Sourcing Parts

Sourcing parts is one of the harder parts of building any tube amplifier. Complete amp kits are convenient, but you can save a lot of money by sourcing your own parts.

I get most of my capacitors from Allied Electronics www.alliedelec.com
and I get most of my resistors at Mouser www.mouser.com.

Here is a spread sheet from an amp build that has some typical resistor types you’ll need to build any tube amp. It really helps to have a spread sheet to keep track of your order. The most crucial column is the Mouser part number. These are just a few resistors from the vast assortment of resistors that Mouser offers, but it should be enough to get you started. You’ll notice in the part number that the difference between 1 watt and ½ watt is one number. Instead of 293 for a half watt resistor it’s 294 for the one watt resistor and the rest is the same. If you need a different value all that needs to be done is change the number in the middle.

Carbon film resistors are best suited for most of the amp circuit. Metal film can also be used. Metal oxide resistors are flame resistant so those will be used in specific areas in your amp. As the wattage rating goes up, the composition needs to change in order to handle the heat. So, when you’re looking at a schematic that calls for a specific wattage you’ll know what composition you’ll need. Then you can reference the chart below and go to Mouser and research the part you need. Most of the time in a schematic the resistors are going to be half watt unless specified. Some builders will use only 1 watt resistor in place of the half watt resisitors.

The full schematic image can be opened in another window for reference.

 

Electrolytic capacitors will be used in the power supply and as a cathode bypass capacitor.
Mica capacitors can be used for bright switches, or as a high frequency roll off capacitor in parallel with a plate resistor.  They can also be used as a high frequency roll off in the phase inverter.

The poly film or pvc capacitors will primarily be used as coupling capacitors. The orange drops should be the 6PS type from Vishay/Sprague or SBE or the PVC type from Mallory or the Cornell-Dublier on the chart below. You don’t want the 715 series polypropylene capacitors.

Here are some other sites to check out for various parts and tools:

www.hoffmanamps.com for hardware, turret board material, turret stacking tool (press fits turrets to the board material). Doug Hoffman is very nice to work with.

http://www.mojotone.com

www.allenamps.com for transformers.

Disclaimer: I will take no responsibility for any injuries or damage suffered by anyone as a result of the misinterpretation or misapplication of the information contained in these pages. Proper high voltage safety procedures and precautions must be practiced at all times when servicing vacuum tube amplifiers. If you are not completely familiar with these precautions, seek guidance from someone who is.

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