Fulltone True-Path ABY-ST User Manual

Aby-st, Owner’s manual

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2013 FMP Inc. All Rights Reserved


Owner’s Manual

Michael Fuller/President


In my studio, there are 20-30 some-odd vintage amps: from a 1959 Bassman, to a 1959 Fawn-colored Vox AC15, to the entire

60’s Fender Blackface line in duplicate, to every year of Marshall 50 & 100 watt amp spanning 1966 through 1971. I was always a

single-amp live-performer until I heard/saw Eric Johnson in the mid 80’s while he was doing a set for Fender at the NAMM show.

Eric ripped that evening, but what most impressed me was his constant switching between the bell-like OD-friendly Fender tones

and the huge, warm, and fuzz-friendly vintage Marshalls...sounding like 2 guitarists in the process. At soundcheck, Eric was nice

enough to explain his setup to this curious 23 year old who was so blown away by the high-volume sounds being created that my

life was changed that very day. I immediately set out to expand my own tonal palette by switching and combining 2 or 3 amps in

my own Jazz/Rock/Blues music, and started immersing myself in effect and amp design, repair, and modification, eventually

leading to this little thing we like to call “Fulltone.”

I designed the True-Path ABY switchers to solve all of the issues that arise from combining amplifiers, and to sound absolutely

transparent in the process. Other ABY’s “thump” when switching, Yes, even if they advertise that they don’t! I developed a circuit

that rapidly pans between the outputs, completely eliminating “thumps.” On this subject: Especially when using single coil pickups,

lights and stray electro-magnetic-fields (EMF’s) can appear to be a slight “ticking” noise, but this is simply those noises coming

through your pickups and cutting on and off as the signal pans between the outputs. To test this, simply turn off your Guitar’s

volume knob and hear that our ABY is dead-quiet. “ST” stands for “Soft Touch,” meaning it has smooth-actuating, non-latching,

momentary footswitches that are absolutely quiet for studio and/or live applications, where even the click of a footswitch could get

you noticed in the wrong way. The ABY-ST allows you to create many amazing sounds not possible with a single-amp set-up!

Play on!

This unit is ONLY to be used to switch between or combine UL (or CSA) listed, properly-grounded amplifiers, and only connecting to the amp’s INPUT.

This product should never be connected to the SPEAKER OUT of an amplifier or you will damage this pedal and the amp(s) involved. There is always

danger of electrocution when combining amplifiers, if you have any questions please contact a qualified technician. Use this product at your own risk,

Fulltone is not responsible for any loss, damage, or injury resulting from the use (or misuse) of this product. True-Path ABY has an isolation transformer

on the B-Out that may aid in certain pedalboard-related grounding issues. Your True-Path ABY also offers the ability to “lift” the ground on the B-Out

although we cannot recommend lifting grounds for legal and safety reasons. Again, contact a qualified technician if you have questions and be safe!


Current draw= 100ma. Compatible with most Pro pedalboard power supplies. Make sure to use a “regulated” power supply!

Size= 5.25”W x 4.0”D x 1.8”H Weight= 1lb 7 oz. Housing= 16 gauge steel

Buffer Specifications: This ABY contains 2 high-headroom, high-quality JFET buffers.

Input Impedance= 1.1 megaohms...very high, optimal for guitar pickups.

Buffer Output Impedance= 100 ohms...extremely low so as not to load down your guitar cables or other pedals in your signal chain.

Transformer: Fulltone custom-wound 1:1 Isolation transformer, high Nickel core content, the best sounding transformer you can get, period.

Primary Impedance= 10K ohms

Secondary impedance= 10K ohms