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Except that when you alter the bias like that, the HT will no longer be 460V, so your maths will be out a little. You're broadly right though, and in the case of the DSL the difference will be negligible, or at least safe.
That's not true in every case though, so it does need pointing out.
Which is why I'd always take an amp to a tech. It's probably simple enough, and I'm quite handy when it comes to learning stuff, but I just don't fancy it. Even if the amp had an external bias pot and stuff, as some do, I wouldn't use it.
I'm a scaredy cat.
"Take these three items, some WD-40, a vise grip, and a roll of duct tape. Any man worth his salt can fix almost any problem with this stuff alone." - Walt Kowalski
"Only two things are infinite - the universe, and human stupidity. And I'm not sure about the universe." - Albert Einstein
"Take these three items, some WD-40, a vise grip, and a roll of duct tape. Any man worth his salt can fix almost any problem with this stuff alone." - Walt Kowalski
"Only two things are infinite - the universe, and human stupidity. And I'm not sure about the universe." - Albert Einstein
That's me.
"Take these three items, some WD-40, a vise grip, and a roll of duct tape. Any man worth his salt can fix almost any problem with this stuff alone." - Walt Kowalski
"Only two things are infinite - the universe, and human stupidity. And I'm not sure about the universe." - Albert Einstein
Great (or even much at all! ) precision is pointless IMO for guitar amps because...
1) There is no need to bias "hot". 25mA per 25W pentode seems to work ok. If of course you insist on running the valves at 90% of their Pa limit, you might have a problem.
2) 5 minutes (or 5 secs!) after your oh so precise setting the mains will shift up or down. Now bias SHOULD track mains V, a bit and it does but not perfectly.
3) Immediately after a good full power thrash, bias with be all over the shop and is unlikely to return to within 5% of original setting.
4) If biasing after fitting new valves (main raison detre!) the grid current of those valves will slowly decrease by up to 400% over an hour or two and once again, bias setting will wander.
Dave.
"Take these three items, some WD-40, a vise grip, and a roll of duct tape. Any man worth his salt can fix almost any problem with this stuff alone." - Walt Kowalski
"Only two things are infinite - the universe, and human stupidity. And I'm not sure about the universe." - Albert Einstein
"Take these three items, some WD-40, a vise grip, and a roll of duct tape. Any man worth his salt can fix almost any problem with this stuff alone." - Walt Kowalski
"Only two things are infinite - the universe, and human stupidity. And I'm not sure about the universe." - Albert Einstein
"Take these three items, some WD-40, a vise grip, and a roll of duct tape. Any man worth his salt can fix almost any problem with this stuff alone." - Walt Kowalski
"Only two things are infinite - the universe, and human stupidity. And I'm not sure about the universe." - Albert Einstein
I agree with ICBM. We are in danger of losing the plot here. But!
Talk of volts, amps and Rs takes me back to first year at tech'! Voltage was also known as "Electro Motive Force and it was the paradox of measurement that you could not have a current without an EMF* to "push" it and you could not have an EMF without a current to cause a voltage drop!
Back in that day, much cleverness was needed to avoid loading effects from screwing voltage measurements, no such thing as "infinite" impedance DVMs (for the equivalent of 20 fags and a pint today!)
*Then came Superconductors of course!
Dave.