Q: How is the Wideband Unity Balanced Amplifier (WUBA) being used in this line amplifier VL10 different from the conventional design?
A: A fully balanced amplifier will cancel out the noises and distortions picked up by the audio cables caused by electromagnetic interferences. The WUBA is a patent pending design that allows a vacuum tube amplifier to be operated in a fully balanced condition, from the input to the output in only a single stage. The WUBA is a single gain stage wideband balanced differential amplifier design that contains no load resistors, no buffers, no followers and no global negative feedback. Hence, the purity of the musical signals can be faithfully preserved.

Q: Is the line amplifier VL10 phase non-inverting?
A: Yes. The output signals are in phase with respect to the input signals at the XLR receptacle. The pin configuration of the XLR receptacle is given as follows: pin-1 is ground; pin-2 is +VE and pin-3 is –VE signals.

Q: What is the break-in time for a new VL10?
A: The VL10 has been gone through a mild break-in at the factory. When you power it up the first time, it should sound reasonably well. But it may take about 50 to 100 hours before it completely breaks in. However, it is not advised to turn on the amplifier continuously all day. It is recommended to turn it off for one hour after it is operated for 3 to 4 hours.

Q: Do I need to bias the tubes of the VL10?
A: Unlike most power amplifiers, line amplifiers such as VL10 do not require to manually bias the tubes.

Q: Can I substitute a tube in VL10 by a same type but different brand?
A: It is recommended that you only use the same tube purchased from JE AUDIO. Because three 6H30 tubes on each channel are connected in a direct coupled fashion to form the WUBA structure so as to minimize phase shift and to enhance low frequency performance. The first 6H30 is a critical tube in setting up the right operating voltages for the second and third 6H30 tubes. JE AUDIO only selects the best 6H30 tubes after over at least 50 hours of burn-in and extensive testing in search of good balancing.

Q: Can I swap the tubes within the line amplifier VL10?
A: It is not recommended to swap any 6H30. The three 6H30s in each channel have been tested so that they work best in the current positions in terms of noise level and operating voltages.

Q: Can I place the VL10 inside a Hi-fi cabinet?
A: It is recommended not to place the VL10 inside a Hi-fi cabinet. Otherwise, it will cause the temperature of the VL10 getting too high. This will shorten the life of VL10. If the VL10 must be placed inside a Hi-fi cabinet, measures should be taken to ensure the ventilation openings of the VL10 are not obstructed and the distance between the VL10 and enclosure is at least greater than 80mm. The cabinet doors should be opened. And the lid of the vacuum tubes compartment must be removed.

Q: Can I remove the lid of the vacuum tubes compartment all time?
A: Removing the vacuum tube compartment lid can improve heat ventilation. However, cautions should be taken to ensure no objects falling into the compartment and the safety instructions given in this manual are strictly followed.