Seeking Bias Checker Input

[RoadShow]

Hi folks,

I wanted to get a couple of bias checkers for my factory amps such as my TRRI.  Anything i've built has the 1 ohm set up.

Here are the ones I know of:
https://el34world.com/charts/BiasChecker3.htm Hoffman checker
https://mojotone.com/products/mojotone-bias-checker-kit-by-hoffman-amps?variant=41689714360416 The Hoffman checker
https://rubytubes.com/products/ruby-bias-probe?_pos=1&_sid=1a47b5cf6&_ss=r Ruby Tubes
https://grangeramp.com/product/bias-probe-current-measuring/ Granger
https://www.tubedepot.com/products/tubedepot-bias-scout-kit Tube Depot
and a wide variety on Amazon, of course.

Any others you know of or would recommend?
Anything you like or don't like about any of these or other?

Right now I'm leaning towards the Tube Depot because it also allows you to read the plate voltage.
Here's a Youtube vid where he has added a black switch box to select between the cathode and plate readings:
https://www.youtube.com/watch?v=A-VtdXYgceA
I think this is a nice feature to add in.

Thanks...

[Merlin]

Personally I would not condone a bias probe that requires a separate ammeter, it is a recipe for mistakes. Ideally all those bias probes would include a 1 ohm resistor so that a separate voltmeter can be used instead, but nobody seems to make them that way. Apart from that, I guess the Tube Depot one is the more useful option. The TAD and Eurotubes bias probes avoid mistakes by having their own dedicated meters.

[RoadShow]

Personally I would not condone a bias probe that requires a separate ammeter, it is a recipe for mistakes. Ideally all those bias probes would include a 1 ohm resistor so that a separate voltmeter can be used instead, but nobody seems to make them that way. Apart from that, I guess the Tube Depot one is the more useful option. The TAD and Eurotubes bias probes avoid mistakes by having their own dedicated meters.

Thanks for the reply.
This is the Tube Depot schematic and uses the 1 ohm resistor and HV conversion that has been discussed in the past and relies on reading mV and not as an ammeter.

[stratomaster]

Why 2W and 5% when checking idle current?

A 1/4W at 1% or better is smaller, more than enough power handling, and much more accurate.

Why spec 1% resistors for plate voltage, but not cathode current?

Odd choice.

[RoadShow]

Why 2W and 5% when checking idle current?

A 1/4W at 1% or better is smaller, more than enough power handling, and much more accurate.

Why spec 1% resistors for plate voltage, but not cathode current?

Odd choice.

Yeah,
I don't know.
I can't explain my wife or kids, how am I able to explain that?

[BrianS]

As a busy repair tech, I use the TAD Biasmaster.  Works very well; keeps the bench tidy and my Fluke free to measure voltages throughout the amp.  Might be overkill if all you are doing is checking & setting bias on your personal amps, but is a nice tool.

[AlNewman]

Why 2W and 5% when checking idle current?

A 1/4W at 1% or better is smaller, more than enough power handling, and much more accurate.

Why spec 1% resistors for plate voltage, but not cathode current?

Odd choice.

Probably to make the meter bulletproof.  They're in the business of protecting their meter, not necessarily the tube or the amp.

[RoadShow]

As a busy repair tech, I use the TAD Biasmaster.  Works very well; keeps the bench tidy and my Fluke free to measure voltages throughout the amp.  Might be overkill if all you are doing is checking & setting bias on your personal amps, but is a nice tool.

The nice thing about that Bias Master is you can basically do a sweep of all 4 tubes with the rotary switch.  Nice.
I just looked, Amplified Parts carries it in the USA, but they're OOS.

[HotBluePlates]

I use the Eurotubes Pro One.  Yes, they are expensive, but you're basically buying a couple of meters at the same time.

I initially got the standard version, then later bought the watts-version when getting some for EL84s.

I have checked them, and they measure Plate Volts and Plate Current at the plate pin, not cathode current.  I like not having to account for screen current (even if that is typically an error in a safe direction).

[pdf64]

It horrifies me how it seems all  vendors selling anode voltage / current probe devices are comfortable providing unshrouded plugs for the meter.
I acknowledge that shrouded plugs add maybe a £/$/€ or 2 to the parts cost, but these things are often marketed to regular valve amp users, not necessarily technically cognisant of how to mitigate the shock hazard (which to me necessitates the use of shrouded plugs anyway).