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AJ2 USER MANUAL. Ver1.1E
Aleph J2 assembly instruction.
Attention!
This device is powered from the AC main that poses threat for life and
health. During the work with a high voltage it is necessary to follow
safety measures. The user bears full responsibility for the
consequences and possible loss as a result of all their actions.
0. INTRODUCTION.
This KIT is based on Aleph J2 scheme by Nelson Pass. Detailed information can be found on
the sites firstwatt.com and diyaudio.com
The scheme contains a number of the additions for the safe operation of the amplifier and
speaker. Clip and Ready indications are provided. You can build P-ch and N-ch versions.
Semisouth transistors not offered.
The offered MULTIKIT is very simple in assembly and tuning. Nevertheless, you must have to
possess elementary skills of installation and understanding of electricity. The order of an
assembled product is possible.
All risks of wrong adjustment, connection, assembling, insufficient
qualification of the assembler, force-majeure circumstances, are
completely accepted by the customer. Some parts or values can be
changed without notices. Claims in subjective parameters of products
are not examined. The fact of the order of KIT confirms full
acceptance of these conditions.
1. TOOLS, EQUIPMENT, MATERIALS.
For performance of assembly operations you need to have minimum: crosswise screw-driver,
nippers, six-sided key and soldering iron (60-100W).
For adjustment operations the multimeter is sufficient. Variac, oscilloscope and the
generator are desirable.
From materials the screened wire and an assembly wire (14-17AWG) will be required. Solder,
flux, shrink tube and plastic ties.
2. PCB ASSEMBLING.
Install according to the scheme and component placement card the demanded components
in the corresponding positions. Lastly install semiconductors, power cap, output transistors
and wires.
For 50W version install output transistors only in a VT4, VT5 position. For 100W version use
VT4, VT5, VT6, VT7 positions, transistors VT4 and VT6 must be ABSOLUTELY identical. It is
always better to use the single hi-power transistor then lo-power pair.
For N-ch ver. you must rev polarity for next components: C3, C5, C6, C8, C9, VD1, VD7 and
VD13. Type next components: VT4, VT5, VT6, VT7 – IRFP240 (or other N-ch); VT1 – SJ74; VT2 –
SJ109; VT3 - MPSA18. VE1, VE2 in N-ch positions.
In input stage you can use 2SJ74 (N-ch ver) or 2SK170 (P-ch ver). Other type also usable
While soldering avoid overheating of components carry out the soldering for no longer than
3-4 seconds. Do not allow cold solder joints, short circuits. Do not inhale fumes of solder,
work in the aired room.
After assembling make sure there are no mistakes, cold solder joints, or short circuits.
3. ASSEMBLY OF THE AMPLIFIER.
Before installation it is necessary to put on output transistors the insulating pad with thermal
paste. Use mica or ceramic only! Thickness of paste has to be minimal - surplus is extremely
harmful.
Attach PCB with four screws. Install transistors clips. Lock in the corresponding screws by
sufficient effort by means of a six-sided key.
Connect indication PCB, level regulators, input and output connectors according to the
assembly diagram.
On the chassis install the transformer (transformers) with the isolating gaskets. Connect a
main 220VAC according to the assembly diagram. Isolate solder places with help of shrinkable
tube. Do not connect secondary windings.
After completion of assembly works make sure of lack of mistakes.
Example of assembling:
4. ADJUSTMENT OF THE AMPLIFIER.
Before power up:
Connect the transformer to the adjusted channel.
Set R8 resistor in mid position.
Connect the voltmeter between XN4 (Dir Out) and XN5 (GND).Power up the amplifier.
Voltage has to be close to zero. Voltage (with some deviations) on R25 must be 280 mV (50W
ver) / 200mV (100W ver.). If it is not - immediately power off and look for mistakes.
Adjustments of the R8 resistor should achieve an output voltage in limits +/-10mV. Final
adjustment is then made on the completely heated-up amplifier. Thermal changes of the
voltage are a normal occurrence.
Position of the R8 resistor defines the structure of harmonic distortions and the
corresponding coloration. You can execute this adjustment according to your taste.
Change of value of the R19 resistor influences the idle current of the output cascade. It is not
recommended to exceed idle current 1,4A (50W ver.) or 2 x 1A (100W ver.).
5. PROTECTION.
This KIT is equipped with output transistors overload protection and the DC-voltage speaker
protection. There is an opportunity to exclude protection that is reflected in the assembly
chart. For a complete elimination of protection you need to remove VT4 and VT8 transistors
also.
However, the system of protection has slight influence only on the tiniest nuances of sound
transmission. But the risk of damage of the amplifier and destruction of the speaker system
sharply increases. Therefore I do not recommend protection mechanisms eliminating.
6. BALANCED AND UNBALACED INPUT.
At unbalanced connection you must install jumper between contacts 1 and 3 of XLR
connector.
© StD 2015