THÖRESS SE845 Mono amplifier Single-Ended Triode . Mono . Power Amplifier
====================================
“SE845 Mono”
……………………………………………………….
P R O D U C T D E S C R I P T I O N
The SE845 Mono Amplifier is an all-tube power amplifier employing the famous 845
filamentary power triode in single-ended (Class-A) operation mode for an output
power of up to 20 watts into a 4, 8 or 16 ohm loudspeaker load. It is the flagship of
our all-tube power amplifier line. The amplifier is entirely based on SINGLE-ENDED
ZERO-FEEDBACK schematics. Decidedly ignoring the fact that many music lovers
persistently believe in the myth that balanced technology (and the associated cable
configuration with XLR connectors) is generally superior over single-ended concepts.
Readers who want to learn more about our view on balanced techniques and our
general design approach are encouraged to read the paper (THÖRESS – Behind the
Curtain) available on request.
The 845 is a brightly glowing filamentary tube which requires around 300V peak-to-
peak voltage swing at the control grid for full excitation while presenting a critically
high internal impedance of about 2000 ohms to the output transformer (OPT).
Designing a driver stage and an OPT which allow to fully exploit the enormous sonic
capabilities of the 845 triode are therefore highly challenging tasks. In our SE845
monoblock the power tube is driven by an extraordinary single-stage arrangement
employing two EL822 power pentodes operated in triode mode with high idle
current. The driver is so powerful that it could (theoretically) drive a loudspeaker
load with very low distortion on its own. Furthermore, the proprietary output
transformer (OPT) is made in-house and features a highly elaborated dual-coil
winding over a large tape-wound cut core (C-core) to ensure very low transformer
distortion and ultimate frequency response. (The OPT allows for precise matching of
a 4, 8 or 16 ohm loudspeaker load to the power tube by way of jumpers soldered to
the secondary terminals.) These design choices are to a large extent responsible for
the richly textured, clear, warm and dynamic sonic presentation of the SE845
monoblock, particularly when combined with our 2CD12 or 1D66 loudspeaker. The
SE845 Mono Amplifier is an ultimate component and as such a worthy complement
to our Dual Function Amplifier or Full Function Preamplifier. It easily outperforms
competitive products regardless of price and certainly measures up to the
expectations of even the most critical and experienced music lover.The SE845 amplifier is built with meticulous hand construction using our proven
point-to-point wiring techniques. Much care has been taken in arranging each aspect
of the internal construction to ensure low noise performance, ease of service and
the highest reliability for many years to come.
LOW NOISE OPERATION
Specific design choices guarantee low noise operation even when the SE845
monoblock is combined with a highly efficient loudspeaker such as our 2CD12 model
or even a more efficient horn component. At first, the 845 tube is DC heated
whereas the cathode point of each individual tube can be balanced with respect to
its filament by means of a control knob (rotary potentiometer) on the rear panel.
Once the balance adjustment has been carried out the signal current is distributed
uniformly over both ends of the 845 filament and residual hum due to ripple of the
heater supply voltage vanishes (reaches a minimum). Secondly, our mono block has
been specifically designed to have a moderate gain (low input sensitivity). This
ensures that the idle noise of the line device remains inaudible in all possible
scenarios. Notably, this design choice also ensures conveniently fine volume
adjustment.
MAINS TRANSFORMERS
The SE845 mono amplifier is equipped with a proprietary mains transformer
produced in-house to ensure the highest possible quality and reliability. This part has
been optimized for low body noise emission and low leakage. Nevertheless, it is
mounted to the chassis via isolation elements in order to eliminate even the
slightest interference of residual transformer vibrations with the circuit. Since the
mains transformer is produced in-house we can easily built transformers for all kinds
of mains voltages on demand, for example 100Vac (Japan), 120Vac (USA, Canada),
220Vac (South Korea, China, Thailand, Indonesia), 240Vac (UK) or 245 Vac (Australia).
F E A T U R E O V E R V I E W
• All-Tube Mono Power Amplifier utilizing the famous filamentary 845 power
triode in single-ended operation mode.
• 2×20 watts of output power.
• Minimalist (pure class-A) zero-feedback schematic.
• Powerful single-stage driver utilizing two CV2382 (EL822) power pentodes
operated in triode mode at high idle current.
• High grade electrolytic capacitors (made in Germany) in the power supply.
• C-core filter choke made in-house.• Ultimate tape wound cut core (C-core) output transformer with dual-coil winding
manufactured in-house.
• Precise 4, 8 and 16 ohm loudspeaker load matching via jumpers soldered setting
to the secondary terminals of output transformer.
• Low noise low leakage mains transformer produced in-house for 230Vac (115Vac
via jumper setting). 100Vac (Japan), 120Vac (USA, Canada), 220Vac (South Korea,
China, Thailand, Indonesia), 240Vac (UK) or 245 Vac (Australia).
• Full hand construction, point-to-point wiring throughout.
• Non-magnetic case (aluminium throughout), anodized printing on front and rear
panel, powder-coated chassis and lids.
• Dimensions: 150x595xH330 mm,
330=20/feet+210+150/tube over case,
595=575+20/speaker terminals, weight 18 Kg (each monoblock).
• Dimensions of the shipping crate: 950x400xH460 mm.
……………………………………………………….
THÖRESS…
A Tribute to Professional Audio Components
from the Golden Age of the Electronic Tube !
……………………………………………………….
