Whammerdyne Truth User manual
Whammerdyne
HEAVY INDUSTRIES
The Ultimate 2A3 Single Ended Triode Amplifier
Owners Manual
www.whammerdyne.com
™
www.whammerdyne.com
SAFETY PRECAUTIONS
The chassis should only be opened by a factory-authorized technician. Any internal
modification or parts replacement (except for AC power fuse or tubes) will void the warranty
and expose the user to hazardous voltages.
Unplug the power cord before replacing the AC power fuse or tubes. Replace the AC power
fuse with exact same type and value (2 Amp Slo-blo 5x20 mm Littlefuse®).
This amplifier requires a grounded power outlet to operate safely.
When replacing tubes, use the same type or an exact equivalent (see specifications). If the
wrong type of tube is used, the amplifier will be damaged and the warranty voided. Do not
force tubes into the socket; check to be sure the pin orientation is correct, then use a gentle
rocking motion to insert or remove the tube.
When performing the bias adjustment, DO NOT use a metal screwdriver; use the provided
adjustment tool. If this is missing, a replacement adjustment tool can be ordered from
Mouser Electronics®, Part Number: 652-H-90. To prevent burns, please use the provided
white gloves when making the bias adjustment.
Whammerdyne strongly urges the owner to avoid aftermarket services that "modify", "upgrade",
or "improve" the parts or circuit of this amplifier. This amplifier has a more sophisticated circuit
than most, and may be extensively damaged if parts or circuits are modified.
www.whammerdyne.com
INTRODUCTION
Congratulations on buying the Truth™amplifier, which combines the beautiful tonality of a zero-
feedback, direct-heated 2A3 triode with the speed, presence and immediacy of an ultra-wideband
amplifier (6 Hz to 140 kHz). The Truth™amplifier has a wider bandwidth than any analog source,
and any digital through 196/24. Part of the reason for the extraordinary bandwidth is the complete
absence of coupling capacitors and cathode-bypass capacitors in the Truth™circuit.
All tubes operate in fixed-bias mode, with very low source impedances in the cathode circuit, and
they are connected by the innovative Z-Direct Interface©, which has zero phase shift, does not store
energy, and provides instant recovery from clipping. It’s a difference you can hear and enjoy for the
life of the amplifier. Speaking of life, the Truth™has a precision bias circuit that lets you optimize all of
the tubes for optimum sound and the longest possible life.
Although the Truth™amplifier is ready to plug-and-play, thanks to the extended burn-in and testing
at the factory, there’s an optional bias setting procedure that lets you dial-in the bias to any good
working set of 6DJ8 and 2A3 tubes. Do you have a personal favorite set of 6DJ8’s and 2A3’s? Bring
‘em on! The multifunction bias meter, unlike a TV-type tube tester, measures the tubes in-circuit, at
the actual voltages and currents of the working circuit, so you can be confident all tubes are operating
at the exact optimum parameters.
We’ve poured our dedication, love of music, and decades of engineering talent into this amplifier.
Welcome to the Truth™!
Whammerdyne Team
www.whammerdyne.com
Table Of Contents
Functional Diagram
6DJ8
Bias
Volume
(fine)
Volume
(coarse)
Input
Autoformer
Volume
Control
Meter Switch
B = Left Ch
C = Right Ch
25-turn trimpot
(fine adjust)
2A3 Bias
Meter Switch
A = Left Ch
D = Right Ch
Filament
Regulator
B+
Regulator
8
4
Ground
6DJ8
6922 2A3
Truth 2A3 Amplifier
Z-Direct ©
Interface
Symmetric
Dynamic
Load Ultrawideband
Output
Transformer
© 2015 Whammerdyne Heavy Industries
current
sense
current
sense
(medium
adjust)
(coarse
adjust)
Symmetric
Dynamic
Load
Design Features ............................................................................................................................1
Controls .........................................................................................................................................2
Installation and Setup....................................................................................................................4
Speakers........................................................................................................................................5
Setting the Bias .............................................................................................................................5
Calibration Procedure Left Channel...............................................................................................7
Calibration Procedure Right Channel.............................................................................................8
Bias Drift Over Time.......................................................................................................................9
Typical Measured Specifications .................................................................................................10
Warranty ......................................................................................................................................11
™
www.whammerdyne.com
1
The unique input autotransformer (Level Control) is a constant-power attenuator at all settings,
transforming voltage and current, in the same way the transmission in a car changes RPM’s and
speed.
By contrast, conventional resistive attenuators (Level Control), whether a potentiometer or a
ladder of discrete resistors, cut down on the power of the signal as the volume is lowered. With
a resistive attenuator, the grid of the input tube sees a low source impedance at full volume, 1/2
the rated value at -6 dB, and gradually less as the volume is lowered. From the perspective of the
input tube grid, the source impedance is both high and variable, depending on volume setting.
This changes the bandwidth of the input tube, and in subjective terms, can affect the sense of
dynamics.
The autoformer of the Truth™amplifier presents a low source impedance to the 6DJ8 grid at
full volume, and then goes even lower as the volume is lowered. For example, if the source
component has an output impedance of 100 Ohms, at the -6dB attenuation setting, the grid of
the input tube sees a source impedance of 25 Ohms; and it goes down from there. A 100 K Ohm
resistive attenuator presents a source impedance of 25K Ohms to the grid of the input tube if the
pot is set to - 6dB.
At every volume setting of the Truth™amplifier, the input tube has maximum bandwidth and the
least interaction with the source impedance (and the interconnect cable between the source and
the Truth™amplifier). We’ve done all the hard work of calculating turns ratios, impedances, and
system bandwidth. All you have to do is turn the volume to the level you prefer.
The 2-stage triode circuit uses the Z-Direct Interface®, with all tubes operated in a stable fixed
bias mode. The Z-Direct Interface®, unlike conventional RC-coupling, does not store energy,
and does not “block” when the 2A3 draws grid-current. This provides immediate recovery from
overload, and the impression of a much more powerful amplifier than the steady-state RMS
power rating. The Z-Direct Interface®also presents a low source impedance to the 2A3 grid,
which optimizes slew rate and gives the widest possible bandwidth.
The output of the 6DJ8 and the Z-Direct Interface®benefit from symmetric dynamic loads on
the plus and minus side of the circuit. The dynamic impedance is both high (orders of magnitude
higher than the plate resistance of the 6DJ8) and symmetrical, so the 6DJ8 operates in the most
linear region, with a flat load-line. Driver linearity is an important consideration with an output
tube as linear as the 2A3; there’s not much point in having a super-linear output tube if the driver
has more distortion, is there? That’s where the Z-Direct Interface®and the symmetric dynamic
loads come in; they provide the most linear working environment for the 6DJ8, as well as a stable
operating environment.
Capacitor coloration (a notorious problem in tube amplifiers) is avoided by the Z-Direct
Interface®. Unlike conventional amplifiers, there is no RC-coupling between the input and output
tube. In addition, there are no cathode resistors with capacitor bypasses, which sidesteps the
problem of finding large-value caps that are free of capacitor artifacts. Last but not least, there
is no cap coloration from the power supply; all tubes are powered directly from super low noise
regulators, which isolate AC line noise and AC line variations from the audio circuits.
DESIGN FEATURES
www.whammerdyne.com
2
Controls
www.whammerdyne.com
3
The ultrawide bandwidth output transformers are custom engineered for this amplifier and have
the widest bandwidth of any single-ended output transformer, past or present. Tube amplifiers
have gotten a reputation as “midrange” amplifiers. Not the Truth™! The response extends from the
deep infrasonic at 6 Hz, to the far ultrasonic at 140 kHz. Although it might seem unnecessary, this
additional bandwidth provides flat phase response in the 20 Hz to 20 kHz audio band.
Why single-ended? One of the subtle advantages of single-ended operation is no zero-crossing
region, either in the tubes or the transformer. The zero-crossing region is where most of the
music is, along with reverberation.
This is where both analog and digital electronics have to be most linear; unfortunately, for most
conventional Class AB amplifiers, the zero-crossing region is where pairs of transistors are
switching on and off, and for tube amplifiers, the region where the magnetization in the core of
the output transformer switches direction. The Truth™2A3 amplifier completely sidesteps both
problems by biasing the core of the output transformer with a DC current, and keeping all tubes in
in the most linear Class A region. As a result, harmonic and IM distortion go down in proportion to
signal level, which matches the perception of the human ear.
All key supplies (including B+) are precision regulated, so the operating points of the tubes are
not affected by random line-voltage variations. More importantly, the sonics are not affected by
line-voltage variations or AC line quality. As we all know, the quality of the 60-cycle AC waveform
has gotten worse over the decades, thanks to noise from switching supplies in TV sets and
computers, and the many RF transmitters in modern households. The electrostatic shielded power
transformer of the Truth™ amplifier acts like a filter against these noise sources so they do not
contaminate the delicate audio signal.
We recommend you do NOT use aftermarket power conditioners with the Truth™amplifier. Unlike
“one-size-fits-all” power conditioners, the precision regulators of the Truth™ amplifier are custom-
designed to match the operating parameters of the 6DJ8 input tube and the 2A3 power tube.
Last but not least, there’s a pair of relative-power meters that show the percentage of power out
of each channel. At the start of the red marker, there’s about 1 Watt RMS into 8 Ohms, and 3.5
Watts RMS at full scale. Since the Truth™amplifier is a zero-feedback circuit with inherently soft
clipping, the range between the 1 and 3.5 Watts is fully usable.
The Left and Right audio signals going to the pair of meters are isolated by buffer circuits,
rectified, and loged to match the meter scaling. Like the VU meters of old, but with wider
dynamic range. So no range switching is required.
The Functional Diagram shows the key features of the Truth™amplifier along with the precision
bias settings for the 6DJ8 input tube and the 2A3 output tube. Each channel has its own fully
adjustable set of bias controls, with a custom milliammeter that measures the operating currents
of each 2A3 and each half of the 6DJ8. Although the Truth™ 2A3 amplifier is already pre-adjusted
and matched to its own set of tubes from the factory, you can replicate the factory adjustments.
www.whammerdyne.com
4
INSTALLATION and SETUP
The Truth™amplifier should be on a placed on a hard surface with good air circulation everywhere
around it! Never on a carpet or in an enclosure without air circulation.
When installing the tubes, confirm that the large 2A3 power tubes have the correct orientation in the
socket. The filament pins are the two big pins, and are spaced apart just a bit more than the smaller
grid and plate pins. When you’re sure the filament pins are correctly in the socket, grasp the 2A3 by
the base (not the glass!) and firmly push downward. When removing the 2A3, wait until cool, grasp
the base, with one hand, place your other over the top of the tube. Use a gentle rocking motion while
pulling upward.
The single 6DJ8 input tube has a missing set of pins; use this to index the tube in the socket, which
also has a corresponding open space. Push downward firmly, rocking the tube a little as it goes
inward. When removing the 6DJ8, wait until cool, grasp the tube, and use a gentle rocking motion
while pulling outward.
The Truth™amplifier is shipped with a custom 14 AWG IEC power cord. The plug is hospital-grade and
the output connector is chosen for a consistent low-resistance connection. We do NOT recommend
aftermarket “power conditioners”, which are usually optimized for high-powered transistor amplifiers
with brute-force power supplies. The Truth™ amplifier is the exact opposite: it has moderate power
output, a very sophisticated power supply, and doesn’t need an aftermarket power conditioner.
For interconnects, we recommend Blue Jeans Cable™LC-1 RCA cables. These provide double copper
braid shielding and very low capacitance, which lowers the high frequency drive current requirement
from the source components.
For speaker cables, we recommend the bulk Audioquest®FLX/DB -14/4 speaker cable, which can be
configured in parallel to give 2-11 AWG conductors. Use the same length cable for both L & R speakers.
Like all audio components, you are free to choose whatever power cable, interconnect, or speaker
cable you like. We strongly suggest auditioning them for yourself, in your own system, rather than
relying on magazine or Internet reviews. The “sound” of a power cable, interconnect, or speaker cable
is strongly influenced by the component it is used with. For example, a speaker cable that sounds
wonderful with a 200-Watt transistor amplifier might not sound good at all with a moderate-power
tube amplifier (and vice versa). Trust your ears, not the reviewer.
Once all cables are connected, power up your source components (first), wait a minute or two for
them to stabilize, turn on the Truth™2A3 amplifier, and wait for the current meter backlight color to
turn from red to white (about 4 minutes).
When turning off your system, we recommend turning off the amplifier first, then turning off the
source components. This prevents power-off transients (if any) from the source components
damaging your speakers.
www.whammerdyne.com
5
Speakers
The Whammerdyne team has spent a lot of time listening to many different speakers powered by
the Truth™2A3 amplifier. We strongly recommend speakers with >92 dB SPL 1W, 1m efficiency (or
better), 8 ohms nominal impedance (or higher), and simple crossovers or no crossover at all (full-
range designs). We have tested this extensively using the Zu Audio©Druid Mk.V, which are 2-way
minimal crossover, 101 dB efficient and a nominal 16 Ohm impedance.
There are many medium to high-efficiency speakers these days, and we recommend listening to the
ones that you enjoy the most. Set aside the reviews, set aside the Internet noise, bring the recordings
that matter to you, and choose the speaker that you really connect with. That’s the right speaker for you.
SETTING THE BIAS
The Truth™amplifier comes pre-adjusted from the factory, and is tested, calibrated, and matched
to the installed 6DJ8 input tube and the pair of 2A3 output tubes. The only time you need to do the
entire setting procedure is when the tubes are replaced. (either the 6DJ8 or 2A3) Or when replacing
the original tubes at end of life. (Usually after several thousand hours of operation). You can also do a
“fine-tuning” so the amplifier is thermally matched to its location in your audio system.
Although the procedure might seem complex, all it does is set each channel of the 6DJ8 input tube to
the optimum range of 8 to 12 mA, and each 2A3 output to the optimum 60 mA. The internal circuits
are so precise that the adjustment procedure actually tests the tube as you make the adjustment.
If a replacement tube cannot be adjusted to the optimum current, its performance may be out of
specification. If the current is out of range, the amplifier won’t be harmed, but the tube may have a
shortened life (if the current is too high) or not sound its best (if the current is too low). When each
tube is set to the the green range shown on the current meter, you can be confident you are getting
the best possible performance from the tube.
Its very rare for a tube amplifier to have regulated high volatge power supplies. Our precision
regulated supplies solve plate current changes due to fluctuations in line voltages. Don’t fret and wear
out the adjustments by trying to tweak out the tiny up and down motions to make it always exactly 60
mA because it will still sound great.
www.whammerdyne.com
6
Bias Controls
The main RUN/CAL switch is directly behind the lighted power switch. Remember to return the RUN/
CAL switch to the RUN position after both channels have been adjusted.
The meter selector switch is directly below the current meter, and selects (A) Left 2A3 current, (B) Left
6DJ8 current, (C) Right 6DJ8 current, and (D) Right 2A3 current.
There are 3 small holes on the left heat sink, and 3 small holes on the right heat sink. The top hole is a
25-turn trimmer that sets the current for the 6DJ8 (fine adjust). The middle hole is a 4-position switch
that sets the 6DJ8 bias (coarse adjust), and the lower hole is a 4-position switch that sets the 2A3
bias (medium adjust).
The fine-adjust trimmer and 6DJ8 bias switch (coarse) change the operating point of the 6DJ8 and the
2A3, while the 2A3 bias switch (medium) only affects the operating point of the 2A3. Each channel has
its own independent set of bias controls, and the meter-select switch lets you see the effect of the
controls on each channel of the 6DJ8 and each 2A3.
When you make the bias adjustments, please use the provided white gloves to prevent inadvertent
contact with the 2A3 tubes, and the provided adjustment tool. If necessary, a replacement adjustment
tool can be ordered from Mouser Electronics®, Part Number: 652-H-90.
Preparation
You’ll need the adjustment label template, the plastic adjustment tool, and cotton gloves.
The amplifier should be adjusted in its usual location in the the audio system. (If the amplifier is
adjusted in a location different than the usual position in the audio system, the local air temperature
may be different, which will affect the accuracy of the adjustment.)
The ideal room temperature for making adjustments is between 68F/20C and 72F/22C.
1) Turn off source components.
2) Reduce the volume of each channel to zero.
3) Turn the amplifier on, and wait 4 minutes till the backlight of the current meter turns from red to
white.
www.whammerdyne.com
7
Calibration Procedure
Left Channel
This procedure sets the 2A3 plate current to 60 mA and the 6DJ8 between 8 and 12 mA. There may be
one or two combinations of switch and trimpot settings to achieve this goal. If possible, avoid currents
higher than 60 mA during the procedure.
1) Locate the RUN/CAL switch behind the power switch. Change the RUN/CAL switch to the “CAL”
position.
2) Locate the selector switch below the current meter. Change the switch to the “A” position. (This
monitors the current through the left 2A3 output tube.)
3) On the Left heat sink, there are three small holes in a vertical line. These set the bias points and
operating currents of the tubes on the left channel of the amplifier. (The holes on the Right heat sink
have the corresponding functions for the right channel.)
4) Put on the white gloves, and insert the adjustment tool into the top hole. Rotate the trimpot so the
meter reads a low value around 10 mA. (In most cases these will be counter-clockwise turns.) This is
a 25-turn trimpot, so it will take several rotations.
5) Insert the tool in the bottom hole (2A3 bias, medium adjust switch). Rotate until the meter falls in
the 40 to 60 mA range.
6) If there are not enough steps, back off two steps, move the tool to the middle hole (6DJ8 bias,
coarse adjust switch) and increase by another step.
7) If necessary, move the tool to the top hole (trimpot) and rotate until the current reads 60 mA. (In
most cases, this is a clockwise rotation.) Please turn slowly so the circuit can stabilize and give an
accurate reading.
8) Move the selector switch for the current meter to the “B” position. This monitors the current
through the left side of the 6DJ8 input tube. Check to see the current falls between 8 and 12 mA
(lower green zone on the meter). A 6DJ8 is still considered serviceable (and listenable) even if it’s a
little out of this range.
www.whammerdyne.com
8
Calibration Procedure
Right Channel
1) Confirm the RUN/CAL switch is in “CAL” position.
2) Move the selector switch for the current meter to the “D” position. (This monitors the current
through the right 2A3 output tube.)
3) On the Right heat sink, there are three small holes in a vertical line. These set the bias points and
operating currents of the tubes on the right channel of the amplifier.
4) While wearing the white gloves, insert the adjustment tool into the top hole. Rotate the trimpot so
the meter reads a low value around 10 mA. (In most cases these will be counter-clockwise turns.)
This is a 25-turn trimpot, so it will take several rotations.
5) Insert the tool in the bottom hole (2A3 bias, medium adjust switch). Rotate until the meter falls in
the 40 to 60 mA range.
6) If there are not enough steps, back off two steps, move the tool to the middle hole (6DJ8 bias,
coarse adjust switch) and increase by another step.
7) If necessary, move the tool to the top hole (trimpot) and rotate until the current reads 60 mA. (In
most cases, this is a clockwise rotation.) Please turn slowly so the circuit can stabilize and give an
accurate reading.
8) Move the selector switch for the current meter to the “C” position. This monitors the current
through the right side of the 6DJ8 input tube. Check to see the current falls between 8 and 12 mA
(lower green zone on the meter). A 6DJ8 is still considered serviceable (and listenable) even if it’s a
little out of this range.
9) Move the RUN/CAL switch to back to RUN. Start your source music playing and increase the Left
and Right volume controls. Enjoy!
www.whammerdyne.com
9
Bias Drift over Time
If a tube is marginal (either old or has residual gas), it will slowly drift over the next several hours
of operation. If it borders on defective, or is outright bad, it will not stabilize during the time the
adjustments are being made. The Truth™amplifier measures all of the tubes in-circuit, with actual
operating voltages and currents. The old-fashioned TV-tube testers used by many resellers are much
cruder, and basically only tell you whether the tube is completely dead or not. They can’t accurately
tell if the tube has problems or is at the end of its working life.
Tubes can test “Good” or “OK” on a vintage tube tester, only to sound pretty bad in a high-quality
amplifier, or not bias at all in a fixed-bias amplifier. (It’s a little counter-intuitive, but “fixed-bias”
amplifiers actually have bias adjustments, along with bias meters.)
If you find the “upgrade” tubes are drifting over time, we strongly suggest removing them and
replacing them with the original tubes the amplifier came with. There are wonderful tubes out there,
but there are some fakes as well. The precision bias circuits of the Truth™amplifier show the real-
world performance of the tube; you can trust the measurements you’re seeing during the bias-setting
procedure.
If the tubes are stable (and all good tubes are), you can set the bias, check it every now and then if
you want to be double-sure, and go ahead and enjoy the Truth™ amplifier as much as you want. It
can’t be harmed by minor mis-biasing; this procedure is here so you can get the best sound, and the
longest life, from any set of tubes you install.
10
Power Output:
Power output, both channels driven at 5% distortion:
4.2 Watts RMS
Peak power output:
6.5 Watts per channel
Frequency Response:
1 Watt RMS -3 dB @ 6 Hz - 140 kHz
Wideband hum and noise:
Input shorted, output into 8 Ohm load
<25 µV RMS
Distortion @ 1 Watt /1kHz:
1.5% THD
S/N Ratio @1kHz, just below clipping:
90 dB
Input sensitivity for full power:
1.3 V RMS
Gain:
14 dB
Gain match left and right channels:
Better than .3 dB
Input Impedance:
at 20 Hz: 30 K Ohms
Output Impedance:
4 Ohm, 8 Ohm
Dimensions:
11.8” W x 18” H x 18” D
Weight:
69 Lbs
Power Consumption @ 120VAC, 60 Hz line voltage:
111 Watts, 1.2 A
Features
The Truth™is a non-inverting, zero feedback single-ended pure class
A amplifier D/C coupled tube stage, with no capacitors in the signal
path.
COMPONENTS/ CONTROLS
Vacuum Tubes:
1x 6DJ8 input tube (selected and factory tested)
2x 2A3 output tube (selected and factory tested)
Compatible tubes:
2A3... JJ 2A3-40
6DJ8... 6922, 7308, CCa, E88CC, E188CC
Front panel indicators and controls:
1x... Custom Simpson®plate current meter
(L/R bias for 2A3, L/R bias for 6DJ8)
2x... Custom Simpson®relative-power meters,
(approx. 1 Watt RMS into 8 Ohms @ the start of the red marker & 3.5 Watts
RMS @ full scale)
2x... Independent coarse L/R stepped volume control,
Rotary switch, 12-position:
0, -5, -8.75, -12.5, -16.25, -20, -23.75, -27.5, -31.25, -35, -38.5 dB, mute
2x... Independent fine L/R stepped volume control,
Rotary switch, 3-position:
0, -1.25, -2.5 dB
1x... Main power switch, push button, w/LED “ON” indicator
1x... Run - Calibrate switch
toggle switch, 2-position
1x... Rotary 4-position selector switch for current meter
(L/R bias for 2A3, L/R bias for 6DJ8)
Rear Panel Connectors:
IEC socket with integral 2 Amp Slo-blo 5x20 mm fuse - Littlefuse®120 VAC
60 Hz line voltage
2x... RCA audio inputs
(left and right)
6x... Speaker connection terminals
(left and right - Common, 4 Ohm, and 8 Ohm)
SPECIFICATIONS
(TYPICAL)
All measurements taken after 1/2 hour warm up time
WHAMMERDYNE HEAVY INDUSTRIES RESERVES THE RIGHT TO CHANGE OR MODIFY THE
SPECIFICATIONS WITHOUT FURTHER NOTICE
www.whammerdyne.com
11
WARRANTY
All parts and materials warranted for 3 years. Vacuum tube warranty, 6 months
Contact the factory for Return and Warranty RMA authorization
Whammerdyne Heavy Industries
2827 NE Alberta St.
Portland, Oregon 97211
USA
Tel: (503) 887-9015 (Pacific Time)
Email: info@whammerdyne.com
Web: www.whammerdyne.com
The Truth™2A3 amplifier is designed, manufactured, and tested in the United States of America.
©2015 Whammerdyne Heavy Industries. All rights reserved. Printed in the USA.
Rev# 4.08.15.0
Website design and branding by DDG - www.doreydesigngroup.com
www.whammerdyne.com
™
Table of contents
