Tubelab

Assembly Manual • Schematic • Parts List • Tubes and Applications • Design • Simulations

There are two parts lists for this amplifier design. The first list is the assembly parts list, and the second is the purchase parts list.

The assembly parts list itemizes each part in alphabetical order, there is a check box next to each part. It is recommended that this list be printed on paper. Check off each part as it is installed. This makes it far easier to keep track of your progress. It is especially valuable if you can't finish the whole board in a single session.

The parts purchase list shows each unique part and the quantity of each that are required per board. Also listed are suppliers and part numbers for each part. It is used to order or gather up all of the parts needed to build a complete amplifier. Some parts such as tubes and transformers, are available in varying quality and power levels and they have their own page. The optional parts are covered on the upgrades page.

This is the assembly parts list. It is used to assemble the PC board, and the complete amplifier. First go over the list to verify that you have all of the parts and they can be properly identified. Mark out parts that are not being used in your amplifier design. R1 is not used if you are using the optional power supply choke. Next make any corrections to component values for your particular build. The cathode bias resistors (R17 and R27) may be a different value in your amp. The power supply capacitors C1 and C2 may be different also. When you are finished marking up your assembly parts list, make a copy of it and use it as the check list when assembling the amplifier.

Note 1: This is the coupling cap. The part number is for a Mallory "150" capacitor. This is a good compromise between cost and performance. Many users will upgrade this part. I use "Auricaps" in high quality amps. The value is also a matter of personal taste. It should be at least .1uF and the voltage rating should be at least as much as the amps B+ voltage.

Note 2: No resistor is placed in this location if a choke is used in the power supply. If no choke is used, place a 150 ohm resistor in this location. A power supply choke is recommended if you have efficient speakers, or they have good low frequency response. I have found that a cheap choke usually works better than a resistor.

Note 3: This is the cathode resistor. This sets the bias for the output tubes. 560 ohms is a typical value for tubes operated at 440 volts. Consult the simulations for the starting value for your operating conditions. If you are not sure, choose a value at the high end of the possible range. Then you can increase the tube current by adding a resistor in parallel to the one on the PC board without unsoldering.

Note 4: A 500 volt capacitor is specified for the two power supply capacitors. In many applications this is necessary because the power supply voltage can go over 450 volts. This is especially important with solid state rectifiers since the B+ voltage comes on instantly and there is no load on the power supply until the output tubes warm up. If you are ABSOLUTELY SURE that your B+ will never go this high, a lower voltage capacitor can be used. A 6V6 ( or other low voltage application) amplifier with a 550 volt CT transformer can use a 400 volt capacitor. The B+ in this case is 300 to 350 volts. These capacitors are often found surplus from SMPS applications. The value is not critical (at least 100 uF for C2 and 22 to 47 uF for C1). A 450 volt capacitor can be used with a 600 VCT transformer, and some 650 VCT applications. These are often easier to find that 500 volt capacitors. A capacitor rated for 105 degree centigrade operation is required for C1 and C2 if the ventilation is poor, and is recommended in all cases if new parts are being purchased. A 105 C cap should be used for C12 and C22 due to the close proximity of the output tubes.