Is the MOD 50 a fixed bias amp?

[richedie]

Talking to some guys about how easy it is to bias the Egnater.....I was told it is a fixed bias amp. Huh?
Can someone explain that one?

 

[aeroic]

Talking to some guys about how easy it is to bias the Egnater.....I was told it is a fixed bias amp. Huh?
Can someone explain that one?

Your friend is smoking crack. YOu don't have bias points on the back of the amp w/ a bias pot to change the hotness of the power tubes if it was a fixed bias amp. Secondly, you couldn't use EL34s, 6L6's, 5881s, 6550s, and KT88s, etc. without changing the bias.

 

[bruce egnater]

This is always a silly, confusing thing. There are really two basic ways of "biasing" the output tubes. One method is called cathode bias. This means instead of a negative bias voltage supply inside the the amp, there is a big resistor that sets the idle current. You can read about it elsewhere (aikenamps.com for example). The other method involves a negative voltage supply that is applied to the grids of the output tubes. Adjusting this voltage in turn varies the current in the tubes. The term fixed bias and adjustable bias are really the same thing. Fixed simply means there is a fixed negative voltage on the output tube grids. This voltage can be adjustable but, in reality, it is a fixed voltage once it is set. The term fixed comes from amps like Boogie and Peavey, for example, that have a fixed resistor (instead of an adjustable resistor), to set the bias. To adjust the bias in those amps requires replacing that resistor. See...I told it was silly.

 

[jmgman69]

This is always a silly, confusing thing. There are really two basic ways of "biasing" the output tubes. One method is called cathode bias. This means instead of a negative bias voltage supply inside the the amp, there is a big resistor that sets the idle current. You can read about it elsewhere (aikenamps.com for example). The other method involves a negative voltage supply that is applied to the grids of the output tubes. Adjusting this voltage in turn varies the current in the tubes. The term fixed bias and adjustable bias are really the same thing. Fixed simply means there is a fixed negative voltage on the output tube grids. This voltage can be adjustable but, in reality, it is a fixed voltage once it is set. The term fixed comes from amps like Boogie and Peavey, for example, that have a fixed resistor (instead of an adjustable resistor), to set the bias. To adjust the bias in those amps requires replacing that resistor. See...I told it was silly.

Boy you fixed this one Bruce,can't wait to say Hi at NAMM!!!!!

 

[richedie]

This is always a silly, confusing thing. There are really two basic ways of "biasing" the output tubes. One method is called cathode bias. This means instead of a negative bias voltage supply inside the the amp, there is a big resistor that sets the idle current. You can read about it elsewhere (aikenamps.com for example). The other method involves a negative voltage supply that is applied to the grids of the output tubes. Adjusting this voltage in turn varies the current in the tubes. The term fixed bias and adjustable bias are really the same thing. Fixed simply means there is a fixed negative voltage on the output tube grids. This voltage can be adjustable but, in reality, it is a fixed voltage once it is set. The term fixed comes from amps like Boogie and Peavey, for example, that have a fixed resistor (instead of an adjustable resistor), to set the bias. To adjust the bias in those amps requires replacing that resistor. See...I told it was silly.

Thanks Bruce, that is essentially what I told this guy and mentioned Mesa/Peavey etc.