Fuchs Audio Technology Mantis Jr User manual


Instrument Amplifier
V 1.0
Operations Manual
For Mantis Jr (head/combo)
Fuchs Audio Technology
407 Getty Ave, Clifton, NJ 07015
[phone] (fax) 973-772-4460
Website: www.fuchsaudiotechnology.com
Email: [e-mail]
 2000-2016 Fuchs Audio Technology. All rights reserved.


A Note From Andy,
First of all, Thank You for purchasing a Fuchs Audio Mantis Jr amplifier!
The Mantis Jr was designed as part of our highly successful Casino Series but for the harder
edged rock and metal player. The Mantis Jr series is available from 4-watts through 100 watts,
to fill the need for a wide range of power levels having classic rock “voicing” similar to a vintage
Marshall™ or Trainwreck™ style amps. Each Mantis Jr is precision handmade by myself and the
staff at Fuchs Audio, built to extremely high standards of excellence using the highest quality
components. With over two decades experience in the service, manufacturing, and design of
tube audio/music equipment, we at Fuchs Audio are extremely proud of the quality and
tremendous musicality of our products.
Please read this manual carefully. Although the Mantis Jr was created to be a simple amplifier
to operate it will perform to its fullest glory by your full understanding of the contents of this
manual.
Feel free to call or e-mail us (we prefer emails!) with comments & questions about your Fuchs
amp or just to find out what’s new here at Fuchs Audio.
Lastly, I recommend checking out our new web site: www.fuchsaudiotechnology.com, for
product/user updates, cool links and other info benefiting our customers.
Sincerely,
Andy Fuchs
President
Fuchs Audio Technology
Fuchs Audio Technology
407 Getty Ave, Clifton, NJ 07015
[phone] (fax) 973-772-4460
Website: www.fuchsaudiotechnology.com
Email: [e-mail]
(“Fuchs Audio Technology” is a registered trademark of Fuchs Audio Technology)
Mantis Jr manual Rev 1.0

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Table of Contents (by section)
1) Introduction to the Fuchs Audio Mantis Jr Amplifier
2) Please Read before powering up your amp
3) Diagrams- FRONT/REAR panels, Tube bias diagram
4) Front panel Controls, inputs & their functions
5) Rear Panel controls, inputs/outputs
6) Biasing power tubes & other technical info.
7) Warranty/repair information & mail-in warranty form
 2000-2005 Fuchs Audio Technology. All rights reserved.
Mantis Jr Rev 1.0

1 Introduction to the Fuchs Audio Mantis Jr ™Amplifier
Representing a new direction for Fuchs Audio Technology, the Mantis Jr ™ brings the high
build quality and awesome tones people expect of Fuchs products, to a new more affordable
price range. The Mantis Jr is based on a dual 12AX7 preamp stage and a push pull output
stage with power levels from 4- through 100 watts. Unlike other amps in this price range, the
Lucky 7™ has a full compliment of extremely flexible tone controls. A surprising amount of
clean headroom is available before the output stage begins distorting with a sweet yet cutting
rock edge. Voiced like its siblings, the Train 45™ and our Blackjack 21 amps, the Mantis Jr™
has a classic rock voice similar to a vintage Marshall™ or Trainwreck™ style amp. It provides a
cutting rock edge, yet filled with harmonic richness and chime. The circuit design also is
“attenuator friendly”. (*see below) The Mantis Jr™ and its sibling the Blackjack 21™ have a
preamp stage designed to allow clean-to-mean from the guitar volume control.
The chassis (like all Fuchs products) is aircraft grade aluminum; our internal construction is
mixed PC board and hard wired. On the Casino series amps, the preamp tubes and power
supply circuitry are on the circuit card, while the power tubes and transformer are mounted
on the chassis. A detachable power cord is standard. By using single point grounding, the amp
is quiet and free of hum at all operating levels.
A single input and single ¼” output jack are provided.
Features:
¾” solid wood cabinet with durable tolex covering.
Anodized aluminum chassis with long lasting silk-screened labeling
Heavy duty Cliff brand jacks. Solid metal-shaft Alpha potentiometers.
Ultra-long-life neon pilot lamp and heavy duty AC power switch.
Simple user adjustable fixed output tube bias.
Specifications:
Size: 8” tall 10.5 inches deep 19” wide.
Weight 10-lbs.
Tube compliment: 3 X 12AX7 preamp tubes. Power tubes depend on amp power rating: 2 X
6SN7 for 4-watt. 2 x 6V6 for 20 watt, 2 x EL34 for 50 Watt and 4 x EL-34 for 100-W versions.
Power output: 4, 20, 50 or 100 watts into 4-8-16-ohms.
Input Impedance -1Meg.
“Trainwreck” is a registered trademark of Ken Fischer
Mantis Jr Manual Rev 1.0

2 Please read before powering up your Fuchs Amp.
Please see Panel Diagrams in next section 3 for assistance.
1) Inspect to make sure power & pre-amp tubes are intact & snuggly seated in
their sockets.
2) Make certain a speaker (load) is plugged into speaker input jack on the back of
the amplifier. Failure to have a speaker connected to the amp will result in
damage to the output tubes! Your amp is supplied with both 4, 8 & 16 ohm
impedance speaker input jacks, select the one closest or matched to your
speaker(s) impedance.
3) Reduce Front panel GAIN controls to moderate low level.
4) Install instrument cable from guitar into front panel INPUT
5) Be sure both POWER switch (front panel) is in DOWN position.
6) Install power cord to amplifier (AC POWER IN) and to AC power source.
7) POWER UP amplifier by: 1) flipping POWER switch UP. Allow at least 30
seconds to 1 minute for tubes to heat up. Then switch rear panel standby
switch to “operate”position.
8) The Amplifier is now fully on and ready to use. Feel free to adjust all controls as
you see fit.
Mantis Jr Manual Rev 1.0l

3 Diagrams of FRONT & REAR Panels, Tube Bias Diagram
Front Panel
Rear Panel
4 Front Panel Controls, inputs & Their Functions
Input Jack:
Input jack is a 1/4" phone plug, designed for 1-Meg impedance, guitar-level signal. This input
will readily accept pedals/effects without any loss in performance. Pedals/effects input is also
inserted to this input in series with your guitar.
Gain Controls:
The gain control sets the overall gain/volume for each channel of the amplifier. Channel one is
a lower gain channel. By adding the footswitchable boost, channel one has increased gain for
greater amounts of distortion. Channel Two is the higher gain channel and without the boost,
the gain level is roughly equal to the gain of channel one with boost. Adding boost to channel
two switches the channel to highest gain available. Through a unique hybrid tube/FET boost
circuit, this gain is obtained at a much lower noise floor than amps with similar gain.
High Control:
Adjust the high control to taste, it controls adjusts the high frequency spectrum of your
Mantis Jr.
Mid Control:
Adjust the Mid control to taste, it controls adjusts the mid frequency spectrum of your Mantis
Jr.
Low Control:Adjust the Low control to taste, it adjusts the low frequency spectrum of your
Mantis Jr.
Mantis Jr Manual Rev 1.0

There are no “correct” Gain settings, finding the desired tone setting depends on the
guitars/pickups used, as well as your own personal tastes. This amplifier works in
unison with your guitar volume to control the nature of the clean/overdrive tones.
By pulling the Channel one Master (or using the footswitch) you can switch between
channels. Each channel has it’s own master volume control. The accent and thrust
controls operate on the high and low frequency ranges respectively, and operate in
the power stage for increased tonal range. Accent adds brightness and bite, which
thrust adjusts the damping and level of lows for drop tunings and speaker cabinets
with limited low frequency output.
5REAR Panel Controls, inputs/outputs
AC power cord input:
Using the supplied 120vac power cord. Connect to AC POWER IN on the amplifier and to AC
power source.
AC power Fuse:
This fuse protects the amplifier if any malfunction occurs. Use ONLY stock fuse rating as
supplied by factory.
Speaker inputs (1 ea-4, 8 and 16 ohms):
(You must have a speaker load inputted to the amplifier before powering on!) Each (1-4 ohm,
1-8 ohm) input optimizes the amplifier for either 4 or 8 ohm speaker impedance. Connect
using a ¼” phone plug to an outboard speaker cabinet. If you have a Combo amplifier, connect
to the combo speaker with supplied wire/1/4” jack.
Footswitch Jack: This is a TRS (stereo style) plug which controls channel switching (tip) and
boost (ring). These are DC control voltages so a remote amp switcher that simply closes a
latching circuit to activate the function. The footswitch supplied with the amp is a dual LED
style footswitch and we do not recommend the use of any other footswitch with the amp.
Audio Patch: This is also a TRS (stereo style) jack. The tip (in this case) is the power amp input.
Using a standard mono ¼” jack you can insert a signal into the power amp for external inputs.
To use this as a loop jack, you will need to obtain an “insert cable”which is easily available
and converts a single stereo plug to two mono plugs. The ring connection is the send and the
tip connection would be the return. Simply connect an external line level device (reverb, echo,
delay) input and outputs to this point.
Mantis Jr Manual Rev 1.0

6Biasing power tubes & other technical info
High Internal voltages inside this amplifier can cause harm or Death!
Output tube Bias Setting:
Each tube is factory set for proper operation. The 6SN7 (4-watt version) is biased to 5 mv per
test point. There are 4 adjustments (one per tube) which should be set with a DC voltage
meter. The 20-Watt version uses 2 6V6 tubes, and each tube is set using its respective trimmer
to 20 millivolts (20-ma) per tube. EL-34’s in the 50 or 100-W version are set to 40 mv per tube.
There is one trimmer on the pc board for each tube bias. Bias is measured at the test points on
the board to ground and set to listed voltages. This should be set with the amp cold, then
reset after the amp has run for about an hour. Use a reliable digital voltmeter for these
settings.
DISCLAIMER: There are exposed Internal high-voltages in this amplifier. Do not attempt to
service, repair or conduct tube biasing unless you are qualified to do so. Please contact Fuchs
Audio beforehand with questions in this regard. Fuchs Audio takes no responsibility or shall be
held liable for any personal harm caused or damage to this amplifier as a result of
unauthorized service, repair or internal adjustments
made to this amplifier.
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7Warranty Information
The Fuchs Audio Technology-Amplifier Warranty
Fuchs Audio Technologyguarantees our products to be free from defective
workmanship or material failure for a period of FIVE years (tubes excluded)from date of new
purchase to the original purchaser. This does not apply to Fuchs amplifiers that have been
tampered with, damaged by shipping carriers, reverse engineered, or modified. Your warranty
form/information must be returned to Fuchs Audio Technologywithin 30 days of purchase, or
your warranty will not be in effect. Fuchs Audio Technologyreserves the right to suspend or
terminate the above warranty at our sole discretion, should damage from any of the above
limitations and or exclusions be detected upon examination.
Keep the information on this page for your records.
Mantis Jr Manual Rev 1.0

Please use our online warranty form on our webpage !
FUCHS MODEL :
SERIAL NUMBER:
OPTIONS INCLUDED:
Fuchs Audio Technology
407 Getty Ave, Clifton, NJ 07015
[phone] (fax) 973-772-4460
Website: www.fuchsaudiotechnology.com
Email: [e-mail]

WARRANTY REGISTRATION FORM
This completed form must be returned to Fuchs Audio Technology within 30 days of purchase along
with a copy of your receipt from your authorized dealer.
Please fill in all requested information on this form so we may register you for future warranty repairs
or future upgrades, should they become available.
Purchasers Name: ___________________________________________________
Address: ___________________________________________________________
City: ____________________ State: _____ Zip: __________ Country:___________
Phone Number: _______________________ E-Mail address: ________________
Model: ___________ Serial Number: ___________________________________
Date of Purchase: ___________________________________________________
Dealer Name: ______________________________________________________
Comments:_________________________________________
Mantis Jr Manual Rev 1.0