Tantal compared: Viva Solista, Sennheiser HEV 90 and the AL4 Rubedo

Two owners, eight years apart, set the Demograf Audio Tantal against amplifiers they knew well. In 2014 Alexander, a collector of electrostatic headphones, compared the first Tantal with his own Demograf Audio AL4 push-pull amplifier, Rubedo, and ranked both against the Sennheiser HEV 90, the Woo Audio WES and STAX’s energisers. In 2022 Maxim compared a Tantal in its top configuration with the Viva Solista on planar headphones. We summarise both.

These impressions are summarised and translated from two owners’ posts on an audiophile forum, written in 2014 and 2022. They are the subjective views of their authors, not measurements or claims of Demograf Audio.

Tantal and Rubedo with the Sennheiser HE 90

Alexander owned Rubedo, a push-pull electrostatic amplifier on AL4 tubes that Dmitriy Gubchenko built for his Sennheiser HE 90 Orpheus. In 2014 he heard the new Tantal, on tantalum-anode tubes, at another collector’s listening session.

What the Tantal added

• He liked almost everything about it, above all its dynamics, its control and the texture of its bass.
• It handled overload well: the jump from a solo violin to a full tutti in violin concertos by Paganini and Tchaikovsky, which he put down to its larger peak-to-peak voltage swing.
• Its sound was more assertive than Rubedo’s, but without an unpleasant, digital edge.
• His Sennheiser HD 800, with a high-end cable, sounded very pleasant on the Tantal: more whole and less distant than he was used to from that headphone.

What he valued in Rubedo

He liked his own amplifier for the way it realised a rich and warm sound, analogue in character without any loss of detail. He wanted more direct comparisons before drawing firmer conclusions, and noted that the Tantal could be upgraded further, chiefly by replacing its Sowter attenuator transformers with Stevens & Billington units of the TX102 Mk3 class or higher.

How he ranked the electrostatic amplifiers

Alexander had owned a fully upgraded Woo Audio WES, a Sennheiser HEV 90 with top tubes and a STAX SRM-007t II with various tubes, had a KGSS at home for almost a month, and had heard several more at friends’ homes and in shops, including a HeadAmp Blue Hawaii SE and several STAX energisers, but not the STAX T2. Of everything he had heard, he placed the two Demograf Audio amplifiers first and second.

• For the STAX SR-009: Demograf Audio first, then the HEV 90, the fully upgraded WES, a stock Blue Hawaii SE, the SRM-007t II and the SRM-006t II.
• For the STAX SR-007 Mk2: Demograf Audio first, then the HEV 90 well ahead of a stock Blue Hawaii SE, the WES with its first capacitor upgrade, and the KGSS level with the SRM-007t II on top tubes, followed by the SRM-006t II.
• Even before two upgrades, he wrote, his own Demograf Audio amplifier was ahead of the HEV 90, which in his view remained ahead of everything else he had heard on the HE 90, SR-009 and the first SR-Omega.
• On the day, the Orpheus amplifier sounded as familiar as ever: behind the Tantal, but ahead of every STAX amplifier he knew.

Headphones on the day

His order for the session was the STAX SR-Omega, the Sennheiser HE 90 and the SR-007. The Omega won on both Demograf Audio amplifiers, and he noted that it gained from any real improvement in amplification, while the SR-007 on one side and the HE 90 and SR-009 on the other responded to a better amplifier in noticeably different ways. Taste and system still matter, he added: chamber music, a large orchestra, rock and brutal metal each ask for something different.

Tantal vs Viva Solista

In 2022 Maxim compared his Tantal, built in its top configuration with an output for electrostatic headphones and speaker terminals, with a Viva Solista on 2A3 tubes. He used light planar headphones, a Meze Elite and a pair of hand-built planars, and a Rockna DAC.

Purpose and power

He stressed the difference in purpose: the Solista drives planar and dynamic headphones of moderate difficulty, while the Tantal drives any of them and adds a bias supply for electrostatic headphones and terminals for loudspeakers. The comparison on light planar headphones, he noted, used only a small part of what the Tantal can do. It would have mattered little if the Solista had been clearly better, but it was not: the two were closely matched.

Sound

• Both have a clear tube colour, excellent resolution and dynamics, and no softness or sluggishness. He called them the two strongest tube amplifiers for planar headphones he had heard.
• Bass: the Solista’s mid-bass was slightly better defined; the Tantal’s low bass was firmer and more precise, and its bass had far more energy.
• That energy ran through the whole range. After a few swaps, instruments on the Solista seemed paler and less individual, playing together in a slightly greyish way, even though the Solista’s midrange is lively, emotional and technically very good on its own terms.
• On the Tantal each instrument was clearly more expressive. He thought the greater energy explained part of this, but not all of it.

Reported limits

• The Viva Solista had slightly better-defined mid-bass and better technical rendering of texture in the midrange.
• Alexander had not heard the STAX T2, and wanted more direct comparisons before firmer conclusions.
• For the SR-007, Alexander heard a different kind of improvement from a better amplifier than for the HE 90 and SR-009, so the match with the headphone matters.

Summary

Alexander heard the Tantal as a more dynamic, controlled and assertive alternative to his warm AL4 Rubedo, and ranked both Demograf Audio amplifiers above the Sennheiser HEV 90, the Woo Audio WES and STAX’s own energisers he had heard. Maxim found a Tantal in its top configuration closely matched with the Viva Solista on light planar headphones, ahead on energy, low bass and the expressiveness of each instrument, and slightly behind on mid-bass definition.

Which Demograf Audio piece fits

• Tantal runs two 3C24 triodes with tantalum anodes in Class A, 3 W per channel, with a STAX-type output built in for headphones such as the STAX SR-007 and SR-009 or the Sennheiser HE 90. It also drives dynamic and planar headphones and sensitive loudspeakers, and its configuration, from parts to outputs, is agreed at order time.
• Rubedo is no longer built; its story is in our archive.

Every amplifier is made to order by Dmitriy Gubchenko, with a one-year warranty (extra warranty available: +1 or +2 years). For the technical side, read our note on electrostatic headphone amplifiers.