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For those who want to know more about tube amps and biasing, a good place to
start is the tube amp faq
More technical and with more math but very interresting is the tech info at
------------------------ wrote:
------------------------
>Its my understanding there are two ways to bias an amp. The old school
>multimeter approach, and the oscilliscope approach. I've heard some pretty
>knowledgable people on the Fender Forum denounce the oscilliscope method.
>With the multimeter approach you simply measure the current at some point in
>the circuit, while tweaking a variable resistor until you get it into the
>right range. The exact point to measure the current and the magic resistor
>to tweak will all vary according to your amp circuit.
>
>This web page shows you how to do it for the Hot Rod DeVille/Deluxe family
>amps:
>
>Its bound to be different for a Bassman.
>
>My advice would be to get a tech to do it for you. The power supply filter
>capacitors can store *lethal* voltages for days, so its best to know what
>you are doing for your sake and the equipment's. Don't get me wrong, you can
>hang out on the Fender Forum and/or find web sites that tell you how to do
>it. Its not rocket science. You do have to know what you are doing though.
>
>You can also buy these "bias meters" that plug right into your tube sockets.
>These may be handy if the resistor to tweak is already accessible without
>taking the amp out of the chassis. However, these are expensive, and if you
>have a multimeter already you are probably wasting your money.
>
>Good luck,
>BN
>
>> -----Original Message-----
>> From: D. P. [mailto:]
>> Sent: Wednesday, March 12, 2003 3:59 PM
>> To:
>> Subject: [SurfGuitar101] setting tube bias
>>
>>
>> Hi group:
>>
>> Many of you all seem to be quite knowledgeable about amp mods and
>> fixes. My question seems simple: I need to learn how to adjust and
>> set the tube bias for my 1963 Bassman 50...I have NOS GE 6L6's that
>> need to be installed...
>>
>> will I need an oscilloscope or any other specialized tools?
>>
>> does anyone know a cool link that describes the bias process?
>>
>> should I just forget about the DIY and seek the assistance my
>> friendly amp tech?
>>
>> as always, any wisdom shared would be appreciated,
>>
>> dp
>>
>> (ps: the Bassman 50 through 4X12" Celestion/Utah cab with outboard
>> Fender Reverb sounds awesome...sort of like Brian Setzer but
>> surfidelic)
>
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