Calliope (TDA1540) NOS DAC: owners’ reviews

Owners of Demograf Audio converters on the Philips TDA1540, the chip now offered as Calliope in the Reference Tube DAC, describe a natural, involving sound that holds rhythm well and ties the parts of the music together. Below we summarise their posts from 2011 to 2014: the sound by range, what they heard on headphones and loudspeakers, and how they compared it with CD players and with the TDA1541 and TDA1547.

These impressions are summarised and translated from owners’ posts on an audiophile forum. They are the subjective views of their authors, not measurements or claims of Demograf Audio.

Which units the owners describe

The owners quoted here received non-oversampling (NOS) converters on the TDA1540 with a tube output stage, built to order by Dmitriy Gubchenko in 2011. They fed them from a computer through a USB-to-S/PDIF converter, or from CD players such as the Philips CD304 used as a transport.

Today the TDA1540 version of the Reference Tube DAC is called Calliope. It takes 16-bit / 44.1 kHz PCM over S/PDIF coaxial with no upsampling; the TDA1540 itself is a 14-bit chip. The stock output stage is solid-state, and a tube output stage is an option. In the designer’s voicing, Calliope is natural and organic.

Sound, range by range

Bass

• One owner heard the low range grow deeper as the DAC warmed up. Where his solid-state sources gave a low-frequency drone, this DAC played a bass guitar, with its nuances.
• Another owner, who had also heard the TDA1541 version, preferred the TDA1540 for its better bass.

Midrange and voices

• Owners mention vocal and string timbres first. One found the vocals excellent and the sound less bright than the TDA1541’s.
• Another writes that he now hears the emotions of the performers themselves, singers and violinists, and at times keyboard players and guitarists, rather than only his own emotional response to the music.
• An owner who has lived with a TDA1540 converter for two years finds that modern DACs make the violin too thin, with too much treble; after the TDA1540, he writes, even live concerts sound a little short of treble to him.

Soundstage

• One owner closed his eyes after an hour of warm-up and found that the loudspeakers and the room had disappeared: a space had opened up instead.
• Another heard a wide and deep stage with clear separation of instruments, larger than the TDA1541’s.

Rhythm and timing

One owner wrote at length about rhythm. The DAC, he says, does not merely mark a rhythmic pattern but plays out both the attack and the decay of each note. Where several instruments carry the rhythm together, each one can be followed and heard through to the end. After living with it, he noticed rhythms on his CD players that he could not make out at all, and moments where the bassist seemed to doze off and catch up with the others at the last moment; he had not noticed this before.

Coherence

The same owner describes the TDA1540 converter as drawing a single picture from all the parts: they do not blur into a mush, but they are woven into one fabric. His other sources, he felt, outlined each instrument separately. He offers an analogy from photography: sharpening a digital photo raises the contrast around edges and loses the fine gradations between them, and in bad cases adds halos; the picture loses its integrity. That, he says, is what his CD players did to music.

With headphones and loudspeakers

• On STAX electrostatic headphones with the entry-level STAX SRM-323 amplifier the differences were audible; with a headphone amplifier by the same designer they became considerable.
• The DAC also made differences between transports far more obvious. Through the designer’s amplifier the gap between a good transport, a Philips CD304, and a laptop grew many times over; through Beyerdynamic DT911 headphones, which emphasise sibilants, the laptop became hard to enjoy. The STAX were kinder in the treble.
• One owner listened on Beyerdynamic DT931 headphones and home-made loudspeakers, through a tube amplifier on ECL82 from the same designer, with a computer and a FluxLab USB-to-S/PDIF converter as the source.
• A third owner found the TDA1540 the most comfortable of the designer’s converters for headphone listening, particularly with a tube headphone amplifier.

A visitor who heard the long-term owner’s system with Sennheiser HD800 headphones liked the vocals, above all solo voice, as well as chamber music, piano and Wagner, and could clearly hear the room of each recording. The violin was less fine than he was used to, and the orchestra came in broad strokes. He called the DAC “specific, but clearly good”. The owner adds that the S/PDIF receiver chip in his unit darkens the treble noticeably.

Compared with other sources

vs CD players

One owner compared it with his Arcam and another CD player. Beyond the rhythm and coherence described above, he heard the music become more alive and more emotional. Listening to a live Rodrigo y Gabriela recording from Tokyo for two or three hours, he found the emotional delivery outstanding.

vs TDA1541 (Persephone)

Owners who heard both preferred the TDA1540 for its bass, its vocals, a larger stage and a less bright sound. One listener, who owns a TDA1541 converter, was charmed by the TDA1540 and heard it as the most analogue of the three Philips chips he compared. He would start a new system by living with the TDA1540, and turn to a more technical chip only if he began to miss brilliance and polish. See our Persephone (TDA1541) owners’ review.

vs TDA1547 (Aphrodite)

The same listener heard the TDA1547 as more striking, brighter and more brilliant, and the TDA1540 as more involving. Another owner, who chose the TDA1547 for himself, writes that if you do not need to know what the double bassist is doing at the back of the stage, you can live with the TDA1540 and forget about the rest. See our Aphrodite (TDA1547) owners’ review.

The designer himself, writing in 2011, heard the TDA1547’s dynamics and resolution as so much higher that his own TDA1540 sounded relaxed by comparison: good on certain music, but without the full palette. Another listener answered that for chamber and vocal music the TDA1540 may be the better choice; he heard nothing relaxed, only an organic sound with more emotional depth in the midrange. The long-term owner agrees that the TDA1540 is more analogue than the TDA1547, but adds that everything needs measure: “analogue quality has its price”.

vs Mytek 192-DSD DAC

The long-term owner bought a Mytek 192-DSD DAC because he wanted more neutrality. He found it hard to beat for detail and for following how a stage is built: in his words, the Mytek “does not sing, it plays what is recorded”, while the Demograf Audio converters sing. A few months later he decided that musicality mattered more to him and sold the Mytek. Next to the TDA1540, he writes, it made timbres much poorer.

TDA1540P or TDA1540D?

One owner tried two versions of the chip in the same converter. With the TDA1540D, classical and live music gained clearer dynamic nuance and a naturalness that held him: he heard every breath of the soloists. Modern electronic music lost the impact it had with the TDA1540P. His conclusion: nothing is universal, everything depends on genre, even two versions of one chip.

Reported problems

• The bass reaches its full depth only after warm-up.
• Less detail at the back of the stage than the more technical TDA1547, in one owner’s view.
• A less fine violin and an orchestra in broad strokes, for one visitor, and a slightly darkened treble from the receiver chip of one unit.
• On one TDA1540 unit, a listener heard background hum with the volume at maximum and no music playing. It was not audible during music, and he would accept it for the sake of the sound; he did not think every unit should be built that way.
• The DAC shows up the weaknesses of the transport, the interconnect and the amplifier; two owners felt it was time to replace their amplifiers after it arrived.

Summary

Owners describe the TDA1540 converter as natural, involving and comfortable: strong on rhythm and coherence, with good vocals, a large stage and a sound less bright than the TDA1541’s. One owner who heard all three Philips chips calls it the most analogue of them, another the most comfortable.

Listeners who want the last degree of detail and brilliance heard more of it from the TDA1547 or from a modern converter such as the Mytek; one owner who tried both ways returned to the TDA1540 for its timbres. The TDA1540 rewards a good transport and amplifier, and owners say it makes the weaknesses of both easier to hear.

Which Demograf Audio piece fits

• Calliope is the TDA1540 version of the Reference Tube DAC: 16-bit / 44.1 kHz PCM over S/PDIF coaxial, no upsampling and no DSD, a solid-state output stage as standard and an optional tube stage on 6Zh4, EF14, EL8, AL4 or ML6 with a 5Ts4M rectifier.
• The same chassis is built as Persephone (TDA1541), Aphrodite (TDA1547), Artemis (PCM63) and Katerina (PCM1704). Our guide to NOS multibit DAC chips explains how they differ in design.

Every converter is made to order by Dmitriy Gubchenko, with a one-year warranty (extra warranty available: +1 or +2 years).