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Sunday, October 7, 2012

10Y Line Preamplifier Follow Up


I already briefly reported about the 10Y Line preamplifier with the Tribute lineout-TVC in a previous post. Obviously the article was too brief since I got many questions about what I think of the Tribute TVCs. So here is a follow up.

The circuit of this preamp follows my usual design philosophies. Completely passive choke filtered supplies, including the filaments. High voltage is obtained from a full wave bridge with 4 6AX4 TV Dampers. Of course other dampers like the 6DQ4 are equally suitable. The rectifier bridge works into a choke input filter, followed by a PI section (LCLC).

The filament supplies for each of the 10Y also use choke input filers. LC in this case. The filament voltages are rectified with Schottky diodes for their superbly low switching noise. All power transformers used are custom wound for me on grain oriented core material and with dual screens between primary and secondary to suppress power line hash. The power supply has it's own housing.

All voltages are brought to the preamp chassis through a shielded umbilical. In the preamp the high voltage is split to each channel through separate LC filter sections for complete isolation of the channels. The filament supplies are already separate from the PSU. The filament voltages are fed to the tubes through another choke. No capacitor after the choke, which could interfere with the signal.

The 10Y / 801A family of tubes with all their derivates like UX210, VT25, VT62 are my favorites for linestages. They are extremely linear and have huge headroom. So they are the natural choice for my top of the line preamplifier.

Especially the 801 with graphite plate and ceramic base works quite well in linestages since it generally is a bit less microphonic. Microphonics are always an issue with directly heated tubes in a preamp so they need extra care. Hence the mounting of the sockets on vibration damped sub assemblies.

Enough technical stuff, how does this preamp sound? How does this line out transformer with tapped secondary compare to a solution with separate Lundahl transformer and intactaudio AVC for volume control? Both have good arguments for them. While the former presents less parts to the signal path, in the latter solution, both the line out transformer and volume control can be better optimized for their tasks.

I like both solutions and will continue to use both. Soundwise they are on a similar level, but they do sound different. As my regular readers know already, I'm quite reluctant to write about the sound of my equipment. So I let someone else speak about them. This is the comment from Jürgen Saile, who has listend to both versions in his own system. He used the linestage to drive a bi-amped system with a PSE 6HS5 amp in the bass and a SE 45 with 10Y driver for the midrange/tweeter horn.

These are his findings:

Two properties are immediately apparent with both versions of the linestage. The reproduction has a unbelievable sovereignity and calmness. The resolution is at a level which I have not heard with other preamps. Although the circuit of both versions is identical, there is a audible difference between them.

The newer version with the Tribute OPT/TVC has enormous dynamics in addition to the properties mentione dabove. The soundtsage has a bit less depth compared to the other variant. So the strength of the new version is on the dynamic side which is very important for a life like reproduction.

The Lundahl/Slagle Version has more flow, more focus and more depth in the soundstage but lacks the dynamics of the Tribute-Version.

Of course these linestages are not worlds apart, but the differences are easily audible.

When changing the 10Y against 801 with ceramic base the sound of both linestages gets clearer and more neutral, especially in the treble, but also a bit less emotional.

There is no better or worse between the two linestages. This is purely personal preference and taste. Luckily there is the choice between the two.

The above is my translation of Jürgens description, for the german speaking readers, here are his original words:

Zwei Eigenschaften fallen bei beiden Versionen sofort auf: zum einen die unglaubliche Souveränität und Ruhe bei der Wiedergabe, zum anderen eine Detailauflösung, wie ich sie bei einem Röhrenverstärker noch nicht gehört habe. Obwohl der Schaltungsaufbau gleich ist, unterscheiden sich beide Varianten klanglich aber dennoch.

Die neuere Version mit dem Tribute OPT/AVC hat neben den genannten Attributen zusätzlich eines zu bieten: eine enorme Dynamik. Die räumliche Darstellung dagegen ist etwas weniger tief, verglichen mit der anderen Variante. Die Besonderheit liegt hier eher auf der dynamischen Komponente, die ja für eine livehaftige Wiedergabe extrem wichtig ist.

Die Lundahl/Slagle Version spielt flüssiger, fokussiert etwas besser und kann räumlich tiefer abbilden. Hat aber nicht die Dynamik der Tribute-Version vorzuweisen.

Zwischen beiden Geräten liegen natürlich keine Welten, die Unterschiede sind aber leicht zu hören.

Mit dem Austausch der 10Y auf die 801 mit Keramiksockel wird die Wiedergabe bei beiden klarer und neutraler, insbesondere im Hochtonbereich. Aber auch nüchterner.

Das hat alles nichts mit besser oder schlechter zu tun, sondern hängt von den geschmacklichen Präferenzen ab. Man ist in der glücklichen Situation wählen zu können.

Thanks a lot to Jürgen for doing this comparison and for writing down his findings. Of course as always, I encourage to take sound descriptions of others with a grain of salt. The results might be different in other systems. I have attended several listening sessions with Jürgen. He has an exceptional ability to hear the differences of components and to characterize them.

Best regards



  1. Hi Thomas,
    from my understanding the differences in sound are may be explained with respect to the technical differences. The big advantage I see for the Tribute TVCs is the dramatically decreasing output impedance for low output volumes which might show "more dynamics". And less depth in soundstage may be related to not 100% equal taps in the Tributes. It may be more difficult to wind equal taps on this OPT than in the traditional TVC. But this is only my guess.

    Best regards,

  2. Hi Bernd,

    the decreasing output impedance with lower volume settings is an attribute which both versions of the linestage have. Ifr both are set to about equal gains, output impedance will be comparable

    Best regards