Guytron Gt-100 User manual

THE
GT-100
100 WATT GUITAR AMPLIFIER
Owner’s Manual
(SEE FV ADDENDUM)
GUYTRON AMPLIFICATION
www.guytron.com

2
PRECAUTIONS
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 and in the operating instructions should be adhered to and all operating instructions
should be followed. Do not use this equipment near water! Care should be taken so that objects do not fall and
liquids do not spill into the unit through any openings. The power cord should be unplugged from the outlet when
left unused for long periods of time.
Operating temperature: Do not expose the GT-100 to excessive heat. This unit is designed to operate between 32
°F and 104 °F (0°C and 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.
Unpacking:
Before you plug in, inspect your GT-100 amp for any damage. Your amp was inspected and sound-tested
before shipment, but shipping can sometimes be tough. Check that the footswitch and power cord have
been shipped with the amp. If parts are missing, or if any damage has occurred, contact your dealer.
Packing Materials:
We designed the original box and packing materials to protect your amp during shipment. Save them. If
you ever need to send your amp to us or to anyone else, the original box and packing materials will ensure
safe transit.
Before you plug in:
Take a quick look inside the back of your amp. Make sure of the following--
1. The tubes are securely seated in their sockets.
2. A speaker cord is plugged between the “Speaker” jack on the amp, and the jack on the speaker cabinet.
3. The impedance selector is set to match the cabinet's impedance.
4. The power cord is plugged in.
5. The footswitch is plugged in (this is optional).
Now look at the front to make sure:
1. The Master Volume control is set at a low level. (9 O’clock is a good starting point).
2. The Power switch is off.
3. The Standby switch is set to standby mode.
Plug in!
Now plug the amp into the wall, plug your guitar into the input jack, and set your controls to one of the
Sample settings outlined here. Then turn on the Power switch. Wait for about a minute for the tubes to
warm up. Turn on the Standby switch.
Have Fun Jamming!
After you've played with your GT100 for a while, check out the rest of this manual for some good tips on
getting the most out of your new GT100 guitar amplifier. And keep an eye on our web site as well, for
sound bite and sample settings to come in the near future, as well as links to musicians using Guytron.

3
GAIN
TONE
LEVEL
VOLUME
INPUT
A
B
FORWARD
Thank you for purchasing the Guytron GT-100. The exclusive patented design delivers that “On
10” sound at any volume (without external power attenuators), restoring power amp distortion and
harmonics missing from conventional master volume technology. The GT-100 is a two channel, 100 watt,
pure tube amplifier with vintage tones and modern features, all hand built in the U.S.A.
INTRODUCTION
The heart of the tone generation is in the unique foot switchable pre-amp design that incorporates
two EL84's running in “Class A” configuration. Class A is the oldest and purest way of amplifying a
signal. Naturally, there are raging disputes among audiophiles as to what is Class A and what is not, but
this section of the amp is Class A, and that is where the feel and basic tonal character get established. The
signal does however make a transition into the Class AB arena and 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 ‘cranked up’ stock amp type of overdrive. The Channel “A” tone control
involves the gain structure and the amp picks up more gain in the treble range as you turn it clockwise,
yielding a progressively more “English” tone along the way. Channel A has become very popular and is
known for its unique brand of sparkle, and punch.
Channel “B” takes over where channel “A” leaves off, encompassing most of the favored tones of
the modded amp era, mid 70's, to present. The gain control in Channel “B” is a monster, by utilizing a
dual pot it controls two stages of gain simultaneously, allowing a continuous sweep from warm and clear
to over the top gain and distortion. The tone control on channel “B” is a post gain type, and 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 adding to the versatility and allowing you to
get a warm distortion with a variety of power amp settings.
A master tone section is provided to shape the final sound before it gets delivered 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 deliver massive amounts of power on demand. The master
tone controls can be used to adjust for different rooms, as well as emulate the tonal characteristics of
different amp types, speaker configurations, etc. It is also at this stage that effects can be blended in to
further enhance the tone.

4
VOLUME
TREBLE
MIDRANGE
BASS
EFFECTS
PRESENCE
LEVEL
HIGH
LEVEL
EFFECTS
LOOPS
LOW
LEVEL
SEND RETURN SEND RETURN FOOTSWITCH
The tone controls which sometimes seem a bit subtle, are set up for emphasis and musicality, and
not designed for an exaggerated wide range of sweep, but to gently add or subtract emphasis on important
musical frequencies, without crossing into a non-musical realm, or introducing excessive phase shift. The
amp does, however, faithfully deliver the usable feel and sound of all my favorite most popular amps, and
does so at the widest possible spread of listening levels ever available in a single package.
Dual level effects loops are provided to allow for simultaneous running of old vintage gear, and
newer rack mount studio effects. Effects loops are transformer driven with operation dual levels of both
+3 and -10 dB, and can be used simultaneously. As a general rule, the LOW level is for pedal type or
old vintage delays, while the HIGH loop accommodates more modern “Rack Gear”. Typically effects are
set to full wet, with no dry sound in the loop, as you would with a studio mixer. A perfect blend between
the loop effects and the original dry sound which never left the amp, can then be quickly achieved quickly
via Effects control on the front panel of the GT100 (above). As a rule, the on board mixer using the
“original” dry sound will provide a quicker response with a more direct, natural tone and 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 would cancel out with the original dry sound in the amp,
because the Guytron’s dry sound is (obviously) in perfect phase with itself. Another option would 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 old series effects
loop for effects units where external blending is the preferred. In either case, the effects must always be
set to unity gain, while the amp is set up as you would normally be using it. During the level setup
process, the channels “Level” controls can be used as variable “Send” controls, and the “MasterVolume”
can be considered the “Return Level”. This comes in handy for some of the more picky effects you might
run across.

5
The front panel channel selector switch is there for convenience, but is disabled while in the
center remote position, to allow for any form of “Latching” remote switching of the channels. The switch
is labeled (Center Remote) to suggest that the remote switch could be any number of remote switching
methods. Example: Using an effects device to switch the GT100 as part of an effects pre-set.
In any case, the front panel switch is set up to override any external switching in order to
accommodate large stage situations where quick adjustments are needed. Thus eliminating the need to run
back to the footswitch or whatever while adjusting your settings.
The amp is shown in the double “ON” position. While set like this, the amp is fully functional,
and ready to play. During short to medium breaks 10-20 minutes, or between sets, it’s best to turn the
“Standby” switch to the “Standby” position. This will shut down the high voltage inside the tubes, thus
extending tube life, but it also leaves the heaters on for quick startup. If the break is very much longer
than that, both switches should be in the down position. If nothing else, just to conserve energy. Tube life
is also extended if the amp is allowed to warm up at least a minute, before turning the standby 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 old tradition of mine that dates back to the late 70’s. I used
to get a lot of these old Kustom amps in the shop. You know, the cool padded ones you could sit on
during those long boring practices. (I still think that was a stroke of genius) They had the cool purple
lights, which also happened to fit my old Fender amps perfectly. After that, every time I did any
“Custom” work on a Fender amp, I would grace it with a “Kustom” purple jewel. Some years later on a
parts run down in Detroit, I came across several hundred of them, and that cemented the tradition. By the
time the 90’s rolled around, they were once again popular and back in production, and so there was never
any decision as to which kind of pilot light we should use on the GT-100.
A
B
PILOT
CENTER
REMOTE
STANDBY MAINS
ON ON
CHANNEL
SELECT
GT
100

6
The GT-100 now comes stock with the ability to travel internationally. The back panel is outfitted
with a fused Primary voltage selector switch, which is built in to the IEC connector. To adjust for
different countries, use a small screwdriver to pry out the square voltage selector cap (shown below)
socket. Simply, install the proper fuse rating for your voltage requirements, and 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 domestic USA amps there are two (5 AMP SLO-BLO) fuses, one is under the voltage
selector cap, and the other is located in the fuse holder marked 5 AMP SLO-BLO.
BOTH of these two fuses MUST get changed to 2 ½AMP SLO-BLO for any voltages higher than
120VAC.
The 1 AMP FAST-BLO fuse remains the same value regardless of input voltage.
The speaker Impedance switch is shown adjusted for 8 ohms, which the standard setting for a
single Guytron GT-212 cabinet. Use a penny to adjust it to the correct impedance for your application.
For (2) Guytron GT-212 cabinets, the correct setting is 4 ohms. The speaker jacks are in parallel, so the
selector should reflect the total parallel impedance for whatever is plugged into the two speaker jacks. I
do know of people deliberately mismatching the amp and cabs, for tonal reasons. An impedance
mismatch will cause different harmonic overtones in the output section. It will also lower the power
efficiency of the output section. I have endeavored to make the transformers as tough as possible, and I
have not seen any come back blown yet. However, It is still a practice that would void your warranty.
IMPEDANCE
SELECTOR
8
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.
RISQUE DE CHOC. NE PAS OUVRIR.
!
WARNING! SHOCK HAZARD!
SPEAKERS
120
Voltage selector cap
(Shown set for 120VAC)
Impedance Selector Switch
(shown set for eight ohms)

7
About the Sample Settings:
These sample settings are provided as a starting point that steers you towards a certain character
of tone, not as proof and comparison study. They were never intended to be exact copies, only functional
equivalents. In addition, many things make for an old amps character, old and worn, or even damaged
parts sometimes add to the uniqueness of tone. That’s what old amps are for!
These sample settings were done with a maple neck Telecaster, it was chosen for it’s excellent
blend of clarity and sustain. It has a light ash body, stock vintage VanZandt pickups, stock wiring with
volume and tone were kept full up (to eliminate coloration). We also used, .010 gauge GHS boomers,
18.6’ pro-co lifeline guitar cord, and matching Guytron 2 x 12 cabinet. (I mention all these things
because they are important factors, and I have found that all things involved influence the production of
tone) During the sampling the master tone settings were all at twelve o’clock and it’s a good idea to
always start there when looking for your tone. The level settings are primarily for relative channel levels
but do make a slight difference in tone. The recommended starting point is straight up. Obviously,
physics dictate that these can only be an approximation, but in terms of usable tone I believe you’ll find
that it’s like splitting hairs. Only much more fun!
CHANNEL “A” SAMPLE SETTINGS
SETTING
GAIN
TONE
LEVEL
DESCRIPTION
Silver face
Twin
Round & clear with lots of mid coloration
Black face
Twin
Round & clear with more clarity and a bit
More Presence and drive.
Tweed Bassman/
early 60's Plexi
Lots of clarity rock tone, cleans up well by
turning down guitar volume, starts to grind.
Late 60's
Plexi
More grind, more upper midrange drive,
Makes Humbuckers more clear sounding.

8
Vox AC30
(see note next pg)
Brilliant highs, cleans up great, warms up
a lot as gain increases, cool sounding Mids.
(Sweep Master Treble, Mid, and Bass to taste.)
Note: On the Vox setting, (previous page) you can see the differences with using the master tone
controls. Some people think it sounds more like an AC30 with the Mids cut and the highs and lows
boosted a little, but I sometimes like the opposite settings. You have to decide for yourself, it matters if
your playing clean or dirty, loud or quiet, etc.
CHANNEL “B” SAMPLE SETTINGS
SETTING
GAIN
TONE
LEVEL
DESCRIPTION
Old Valco amps
(see note below)
Clean, sort of borders on cool edge, Kind of muddy,
But not really, lots of character.
70's aluminum
panel
Can you say Kiss? This is a classic type of
Overdrive, a must for us!
beefy JMP,JCM
This is more of what you’re rockin’ for!
Over the top
Hot / rod Tones
Not for the weak of heart at high volumes, But at
very low sound levels it’s a great substitute
for moving a lot of air.
A little unsolicited history: the unsung “Valco” was an amplifier company based out of
Chicago. In addition to the Valco amp line, they also built amps for many other companies well into the
50’s, like Supro, and other Hawaiian lap steel amps. When Hawaiian music was all the rage, back in the
late 30’s and well into the 40’s and even 50’s. Most “Lap Steel” companies offered a matching amp with
their best Lap Steels. Several smaller Lap Steel companies just had Valco make them and put their own
name on it. These amps usually had a dark full sound, never totally clean, but often beautiful and colorful
tones. They were cool sounding, and certainly one of my favorites for recording, but the speakers were
weak! They were almost always blown when they came in the shop.

9
Incidentally, Leo Fender was the exception, starting out in the repair field; he built his own amps,
and used “over-spec” speakers anticipating real life stage abuse. So later on, when the kids started using
their parents old equipment for this new “Rock and Roll”, Fender amps held up much better, and went on
to become famous guitar amps. To this day, if you find an old Valco amp, it usually has a blown,
damaged, or incorrectly replaced speaker in it. When you tried to replace the speaker, the proper kind was
never available, so the amp tone changed drastically for the worse.
These kinds of observations, as well as many other proven examples witnessed while running my
little repair shop, are the reason Guytron amps will remain “Overbuilt to the Hilt”.

10
My GT-100 Sample Settings
Note: You might like to photocopy this page, you may find it a useful reference. Check out our web page soon,
www.guytron.com , for contact with other GT-100 players to trade settings, and exchange good ideas, etc.
It’s also a good idea keep a folder with external notes sheets, for any external effects, or more descriptive notes, etc.
Example: Effects Yes/No =( Y) Effects =( 3) See Note # =( 22 ) ∗∗ Effects =( ) is for GT100 front panel setting.
SETTING
GAIN
TONE
LEVEL
NOTES / DESCRIPTION
Channel A/B ( )
Date:
Master =( ) Treb =( ) Mid =( ) Bass =( ) Pres =( )
Effects Yes/No =( ) Effects =( ) See Note # =( )
Channel A/B ( )
Date:
Master =( ) Treb =( ) Mid =( ) Bass =( ) Pres =( )
Description.
Effects Yes/No =( ) Effects =( ) See Note # =( )
Channel A/B ( )
Date:
Master =( ) Treb =( ) Mid =( ) Bass =( ) Pres =( )
Description.
Effects Yes/No =( ) Effects =( ) See Note # =( )
Channel A/B ( )
Date:
Master =( ) Treb =( ) Mid =( ) Bass =( ) Pres =( )
Description.
Effects Yes/No =( ) Effects =( ) See Note # =( )
A note for the digital generation only!
Settings are most often expressed in terms of old analog clocks. (Yes, I have had to explain this before.)
Example: Treble = 12 O’clock means, a straight up knob setting, (⇑). Therefore, 3 O’clock would be
(⇒), and likewise, 9 O’clock would be (⇐), etc. Just like the hands of an old clock.