FAQ  Page 1

What is TubeSync?

TubeSync is an intelligent auto-bias device for thermionic amplifier output tubes. Tubesync is designed to monitor the cathode current of each tube and adjust the grid bias to maintain the cathode current. Tubesync can be used in single ended and push pull amplifiers, using either pairs or quads, of output tubes.

Why Do I need TubeSync (1) ?  

TubeSync overcomes many of the problems associated with conventional tube amplification. It addresses these problems without changing the fundamental tube amplification process. After TubeSync has been fitted into an amplifier all the biasing is done automatically, without the need of a specialised amplifier technician. This saves both the amplifier manufacturer and the end customer time and money.  Also, tubes do not have to be purchased in matched pairs, as TubeSync takes take care of the biasing. TubeSync will inform the user if a tube goes faulty and can provide and optional output that can be used to turn off the offending tube.  

Why Do I need TubeSync (2) ?  

If you are an amplifier manufacturer, the chances are you will receive amplifier warranty returns due to faulty tubes causing over current and thermal runaway conditions. Such faults can even blow up the amplifier output transformer. TubeSync eliminates these issues, which is of great benefit to both the manufacturer and end user. 

How does TubeSync control the bias? 

As TubeSync is designed to maintain the cathode current for the chosen output tube /valve by varying the bias voltage applied to the grid, and is pre programmed with a nominal bias setting, which is stored in its non-volatile memory. When first switched on the module monitors the cathode current of each valve with the pre programmed bias setting applied. The module then adjusts the bias voltage applied to each valve in turn to give the pre programmed cathode current, the bias voltage setting for each tube is then stored in memory as the new reference value for each tube. The bias process only takes milli-seconds to check and adjust, and then the amplifier is ready for use.

How does TubeSync maintain the bias? 

TubeSync checks, adjusts and maintains the bias during silent periods, when the amplifier has no signals applied. As soon as a signal is applied TubeSync maintains the stored value and monitors the cathode current to ensure that it does not exceed the defined limits of signal current for the tube.

What happens if the signal current is excessive?

TubeSync is pre programmed to average out the peak signal currents, but should the module detect a sustained overload the module can switch off the high tension (HT) supply to the power amplifier to protect the valves, output transformer and power supply transformers from damage. A light emitting diode (LED) is used to indicate any tube, which is suspected of overload.

What happens when the amplifier is in standby?

TubeSync is pre programmed to automatically switch the output tubes to a standby cathode current setting if the amplifier is not in use for a pre programmed time, by increasing the bias to the pre programmed value. This ensures that the output tubes are not left dissipating power for prolonged periods when no signal is present.

How does TubeSync switch out of standby?

In standby mode TubeSync continuously monitors the amplifier for an input signal and as soon as a signal is detected the bias is virtually instantaneously set back to the stored pre programmed value.

What happens if one of the tubes is faulty? 

If one of the output tubes cannot be set to the correct bias current this could be due to low emission not giving enough cathode current or excessive current due to an electrode short circuit or leakage. TubeSync will detect the valve and light a light emitting diode (LED) associated with the tube to indicate a fault and the high tension power supply to the amplifier can be automatically switched off.