From the website:
Black Diamond Series Vacuum Tubes
TELEFUNKEN vacuum tubes have been the benchmark of
excellence in all audio applications, both production and
reproduction, for many decades. This rich history continues
with the introduction of new production tubes from
TELEFUNKEN Elektroakustik, in partnership with JJ Tubes from
the Carpathian Mountains of Cadca in Slovakia.
Each tube is meticulously measured for all critical
parameters of performance including transconductance, gain,
noise, and microphonics. All TELEFUNKEN branded tubes are
hand picked to be the best examples of Eastern European
construction in the proud tradition with which the name
TELEFUNKEN Elektroakustik has become synonymous.
In addition to the rigorous testing procedure, all new
production TELEFUNKEN tubes are cryogenically treated to
ensure durability, and subjected to an extended burn-in
period to ensure superior stability. The tubes are re-
measured subsequent to burn-in in order to guarantee that
only the best, lowest noise tubes are offered for purchase
through your TELEFUNKEN Elektroakustik reseller.
What is the difference between Black Diamond Series vacuum
tubes and the JJ-branded tubes?
The TELEFUNKEN Black Diamond Series tubes are built in the
JJ Electronic Factory in Eastern Europe based on their
existing models. The Black Diamond Series tubes go through
an extensive multi-tier testing and quality control process,
as well as a cryogenic treatment in the USA to ensure they
are the best representation of European made tubes. Each
vacuum tube is burned in for 24 hours, tested for all
critical parameters, cryogenically treated, and tested a
final time. TELEFUNKEN Elektroakustik guarantees this by
branding them with the legendary diamond logo.
What is the cryogenic treatment process?
After the initial 24-hour burn-in process, the Black Diamond
Series tubes are placed into a cryogenic processor where a
computerized system gradually cools them from ambient
temperature to -300 �F (-184 �C), where it
remains for 24
hours until slowly returning to room temperature.
What sonic differences will you notice with cryogenically
treated vacuum tubes?
The cryogenic process is done for a number of benefits, both
sonically and constructional. Cryogenically treated vacuum
tubes have a lowered noise floor, less microphonics,
expanded dynamic range with more tonal depth, and a more
consistent tone for a longer lifespan. In guitar amps, Black
Diamond Series vacuum tubes have more harmonic content and
improved saturation, which results in a richer tonal quality
and deeper overdrive character.
What effect does the cryogenic process have on improving the
construction of Black Diamond Series tubes?
The cryogenic freeze process plays a key role in treating
and strengthening the tube's internal metal construction. By
bringing the tubes to these extremely low temperature
conditions, the stresses of the internal metal structure
from the high temperature manufacturing process are reduced
and settled. This strengthens the construction as a whole.
The cryogenic process also aligns the grain structure of the
carbon in the metal to be more uniform, which yields a more
efficient system with lower operating temperatures, longer
life, and improved electron flow. The results are tubes with
superior durability and stability. Preamp tubes offer
expanded dynamics and a richer tone, while the power tubes
are more stable and efficient.
What are the benefits of burning in vacuum tubes?
All Black Diamond Series vacuum tubes are burned in for a
24-hour period at real world voltages. One of the major
benefits of burning in is to heat the cathode and remove any
impurities or unevenness on the cathode coating. The cathode
is the element in the tube that is heated and releases
electrons. By burning the tube in, it reduces any popping,
static sounds and erratic behavior. This is proven to
benefit the vacuum tube's lifespan and durability.
What is the significance of the black ink on the new Black
Diamond Series tubes?
TELEFUNKEN's Black Diamond Series tubes have been screen
printed with black ink to clearly differentiate them from
the original, white inked diamond-based TELEFUNKEN tubes,
originally produced in Germany in the early and mid 20th
Can these Black Diamond Series tubes be used in TELEFUNKEN
Black Diamond Series tubes have been developed for the
Musical Instrument and Hi-Fi Audio markets and are excellent
for use in applications like guitar amps, preamplifiers and
power amplifiers. None of these tubes are currently used in
TELEFUNKEN Elektroakustik microphone production.