TAD does all TAD Tube
quality control processing in-house under strict control of their technical
staff. Their techs which are also musicians and guitar players, developed and
constructed their custom tube testing systems and aging rigs to run tubes in
real amplifier circuits and operation conditions.
For TAD, real tube
quality control is way more than just a simple test. Before a TAD Tube gets
accepted at all the techs perform extensive sample evaluation testing for
consistency, power test, shock resistance test, soak test (long term operation
at full power) and of course a musical test in known amplifiers to learn about
its sound character in different styles. The main tests are made after a proper
pre-aging to stabilize the cathode emission. While most tube test equipment
does work at 250V as a maximum TAD built their test rig to operate at voltages
of 360 to 600V depending on the tubes being tested. Every TAD Tube is tested by
their qualified staff. Each pentode is inspected and tapped while operating and
listened for noise floor, hum and odd noise.
Finally measured for a
set of parameters and matched by Ia (PC) and Gm (TC). TAD tests batches of 400
to 500 pieces per run to allow tightest tolerances of typically 0.5mA for PC.
All TAD Tubes and boxes get labeled with the PC and TC test results and a
unique serial number to identify every tube they’ve ever tested. TAD techs
permanently verify and monitor selected and matched TAD Tubes by using them
every day in their own amp service department and in the TAD Amp Kits they
assemble. This is the most complete quality control system they can imagine.
All done in-house at
TAD in Germany