that once I get it in, I'll just make an HDMI to RJ45 cable even if it means sacrificing the balanced connection available through HDMI transmission. I made the order and waited.. Each day wondering how better it would sound than AES/EBU.. After days of wondering and contemplating, I broke down. Single ended RJ45 I2S just isn't good enough for me.
The HDMI connection for I2S internal protocol is superior as it offers a balanced way to transmit data thus less susceptible to interruptions. The RJ45 connection can do it too. Empirical Audio for example does it well. This just isn't the case with Metrum Acoustics however, as it shares a common ground. I've made a request to Metrum Acoustics to see if they can offer independent grounds so I can still utilize balanced even with the RJ45 connector but to no avail. If that couldn't be done, at least offer it in HDMI single ended i told him, but that wasn't possible either as the default USB hole is too small to fit the HDMI connector and he didn't want to make a new input board.
I don't have too much knowledge with audio circuitry, but I decided to contact Kingwa over at Audio-GD. He offered me an I2S input board with HDMI!
The deal was that I had to pop out the USB Input board and analyze the circuit for him. Below the board I found a Texas Instruments ISO7640FM digital isolator that controlled the input and outputs. I checked the technical datasheets and found it to be fairly simple.
Below is the created circuit diagram for the new I2S transmission.
I didn't want to solder wires directly to the ISO7640FM SOIC chip, so I used a multi-meter and did a
continuity check on the nearby header pins that was coming out from the main board (near the chip). To my luck, these header pins connected directly to the SOIC chip's input side. I decided to use these headers with the HDMI input module as it was more convenient and required no soldering.
Turns out MCLK (masterclock) is not connected to Pin 6
(INPUT D) on the SOIC. Instead, it's connected to ground and isn't used on any of the headers either. I've contacted Metrum Acoustics and the designer, Cees Ruijtenberg says it's not used in their design. Great! One less to worry about.
In I2S internal protocol, these are the 3 main bits
(in bold) that are transferred over. Depending on design, the MCLK isn't always needed.
- DATA (Serial Data) - also known as SDATA
- LRCLK (L/R Clock, Word Clock, or Frame Clock) - also known as LRCK, WCLK, or WCK.
- BCLK (Bit Clock or Serial Clock) - also known as BCK, SCLK, or SCK.
- MCLK (Master Clock) - also known as MCK
- Pin 1 = Ground
- Pin 2 = NC (No Connection)
- Pin 3 = Ground
- Pin 4 = BCLK (BCK) / SCLK (SCK)
- Pin 5 = Ground
- Pin 6 = LRCLK (LRCK) / WCLK (WCK)
- Pin 7 = Ground
- Pin 8 = SDATA / DATA
I'll need to find a way to mount the HDMI Module. I plan on using the default USB hole so no additional cutting is required. Mounting it there would be optimal as the I2S wires will be as short as possible being right above the digital isolator. Whether or not the default hole size is sufficient, we'll find out.
Kingwa offered to make me a matching cable
(female dupont) that connects perfectly from the input module to the header pins. All that's needed is to just plug in and play. Normally I would accept, however in the case of I2S, I wanted to do it myself to shorten the length as much as possible to minimize jitter. A pre-made cable doesn't achieve that. And because of how close the input module will be to the SOIC chip, a pre-made cable might not be able to fit. The cable's flexibility also becomes a concern.
Since the HDMI cable I will be using to connect to the Metrum Pavane is a
Apollo AV Lightning V2, the wiring will be of the same material.
- 26 GAUGE
- POLYETHYLENE INSULATION (PE)
- SILVER PLATED COPPER COMPOSITION
The connector used to connect to the header pins will be
Dupont Female Pin Connector (2.54mm).
///////////////////////////////////////////
SOUND IMPRESSION
I received the HDMI i2S Module from Audio-GD. After plugging everything in correctly, there was still no sound coming from USB input (now i2S). I checked the voltages and realized the digital isolator chip that was suppose to output VDD1 +3.3V (pin 1) for the module to work, did not output 3.3V, but 5.47V instead.
Kingwa said that the chip will work anywhere from 3-3.6V and so I stacked two large 1.5V batteries in series which gave me 3.2V. It still did not work. Being confused, I took a look at the RJ45 module sold by Metrum Acoustics and noticed that the signal wires in which connected to the digital isolator were different than the diagraphm that I had found online. I realized that LRCK and BCK needed to be switched with one another so I went to the i2S module and resoldered them opposite, then Bam! There was music!
(I updated the original diagram so there isn't any confusion)
When it comes down to inputs and their sound quality, i find AES/EBU and Coaxial to sound nearly identical. AES being the better performer at longer lengths as it suffers less from jitter due to its balanced design which removes common mode noise. At longer runs they start to differentiate themselves but only by 2-3% at most. The AES connection has a slightly blacker background, more stage depth, better instrument timbre and decay, and the imaging was a bit more stable when compared to S/PDIF. This only becomes apparent when using a cable longer than 2-3 meters. At short 0.5-1M, they sound very much the same. I's have to have longer than a 30 minute listening session to spot the difference and with the right songs too.
And last but not least, THANK YOU Metrum Acoustics for the input buttons. I was able to switch from i2S, AES, and S/PDIF in a jippy. I will eliminate S/PDIF from this comparison as it sounds too much like AES to differentiate it as its own category. Immediate I noticed the improved laid back sound. Like how R2R Ladder sounds more detailed but not forced, and how NOS sounds more lifelike and can be compared to vinyl, the i2S connection took the benefits gained from those two things, and added another 10% above it. What's amazing was that the sound stage widen up by a good 10%. It was also deeper (taller) as well by 8%. Before the sounds I heard through AES was extremely natural, but after switching to i2S, i instantly found it to be heavy and not as musical. I had a badly implemented SABRE chip DAC at one point in time and to me that sounded bright, sharp, ringy treble, digital, bleached, and artificial. When I bought the Metrum Pavane, I found all those things gone. I really thought there wasn't any way sound could get anymore musical or realistic, but listening through i2S, it became apparent. The treble is now more natural and thus less fatiguing. High pitch vocals like Sam Smith no longer hurts to listen to. It comes out effortlessly and doesn't pierce the ear canal. It becomes more apparent on electronics genre's such as EDM in which the DJ's adds some digitalization to vocals, especially female vocals, but through i2S it's no longer filled with digital glare of a "zzzzzz" sound. The imaging of every vocal and instrument is so precise that there's no Second guessing from the ears or brain receptors.The bass along with all other instrument timbre's were less thumpy. It was like a weight or veil has been lifted. The best way I can put it is like going into a small venue and hearing a band sing and play music. Sometimes the music is recorded through a microphone, amplified, and projected onto the crowd. The problem is that the microphone has its own tone to it. A hollow sounding response as it picks up sound at a single direct point. The thing about i2S is it makes all this go away! It sounds like a live performance, very audible, but without a microphone-ish tonality to it. Like a well mastered recording. There's just so much precision, realism, and air.
For a long time, I didn't think digititus affected bass, midrange, or instrument timbre by much. I just assumed that it simply took away some clarity and made treble sound sharper than it should. Boy was I wrong. Once you improve on a transmission and remove extra digital transmitters and receivers, you get a sound that is better throughout the frequencies and more true in tonality to how it SHOULD sound.