SS-11B

The AMT Electronics SS-11B "Modern" Tube Preamp Pedal is a remarkably complicated pedal. If the MXR Phase 90 is one of the simplest pedals, with one knob, then the SS-11B is *almost* up there with the Boss DD-20 in terms of complexity and configurability.

Thermionic Studios has one(1) SS-11B available for rental.

Controls

Image from Prymaxe website

• Switch 1 - "Output Select": When viewing the pedal straight-on, this switch is difficult to see as it is flush with the left-facing side. It can be found near the OUTPUT jack, opposite the RETURN jack. This switch toggles the function of the OUTPUT jack between -10 dB (for a standalone amplifier or another pre-amplifier), and + 4 dB (for a mixer or power amp).

On this pedal, all knobs have similar behavior. For any particular function, turning the corresponding control knob clockwise will increase the intensity of that particular knob's function. Clockwise = more.

Clean Channel

When the Clean channel is engaged, the corresponding left-side "Clean" blue LED is lit.

• Knob 1 - "Level": Volume output for the Clean channel.
• Knob 2 - "Low": Bass frequencies tone control.
• Knob 3 - "Mid": Midrange frequencies tone control.
• Knob 4 - "High": Treble frequencies tone control.
• Knob 5 - "Gain": Overdrive level. The Clean channel will never get fully saturated, even with the Gain control is maxed out.
• Toggle 1 - "Bright": When activated, this switch accentuates (increases) the treble frequencies for the Clean channel. Flipping the switch to the right engages the Bright.
• Footswitch 1 - "Clean/Drive": The Clean channel is self-contained, and the Clean/Drive footswitch toggles between the Clean and Drive channels.

Drive Channel

The "Drive" channel is split into 2 "sub" channels, Crunch and Lead. Both Crunch and Lead share a common set of tone controls. When the Drive channel is engaged, the corresponding left-side "Drive" red LED is lit.

Drive "Crunch"

When the Crunch subchannel is engaged, the corresponding right-side yellow LED is lit.

• Toggle 2 - "T.Shift": Off/On. Engaging this switch boosts middle and high frequencies in the Crunch channel. Flipping the switch to the right engages the T.Shift.
• Knob 6 - "Level Cr.": Sets the output volume for the Crunch channel.
• Knob 10 - "Gain Cr.": Sets the Distortion level for the Crunch channel.

Drive "Lead"

When the Lead subchannel is engaged, the corresponding right-side red LED is lit.

• Toggle 3 - "T.Shift": Off/On. Engaging this switch boosts middle and high frequencies in the Lead channel. Flipping the switch to the right engages the T.Shift.
• Knob 11 - "Level Lead": Sets the output volume for the Lead channel.
• Knob 12 - "Gain Lead": Sets the Distortion level for the Lead channel.

• Knob 7 - "Low": Bass frequencies tone control.
• Knob 8 - "Med": Midrange frequencies tone control.
• Knob 9 - "High": Treble frequencies tone control.
• Footswitch 2 - "Crunch/Lead": When the Drive channel has been selected, this footswitch toggles between the Crunch (less gain) and Lead (more gain) channels.

Jacks

• Input - "Input": This is the "second" jack down on the right side. Put your instrument cable in here.
• Effects Out - "Send": This is the "top" jack on the right side. This is an "Out" or a "Send" to any effects you wish to loop into the SS-11B.
• Effects In - "Return": This is the "top" jack on the left side and is the effects "Return". Any effects that were "Sent" to from the "Send" return in this jack.
• Output - "Output": This is the pedal output jack. It is found on the left side and is the "second" jack from the top. Depending on the OUTPUT SELECT setting, the instrument cable from this jack gets plugged into an amplifier, a mixing board, or other effects.

Bypass: True

The AMT SS-11B uses true bypass circuitry.

General Information

This is an actual vacuum tube pedal, loaded with two (2) 12ax7 preamp tubes - meaning that there are four (4) tube amplification stages. The operating voltage of these tubes is around 300 volts, but if the tubes cascade into a very rare meltdown situation, voltage can be as high as 500 volts. If you own this pedal and are looking to replace the tubes, be careful that you don't open up this pedal until sufficient time has passed (12 to 24 hours) for the voltage on the tubes and capacitors inside to dissipate to safe levels.

One of the idiosyncrasies of the SS-11B is that if it's plugged into your signal chain, it is always on. There is no way to "turn off" this pedal except to remove it from your signal chain, or include it into the loop of another pedal designed to loop effects into and out of your signal chain. If you're going to have the SS-11B as one of your pedals, the likeliest unobtrusive way to replicate "bypass" would be for you to set the pedal to the "Clean" channel.

Another interesting thing to note from the schematic below is that the Clean channel has a single amplification stage, then goes to tone shaping, and then a second amplification stage. The Crunch and Lead channels have all their amplification stages cascading into one another, and then tone shaping is done at the end. Some interesting food for thought for designers of preamps and amplifiers.

Pedal Manual

• AMT SS11b Distortion Preamp 2-channel pedal Manual

Phase Inversion: "It Depends..."

So "It Depends..." is not a very confidence inspiring comment. However, whether or not phase inversion occurs actually depends on which channel setting you're using in the pedal. If we follow the signal paths, along with the switching, through the pedal, we get 2, 3, and 4 amplification stages depending on the channel selected.

1. "Clean" = 2 stages = Non-inverted signal
2. "Crunch" = 3 stages = Inverted signal
3. "Lead" = 4 stages = Non-inverted signal

Clean Channel: No

Schematic ID	Electronic Part	Action	Phase State
V1.1 (X1 per schem)	12ax7 first half	Inverts	Inverted
V2.2 (X10 per schem)	12ax7 second half	Inverts	Reverted

Crunch Channel: Inverted

Schematic ID	Electronic Part	Action	Phase State
V1.1 (X1 per schem)	12ax7 first half	Inverts	Inverted
V1.2 (X7 per schem)	12ax7 first half	Inverts	Reverted
V2.2 (X10 per schem)	12ax7 second half	Inverts	Inverted

Lead Channel: No

Schematic ID	Electronic Part	Action	Phase State
V1.1 (X1 per schem)	12ax7 first half	Inverts	Inverted
V1.2 (X10 per schem)	12ax7 second half	Inverts	Reverted
V2.1 (X1 per schem)	12ax7 first half	Inverts	Inverted
V2.2 (X10 per schem)	12ax7 second half	Inverts	Reverted

Schematic

Non-AMT drawing found on Russian Pedal forum. Copyright unknown. Assumed Public Domain.

Sort of blown away that we found this... The schematic includes the available switches:

• The Bright switch for the Clean channel, and,
• The T.Shift switches for the Crunch and Lead subchannels.

The T.Shift switches are found unlabeled on the Schematic in the lower-right "TB Board" section just above the Crunch/Lead tone controls.

Artists

We are currently unaware of any artists actively using the pedal now, or who have in the past.

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Additional Sources

• Guitar-Gear.ru Forum (where schematic found)
• http://amtelectronicsusa.com/productpagess11bv2.html