Home           Products           Tutorials           Forums           Contact  
Augustica Technologies Inc Electronic Kits
 
 

  

  

  

  

  

   Headphone Amplifiers

  Corvette
Frigate
  Brig

   Power Supplies

Doubloon
Trident
Janus

   VU Meters

Dejavu

   Parts

  LED
PCBs
Transformers
  Tubes
   

Headphone Amplifier Corvette Tutorial

Step by Step Instructions

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 tester Amplitrex 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 capacitors.

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. 

Step 1
      
Headphone Amplifier Corvette IC1   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. 
         
Step 2        
          
Corvette D1-D4   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.
         
Step 3        
          
Corvette D1-D4   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.
         
Corvette B-plus Bus   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.
         
Step 4        
         
Corvette IC2   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.
         
Step 5        
         
Corvette IC2   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 after rectification.
         
Step 6        
         
Corvette IC2   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.
         
Corvette Power Supply   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 DC.
         
Corvette Power Supply   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 situated.
         
Step 7        
         
Corvette V1   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.
         
Corvette Left Channel   Finally, solder volume control potentiometer R1, headphone stereo jack, and terminal block K1.
         
Corvette Volume Control   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.
         
Corvette Volume Control   Solder the wire to the ground pad on the bottom side of the PCB.
         
Corvette Volume Control   Put on washer and nut included in the kit together with the potentiometer R1.
         
Step 8        
         
Corvette Volume Right Channel Solder resistors, capacitors and tube socket of the right channel of the headphone amplifier Corvette.
         
Corvette Volume Right Channel   Start with the tube socket, followed by the resistors and the capacitors.
         
Corvette Complete   You completed assembly of the amplifier Corvette
         
Corvette Complete   Before testing the headphone amplifier Corvette, visually inspect the PCB for breaks in symmetry between the left and right channels.
         
Step 9        
    Attach only the low voltage filament power supply’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.
         
Step 10        
         
    If you are using a variac, slowly bring up the low AC voltage, while looking for smoke or part discoloration or bulging.
         
Step 11        
         
    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.
         
Step 12        
         
    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.
         
Step 13        
         
    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.
         
Step 14        
         
    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).
     

 

 
� 2012  Augustica Technologies Inc.

Privacy Policy      Terms & Conditions      Disclaimer