Audio Alto Anniversary Reference 10 ANL tube preamplifier review part 1

Audio Alto Anniversary 10 ANL is not yet another tube preamplifier. It’s a result of Saša Burian‘s painstaking in-depth quest for an ultimate preamp, that was designed from ground up with the utmost attention to the part selection, optimized signal paths and to deliver uncompromised sonic performance. 

No corners were cut with the Anniversary 10 project! For example… The PCB boards are of the same level of quality as used in satellite’s electronics, it’s a two chassis design, fully balanced with a tube rectifier, no global negative feedback, fully symmetrical mechanical design, 20 – 200.000 Hz -0,1 dB @ 100K ohm load (no output transformer) and much more. 

With ANL 10 there is a lot to cover so let us look what makes it so special…

After 10 years of design, projects and manufactured audio units  Audio Alto wanted to introduce the reference line starting with the Line preamplifier.

As Audio Alto mostly uses vacuum tube amplification the decision was to design and develop a Cost No Object line preamplifier based on vacuum tubes.  The ideas was to embrace all the benefits that vacuum tube triode amplification can offer but supported with surrounding circuits to minimize and overcome the triode shortcomings.

The audio paths consist just of strictly necessary elements. All used elements are high-grade state of the art components. The circuitry is a truly balanced concept. Balanced concept in a way actually doubles the audio path length and reduces few decibels to the noise signal ratio, but Audio Alto disregarded this drawback to taking advantage of the much more important feature that balanced topology offers – eliminating ground loops, that are the major case of sound degradation of most systems and much better common mode noise rejection. One of the benefits is also lower 2nd harmonic distortion. All audio circuits are designed to consume constant power (current). 

With no change in power supply current consumption, Audio Alto has also eliminated power supply voltage fluctuation related to signal and with this the possible unwanted influence between different circuits. With this approach and without using any global negative feedback the resulting circuit hum and noise is very low.

Inputs are balanced and single-ended (RCA). All RCA inputs are differentially processed so the sources are not connected to common ground. Inputs which are not selected are all electrically disconnected from the preamplifier, so they have no influence on reproduction while not in use. The connectors that interface the outside world are WBT and Neutrik connectors.

Inputs and outputs are also electrically isolated with a high-grade output transformer. This arrangement also lowers the output section impedance to less than 600 ohms. The transformer is made on the amorphous core and wound with high-grade Cardas wire. 

Outputs are balanced and RCA and both as mentioned before are galvanic isolated. ANL provides also the mostly forgotten monitor input and output. This is the fifth input but also provides an output-input return that can be used with different apparatus (also with sound and room correction systems).

All the switching functionality in the preamplifier is managed with hermetically closed signal relays with Au/Ag contacts. The relays are “latching” (even after the control voltage is interrupted, this relay maintains its set or reset condition until it receives the next inverting input). With this feature, while the relay is in use it radiates no magnetic or any other annoying signal to the reproduced music. The relays are driven with impulses only when they need to change state and managed with special software logic. 

The amplification circuits consist of two balanced connected triodes (per channel), that are matched and have golden pins, without using capacitors in the signal path (only one oil capacitor is used in the parafeed configuration with the output transformer). The triodes are supported by FET current sources with cascade configuration for maximum current source output resistance. The resistance is higher than 30Mohm so the current sources are practically excluded from the audio path. The gain level is selectable at the rear of the enclosure. 

The main gain can be selected with a three position switch that selects main gain of +12dB, +15dB or +18dB. Each channel has also a so-called balance switch with three positions that selects gain -2dB, 0dB, and +2dB. This gain option offers the user gain optimization according to his/her system needs.

The power supply is regulated with very fast shunt regulators (with Zero-Temperature Coefficient reference Zener diodes). All shunt current regulators use FETs.

All the supporting components are high-quality audio dedicated and selected components (Kiwame, Tackman resistors, golden pins sockets, polypropylene capacitors…). The printed circuit boards are made of special higher temperature stable material with gold plated copper connections. The boards are without protection solder layers lowering the dielectrically influence. Printed circuit boards are mechanically damped to lower vibration and stress for components and vacuum tubes.

The internal audio path connections are realized with silver wire in Teflon sleeve. As a volume control, ANL 10 use top grade 48 position golden contacts switch from Elma connected in shunt mode. In this configuration, the balanced attenuator consists of just 4 precision and developed for audio purposes resistors (Tackman). The attenuator is truly balanced.

 

The whole enclosure, printed circuit boards and all components in the preamplifier follow mechanical symmetry design.

– vacuum tube preamplifier

– no global negative feedback

– input and output section realized as a module

– module base realized with 2 mm thick special treated copper sheet

– minimalistic no-compromise design (cost no object)

– Electro Harmonix  6922 dual low noise matched gold triode amplification (balanced)

– vacuum tube ceramic sockets with gold plated contacts

– truly balanced design

– dual mono completely separated channels

– mechanical symmetry design

– balanced and differential inputs (XLR and RCA)

– balanced and single-ended outputs (RCA)

– WBT nextgen 0210 Cu RCA input and output socket connectors

– Neutric XLR input and output connectors

– a signal passing wire is pure silver with Teflon sleeve to minimize the impact on reproduced sound

– not used sources completely detached from the preamplifier to minimize interference and noise impact

– source selection with special latching signal relays with gold and silver contacts 

– all switchable functions active realized exclusively with latching relays

– latching relays used to eliminate the magnetic field when the relay is active

– no electrolytic capacitor in audio path (including in power supply circuits)

– use of only high-grade polypropylene capacitors

– one or two high-grade silver oil capacitors (Mundorf MCap Supreme Oil) in audio path (only one capacitor with output transformer installed) 

– Lundahl high-grade output transformer for completely eliminate potential ground loops (transformer in an option)

– Lundahl transformer wound with Cardas high purity post-annealed audiophile grade copper wire

– audio high-grade low noise high tension resistors Kiwame 

– audio high-grade resistors Tackman

– Elma 48 positions shunt volume attenuator 

– volume attenuator with stepped microprocessor controlled motor for remote control (remote volume control is an option)

– printed circuit boards use special board material that is thermal more stable printed circuit boards are without solder mask layer to minimize the dielectric constant influence on reproduction

– printed circuit boards connections are copper gold-plated

– printed circuit boards are mechanically damped to lower vibration and stress for components and vacuum tubes

The mains power supply is separately filtered for each channel power supply. In the power path two DC blockers are blocking potential DC voltage component that can be present in the mains power, so the potential unwanted interaction is eliminated with custom designed and wound toroidal transformers. As toroidal transformers have high inductance and low magnetic field dispersion mains DC voltage component can lead to buzzy toroidal transformers.

The left and right PSU are symmetrical modules using as base 2mm thick copper sheets. Cooper is specially treated in a special way against corrosion while still maintaining its electrical parameters.

The whole power supply unit uses 4 custom wound toroidal transformers with an electrostatic shield between primary and secondary windings. The shields eliminate the electrostatic – capacitive coupling between primary and secondary windings so noises from the mains power lead are eliminated. All transformers are also enclosed and potted to minimize vibrations in Ferro-Magnetic enclosures to lower external magnetic field and disturbances.

Power supply unit is connected to the preamplifier unit with two shielded multi-core cables using professional stainless steel 12 pole connectors. Each cable delivers power to one channel. All the voltages and currents that are transferred through the cables are constant, so the connections are free of any variable magnetic field and with it related radiations.

High voltage required for vacuum tubes operation is rectified with vacuum tubes diodes providing as low as possible current spikes and distortion. Smoothing the voltages is realized with high-grade polypropylene capacitors (no electrolytic capacitors are used!). To lower any noise coming from power lead and lowering ripple from smoothing the DC voltage ANL 10 implements a specially designed capacitor with four contacts. The approach is known as Kelvin connection and gives amazing suppression of unwanted noise down to -120dB up to the more than 1 MHz bandwidth. High voltage is also smoothed with high-grade Lundhal choke connected in symmetrical – balanced mode.

Heater power for vacuum tubes is done with constant current generators. With this approach high current spikes and stress for vacuum tubes when they are cold (turning on the system)  are avoided and this maximally prolongs their operational time. 

Power supply unit delivers also required voltages and current for low voltage current generators and supply voltage for the control unit and its functionality.

At the rear of the enclosure is mounted the hour meter that shows elapsed time. The hour meter can be reset opening the cover and is restarted from zero normally when the new tubes are inserted.

Power supply summary

– power supply (PSU) in a separate enclosure

– completely separated power supply for left and right channel

– mechanical symmetry design

– power supply section realized as a module

– module base realized with 2 mm thick special treated copper sheet

– the power line is separately filtered for each power supply unit with »PI« filter

– toroidal transformers protected from power line DC voltage with special DC blocker circuits

– use of four custom designed and wound 100VA toroidal transformers with high output power and low load for lower power supply distortion and unwanted harmonics generation

– separated transformers for high voltages

– separated transformers for vacuum tubes heater and low voltages

– toroidal transformer enclosed in iron pots to minimize the magnetic impact

– toroidal transformers with the electrostatic shield between primary and secondary windings to eliminate the noise on the power line

– tube heaters energy is supplied with current sources to maximally extend vacuum tube life

– high voltage for tubes is rectified by 6CA4 vacuum tube and smoothed with Lundahl symmetrical chokes

– rectifier vacuum tube heater is time delayed to extend tube life

– the high voltage power supply is designed in an innovative way to minimize the current spikes (drastically lowering PSU noise)

– use of special polypropylene filtering capacitor with »Kelvin« connection to extend the low impedance filtering and noise reduction up to 1 MHz

– all high and low voltages are regulated with shunt regulators

– shunt regulators are without negative feedback, stable and very fast

– the digital counter of expired hours to display vacuum tubes usage time 

The control unit consists of a microcontroller that is enclosed in a special stainless steel enclosure. With this approach, all the radiated noises are maximally reduced. The peripherals are connected and controlled by the microcontroller with static signals with no generated high-frequency noise. All control logic signals are electrically isolated from the rest of analog circuits.

The remote control uses radio frequency receiver mounted on the main control board with a small antenna at the rear of the main enclosure. The control unit software is proprietary and developed in house.

Control unit section summary:

– CPU control unit designed to drive latching signal relay and to minimize radiated noise

– control circuitry enclosed in separated space to minimize radiated noise

– The CPU control unit is galvanic isolated from the rest of the circuits for lower noise

– the remote control is activated with a special radio frequency transmitter in the remote unit and receiver as part of the control unit

– two +12V trigger outputs

Both enclosures are internally made from 2 mm anodized aluminum sheets; the separation walls between preamplifier sections and channels are made of polished stainless steel sheets. The exterior is made of CNC machined 5 mm anodized aluminum. Special parts are made of polished stainless steel or depending on options from gold plated brass. The inscriptions are laser engraved.

Enclosure section summary:

– preamplifier and power supply unit in two enclosures

– enclosures made of high-grade aluminum, copper and stainless steel sheets

– cover, front and rear plates from high-grade high quality 5 mm thick CNC extruded anodized aluminum sheets

– all enclosures design with addition aluminum heat sink fins to lower internal temperature to prolonged electronic parts life

– enclosures include specially designed low profile anti-vibration feet to minimize microphonics effect on vacuum tubes and capacitors

This cost no object preamplifier was made from the very start with only one goal in mind… Pure, unaltered music reproduction! And Reference Anniversary ANL 10 delivers it! 

Audio Alto’s flagship preamp comes with highly impressive build quality and most important a stress-free sonic performance. You will find no traces of usual or expected tubist sonic imprint. Even some of the most coveted tube preamplifier does not escape a designated and instantly recognizable sonic tint. This is where the ANL 10 makes all the difference. Utmost refined circuit design aloes the extreme bandwidth and purity, that lets Reference Anniversary act as sonic via medium. No… By all means, this is not your ordinary tube preamplifier!

Among many other things, the Anniversary 10 preamp is also special as it was designed and built up from scratch by one man and one mind. Saša Burian is an electronic wizard, with impressive skills and the decades of experiences in various fields. Rarely a single person can design and execute all the needed bits (including programming), but here you have it! 

Saša Burian wanted to create something worthy of celebrating the Audio Alto 10th anniversary and he really pushed the agenda to the extremes. 

Reference Anniversary ANL 10 is the 21st-century tube preamplifier executed beyond of just right. It’s one of those products, that embraces the forgotten art of taking the time to plan, design and construct everything properly. And the end result? An upper echelon pleasure for both the mind and the senses…

You can already decipher, how this is Saša Burian’s Meisterstück! Rarely the dynamic resolution is seamlessly partnered with the faultless tonal balance, yet Audio Alto flagship tube preamplifier embraces the greater clarity with consistent music’s energy fortitude.

The two chassis design with separate power supply and tube rectification, fully balanced-fully symmetrical mechanical design with no global negative feedback deliver one of the lowest fatigue tube preamplifier performance for it’s given the price. 

Audio Alto Anniversary Reference 10 ANL tube preamplifier is not cheap by any means, but compared to what some exotic preamplifier will cost you, ANL almost comes as a bargain. 

Anniversary Reference 10 ANL proves the point that a contemporary tube preamplifier doesn’t have to sound like one. It’s low distortion and high-frequency bandwidth deliver exceptional coherent frequency responses that rivals even a few of the top tier solid state preamplifiers. 

Audio Alto Anniversary Reference 10 ANL tube preamplifier allows more of the music material deciphering translating to impressive spatiality, refreshingly unaltered gain handling and capability to deliver a stress-free prolonged listening. 

For what it represents and even before the final review, I’m wholeheartedly giving out the Mono and Stereo Upper Echelon Product Award!

Stay tuned for part two where I’ll focus on the music references and go more in-depth with the sonic descriptions…

Matej Isak

– 24.990 EUR (with VAT)

Electric parameters

– Frequency range

– 10 Hz — 120 kHz +/- 0.5 dB @ 600 ohm load

Distortion 

– Less than 0,01 %

Gain

– Main gain selection per channel: 12 dB, 15 dB, 18 dB

– Additional gain selection per channel: -2 dB, 0 dB, +2 dB

Maximum output amplitude:

+29 dBU – 21,8 Vrms, 61 Vpp,

– Input and Output Connections

Sources

– 3x balanced or differential (selection)

– 2x differential

– tape monitor loop

Output

– 2x balanced

– 2x single ended (RCA)

Audio Alto

SBBS Plus d.o.o.

Valvasorjeva 12

1000 Ljubljana

Slovenia

phone: +386 1 438 47 85, +386 41 399 256 

fax: +386 1 433 91 96

email: info@audioalto.com 

web: www.audioalto.com