iFi-Zen Signature DAC and 6XX AMP Review

Specifications

INPUTS

RCA: 3.5 (SE), 4.4mm (BAL))

Headphone output: 6.35 mm, 4.4 mm

Gain: 0 dB, 6 dB,12 dB,18 dB adjust

THD+N (A-Weighting): 0.0066% (BAL), 0.0058% (SE)

Maximum output power

(16 ohms)

3.0 V / 600 mW (BAL), 4.0 V /

1000 mW (SE)

Maximum output power

(300 ohms)

5.1 V / 756 mW (BAL), 7.6 V /

196 mW (SE)

Maximum output power

(600 ohms)

15.2 V / 385 mW (BAL), 7.6 V /

98 mW (SE)

SNR: 122 dB (BAL)

Dynamic range: -122 dB (BAL)

Frequency response (-3dB): 10 Hz – 200 kHz

Function Button: HD6XX adaption and/or XSpace; Bypass

IMD: 0.01%

Maximum power

consumption: 13 W / 2.6A

Dimensions: 4.6 x 3.9 x 1.2 in (11.7 x 10 x 3 cm)

Weight: 1.87 Ibs (0.85 kg)

Zout (headphone out) 0.25 ohms (SE), 0.5 ohms (BAL)

Zout(balanced line out) 200 ohms

Specifications from iFi.com

What is included in the box?

Included in the bundle is a short USB 3.0 cable, a short pair of RCA cables, the ZEN Signature V2.0 DAC, 6XX Headphone Amp, and a short Pentaconn 4.4mm cable. Both the Zen signature and 6XX Amp are housed in a sleek midnight blue aluminum chassis. Additionally a pair of 5v power adapters are included in each box.

The Zen Signature can pass PCM signals up to 24/192, 12.4MHz DSD, and 384KHz DXD. This is thanks to the Burr-Brown DAC chip. Additionally, the DAC supports full MQA.

The DAC has a volume knob that may be disabled on the rear, running in “fixed” volume mode. The volume knob will glow different colors according to file format.

The rear of the DAC from left to right has a, 4.4 Pentaconn output, a switch to control the volume knob state to variable or fixed a pair of RCA connectors, and a V5 connector. For more information visit https://ifi-audio.com/products/zen-signature-set/.

Now to the star of the show, the 6XX AMP. From left to right, is the power button, an input button (to select) from three sources, a gain or “power match” switch with four settings, a volume knob ¼ output, a balanced 4.4mm Pentaconn output, and a combination “6XX/XSpace” button. Power Match is the iFi term for gain, and the 6XX has +0dB, +6dB, +12dB, and +18dB of gain. XSpace, is DSP to “widen” the soundstage.

On the rear of the 6XX Amp left to right is a, 4.4mm Pentaconn input, a 1.8mm in, RCA connectors, a 4.4mm Pentaconn output, and a 5V power input. I will discuss the “special “sauce, that makes the “6XX” button work or does not work, just like the XSpace setting.

How does the 6XX sound?

For this review, I used a pair of Sennheiser HD 660s, and a pair of FIR Audio V x V IEMs. For the source, of music, I used Qobuz via Roon. For the cleanest soundstage I used the balanced 4.4 Pentaconn interconnect. I listened to each of the tracks with my FIR Audio V x Vs as a baseline first, without DSP. These IEMs are highly detailed and have reference-level bass. This lets me know what to listen to in the 660s, as they can be light in the sub-bass.

Our first track, “We Are All Made of Stars” by Moby is an excellent example of how the “6XX” button does work with the 660s. The subtleties of the opening piano are captured superbly. As is the kick drum of the drum kit. “The 6XX” button gently raises frequencies 100 hertz and below. This song is not the cleanest recording, and the use of DSP, “6XX” brings out this minimally. For more information on this visit https://ifi-audio.com/products/zen-signature-set/

“Eileen”, by Keb’ Mo” is one of those songs that is recorded quite well and has little to no effect from the “6XX” or “XSpace” button. This is quite rare that a song alone in an album is recorded this well. I highly recommend the Keb’ Mo’ album, “Suitcase” as a reference album.

As we travel on to our next selection we chose, “What do You Want from Me” by Pink Floyd.” Using the “6XX” fills out the sub-bass nicely as well as adds just the right amount of air, as it raises the upper frequencies slightly. Generally, the “XSpace” button does not do much in my testing, but that is not the case here. There is a greater sense of air and depth.

In “I. Adagio – Moderato,” we go from a piece on a page to a piece full of life and vigor with the use of the “6XX” and the “XSpace” buttons. I am most impressed, and this is from one who generally does not use DSP.

The Zen DAC allows for the use of fixed (full volume) or variable mode. Variable more is excellent for the use of IEMs. IEMs benefit from variable more when minute volume is needed compared to full-sized headphones.

As mentioned earlier, the 6XX Headphone amp has four “PowerMatch” or gain stages. This is fantastic, as the amp can power just about any headphone from IEM too hard to drive planars. I did not need anything higher than than the 6dB+ stage on my HD 660s.

Suggestions

This was a difficult one, in that I had to think a length to find flaws any huge flaws. So, I am reaching here.

If I had to think of any flaws there would be two, the rubber feet on the bottom of each unit and the volume knobs of each unit.

The rubber feet of each unit feet need to be slightly taller on each unit, to prevent scratching when stacked on each other.

And the volume knobs need to show better visual indicators on the volume for the user.

Final Thoughts

The 6XX AMP/Zen Signature DAC is an excellent pairing that can power everything from IEMs to full-sized headphones. And sound excellent as well. Despite the small. Suggestions, this a full recommendation.

Gear Used

M1 Mac Mini

Roon Nucleus

Fir Audio V x V

Music Used

Moby - We Are all Made of Stars (Reprise Version)

https://open.qobuz.com/track/117451831

Keb' Mo' - Eileen (Album Version)

https://open.qobuz.com/track/375236

Pink Floyd - What Do You Want from Me

https://open.qobuz.com/track/47683885

Sheku Kanneh-Mason - I. Adagio - Moderato

https://open.qobuz.com/track/84105283