Needful Things

Kit of a bias probe for indirect measurement of the quiescent bias current of a tube. The adapter is placed between the tube and the socket and is connected to a standard voltmeter (not included). Pay attention to the quality of the meter and to sufficiently charged batteries!

The quiescent current is measured indirectly via a precision resistor built into the adapter. The advantages of this measuring method are harmless voltages in the mV range at the measuring plugs as well as short ways for the current, since it does not have to be led through the measuring device (common practice with many measuring adapters of Far Eastern production). As a result, there is no risk of oscillation of the amplifier, which could damage the tubes or the amplifier itself.

Note: This adapter cannot be used when additional tube brackets are installed. These must be removed before using the measurement adapter and reattached after the measurement is complete.

Measurement procedure
Determine the resistance of the adapter, including the test leads. Connect the adapter to the meter, but do not connect it between the tubes and the amplifier. Select the ohms range on the meter and note the reading, e.g. 1.1 ohms.
For the final measurement, insert the adapter between the tube and the de-energized amplifier, connect it to the meter, select the mV range and switch on the amplifier. When the amplifier has reached a stable operating condition, read the value in mV from the meter and calculate the quiescent current using Ohm's law.

Example
Measured voltage = 47 mV, adapter resistance = 1.1 ohms.
Formula (I = V / R) or in this case
Bias Current (in A) = Measured Value (Voltage in V) / Measured Value (Resistance in Ohm)
0.047V / 1.1 Ohm = 0.042A or 42mA

For the calculation of the correct bias current as well as further information on bias measurement please refer to further documents or the bias setting instructions in the info section as well as the manual of the amplifier itself.
This adapter is suitable for all EL34, 6L6, 6550, KT88, 6V6, 6CA7 and other tubes with the same pinout.

Attention HIGH VOLTAGE ! Measurements and work on tube amplifiers should only be done by qualified personnel.

Files:

• Datasheet

Double Relay Switcher for channel switching and similar applications.

The kits comes with all components incl. 6 V Finder relaise but without switches for the front panel.
Works with 6,3 V heater voltage.

Files:

• Datasheet

• Operating voltage: 8 - 16 V/DC
• Current consumption: max. 800 mA
• Input sensitivity: < 80 mV
• Loudspeaker connection:    4 - 16 ohm
• Music power: max. 12 W with 16 V at a 4-ohm loudspeaker
• Frequency response: approx. 40 - 20.000 Hz
• Dimensions: approx. 70 x 36 x 23 mm (without fixing straps)

• Operating voltage: 4.5 - 12 V/DC
• Output: max. 3.5 W music power
• Loudspeaker connection: 4 - 16 ohm
• Input sensitivity: < 80 mV
• Frequency response: approx. 40 - 20.000 Hz
• Dimensions: approx. 40 x 40 x 12 mm (without fastening straps)

• Musical power: max. 40 W at 4 Ohm loudspeaker load in case of an operating voltage of 16 V
• Operating voltage: 6 - 16 V
• Connectable loudspeakers: 4 - 8 Ohm
• Sensitivity: < 500 mV
• Frequency range    approx.: 20 - 25.000 Hz
• Dimensions: approx. 70 x 45 x 29 mm (with cooling angle)

• Datasheet

• Tube-Town kit for DC Heater, for schematic check product pictures
• Size PCB: 74,5 mm x 34,3 mm
• The kit includes all parts needed for the complete build

Files

• Board dimensions

• Operating voltage: approx. 9 - 24 V/DC
• Frequency range    approx.: 20 - 20.000 Hz ±3 dB
• Input voltage    approx.: 2 - 50 mV
• Output voltage    approx.: 0,2 - 5 V
• Input impedance    approx.: 50 kΩ
• Output impedance: approx. <1 kΩ
• Amplification: approx. 40 dB (100 x) ±10%
• Distortion: <0,02%
• Current consumption: <5 mA
• Dimensions: approx. 30 x 25 x 15 mm (without fastening strap)