example Bias-probe readings from your Hot Rod DeVille?

[StompBoxBlues]

Could anyone share with me their readings, if they use Bias Probe (or actually, even not...) on the power tubes in the Hot Rod DeVille?

Bias probe gives plate voltage, current, and calculated watts.
I'm reading around 10w on mine (20 watt amp? out of a DeVille?)

What am I missing here?

[Trout]

Could anyone share with me their readings, if they use Bias Probe (or actually, even not...) on the power tubes in the Hot Rod DeVille?

Bias probe gives plate voltage, current, and calculated watts.
I'm reading around 10w on mine (20 watt amp? out of a DeVille?)

What am I missing here?

10W each tube?

[StompBoxBlues]

10W each tube?

Yes! when I had it set to factory spec (using their test point, read the voltage and set it to what was recommended in the schematic) it was reading just about 11 watts per tube.

Something I am just missing. I have to doublecheck what the readings were (the watts are calculated) but the plate voltage I think was around 475, then and current I think like 23mA or something...

I keep thinking I'm missing something very basic...

[Dave C]

I think what you're missing is that you have to bias your tubes in your amp and it's not a set point on a schematic...it's more a range of acceptable bias which is generally stated to be 50%-70% of maximum plate disipation. A 6L6GC has a max disipation of 30w so anywhere between 15w-21w would be in range

Your stated values would indicate that your bias is definitely on the cool side at approx 37% disipation. I would shoot for 60% with current in the mid 30's or so, but anywhere in the 50-70% range would be acceptable...it's what sounds best to you within the range. Good luck...I hope this helps.

[StompBoxBlues]

I think what you're missing is that you have to bias your tubes in your amp and it's not a set point on a schematic...it's more a range of acceptable bias which is generally stated to be 50%-70% of maximum plate disipation. A 6L6GC has a max disipation of 30w so anywhere between 15w-21w would be in range

Your stated values would indicate that your bias is definitely on the cool side at approx 37% disipation. I would shoot for 60% with current in the mid 30's or so, but anywhere in the 50-70% range would be acceptable...it's what sounds best to you within the range. Good luck...I hope this helps.

Yes, helps. I know that about it isn't a point on a schematic, but I figure it is an okay starting point using the recommended setting.

I guess the thing I was getting hung up on is... this is embarrasing, but I was thinking the De Ville is a 60 watt amp, but it has nothing to do with the tubes wattage, I wasn't thinking that it has more to do with the output after the OT, right? (and it's rms to boot...what I'm reading are static voltage, and current with no input signal)...

That's kind of what I was getting at.

I did some mods from a modder, pretty extensive, and at the higher wattage it didn't sound as good to me as it once did...I lowered it and it started sounding more....stabile, if you know what I mean.

Anyway I hadn't thought much about amp wattage, RMS, vs. tube wattage with no input, bias is setting the operating bias, so when a signal comes in I expect the voltage and current will be inversely fluctuating, but the wattage will remain fairly constant? But then the signal goes through the OT and that's where the pedal hits the metal?

[StompBoxBlues]

I appreciate the info...just to bump for more, I was still wanting to verify how they are set from factory generally,
and the relationship between tubes and amp watts rating? They aren't the same or calculated differently?

an amp, no signal, running each tube at even 15 watts is just half what the amp is rates (60W rms), but how does the ouput transformer affect rating? etc.?

[Dave C]

Some manufacturers intentionally bias on the cool side to promote longer tube life, but mostly to reduce warranty service. This can vary from different builders and even models from the same builder.

Amp biasing is setting the idle or start point with no signal. Introduce a signal and current flow increases producing more wattage. Hook up your bias probe, plug in your guitar and hit a few chords with the volume turned up and you should see a dramatic increase in current...probably double your bias point or more.

Many things affect an amps output... class of operation, transformer efficiency, circuit design, quality of components, operating voltages...etc.Two amps using the same tubes can have different output ratings trying to satisfy tonal requirements, a model niche or price point.

[StompBoxBlues]

Thanks, that was what I was thinking...the idle is...idle, not RMS of the amps wattage when actually doing work.

[rockon1]

I'd try them at around 32- 35 ma and see how its sounds. Thats about 50-55% idle dissapation. Bob