TL Audio 5052 - Manual (Page 30)

have found the Sovtek brand to offer a good balance of quality and
affordability.
Q: What is the life expectancy of the valves in my TL Audio unit, and how do I
know when the valves need replacing?
A: We would normally estimate around 4 years, but much will depend on the way
the units are used.
Leaving units powered up permanently will certainly reduce the valve life - we
would recommend that the unit is switched off at the end of a session
(although our use of dc heater supplies reduces the fatigue on the valve
heaters). Traditionally, as a valve starts to deteriorate with age, its HF
performance will be affected, so that there is a perceived loss of brightness,
and the sound tends to become "woolly". TL Audio products make extensive
use of localised internal feedback circuitry to ensure that if a valve's
characteristics change with time then the performance of the unit is not
compromised - thus extending the useful life of the valve.
Q: When replacing valves, is any calibration necessary?
A: Small gain changes may occur when replacing valves, and ideally you should
have a technician re-calibrate the unit – this involves checking signal levels at
various test points and adjusting if necessary. However, these gain changes
are often small - so many users simply change valves and carry on as before.
It is advisable to replace all the valves in a unit at the same time, particularly
on stereo units where valves of different brands and ages may cause a
difference in tone between channels.
Q: When I connect the output of my 5052 to the input of my mixer, I get lots of
noise and distortion. Why is this?
A: The most common mistake when connecting up our products is to feed the
balanced XLR line output of the TL Audio unit into the XLR microphone
input of a mixer. Although both mic and line connections often use XLR
sockets, they have different impedances and signal levels. A line level signal
fed into a mic input will cause it to distort very easily, since a line output