Guytron Gt-100 User manual

THE
GT-100
100 WATT GUITAR AMPLIFIER
Owner’s Manual
Guytron Amplification
586-254-5717
www.guytron.com
PRECAUTIONS

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NOTE: IT IS VERY IMPORTANT THAT YOU READ THIS SECTION TO HELP
INSURE MANY YEARS OF TROUBLE FREE USE. THIS UNIT REQUIRES CAREFUL
HANDLING.
All warnings on this equipment an in the operating instructions shoul be a here to an
all operating instructions shoul be followe . Do not use this equipment near water! Care
shoul be taken so that objects o not fall an liqui s o not spill into the unit through any
openings. The power cor shoul be unplugge from the outlet when left unuse for long
perio s of time.
Operating temperature: Do not expose the GT-100 to excessive heat. This unit is
esigne to operate between 32F an 104F an 0C an 40 C
DO NOT ATTEMPT TO SERVICE THIS EQUIPMENT YOURSELF!
THIS EQUIPMENT SHOULD BE SERVICED BY QUALIFIED PERSONNEL ONLY.
DO NOT MAKE ANY INTERNAL ADJUSTMENTS OR ADDITIONS TO THIS
EQUIPMENT AT ANY TIME. DO NOT TAMPER WITH INTERNAL ELECTRONIC
COMPONENTS AT ANY TIME. FAILURE TO FOLLOW THESE INSTRUCTIONS MAY
VOID THE WARRANTY OF THIS EQUIPMENT, AS WELL AS CAUSING THE RISK OF
A SEVERE SHOCK HAZARD.
Unpa king:
Before you plug in, inspect your GT-100 amp for any amage. Your amp was inspecte
an soun -teste before shipment, but shipping can sometimes be tough. Check that the
footswitch an power cor have been shippe with the amp. If parts are missing, or if any
amage has occurre , contact your ealer.
Pa king Materials:
We esigne the original box an packing materials to protect your amp uring shipment.
Save them. If you ever nee to sen your amp to us or to anyone else, the original box an
packing materials will ensure safe transit.

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Before you plug in .
Take a qui k look inside the ba k of your amp and make sure of the following:
• The tubes are securely seate in their sockets.
• A speaker cor is plugge between the Speaker jack on the amp, an the jack on the
speaker cabinet.
• The impe ance selector is set to match the cabinet s impe ance.
• The power cor is plugge in.
• The footswitch is plugge in (this is optional).
Now look at the front to make sure:
• The Master Volume control is set at a low level. (9 O clock is a goo starting point).
• The Power switch is off.
• The Stan by switch is set to stan by mo e.
Plug in!
Now plug the amp into the wall, plug your guitar into the input jack, an set your
controls to one of the Sample settings outline here. Then turn on the Power switch. Wait for
about a minute for the tubes to warm up. Turn on the Stan by switch.
Have Fun Jamming!
After you’ve playe with your GT100 for a while, check out the rest of this manual for
some goo tips on getting the most out of your new GT100 guitar amplifier. An keep an eye on
our web site as well, for soun bite an sample settings to come in the near future, as well as
links to musicians using Guytron.

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GAIN TONE LEVEL
V
OLUME
INPUT
A
B
FORWARD
Thank you for purchasing the Guytron GT-100. The exclusive patente esign elivers
that "On 10" soun at any volume (without external power attenuators), restoring power amp
istortion an harmonics missing from conventional master volume technology. The GT-100 is a
two channel, 100 watt, pure tube amplifier with vintage tones an mo ern features, all han built
in the U.S.A.
INTRODUCTION
The heart of the tone generation is in the unique foot switchable pre-amp esign that
incorporates two EL84’s running in "Class A" configuration. Class A is the ol est an purest
way of amplifying a signal. Naturally, there are raging isputes among au iophiles as to what is
Class A an what is not, but this section of the amp is Class A, an that is where the feel an
basic tonal character get establishe . The signal oes however make a transition into the Class AB
arena an that is one of the secrets of the Guytron tone.
Channel "A", favoring the 50’s to 60’s stock amp tone, starts out crystal clear at low gain
settings, progressing smoothly up to a ’cranke up’ stock amp type of over rive. The Channel
"A" tone control involves the gain structure an the amp picks up more gain in the treble range as
you turn it clockwise, yiel ing a progressively more "English" tone along the way. Channel A has
become very popular an is known for its unique bran of sparkle, an punch.
Channel "B" takes over where channel "A" leaves off, encompassing most of the favore
tones of the mo e amp era, mi 70’s, to present. The gain control in Channel "B" is a monster,
by utilizing a ual pot it controls two stages of gain simultaneously, allowing a continuous sweep

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VOLUME TREBLE MIDRANGE BASS EFFECTS PRESENCE
LEVEL
from warm an clear to over the top gain an istortion. The tone control on channel "B" is a
post gain type, an serves as a treble gate to the power amp, it has no effect on the gain
structure, (unlike Channel A). It serves well in setting the relative brightness of the two channels,
ultimately a ing to the versatility an allowing you to get a warm istortion with a variety of
power amp settings.
A master tone section is provi e to shape the final soun before it gets elivere to your
speakers. The master tone section is integral to the 100 watt all tube output section; utilizing four
EL34’s running in class AB2. This configuration can eliver massive amounts of power on
eman . The master tone controls can be use to a just for ifferent rooms, as well as emulate
the tonal characteristics of ifferent amp types, speaker configurations, etc. It is also at this
stage that effects can be blen e in to further enhance the tone.
The tone controls which sometimes seem a bit subtle, are set up for emphasis an
musicality, an not esigne for an exaggerate wi e range of sweep, but to gently a or subtract
emphasis on important musical frequencies, without crossing into a non-musical realm, or
intro ucing excessive phase shift. The amp oes, however, faithfully eliver the usable feel an
soun of all my favorite most popular amps, an oes so at the wi est possible sprea of
listening levels ever available in a single package.
Dual level effects loops are provi e to allow for simultaneous running of ol vintage
gear, an newer rack mount stu io effects. Effects loops are transformer riven with operation
ual levels of both +3 an -10 B, an can be use simultaneously. As a general rule, the LOW
level is for pe al type or ol vintage elays, while the HIGH loop accommo ates more mo ern
"Rack Gear". Typically effects are set to full wet, with no ry soun in the loop, as you woul
with a stu io mixer. A perfect blen between the loop effects an the original ry soun which

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HIGH
LEVEL
EFFECTS
LOOPS
LOW
LEVEL
SEND RETURN SEND RETURN FOOTSWITCH
never left the amp, can then be quickly achieve quickly via Effects control on the front panel of
the GT100 (above). As a rule, the on boar mixer using the "original" ry soun will provi e a
quicker response with a more irect, natural tone an feel than you sometimes get with most
mixing. The only time this presents a potential problem, is when an effects units Input is out of
phase with its own output. This woul cancel out with the original ry soun in the amp,
because the Guytron’s ry soun is (obviously) in perfect phase with itself. Another option
woul be a phase reversing buffer amp in the loop to return the signal to it’s original phase
relationship, if you have a problem effects unit.
A complete clockwise setting of the Effects control will function exactly like an ol series
effects loop for effects units where external blen ing is the preferre . In either case, the effects
must always be set to unity gain, while the amp is set up as you woul normally be using it.
During the level setup process, the channels "Level" controls can be use as variable "Sen "
controls, an the "MasterVolume" can be consi ere the "Return Level". This comes in han y for
some of the more picky effects you might run across.
The front panel channel selector switch is there for convenience, but is isable while in
the center remote position, to allow for any form of "Latching" remote switching of the channels.
The switch is labele (Center Remote) to suggest that the remote switch coul be any number of
remote switching metho s. Example: Using an effects evice to switch the GT100 as part of an
effects pre-set.
In any case, the front panel switch is set up to overri e any external switching in or er to
accommo ate large stage situations where quick a justments are nee e . Thus eliminating the
nee to run back to the footswitch or whatever while a justing your settings.
The amp is shown in the ouble "ON" position. While set like this, the amp is fully
functional, an rea y to play. During short to me ium breaks 10-20 minutes, or between sets, it’s
best to turn the "Stan by" switch to the "Stan by" position. This will shut own the high
voltage insi e the tubes, thus exten ing tube life, but it also leaves the heaters on for quick

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startup. If the break is very much longer than that, both switches shoul be in the own position.
If nothing else, just to conserve energy. Tube life is also exten e if the amp is allowe to warm
up at least a minute, before turning the stan by switch to the "On" position. This is less of a
strain on the tubes, as well as the rest of the amp.
As for the Purple pilot light, this is an ol tra ition of mine that ates back to the late
70’s. I use to get a lot of these ol Kustom amps in the shop. You know, the cool pa e ones
you coul sit on uring those long boring practices. (I still think that was a stroke of genius)
They ha the cool purple lights, which also happene to fit my ol Fen er amps perfectly. After
that, every time I i any "Custom" work on a Fen er amp, I woul grace it with a "Kustom"
purple jewel. Some years later on a parts run own in Detroit, I came across several hun re of
them, an that cemente the tra ition. By the time the 90’s rolle aroun , they were once again
popular an back in pro uction, an so there was never any ecision as to which kin of pilot
light we shoul use on the GT-100.
The GT-100 now comes stock with the ability to travel internationally. The back panel is
outfitte with a fuse Primary voltage selector switch, which is built in to the IEC connector. To
a just for ifferent countries, use a small screw river to pry out the square voltage selector cap
(shown below) socket. Simply, install the proper fuse rating for your voltage requirements, an
rotate the cap until the correct voltage lines up to the triangle marker on the right.
There are a total of three user accessible fuses for the GT100 for extra protection and safety.
IMPORTANT!
For omestic USA amps there are two (5 AMP SLO-BLO) fuses, one is un er the
voltage selector cap, an the other is locate in the fuse hol er marke 5 AMP SLO-BLO. BOTH
IMPEDANCE
SELECTOR
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GUYTRON L.L.C. MADE IN U.S.A MODEL: GT-100
BROOKINGS, OR PATENT PENDING SERIAL:
5 AMP SLO-BLO 1 AMP FAST-BLO
100 120VAC ~ 5.0A SLO-BLO
220 240VAC ~ 2.5A SLO-BLO
50 60 HZ — 650 WATTS
NO USER SERVICABLE PARTS
INSIDE.
!
WARNING! SHOCK HAZARD! SPEAKER
120
Voltage selector cap
(Shown set for 120VAC) Impe ance Selector Switch
(shown set for eight ohms)

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of these two fuses MUST get change to 2 1/2 AMP SLO-BLO for any voltages higher than
120VAC.
The 1 AMP FAST-BLO fu e remain the ame value regardle of input voltage.
The speaker Impe ance switch is shown a juste for 8 ohms, which the stan ar setting
for a single Guytron GT-212 cabinet. Use a penny to a just it to the correct impe ance for your
application. For (2) Guytron GT-212 cabinets, the correct setting is 4 ohms. The speaker jacks
are in parallel, so the selector shoul reflect the total parallel impe ance for whatever is plugge
into the two speaker jacks. I o know of people eliberately mismatching the amp an cabs, for
tonal reasons. An impe ance mismatch will cause ifferent harmonic overtones in the output
section. It will also lower the power efficiency of the output section. I have en eavore to make
the transformers as tough as possible, an I have not seen any come back blown yet. However, It
is still a practice that woul voi your warranty.
About the Sample Setting :
These sample settings are provi e as a starting point that steers you towar s a certain
character of tone, not as proof an comparison stu y. They were never inten e to be exact
copies, only functional equivalents. In a ition, many things make for an ol amps character, ol
an worn, or even amage parts sometimes a to the uniqueness of tone. That’s what ol amps
are for!
These sample settings were one with a maple neck Telecaster, it was chosen for it’s
excellent blen of clarity an sustain. It has a light ash bo y, stock vintage VanZan t pickups,
stock wiring with volume an tone were kept full up (to eliminate coloration). We also use , .010
gauge GHS boomers, 18.6’ pro-co lifeline guitar cor , an matching Guytron 2 x 12 cabinet. (I
mention all these things because they are important factors, an I have foun that all things
involve influence the pro uction of tone) During the sampling the master tone settings were all
at twelve o’clock an it’s a goo i ea to always start there when looking for your tone. The level
settings are primarily for relative channel levels but o make a slight ifference in tone. The
recommen e starting point is straight up. Obviously, physics ictate that these can only be an
approximation, but in terms of usable tone I believe you’ll fin that it’s like splitting hairs. Only
much more fun!
CHANNEL A SAMPLE SETTINGS
SETTING GAIN TONE LEVEL DESCRIPTION

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Silver face
Twin Roun & clear with lots of mi coloration
Black face
Twin
Roun & clear with more clarity an a bit
More Presence an rive.
Twee Bassman/
early 60’s Plexi
Lots of clarity rock tone, cleans up well by
turning own guitar volume, starts to grin .
Late 60’s
Plexi
More grin , more upper mi range rive,
Makes Humbuckers more clear soun ing.
Vox AC30 Brilliant highs, cleans up great, warms up
a lot as gain increases, cool soun ing Mi s.
(Sweep Master Treble, Mi , an Bass to taste.)
Note: On the Vox setting you can see the ifferences with using the master tone controls. Some
people think it soun s more like an AC30 with the Mi s cut an the highs an lows booste a
little, but I sometimes like the opposite settings. You have to eci e for yourself, it matters if
your playing clean or irty, lou or quiet, etc.
CHANNEL B SAMPLE SETTINGS
SETTING GAIN TONE LEVEL DESCRIPTION
Ol Valco amps
(see note below) Clean, sort of bor ers on cool e ge, Kin of mu
y
But not really, lots of character.
70’s aluminum
panel
Can you say Kiss? This is a classic type of
Over rive, a must for us!

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beefy JMP,JCM This is more of what you re rockin for!
Over the top
Hot / ro Tones
Not for the weak of heart at high volumes, but at
very low soun levels it s a great substitute
for moving a lot of air.
A little unsolicite history: the unsung "Valco" was an amplifier company base out of
Chicago. In a ition to the Valco amp line, they also built amps for many other companies well
into the 50’s, like Supro, an other Hawaiian lap steel amps. When Hawaiian music was all the
rage, back in the late 30’s an well into the 40’s an even 50’s. Most "Lap Steel" companies
offere a matching amp with their best Lap Steels. Several smaller Lap Steel companies just ha
Valco make them an put their own name on it. These amps usually ha a ark full soun , never
totally clean, but often beautiful an colorful tones. They were cool soun ing, an certainly one
of my favorites for recor ing, but the speakers were weak! They were almost always blown
when they came in the shop.
Inci entally, Leo Fen er was the exception, starting out in the repair fiel ; he built his
own amps, an use "over-spec" speakers anticipating real life stage abuse. So later on, when the
ki s starte using their parents ol equipment for this new "Rock an Roll", Fen er amps hel
up much better, an went on to become famous guitar amps. To this ay, if you fin an ol Valco
amp, it usually has a blown, amage , or incorrectly replace speaker in it. When you trie to
replace the speaker, the proper kin was never available, so the amp tone change rastically for
the worse. These kin s of observations, as well as many other proven examples witnesse while
running my little repair shop, are the reason Guytron amps will remain "Overbuilt to the Hilt."