Which bias probe do you like?

[BABMusic]

I know I would get shocked if I had to connect something inside the amp guts, so I stick to the Eurotubes expensive probe.

 

[errrrrl]

I use the Weber Bias Rite. All four tubes at one time and plate voltage

Yup, thats what I got too...

 

[FourT6and2]

The Eurotubes Pro One. Yes, it only measures one tube at a time. But the benefit of this device over the others is that it measures current from inside the tube itself. You are seeing the actual plate current and NOT the plate current calculated by using Ohm's Law to measure voltage across a 1-ohm resistor. This means 1) it's more accurate because you eliminate variance and tolerance of a resistor and 2) you eliminate the error due to the current drop across the screen resistor.

It's worth the price. I have four of them just to make biasing faster/easier.

And no, you don't need the version that displays watts. You can simply use a calculator to determine your desired bias setting.

 

[napalmdeath]

I have (2) Eurotubes Pro Ones. They work great! Only need one most of the time, but the extra comes in handy when there's adjustments for each tube/pairs.

 

[ners]

Another +1 for Eurotubes Pro, though I only have one and use a generic socket probe + meter off Amazon for the second tube.

 

[Findthetone1]

Longtime user of the Weber Bias Rite here as well.

 

[PBGas]

I use one of the Tube Amp Doctor units with 4 sockets. Works great, no issues.

 

[Shreddy Mercury]

The Eurotubes Pro One. Yes, it only measures one tube at a time. But the benefit of this device over the others is that it measures current from inside the tube itself. You are seeing the actual plate current and NOT the plate current calculated by using Ohm's Law to measure voltage across a 1-ohm resistor. This means 1) it's more accurate because you eliminate variance and tolerance of a resistor and 2) you eliminate the error due to the current drop across the screen resistor.

It's worth the price. I have four of them just to make biasing faster/easier.

And no, you don't need the version that displays watts. You can simply use a calculator to determine your desired bias setting.

The manual says "Your Citizen Gain comes from the factory biased for EL34 tubes with an idle current draw of 28ma". So I guess I can get the non-watt display one and set it for 28 and be back to factory spec, easy peasy lemon squeezy.

 

[Rick Lee]

What am I missing here? I have the EuroTubes one. How is paying extra for one that measures all four power tubes any better, when there's still only one bias pot controlling dissipation to all four? I suppose it could show if tubes are mismatched, but nothing you can do about that other than replace or live with it.

 

[PDC]

What am I missing here? I have the EuroTubes one. How is paying extra for one that measures all four power tubes any better, when there's still only one bias pot controlling dissipation to all four? I suppose it could show if tubes are mismatched, but nothing you can do about that other than replace or live with it.

Particularly with 100 watt amps, having 4 sockets does help identify how closely matched the quad is. If you have a decent stash of similar tubes, you can identify which one(s) to swap out for a more closely matched set. But you are 100 % correct that the majority of amps bias the full quad together. And as long as the place you get your tubes from does a good job of matching, it really shouldn't be an issue.

 

[FourT6and2]

What am I missing here? I have the EuroTubes one. How is paying extra for one that measures all four power tubes any better, when there's still only one bias pot controlling dissipation to all four? I suppose it could show if tubes are mismatched, but nothing you can do about that other than replace or live with it.

Particularly with 100 watt amps, having 4 sockets does help identify how closely matched the quad is. If you have a decent stash of similar tubes, you can identify which one(s) to swap out for a more closely matched set. But you are 100 % correct that the majority of amps bias the full quad together. And as long as the place you get your tubes from does a good job of matching, it really shouldn't be an issue.

Right. It helps to know which tube is pulling the most or the least current. If you bias the amp for the coldest tube, the hottest tube might be set too high. You can also move tubes around to balance out each side. So if your tubes are mismatched, you can at least put the highest and lowest together and the other two together and still have a balanced side when you add them together. Time consuming to do with only one probe.

I've purchased "matched" tubes before and one or two might be 10mA higher than the others because instead of a true matched quad, they sent two matched pairs. And you can still use them, but you have to order them a certain way.

It also helps in the case one of your tube sockets is bad or problematic. You might never notice it because you never installed the probe in that socket before.

 

[Alpha Stryke]

If ET probes are anything like their tubes they'll Fuck up your amp.