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The CAT SL1 Legend full-function preamplifier is sweeter, the Accuphase C-2810 warmer, the Luxman C-1000f warmer still, the Nagra PL-P quite ‘tubey’. If I sorted these contenders by timbre from warmest to most neutral, the lineup would work out to Luxman C-1000f → Nagra PL-P → Accuphase C-2810 → CAT SL1 Legend → Ayon Polaris III → Thrax Dionysos → Music First Audio Mk II Copper (TVC passive). Here proceeding from warmest to most neutral (or even slightly bright as in the Music First) equates to moving from the most ‘closed in’ to the most ‘open’ sound. As you can see, choosing between tube and transistor technologies has nothing to do with it. If I would have to identify one rationale for this sequence, I’d probably point at diminishing complexity. What could be simpler than a passive circuit with transformer attenuators like the Music First?


I’d rather refrain from such beliefs however and admit that I don’t know the real reason. The Ayon and Thrax are similarly simple/complex with transformer volume controls and single-stage voltage gain. It’s interesting too that this progression is about an increase in resolution. When we consider saturation and the tautness and fleshiness of the bass, the order reshuffles to Music First Audio Mk II Copper → Nagra PL-P → Luxman C-1000f → CAT SL1 Legend → Accuphase C-2810 → Thrax Dionysos → Ayon Polaris III. Regardless of the qualifiers I might use to reassemble this list, the Dionysos was the most versatile as though it sat at the center around which the dualities of warm/cold and light/heavy revolved.

Even so it won’t perform as good as the others in each and every instance. Its tremendous openness won’t suit systems with lit-up treble and specifically high presence region energy. Here the CAT would be the better integrator that brings everything together such that treble and bass considerations disappear into simply music. For very low powerful bass the Polaris is the choice. From amongst these only the Thrax maintained generally similar textures and amplitude but differentiated even better specific aspects of an upright or electric bass to make us momentarily forget that we're dealing with a recording.


The soundstage could perhaps have been shown a little better still yet I’m not 100% certain of this particular impression. It seemed that the Polaris III and CAT cast a more saturated denser soundstage. After switching to the Thrax everything seemed to be drawn to the virtual performers. This might have been superior focus in action but to me it appeared like a slight dimensional contraction. Whatever one might conclude here, the Dionysos is a fantastically made brilliantly featured one-box preamplifier that sounds as good and in some aspects better than far bigger twin-chassis efforts from firmly established companies. Bravo, bravo, bravo!!!

Description: The Dionysos preamplifier is the first product from the new Bulgarian Thrax Audio company who are based in their country’s capital of Sofia. It is a linestage preamplifier fully realized with tubes. Rectification is handled by a 6C4P-EV (6Ц4П-В), voltage is stabilized by constant current sources feeding a shunt regulator with a SG15P (СГ15П) reference and voltage amplification is via a single 6N6P (6Н6П) double triode. All tubes are NOS Russian issue. Interestingly the amplification tube is the only active element in the signal path. One half works in the right, the other in the left channel. This single-stage topology recalls the more expensive Conrad-Johnson preamplifiers or my Ayon. This also means that the unit inverts absolute phase.


The enclosure is executed brilliantly from thick aluminium panels bolted together without visible fasteners and a barely discernable seam. The front is carved from very thick aluminum stock to gracefully flow around the control elements. The most important of these is the big cenral volume control and two green LED displays hidden behind acrylic windows which show the volume for each channel. Balance can be set from the remote control or small buttons on the fascia. The remote is very chic black anodized metal with chromed ends and  easy to operate. It controls volume, balance, inputs, absolute phase for each input, mute and power. All these functions are also duplicated on the front panel. Unfortunately the knobs and indicators are not identified which seems a bit too much of an extravagance even if it helps to keep the fascia clean [they are properly coded/named on the belly of the machine as shown next- Ed].


Looking from the left we start with the power switch with an indicator LED that changes from red to green after the unit is powered up. The next button activates the fixed output. To the right we have two buttons to select the active input and between them a button for changing absolute phase. Its activation is indicated by the LED of the chosen input. It changes from green to orange (unfortunately the LEDs are not described so you have to guess which input is active). The back is as solid a slab of milled metal as the front, not very typical for the hi-end. Here we get wonderful RCA and XLR sockets. Although the preamplifier is not balanced, the XLR inputs and outputs run desymmetrizing and symmetrizing transformers to accommodate balanced sources and amplifiers.


There are four unbalanced inputs and two balanced ones. One of the inputs can be set to bypass for home cinema systems to become a loop-thru. There are also rec outputs, switches to cut signal ground from chassis ground and four outputs – two RCA, two XLR. Interestingly the recording output is buffered by a floating amplifier with a transformer input. Thus its usage does not influence the sound quality. In a separately milled recess sits the IEC socket, a mechanical power switch and a level set button. This can be used to set the level of any chosen input and place it in bypass mode. This input's LED will then turn red. The voltage level is set in internal memory and won’t default with power-down. Unity gain equates to 24 on the display.


To get inside this chassis we have to remove the carbon-impregnated plastic footers. After unbolting the bottom plate, we get access to the screws fixing the top cover. We immediately see a combination of splendid engineering—thought-through mechanics and topology—and NOS parts combining with modern parts. It’s apparent that each element was considered for its sonic contributions first and on price a faint second. After the Absolutor preamp I once again stared at Soviet parts so disdained not so very long ago but returning to active duty. Of course here they weren’t exclusive but included tubes (I couldn’t stop thinking that my Lektor Air player too uses Russian 6H30), resistors and mighty oil capacitors in the power supply to see army surplus put to good use again.


What first catches the eye is the fabulous mechanical structure. The PCB with the amplification section and power supply is bolted to two blue-anodized aluminium bars which themselves are not bolted to the bottom plate but the chassis cheeks. The entire power supply also mounts there with a nice big transformer, NOS oil capacitors from the USSR and a very big Lundahl choke. To the other side panel bolt two big Japanese Hashimoto Electric output transformers and the volume control and input decoupling transformers enclosed in catchy solid metal cans. From below we can spot a few integrated stabilizers and many transistors working in the solid-state voltage regulator circuits. All are bolted to a long big heat sink located on the other side of the PCB.

The inputs are soldered into small oblong channel-specific PCBs with relays. From there the signal goes to the Permalloy transformers from SLK Transformer and then extravagant Oyaide cables—high quality PCOCC-A wires rarely seen —connect to the main board. The internal heat sink divides the PCB in two parts, power supply and amplification circuit. In the latter we only have one 6N6P (6Н6П) twin triode. Next to it we see a few high-quality passive Wima caps, precision resistors and active OPA656 op amps. To the side there is an additional PCB with two rows of relays to key the individual TVC secondaries. The relays are controlled by integrated switches. On the other side of the heat sink divider sits the power supply with the 6C4P-EV (6Ц4П-В) tube rectifier and a voltage stabilizer using the SG15P (СГ15П). On the tubes we can see ferrite muffs for EMI shielding. The heater circuits are rectified by solid-state bridges separately for the power supply and amplification tubes. This is fantastic brilliant execution!
opinia @ highfidelity.pl
Thrax website