Corvette is a high end pure class A headphone
amplifier designed for the highest quality music reproduction with the
minimum of distortion. An essential part of any good sounding headphones
is the amplifier that is driving them. Corvette is capable of driving a
wide range of headphones and it will give you the best advantage in
listening pleasure. Corvette uses only the
finest audiophile quality components that have been carefully selected
with no expense spared. Corvette uses two 6922 tubes for their linearity and
ultra low distortion. The 6922 tubes are matched with an aid of tube
and a computer. High quality Kemet, WIMA, Nichicon capacitors are
used along with an audio grade ALPS volume potentiometer. Military grade
Vishay/Dale metal film resistors used throughout the kit. A high quality
built in dual bus power supply with ultra low noise characteristics
delivers anode and filament voltage and a very generous amount of post
and pre regulation smoothing capacitance provided by Nichicon and Kemet
This amplifier kit has a high-voltage power supply, which provides high voltage and therefore may produce a lethal shock. Only persons who are competent at electronics assembly and understand the dangers of high voltages may attempt to assemble this kit! Safe assembly and operation of this kit is the users'
responsibility. The kit and this tutorial are provided 'as is'.
Augustica Technologies Inc. accepts no responsibility for any damage, injury or death as a result of assembling this kit or using the information herein. The assembled kit must be properly enclosed to prevent contact with high voltages and
to be kept out of reach of children. Keep this kit away from water and other damp environs. As with any self-assembled electronics project improper assembly could cause damage to the kit, overloading of a circuit or an electrical fire. If you don't feel comfortable in assembling the kit or using the amplifier, please contact us to return it for a full refund.
Ideally, a variac should be used to slowly power up the power supply of the kit, as it is better to have a misoriented electrolytic capacitor or a mislocated resistor blow at low voltages, rather than at high voltages. Once the power supply is powered up, be cautious at all times. In fact, even when the power supply is disconnected or shut down, assume that capacitors of the power supply will have their high voltage charges retained and, therefore, still will be able to provide a lethal shock.
Wear safety eye goggles, which is not as bizarre as it may sound
- a bursting power supply capacitor may spray hot caustic chemicals in
your face. Make a habit of using only one hand, with the other hand
behind your back, while attaching probes or handling high voltage gear,
as a current flow across your chest can result in death. In addition,
wear rubber-soled shoes and work in dry environment. Remember, safety
first, second, and last. If you are not an experienced electrical
practitioner, before attaching the transformer windings to the printed
circuit board (PCB) of the amplifier, have someone who is well
experienced in electronics review your work. Again, if you don't feel
comfortable in assembling the kit or using the amplifier, please contact
us to return it for a full refund.
Cleanliness is essential. Before soldering, be sure to clean both sides the PCB with 70% to 90% isopropyl alcohol. Do not use dull looking solder. Solder should shine. If it does not shine, first clean away the outer oxidation with some steel wool or a copper-scouring pad. If the resistor leads look in the least gray, clean away the oxidation with either steel wool or a wire
snipers with sharp edges. Admittedly, with new resistors and a fresh PCB, such metal dulling is rare, but if the parts have sat in your closet for a year or two, then expect a good amount of oxidation to have developed.
Be consistent in orienting the resistors, capacitors and diodes. Keep nominal information on a resistor's or capacitor's body flowing from the left side to the right side as you face the resistor or the capacitor straight on. This will pay dividends later, if you need to locate and de-solder a resistor, a capacitor, or a diode placed in a wrong location. Because the board is double sided, with traces and pads on each side, it is easier to solder the resistors from their topside. As the PCB is overbuilt, it is difficult to remove an incorrectly placed part. Be sure to confirm all the electrolytic capacitor orientations, as a reversed polarized capacitor can easily vent (or even explode) when presented with high-voltage. Confirm trice, solder once.
Start with assembly of the high B-plus DC voltage bus of the
power supply and first attach the MOSFET transistor IC1 to its
heatsink. This transistor is extremely sensitive to electric
static, therefore, you must use ESD safe soldering station and
you also must ware an ESD bracelet. Once you attached the MOSFET
transistor to its heatsink, you can insert heatsink leads and
the MOSFET transistor leads into the PCB. Solder the leads of
the MOSFET transistor to the PCB. At this point do not solder
the heatsink's leads to the PCB - you will do it later.
Solder the rectifying bridge D1-D4 and capacitors
C11, C12, C13, and C14. Pay attention to the polarity
of the rectifying bridge D1-D4. Now solder terminal block
K2. Connect a transformer or variac to the terminal block
K2 and slowly bring voltage to 220 Volt AC. Measure the
high B-plus DC voltage produced by the rectifying bridge
D1-D4. If you applied 220 Volt AC to the rectifying bridge,
after rectification you should obtain about 320 Volt DC
without any load.
Solder diodes D5 and D6 and then solder resistors R24 and R25
followed by capacitors C15, C16, C17, C18, C19 and C20. Now
solder red LED D7 and resistors R26 and R27.
Connect a transformer or variac to the terminal block K2
again and slowly bring voltage to 220 Volt AC. Measure
the high B-plus DC voltage produced by the high voltage
bus of the power supply as a whole. If you applied 220
Volt AC to the terminal block K2, the power supply should
deliver about 320 Volt DC without any load. Measure AC
component that is present in the DC voltage after it is
regulated and filtered by the MOSFET transistor IC1.
The AC component of the high B-plus DC voltage should
fluctuate between 2 millivolts and 20 millivolts AC.
If your measurements show substantially higher values
of the AC component present in the high B-plus DC voltage,
your MOSFET transistor IC1 is probably burned out and it has
to be replaced. Otherwise, the MOSFET transistor is
regulating and filtering the high B-plus DC voltage
properly and now you can solder to the PCB the heatsink
on which the MOSFET transistor is situated.
Assemble the low DC voltage (filament) bus of the
power supply and start with attaching IC2 LD1084V
low drop voltage regulator to its heatsink. Once
you attached the LD1084V to its heatsink, you can
insert heatsink leads and LD1084V leads into the PCB.
Solder the regulator's IC2 leads to the PCB. At this
point do not solder the heatsink's leads to the PCB -
you will do it later.
Solder the rectifying bridge D8-D11 and capacitors C21, C22,
C23, and C24. Pay attention to the polarity of the rectifying bridge
D8-D11. Solder terminal block K3. Connect a transformer or variac to the terminal block K3
and slowly bring AC voltage to 8 Volt AC. Measure the DC voltage
produced by the rectifying bridge D8-D11. If you applied 8 Volt
AC to the rectifying bridge, you should obtain about 11 Volt DC
Solder diodes D12 and D13 and then solder resistors R28 and R29
followed by capacitors C25, C26, C27, C28, C29 and C30. Now
solder green LED D14 and resistor R30.
Connect a transformer or variac to the terminal block K3 again
and measure the DC voltage produced by the low voltage bus of the
power supply as a whole. If you applied 8 Volt AC to the
terminal block K3, the power supply should deliver about 11 Volt
Measure AC component
that is present in the filament DC voltage after it is regulated
and filtered by the IC2 LD1084V. The AC component of the
filament DC voltage should be about 0.6 millivolts AC. If your
measurements show substantially higher value of the AC component
present in the DC voltage, your IC2 LD1084 is probably burned
out and it has to be replaced. Otherwise, the IC2 LD1084V is
stabilizing and filtering the filament DC voltage properly and
now you can solder to the PCB the heatsink on which the LD1084V is
Solder resistors, capacitors and tube socket of the left channel
of the headphone amplifier Corvette. Start with the tube socket,
followed by the resistors and the capacitors.
Finally, solder volume control
potentiometer R1, headphone stereo jack, and terminal block K1.
Grounding of the
volume control potentiometer is required as without it, the
amplifier Corvette may be subject to noise and/or interference. Cut
out a wire having length of at least 15 centimeters. Strip out
isolation from the wire. Wrap the wire around the threaded
portion of the potentiometer's neck making two loops and after
that twist together the two ends of the wire.
Solder the wire to the ground
pad on the bottom side of the PCB.
Put on washer and nut included in
the kit together with the potentiometer R1.
Solder resistors, capacitors and tube socket of the
right channel of the headphone amplifier Corvette.
Start with the tube socket, followed
by the resistors and the capacitors.
You completed assembly of the amplifier Corvette
Before testing the headphone amplifier Corvette, visually
inspect the PCB for breaks in symmetry between the left and
Attach only the low voltage filament power supplyâ€™s transformer
leads to the terminal block K3, leaving the high voltage
transformer leads unattached and electrical tape shrouded. Do
not install 6922 tubes in their sockets.
If you are using a variac, slowly bring up the low AC voltage,
while looking for smoke or part discoloration or bulging.
Measure the filament voltage regulator's LM1084V output voltage with load
provided by the amplifier Corvette. If the filament voltage regulator LD1084V fails
to regulate, try either lowering the DC filament voltage a tad, or
increasing it a tad, for example try 10 Volt instead of 11Volt,
as the 1 Volt difference might be enough to bring the regulator
back into regulation. Power down the filament bus of the power
supply by disconnecting low voltage filament transformer or variac.
Attach the high B-plus voltage transformer or variac leads to
the terminal block K2 and slowly bring up the high AC voltage,
while looking for smoke or part discoloration or bulging.
Measure the B-plus voltage provided by the MOSFET transistor
IC1. If you applied 220 Volt AC to the terminal block K2, the
power supply should deliver about 270 - 280 Volt DC with the
load provided by the amplifier stages of Corvette.
Measure the voltage across ground and B-plus pads of the PCB. If
the two channels differ by more than 10 VDC, try switching 6922
tubes from one channel to the other. If the imbalance does not
follow the tubes, there is a problem, probably a misplaced part.
Only after you are sure that both filament and B-plus power
buses are working properly should you attach the amplifier Corvette
to a headphone.
If you would like to see some new audio
PCB or kit or recommend a change to an existing product, drop us
a line by e-mail on the website www.Augustica.com (begin the
subject line with Corvette� or the spam filters are sure
to eat your message).