New Audio Driver Stages for 909 and 990

 20th Oct 2011

Retrofittable new gain stages for 909 and 990 from Autumn 2011

One of Trilogy's key strengths is to explore and exploit technology without prejudice. Our policy is to pursue continuous research to continue delivering the highest possible levels of performance. From autumn 2011 the award winning Trilogy 909 pre amplifier and 990 power amplifier will receive all new voltage gain stages. Because we believe in delivering lasting satisfaction for our customers past and present, both can be retrofitted to existing units by a Trilogy authorised dealer.

Both employ a revised topology using the 6H6П super tube for voltage gain. This Russian military triode is a relatively recent design with high transconductance and low mu for exceptional performance at audio frequencies.  The grounded grid configuration allows the tube to operate with the highest linearity and the lowest distortion. A cathode follower keeps output impedance low for excellent drive capability.
The finest components available are used throughout. DC coupling is via Mundorf film foil and custom Trilogy polystyrene capacitors, both mounted on a damping element to keep microphony to a minimum. Silver gold alloy solder is used for the signal path.

909 billet gain stage vert

For the 909 Pre Amplifier the circuit is split and folded around a 0.6kg billet of aluminum; the gain stage on one side, the HT regulator on the other.

This three dimensional arrangement has several advantages. The regulator and audio boards can be made physically smaller, keeping the signal path shorter and suppressing resonances through superior mechanical integrity.

The regulator also benefits from a stable thermal sink for its output devices. Power from the regulator passes through the billet itself via short links, keeping the two sections tightly coupled, but fully screened from one another.

The 990 Hybrid Power Amplifier receives the same update to its valve complement, the symmetrical input stage using now using the 6H6П super tube for voltage gain.

It also features a revision to its unique output stage which lowers output impedance, improving drive capability into difficult loudspeaker loads.

990 2011 driver


The result is that the effortless, flowing musical presentation of the 909 and 990 is substantially improved. Both frequency extremes benefit from greater resolution and the noise floor is lowered. Both large scale dynamic contrasts and the subtle harmonic and spatial details that make magic in music are further revealed.

The result of many hours of research and development, the revisions amount to more than just an upgrade. Together the 909 and 990 have taken a significant step closer to that elusive line that separates the real from the facsimile.


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