High-End, Single Ended Class A1, All Triode monoblock, 10 W into 4 and 8 Ohm. JJ239 uses one ECC99 and one 2A3-40 JJ Electronic tube.
Mono Blocks JJ 239 use 2A3-40W and ECC99 tubes (similar to Mono Blocks JJ309 which use 300B and ECC99).
The JJ239 was developed on request from customers from Southeast Asia and Japan after the 2A3-40W tube was introduced. The 2A3-40W showed as having the best sound in the group of power triodes.
Like the 300B, the 2A3 has perfect linearity due to the design of the internal geometry.
The sound quality however, is even better because the cathode heater voltage is only 2.5V and the filament ends potential difference with respect to –Ug is smaller than in the 300B tube. Therefore, a much bigger cathode area is active during operation. (The maximum current flows at the positive filament end). Power source filtration capacitance of RC filters is 1200 μF.
The electrolytic capacitors of JJ Electronic production are bypassed with high quality polypropylene capacitors. Filament voltages for all tubes are of DC type.
The signal is amplified(in class A) by either of the ECC99. The ECC99 drives 2A3 which has an amplitude swing Uamax = 205V. The output transformer ratio of 31 : 1 / 4 Ohm helps to achieve the damping factor of 3,5.
The output transformer is a double c-core and its topology is similar to the JJ322.
All circuits in the signal path are optimized and THD at 9W is less than 1%.
JJ239 allows the anode current of 2A3-4W to be set using a potentiometer on the back panel. The LED under the potentiometer indicates the correct settting. The current is set correctly if the LED light just comes on.
A soft-start circuit turns the plate circuitry on with a delay of approximately 30 sec.
|Tube Complement||1 x JJ ECC99
1 x JJ 2A3 - 40 W
|Output power||10 Watt|
|Load impedance||4 Ohm/8 Ohm|
|Input impedance||50 kOhm|
|Input sensitivity||0,775 V at 10 W|
|Input sensitivity||20 Hz - 20 000 Hz (-1 dB)|
|S/N Ratio||less than 0,8 mV|
|Output transformers||Double „C.cores“|
|Power Supply||230 V (120 V, 100 V) 50/60 Hz|
|Power Consumption||80 Watt|
|Dimensions||340 x 380 x 255 mm|
|Finish||supply cover: brown or black (pulver lack)
top plate: chrome or 24 carat gold platted
wood: brown, natural (glossy) or black (dull)
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