Wednesday, October 23, 2019

Femto DAC technical note

décembre 10, 2012 by · Leave a Comment 


Calyx Femto DAC Technical Notes

Femto DAC by Calyx

Whenever we receive a new piece of hi-fi equipment, I like to get the opinion of a technician and as usual, Eric Juaneda is the one.

I do this for two main reasons:

• Find out if the product is really what it says it is
• Check the choice of components against what we hear in the listening session.

Even more than in his competence and his integrity, I have perfect confidence in his judgment.

All the same, if you’re getting to know me you realize that the technical notes are one thing, but often enough the listening impressions are quite another.

So Eric, what do you think of the Femto DAC?

The product is well equipped with inputs and outputs.


• 2 x S/PDIF RCA
• 2 x S/PDIF BNC (no RCA inputs)
• 2 x S/PDIF Toslink
• One USB which accepts up to 24 bits/192 KHz


• RCA unbalanced
• XLR balanced

Back side Femto DAC by Calyx

Among the functions are:

A frequency indicator on the front panel which shows the conversion rate. This is a plus for users who use a computer source, where it is sometimes hard to know at what frequency the audio signal is really being transmitted to the converter.

A choice of three digital filters. A phase inverter for the analog signal.

A volume control in the form of a digital attenuator. The converter will give its best when the volume is at maximum. Setting the volume from the computer or from the DAC will give essentially the same result.

Femto DAC by Calyx


We start with the magnificent chassis.

When we take off the top panel we find a power supply enclosed in a black box subassembly which incorporates a good-sized transformer. This transformer, just as much as the chassis, plays a primary role in the sound of the final output.

Femto DAC by Calyx

On the electronic side the design is more conventional: surface-mount components, electrolytic capacitors and op amps are all present. There seems to be a strong orientation towards measurements, the user manual will delight curve lovers.

On the conversion side we find two ESS 9108 Sabre chips, the same kind we’ve seen on DACs previously tested for the magazine. The manufacturer has taken care to enclose three of the four clocks in small aluminum blocks.

Femto DAC by Calyx

A reminder for people who like measurements

Any performance measurements should not make us forget that the real performance in terms of residual noise and distortion is actually that of the microphones used and not that declared by the DAC manufacturer. The DAC’s “imperfections” are added on top of those of the recording studio and do not replace them.

I’ll quote Demian Martin on this subject:

“The measured performance of the ESS chip is exceptional but getting good sound out of it is quite difficult, like any DAC. The ESS promises easier implementation since so much is on the chip. But that could be a trap if the details are not just right. Their demo board can measure very well but doesn’t seem to sound as good as the measurements suggest. Some of us believe the DAC chip isn’t really the choke point in good digital reproduction today. Execution of the stuff around it has more influence on the sound than the particular converter or its topology”.

Femto DAC by Calyx

Before I even got Eric’s technical notes, the Femto DAC had been running several hundred hours in my system. It is now at, where it seems to be appreciated as of this writing.

Against all expectation (since the circuitry is nothing esoteric), the sound revealed a new day. As of now I am convinced of the importance of the quality of the combination of chassis and power supply. These two together must count for around 60 to 70 per cent of the overall performance of this kind of unit.

The benefits are therefore proven of massive construction and of a separate shielded power supply of large size—in short, giving room to the circuits and the different connectors. Let it be said that the less things are compacted inside the box, the better the chance of getting good performance. When you understand how much influence certain components can have on others, it seems obvious to me that the Calyx approach, with the Femto, is logical.

Next part: the listing!


Charisma Audio

Manager : Bernard Li

Suite 86
4261, Highway 7
Markham, Ontario
Canada L3R 9W6
Telephone: (905) 470-0825
Fax: (905) 470-7966


Web site :

Article by Marc Philip, independent publisher, all rights reserved, copyright 2012, text and photos are the property of the author and the magazine, under creative commons licence.

Have a nice day and happy listening !

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