Bias Probes

  • Thread starter Thread starter skoora
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skoora

skoora

Well-known member
Anything out there like the Eurotubes Pro one that shows plate voltage and current but in a dual setup so you can read two tubes at a time? I know I could buy two pro ones but hoping there was an all in one scenario. Also the fact you can play the amp while the Pro one is in place is a plus.
 
I haven’t seen one, but would be a nice option for people not wanting to poke inside the amp.
You can always check your PV by measuring pin 3 on your output tube socket with a multi meter.
 
I made my own.

I made a tool that lets you use any multimeter you want and you select the tube you want to measure while the amp is on up to 4 different tubes. You plug in the octal probes and it accepts up to 4 so it saves space. Mine only do mV readings that are equal to mA for each tube. Nothing like it existed so I made my own.

If there’s demand I can look into making something for others but it’s not going to be cheap as I do mean every bit of it is hand made, time consuming, and no bulk discounts exist. All 4 probes hand built and universal selector box in all its not worth it for less than $300.

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glpg80 said:
I made my own.

I made a tool that lets you use any multimeter you want and you select the tube you want to measure while the amp is on up to 4 different tubes. You plug in the octal probes and it accepts up to 4 so it saves space. Mine only do mV readings that are equal to mA for each tube. Nothing like it existed so I made my own.

If there’s demand I can look into making something for others but it’s not going to be cheap as I do mean every bit of it is hand made, time consuming, and no bulk discounts exist. All 4 probes hand built and universal selector box in all its not worth it for less than $300.

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Very cool! That's like a 'supercharger' version of mine; I got it on eBay long ago. Just 1 tube adapter though, and the end plugs into the multimeter and I set it to ma/mv. Works great. More labor intense than yours though!
 
I looked for something like this awhile back .... I ended up with a pro 1 plus their regular one that just pop into a Multimeter ....
 
CEG85 said:
I haven’t seen one, but would be a nice option for people not wanting to poke inside the amp.
You can always check your PV by measuring pin 3 on your output tube socket with a multi meter.
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Yeah, I’m trying to not bother removing the chassis if I don’t have to. Don’t mind poking around in an amp but I’ve got current weight restrictions on lifting that an amp head gets real close to. Plus the nature of how we’re usually extended as we pull it from the head shell makes it worse. I think I’ll go Griff’s way as I have a basic Eurotube socket lead already.
 
MadAsAHatter said:
Weber used to make one that could read voltage and current on 4 tubes, but it's been out of production for a while. Maybe you could find one used.

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This is what I'm looking for. Seems like common sense to be able to read mA and plate voltage on four sockets at once, but it's not, apparently.
 
Soundstorm said:
This is what I'm looking for. Seems like common sense to be able to read mA and plate voltage on four sockets at once, but it's not, apparently.
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I know how to design the probes to do both, the problem is there isn’t enough safe space within the sockets to do so safely. You don’t want plate voltage shorting out another pin of the tube by accident or due to wear and tear. It’s safer to flip the chassis upside down and measure pin 3 and write the plate voltage down and the wall voltage you measured it at.
 
glpg80 said:
I know how to design the probes to do both, the problem is there isn’t enough safe space within the sockets to do so safely. You don’t want plate voltage shorting out another pin of the tube by accident or due to wear and tear. It’s safer to flip the chassis upside down and measure pin 3 and write the plate voltage down and the wall voltage you measured it at.
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So if all my amps are on a tightly regulated 120V, then should I still need to read my plate voltage every time after the initial reading?
 
Soundstorm said:
So if all my amps are on a tightly regulated 120V, then should I still need to read my plate voltage every time after the initial reading?
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your plate voltage will shift a bit after the amp warms up ..... as well your bias ....

you can take a initial measurement ..... then bias .... then let the amp warm up for 15 minutes or so .... then repeat ......and that's pretty much it .. unless there's a problem .

Eddie will show you the way ...
 
Soundstorm said:
So if all my amps are on a tightly regulated 120V, then should I still need to read my plate voltage every time after the initial reading?
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Bias will cause plate voltage to change and so will wall voltage - especially on a circuit breaker with people turning things on and off while you’re biasing.

As said you need to let your amp warm up to full operating temperature. I like to monitor and adjust the bias of tubes over a 30-45 minute period that have no burn in period at all. I don’t touch the bias pot until it’s been on after 15 minutes.

I clip a probe on the screen voltage tab when the amp is off and monitor that across the amp as a whole. Much safer than using a janky probe that can fail and short to a tube pin unsafely when the amp is on.
 
FLUXX said:
Tube Amp Doctor BiasMaster.
I love mine

https://www.tubeampdoctor.com/en/biasmaster-system

https://www.amazon.com/Bias-Master-TAD-Octal-Probes/dp/B01MSZZ10L
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I have one of these - I do wish it would provide plate voltage. But, if you have a single probe device that measures plate voltage, the Bias Master is such a great way to check how close allegedly ‘matched’ pairs and quads really are.
If any forum members are within driving range of KC, I would gladly hand mine over for the weekend to use!
 
I like using a multi meter. All of my amps have internal bias pots anyway, so I use the transformer shunt method. I do own a Weber bias rite though.
 
psychodave said:
I like using a multi meter. All of my amps have internal bias pots anyway, so I use the transformer shunt method. I do own a Weber bias rite though.
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I’m in the market for a bias rite if you’re ever looking to sell it
 
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