Congratulations on the purchase of your new TAB Funkenwerk V78M!
This unit is a single channel, tube driven mic-preamplifier constructed to
handle signals as low as ribbon microphones all the way to the hot line
level signals used for mastering your final recording. Based on the
circuit design of the historic V72s tube mic-preamplifier, the V78M uses
transformers that we manufacture to the specs of the originals. The
unique aspect of the V78M is the split sensitivity and gain control that enables the flexibility to deal with
the most challenging recording problems while providing the head room and sound character to make a 57
sound like a 47! The V78M is an enclosed plug and play unit in a 19” one rack space enclosure.
Overview
1. Make sure the V78M power switch on the front panel is down.
2. Turn the Input Sensitivity knob (on the left) up to the right to 0 dB.
3. Turn the Make Up-Gain knob (on the right) down to the left to
22vdB. (The unit is shipped at these settings)
4. Flip the three switches between the knobs (Low Cut, +48V, and
Polarity Reverse) to their down positions.
5. Plug the AC cable into the back and then into a working AC outlet.
6. Plug a microphone cable into the XLR Output jack on the back (center of panel) and plug the other
end into the mixing console, snake channel or recording unit.
7. Plug another microphone cable into the XLR Input jack on the back (right side of panel) and plug the
other end into your microphone or microphone power supply unit.
8. Flip the power switch to the upright position. The light above the switch should light up.
9. Warning! Always allow any unit with vacuum tubes to warm up for at least 5 minutes before running
signal through it. This will help the unit perform optimally and extend the life of your tubes.
10. Start experimenting!
Getting Started
This preamplifier utilizes a split control system featuring an Input
Sensitivity adjustment knob coupled with a Make-Up Gain knob. This
allows the user to set the system up in either the historic V72s setting
(-60/40) or overdrive the input transformer to add tube harmonics to
create your own sounds. The Input Sensitivity knob allows the user to
switch between -60 to +6 dB in six positions (-60 / -40 / -20 / -10 / 0 /
+6dB) depending on the type of microphone or buss level being input to the V78M. The Make-Up Gain
knob allows the user to switch between 22 to 60 dB by 3dB increments over 12 steps, with the last three
settings increasing by 6, 4 and 4 dB respectively (22 / 25 / 28 / 31 / 34 / 37 / 40 / 43 / 46 / 52 / 56 / 60).
Amplification and noise floor are rated at an optimum, therefore with wide range, the influence of the
amplifier on the signal-to-noise ratio (dependent on the input signal itself) remains far below 1 dB. The
noise level component of the input tube is unimportant and generally does not require selected tubes.
When the tubes are in need of replacement you should use NOS tubes of Western manufacturing origin.
The input stage uses an EF86 type tube (6267, EF806, E80F. or EF86). The output stage, having rela-
tively small gain, is provided with a strong low impedance EF844 type tube (6BX6, EF80, EF800, EF860,
EF844s) to drive any kind of resistive, inductive or capacitive loads.
All of the transformers are custom built and made of high quality NI/FE/CO, resistant against stray fields
and magnetically screened with a multi-layer Mu-Metal shield. Low sensitivity against ring is achieved
by shock mounting the input stage. In spite of the compact mounting of this enclosed unit, the
development of heat remains within permissible limits. The wide open frequency response is designed to
capture the entire acoustic range and resolution of the recorded instrument, and is inter-modulation stable
to meet these requirements.
Mode of Operation
These are suggested settings for input sensitivity vs. clipping with
reference to 20/1K/20K Hz at 0dB gain.
+6dB max input 23dBu (10V): mix buss, two bus, etc.
+0dB max input 17dBu (5V): mix buss, two bus, etc.
-10dB max input 12dBu (3V): high output modern condensers
-20dB max input 6.6dBu (1.643V): classic condensers and their modern replicas
-40dB max input 0dBu (0.775V): standard dynamics, dynamic condensers and modern ribbons
-60 dB max input -8.5dBu (0.2945V) vintage ribbons and low output dynamics
These are suggestions with reference to 0dB or -0.775V. The V78M was designed for sound-forming by
over or under loading the preamplifier input, enabling the V78M to sound like many different mic-pre’s in
one box! The V78M’s input transformer can withstand input levels up to +30dBu without becoming
damaged. All technical specs are given with the Input Sensitivity at –60dB and the Make-up Gain at 40
dB. Not only does this setting replicate the historic V72s specs used during countless classic recordings
but also when changing the input sensitivity over the make-up gain, the frequency and harmonic
distortion specs change as well. Which is precisely why we built the V78M with the split controls...
Suggested
Settings
1. Power Hookup: Provides AC to the unit via standard IEC monitor cable
2. 100 Ω(Ohm) Ground Switch: 100 Ωresistive buffer switch in between the
audio and chassis ground
3. XLR Output: Standard XLR connector with 600 Ω(relative) output
impendence, Pin 2 Hot
4. TRS Output: Hooked up to XLR Output in parallel, Tip Hot
5. TRS Input: Hooked up to XLR Input in parallel, Tip Hot
6. XLR Input: Standard XLR connector with adjustable input impedance, Pin 2 Hot
7. Input Sensitivity Switch: Six position rotary switch that sets the input sensitivity/impedance
8. Low Cut Switch: Switchable 120Hz high pass filter with 6dB per octave
9. +48V Switch: Activates the built-in microphone voltage supply with a 5 second ramped timing circuit
10. Polarity Reverse Switch: Reverses the output 180 degrees via relay
11. Makeup Gain Switch: Twelve position rotary switch that sets the output gain
12. Power Switch: Energizes the unit with either 115V/50Hz or 230V/60Hz, switchable by qualified technician
Unit Layout
2. 100 ΩGround1. Power Cable Socket 3. XLR Output 4. TRS Output 5.TRS Input 6. XLR Input
12. Power Switch10. Polarity Reverse Switch9. +48V Phantom Power8. Low Cut7. Input Sensitivity 11. Make-up Gain
