Making the Ultra more ” Musical ” - easy external DIY

[Musician]

Here are some simple tips about changing the sound when using the built-in DA converter in the WiiM ultra, using rca cables. The analog output of the Ultra is technically as good as it gets , with low output impedance and good op amps opa 1611 used . Nothing inside the ultra can be done in a better way .

To get the sound more earfriendly like most highend dacs , we have to make the sound slightly worse .

1. Change the digital filter to Minimum phase, fast rolloff.

The sound opens up a little better in the midrange. This is the kind of filter used in Linn klimax ds ( first generation ) and the Rega dac R ( filter nr 2 ).

2. Change the output impedance of the WiiM ultras analog rca output.

The Ultra has a very low output impedance of only 11 ohms. It is good from a technical perspective, all poweramps can be driven even the most sluggish ones with low input impedance. But maybe we want a softer sound….

One way to make a change to the output impedance, making it higher is to solder a 1 Kohm carbon resistor in series with each positive terminal inside the rca connector on the separate cable itself - this way nothing is done inside the ultra so the warranty is perfectly safe . Now , using this cable your ultra sounds more like a Bluesound even if its technically slightly worse than before .

3. Using Supra AGS - 10K line level transformer

The advantage is galvanic separation sounding more ” analog ” or less dynamic and more earfriendly . This last modifikation is easy to do , just buy the supra transformer and one more rca cable .
This technique is used inside the Linn klimax ds , using Lundahl transformers.

 

[canard]

the next step is the use of a tube output stage as was assumed on generations of "audiophile" CD player DACs... the antithesis of the "ASR" fashion approach...
ps... in the case of using this type of small transformer "to modify the sound" "analogize"... I invite you to carry out some measurements... you will certainly see that the impact is not only the galvanic isolation... ;-))

 

[Musician]

the next step is the use of a tube output stage as was assumed on generations of "audiophile" CD player DACs... the antithesis of the "ASR" fashion approach...
ps... in the case of using this type of small transformer "to modify the sound" "analogize"... I invite you to carry out some measurements... you will certainly see that the impact is not only the galvanic isolation... ;-))

Yes I know

 

[canard]

(
Frequency Range: 15 Hz - 22 kHz
when we see the modesty of these figures we understand the modesty of the transformers used and the impacts sought....(if we are talking about "sound" and not the antihum function)
a very 90s approach (or very commun in pro for anti-hum) ;-)
)
(https://www.jensen-transformers.com/product/ci-2rr/)

 

[harkpabst]

 

[adias]

Play this, leave the room and see if it sounds like a piano playing on the room you just left.

 

[Musician]

In my adventures with modifying cd- players in the late -90 , I discovered another thing than make the sound earfriendly - its driving the Op amps with two or four 100 ohms carbon resistors in series for the power supply - after the regulator.
This makes the power supply to the Op amps very un-stiff. This way you get some compression effect and the sound is more earfriendly , like eating candy. This technique is used in many Marantz cd-players ( Ken Ishiwata ) and also used by some highend British manufacturers.

This can also be done constructing a ”musical” preamp. Use A 50 kOhm stereo pot and 2 opa 2604 ( soft sound ) or 2 lm4562 ( more detail). Power supply with lm314 , 317 and 15 V DC - use the 100 ohm resistors from regulator to the Op amps, both in series of ground and + voltage .

This is not something one can do DIY in the ultra without ruin the guaranty, but maybe a tip for the constructors of the WiiM streamers for the future.

 

[Musician]

Playing with ferrite chokes on the AC power cable for the Ultra to attenuate EMI and RFi.
I bought a bunch of those and used 3 of them on the Ultra.
The middle big ferrite choke had the AC cable turned multiple times around the choke. The RF is attenuated about 20 dB above 1 mHz.

I put two chokes on each of the AC powercables for my Dac and my Hypex poweramp. One ferrite choke on the coaxial spdif cable . One on the hdmi cable. No chokes on analog RCA or speaker cables.

After long therm listening, I can conclude that the sound is slightly darker than before, its like everything is -1 dB down from 3 kHz and upwards. Exactly the result to expect and what Rob Watts from chord has teached us. Less RFi will sound slightly darker. This can be corrected with the PEQ shelving + 1 dB from 3 kHz upwards in the ultra and the result are slightly better sound than before.

Reckommended ( If you use the peq shelving or if you already have bright sounding speakers.)
The result is the same If I use the internal Ultra Dac ( slightly darker sound with the ferrite chokes ) or use the spdif coaxial to my Rega dac R ( also darker sounding )

Before this, I had some popping sound about one time a day when using hdmi cable to the ultra from an Apple tv4k. This is completely gone now.