changing power amp tubes...
- Thread starter Coltron
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bbking1021
New member
Re: changing power amp tubes...
https://forum.seymourduncan.com/showthread.php?t=99780
Look at the link above to find out one way to bias your amp. You should bias your amp when you change your power tubes to ensure that your not underpowering or overpowering your tubes. If you don't feel comfortable doing it you can take it to an amp tech and they can do it. Especially if you don't know what you are going, because amps create lethal voltages and currents.
https://forum.seymourduncan.com/showthread.php?t=99780
Look at the link above to find out one way to bias your amp. You should bias your amp when you change your power tubes to ensure that your not underpowering or overpowering your tubes. If you don't feel comfortable doing it you can take it to an amp tech and they can do it. Especially if you don't know what you are going, because amps create lethal voltages and currents.
guitarded
New member
TwelveGauge-GT
New member
Re: changing power amp tubes...
'Fixed' bias means that you do have to bias the amp. It's cathode biased amps that don't need to be be biased, "usually".
The "fixed" in fixed bias actually means that the bias needs to be set to a specific spec. Where "cathode" biased actually has a range to the spec.
'Fixed' bias means that you do have to bias the amp. It's cathode biased amps that don't need to be be biased, "usually".
The "fixed" in fixed bias actually means that the bias needs to be set to a specific spec. Where "cathode" biased actually has a range to the spec.
Last edited:
Gearjoneser
Gear Ho
Re: changing power amp tubes...
Just pop some JJ's in there, and I'm sure it'll be fine. If you take off the panel, exposing the circuit board, you can look around and see if there's any mini bias pots on the board.
It's just like setting the idle on a car. You just want the amp to sound strong and punchy. The only thing you don't want to do is turn the bias pot all the way clockwise and possibly turn the tube plates orange. As long as they have a normal glow and the amp sounds good, you're fine.
Just pop some JJ's in there, and I'm sure it'll be fine. If you take off the panel, exposing the circuit board, you can look around and see if there's any mini bias pots on the board.
It's just like setting the idle on a car. You just want the amp to sound strong and punchy. The only thing you don't want to do is turn the bias pot all the way clockwise and possibly turn the tube plates orange. As long as they have a normal glow and the amp sounds good, you're fine.
wixedmords
New member
Re: changing power amp tubes...
I would likely consult one of the tube selling guys to get a colder tube to put in the rack amp. It is a non-adjustable, fixed bias amp, so you won't be able to adjust the bias. If the bias is too hot you would have to change a resistor.
You would approach this one like many Mesa's. You gotta buy a tube that runs in the appropriate bias range.
Fixed bias means it needs to be biased, but this one seems to lack bias adjustability so you would need to buy a tube that would fit within a safe range.
It may come down to actually biasing the amp to make sure the tubes operate in a safe range, and that really means starting with plate voltage.
I would likely consult one of the tube selling guys to get a colder tube to put in the rack amp. It is a non-adjustable, fixed bias amp, so you won't be able to adjust the bias. If the bias is too hot you would have to change a resistor.
You would approach this one like many Mesa's. You gotta buy a tube that runs in the appropriate bias range.
Fixed bias means it needs to be biased, but this one seems to lack bias adjustability so you would need to buy a tube that would fit within a safe range.
It may come down to actually biasing the amp to make sure the tubes operate in a safe range, and that really means starting with plate voltage.
TwelveGauge-GT
New member
Re: changing power amp tubes...
wixedmords, you taught me the ancient arts of biasing.
:bowdown:
Listen to the man, he speaks true words.
wixedmords, you taught me the ancient arts of biasing.
:bowdown:
Listen to the man, he speaks true words.
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