THÖRESS SE300B Mono Power Amplifier . Single-Ended Triode .
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“SE300B Mono”
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P R O D U C T D E S C R I P T I O N
The SE300B Mono Amplifier is an all-tube power amplifier employing the famous
300B filamentary triode in single-ended (Class-A) operation mode for an output of
up to 10 watts into a 4, 8 or 16 ohm loudspeaker load. 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 as download on the ABOUT button of our
website.
The 300B power tube is excited by an extraordinary single-stage driver employing
two EL822/CV2382 power pentodes operated in triode mode with high idle current
and works into a tape wound cut core (C-core) output transformer (OPT) which is
built in-house to the highest possible standards to ensure ultimate performance. The
driver stage is so powerful that it could (theoretically) drive a loudspeaker load with
very low distortion on its own whereas 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 its
secondary terminals. These design choices are to a large extent responsible for the
richly textured, clear, warm and dynamic sonic presentation of the amplifier,
particularly when combined with our horn based 2CD12 or underhung-motor based
1D66 loudspeaker. The SE300B 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 will
certainly measure up to the expectations of even the most critical and experienced
music lover.
The amplifier is built with meticulous hand construction using our proven point-to-
point wiring techniques, whereas 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 SE300B mono
block is combined with a highly efficient loudspeaker such as our 2CD12 model. At
first, the 300B power tube is DC heated whereas the cathode point of the amplifier
circuit can be balanced with respect to the filament of the given power tube 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 300B filament and residual hum due to ripple of the heater supply
voltage vanishes (reaches a minimum). Secondly, the amplifier 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 SE300B mono amplifier is equipped with a 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 readily customize the amplifier for all kinds
of mains voltages, 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 classic
300B filamentary power triode in single-ended (class-A) operation mode.
• 2×10 watts of output power.
• Powerful single-stage driver utilizing two EL822/CV2382 pentodes
operated in triode mode at high idle current.
• Minimalist (pure class-A) zero-feedback schematic.
• Ultimate tape wound cut core (C-core) output transformer
manufactured in-house.
• Precise 4, 8 and 16 ohm loudspeaker load matching via jumpers soldered
to the secondary terminals of the output transformer.
• C-core filter choke made in-house.
• High grade foil-in-oil capacitors (made in Germany) in the power supply.
• Ultra-low noise mains transformer produced in-house for 230Vac, 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 (aluminum) case, anodized printing on front and rear panel,
powder-coated chassis and lids.
• Dimensions: 150x595xH330 mm,
330=20/feet+210+100/power tube over case,
595=575+20/speaker binding posts;
• weight: 14 Kg each Mono Block.
• Dimensions of the shipping crate: 950x400xH460 mm.
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THÖRESS…
A Tribute to Professional Audio Components
from the Golden Age of the Vacuum Tube !
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