Orthos 50 / 100

(7 customer reviews)


Dual channel, 100W (or 50W), dual Master Volume, configurable response guitar amplifier.

We will install the internal lighting kit for you! This can be installed for any field panel type, however it is included with the grill close option already.

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SKU: 180-12861 Categories: , Tags: , , , ,



The Orthos™ amplifier was designed as a more streamlined version of the Gemini™. While there is no MIDI or advanced control built-in to this amp, there are still some cool features. For example, there are assignable Bright/Voice/Loop functions on each Master Volume setting, in addition to dual Gain controls.

Built-in to this compact head is a 100W power section capable of running a number of different power tubes. A transparent, yet fully bypass-able, effects loop seamlessly couples the preamp to the power section.

Channel Descriptions

The Orthos™ amplifier consists of two channels, each with its own gain, 3-band EQ, various Bright/Voice/Loop assignment switches, and level controls. In addition, the Lead channel features dual Gain controls, one for Master 1 and the other for Master 2.

Clean Channel

This channel produces a wonderfully warm tone that aims to be the best of any channel switching amplifier. Where most other high gains amps seem to include a clean channel out of necessity rather than desire, the Orthos™ has a no-compromises clean channel with its own dedicated preamp tube voiced specifically for huge headroom and sparkling cleans. With the included Gain control on the clean channel, one can also dial in a very cool vintage style distortion.

We include a Bright switch for each Master allowing you to add sparkle and clarity to the clean tones. Whichever Master is active determines which switch is used to activate the Bright function.

Dual Loop switches are present on the Clean channel as a way of engaging/bypassing the effects loop for each Master. This allows you to easily engage the Loop automatically for one of the Masters.

Lead Channel

The Orthos™ Lead channel is based on our signature high-gain sound that aims to give you one of the most unique, round, warm, yet extremely usable and cutting high gain tones available. The Lead 1 and Lead 2 voicings from the Colossus are both available via the Voice switch. Lead 1 has a nice solid and tight mid voicing that is great for rhythms and leads alike. Lead 2 has a lower mid-point and is favored by most for smooth singing leads.

The Lead channel sound is technically fixed to Colossus Mode On and Fat On. This is one of our most popular high-gain tones, and it made sense to build a stripped-down amp around it. This sound is great for metal and rock alike, depending on the overall Gain and Bright settings.

We include both Bright and Voice switches for each Master allowing you to adjust attack and feel for rhythm and solo tones. Whichever Master is active determines which set of switches is used to activate the Bright and Voice functions.

Dual Loop switches are also present on the Lead channel as a way of engaging/bypassing the effects loop for each Master. This allows you to easily engage the Loop automatically for one/both/neither of the Masters.

Master Section

The Orthos™ features the same proven transparent and wonderfully performing effects loop as our other amps. The loop circuit is true-bypassable via the front panel Loop assignment switches, as well as a rear panel 1/4″ contact closure jack. In addition, the loop has independent Send and Return Level controls for maximum flexibility.

Dual master volumes allow for two overall performance levels to be set and recalled by the user. One player may prefer to set the second level as a solo-boost, others may prefer to use it as a volume cut. In addition, the current Master also selects the active row of assignment switches. Master 1 selects the top row of switches, Master 2 selects the bottom row.

The master section also includes power amp response controls, Top and Bottom. The Top control affects the response of the power section to treble frequencies, whereas the Bottom control affects the bass frequencies. These controls are great for dialing in the amp’s response to different speaker cabinets. They also allow the player to optimize the amp for different master levels. It’s especially useful for adding awesome bottom and clarity end at low volumes.

The power section consists of a quad of 6L6GC tubes, standard. However, just about any octal power tube can be installed — EL34, KT88, 6550, etc. Each tube is individually fused in order to protect the amplifier in the event of a tube failure. A Fault LED lights to indicate a fuse has blown and the tube is no longer functioning. One can also remove a pair of fuses as an easy way to run the 100W amp at half-power.

A custom wound USA made output transformer is a top performer and one of the highlights of this amplifier. Parallel speaker outputs allow one to easily drive two cabinets with a total impedance of 4/8/16 ohms.

Another one of the unique features of this amplifier is its universal power input. This allows easy use by any player around the world and eliminates the neat for power converters or transformer swaps for shipment to any international country.

Options and Accessories

Field Panel

Either a lit acrylic, metal lit, or standard solid logo is available on the face plate of the amplifier. The lit logos are capable of displaying any color for a number of different amp settings. This is all programmable via a DIP switch system on the back of the amp. A different color can be selected for each of the 4 settings Clean Master 1, Clean Master 2, Lead Master 1, and Lead and Master 2.

Foot Switch

A custom foot switch is included with the Orthos as an option. Further, the amp is compatible with any standard 2-button 1/4″ TRS foot switch.

In addition, control of individual functions is possible via standard 1/4″ contact closure connections on the back of the amp.

Note: Once a jack is plugged into one of the rear panel control functions, the respective function is defeated and the plug takes priority. This means if the foot switch is plugged in, the front panel Channel / Master controls will no longer function.

Weight: 48 lb.
Dimensions: 26.75in. × 11in. × 9.5in.

Default specs…

Additional information

Weight 56 lbs
Dimensions 32 × 16 × 16 in

100W, 50W

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Knob Style


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Channel Configuration Clean and Lead
EQ 3 band EQ per channel
Voice Switches Clean (None), Lead (1/2) — for Master 1/2
Bright Switches Clean (on/off), Lead (on/off) — for Master 1/2
Loop Switches Clean (on/off), Lead (on/off) — for Master 1/2
Clean Channel Controls Gain, Bass, Middle, Treble, and Level knobs; Bright, Loop, and Channel Select switches
Lead Channel Controls Gain 1, Gain 2, Bass, Middle, Treble, and Level knobs; Bright, Voice, and Loop switches
Master Controls Master Volume 1, Master Volume 2, Top, and Bottom knobs; Master Volume Select switch
Foot Switch Custom 2 button with Channel 1/2 and Master 1/2 select
Remote Controllable Functions Channel select, master volume select, Gain 1/2 select, Voice 1/2 select, Bright on/off select, loop bypass
Control Options Front Panel and 1/4″ contact closure
Bias Test Points Measure with any DMM capable of DC millivolts, 1 mV = 1 mA of plate current, assume 460 plate volts
Bias Adjustment Pot Location On top of chassis. Guaranteed to bias properly with most tubes
Output Power At least 100-120W with quartet, 50-60W with duet (two outer tubes removed)
Output Impedance Switchable between 4, 8, or 16 ohms into parallel jacks
Compliance Designed to comply with CE, UL, CSA, TUV, FCC, and RoHS standards
Head Shell Dimensions 26.75″ L x 11″ W x 9.5″ H (excluding handle and feet)
Weight 48 lbs
Shipping Dimensions 32″ L x 16″ W x 16″ H
Shipping Weight 56 lbs

7 reviews for Orthos 50 / 100

  1. carlroa77

    Orthos 2 is one of my all time favorite amps. Does it all from cleans, crunch and heavy overdrive. Love that I can get the amp super tight with the feel knob. Tones are superb. Record with it all the time. I got mine with the weight relieved option. Built like a tank. Highly recommend. A++++.

  2. fretwizrd13

    I’ve owned a lot of amplifiers…. Well over 20 high end / high gain monsters. Including the popular “German ones”. I’ve sold them all, there is no need to BS around with another other amp while the Orthos roams the streets untethered and willing to fight. This amp is my hands down go to. Playing live and touring with my Orthos Mk2 has been an absolute pleasure. The one thing I can say about this amp (besides it being my favorite amp I’ve ever owned) it’s that it’s consistent. I always get the tone I want on tap and as strong as it was the night before.
    The feel knobs add a whole new level of flexibility and “dialability”. It’s basically what sold me on this amp.
    You can go from “dry and focused” to “wet and ready” at the turn of a single knob. Find your preferred EQ setting and perfect it with the feel knob/s.
    10/10 will riff again.

  3. Paul Morrisette

    I was looking for a high end amp with a great clean channel and a lot of tone shaping options as well as being high gain. This amp is incredible and beat out a lot of the other amps with more channels! Can’t wait to get a matching 212 and try other things from Kyle later on! Definitely will be a ksr user from here on out!

  4. adamfriend7

    First impressions: I ordered the metal field grill with internal lighting modification in black taurus and black hardware. It is a solid amp weighing about 30kg. This amp performs very well at low volumes. I would describe the clean channel as sitting somewhere between the Mesa Mark V Clean Channel set on Fat and Bold on, and the PRS Archon. It is a nice thick sounding clean that responds very well. I did a side by side with all aforementioned amps as I have all three and the KSR Orthos holds its own.

    I would describe the gain channel as sitting somewhere between a Bogner Uberschall Revision Blue, and an early 2000 Dual Rectifier that is less congested and more clear across the tonal spectrum. I hear slight Mesa Mark V/PRS Archon gain influences on gain channel, yet less nasally. It is a very pleasing smooth gain with the bright off and with bright on it adds just enough bite. I run my KSR Orthos 2 through my Marshall Mode Four Cabinet (MF280) with Marshall Celestion V30s and it is clear, tight and articulate on both channels.

    I bought this amp direct through Kyle without trying it first and I am very happy with it overall. I use a PRS MCCarty with JB style pickups and a Charles Cilia (PRS P22 Style) with WCR Godwood style pickups, and both guitars work very well with Channel 1 & Channel 2 Masters on or off. I want to mention that Kyle Rhodes has the best customer service in the business and we exchanged over 100 emails back and forth discussing the KSR Orthos 2 and my best options for ordering mine!

  5. Kyle Augustin (verified owner)

    This amp absolutely slays! I love my Juno but this Orthos takes the cake for me! Impeccable build quality and top notch customer service!

  6. Tommy W. (verified owner)

    Amazing amp. Its like a 5150iii and a Dual Rec had an illegitimate child, and now we have this demon of an amp

  7. Tommy W. (verified owner)

    Amazing amp. Love the grittiness and gain structure. Extremely detailed with good note clarity. Buy it now, but your riffs will still be weak, bro.

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