R
TAD Bias Master BM4
This model comes with 4 octal probes, but I ordered 2 noval probes as well so that I can set up EL84's as well as 6V6's and 6L6's etc.
WARNING! - There are no instructions! - If you don't know what you are doing, don't try to use this unless you have a friendly tech to show you. You can download them from the TAD site, only 2 sides of A4 folded into a leaflet. Very basic instructions.
The probes each contain a 1 ohm resistor in the cathode lead, so they are measuring total cathode current (anode + screen grid). Circuit schematic diagrams usually state a bias Voltage (e.g. -37Volts) rather than current. This is a good starting point, but then you need to find the valve manufacturer's specifications from their data sheets. Then you can balance up each side of the push-pull stage.
The readout on the unit is 00.0 mA to presumably 99.9 mA.
A "Chicken head" pointer knob selects each of the 4 individual valves, or the OFF position.
It's really simple and easy to use (as another reviewer has said) and you don't have any high voltage connections to make through a test meter. The real skill is knowing just where to set the current level, which is of course different for each and every valve type and can be slightly tweaked for your preferred sound.
WARNING! - There are no instructions! - If you don't know what you are doing, don't try to use this unless you have a friendly tech to show you. You can download them from the TAD site, only 2 sides of A4 folded into a leaflet. Very basic instructions.
The probes each contain a 1 ohm resistor in the cathode lead, so they are measuring total cathode current (anode + screen grid). Circuit schematic diagrams usually state a bias Voltage (e.g. -37Volts) rather than current. This is a good starting point, but then you need to find the valve manufacturer's specifications from their data sheets. Then you can balance up each side of the push-pull stage.
The readout on the unit is 00.0 mA to presumably 99.9 mA.
A "Chicken head" pointer knob selects each of the 4 individual valves, or the OFF position.
It's really simple and easy to use (as another reviewer has said) and you don't have any high voltage connections to make through a test meter. The real skill is knowing just where to set the current level, which is of course different for each and every valve type and can be slightly tweaked for your preferred sound.
6
0
Report
TS
Very handy
This is a great thing to have around if you use tube amps. Gives a clear mA readout of each tube. The probes are in pairs and have white and red RCA connectors in the other end. I only wish that they had marked the probes so you would know which is which. I've done this myself of course, but I think it should have been like that out of the box.
1
0
Report
K
Quality piece
Good quality instrument that makes biasing a breeze
0
0
Report
A
Must have tool for anyone who uses a tube amp that has adjustable fixed biased power tubes. I use these mainly to keep the bias within general tube specifications while biasing by ear. Keep in mind that these do not give any voltage reading, only milliAmps), so it's impossible to know how hard you are pushing the tubes exactly. But good enough to give you an accurate estimate if you're in a good operational window.
Keep in mind that your safety has to be priority when opening up high voltage amplifies. There are lethal voltages that could kill when not knowing what you are doing.
Keep in mind that your safety has to be priority when opening up high voltage amplifies. There are lethal voltages that could kill when not knowing what you are doing.
0
0
Report
G
Great product!
Perfect if you change tubes by yourself and don't want to spend money on a amp tech to set the bias. Very easy to use.
0
0
Report