3
HEY! You gotta read this first!
This kit contains parts which operate at high,
potentially deadly
, voltages. In constructing,
operating, and modifying this kit you agree to assume liability for any damage or injury resulting from
exposing yourself or others to this high voltage, high temperature hazard. This kit contains only a
partial enclosure and thus has not been designed to be shockproof or thermally isolated. The builder
must have, or must acquire the knowledge to construct an enclosure which properly isolates this
high voltage and high temperature from anyone coming in contact with the kit if deemed necessary.
PLEASE NOTE! If you do not feel that you possess the skills, knowledge, or common sense
necessary to safely construct and operate this electronic kit,
do not attempt its construction!
You
may return the unused kit within 14 days of receipt for a refund of the purchase price, less shipping
and handling, if you decide that you cannot safely execute its construction.
DO NOT:
leave the kit operating in the presence of unattended children. Along with the shock
hazard, there is also a potential for serious burns from touching hot vacuum tubes.
leave out the fuses, power switches or power supply bleeder resistors
Never
assume that the shock or high temperature hazards are neutralized, even when the
unit is unplugged!
Safety and the Bottlehead
As more and more audiophiles come to the long forgotten conclusion that building your own tube
gear is the best way to sonic heaven, the issue of safety around high voltages becomes terribly im-
portant. With the near demise of commercial tube audio gear in the late 60's, and the similar decline
of kit building in the late 70's, safe test and construction techniques have been well nigh forgotten by
most audiophiles who were there 'way back when' and information on the topic of dealing safely with
the kind of high voltages present in the current crop of kit and DIY tube designs seems to be cov-
ered lightly if at all.
The basics
Tube audio gear tends to operate a much higher voltages than the current day solid state audio
equipment. While a high power solid state amp might draw amps like an arc welder, it usually runs at
75V DC or less. Not to say that these kinds of voltages and currents can't hurt you, but a typical tube
circuit may operate at anywhere from 120VDC to as high as an 'electrifying' 1500VDC or even
higher! While these voltages are intimidating ( in fact many experienced tube DIYers limit their con-
struction to circuits running at 500V or less), that high voltage is only half of the safety issue.
Is high voltage dangerous in and of itself?
Spend some time around a small town TV repairman and eventually you will see him check the HV
supply of a picture tube by touching the high voltage lead from the voltage tripler with his bare finger.
A small snap will ensue,his hand will fly back, and he'll say, "Yup, it's working". Is there a destructive
streak in TV repairmen? That supply is probably at a potential of 5kV to 10 kV!
Nope, the repairman knows that there is virtually no current available from the supply, so while the
high voltage may give him a slight 'zap', the supply can't push enough electrons through our intrepid
TV guy to really do any short term damage.