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1.0.0 (2023-07-04) PROJECT SUMMARY A pedal adaptation of the two-channel preamp of the Lab Series® L5 amplifier from the late 1970s, often considered to be the best solid-state amp ever designed. Actual size is 5.48” x 2.61” (main board) and 4.90” x 0.71” (bypass board).
20 Document Revisions INTRODUCTION The L5 Preamp is a pedal conversion of the preamp of the Lab Series® L5 guitar amplifier, a Moog- designed solid-state amplifier from the late 1970s that is widely considered the best and most tube-like solid-state amplifier ever made. It has two channels which are both merged into a shared distortion/ master volume circuit as well as a compressor/limiter.
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USAGE The L5 Preamp has the following controls: Channel 1 • Bright (toggle switch) adds a treble-bleed capacitor to the volume control, which preserves some of the treble at lower volume levels to keep it from getting dull. • Treble, Mid and Bass form a standard Fender-style 3-band passive EQ. •...
When developing the original Lab Series L5 Preamp, we adapted a supply scheme from Alesis rack units in the early 1990s that involved a 9VAC adapter and an AC voltage tripler. This was then rectified to bipolar +/-19V DC and regulated down to 15V on each rail.
PARTS LIST This parts list is also available in a spreadsheet format which can be imported directly into Mouser for easy parts ordering. Mouser doesn’t carry all the parts (most notably potentiometers) so the second tab lists all the non-Mouser parts as well as sources for each. →...
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PARTS LIST, CONT. PART VALUE TYPE NOTES 390R Metal film resistor, 1/4W Metal film resistor, 1/4W 300k Metal film resistor, 1/4W 430R Metal film resistor, 1/4W Metal film resistor, 1/4W 240k Metal film resistor, 1/4W 390R Metal film resistor, 1/4W Metal film resistor, 1/4W 300k Metal film resistor, 1/4W...
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PARTS LIST, CONT. PART VALUE TYPE NOTES Metal film resistor, 1/4W Metal film resistor, 1/4W Metal film resistor, 1/4W Metal film resistor, 1/4W Metal film resistor, 1/4W Metal film resistor, 1/4W 100k Metal film resistor, 1/4W 100k Metal film resistor, 1/4W Metal film resistor, 1/4W Metal film resistor, 1/4W Metal film resistor, 1/4W...
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PARTS LIST, CONT. PART VALUE TYPE NOTES Film capacitor, 7.2 x 2.5mm Film capacitor, 7.2 x 2.5mm Film capacitor, 7.2 x 2.5mm Film capacitor, 7.2 x 2.5mm Film capacitor, 7.2 x 2.5mm Film capacitor, 7.2 x 2.5mm 2.2uF Film capacitor, 7.2 x 5mm Original amp uses 2.7uF tantalum, but 2.2uF film will work the same.
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PARTS LIST, CONT. PART VALUE TYPE NOTES 2N3904 BJT transistor, NPN, TO-92 2N3904 BJT transistor, NPN, TO-92 2N5457 JFET, N-channel, TO-92 Original uses PN4303, but 2N5457 will perform the same. 2N3906 BJT transistor, PNP, TO-92 MPSA13 Darlington transistor, NPN, TO-92 LF356N Operational amplifier, DIP8 IC1-S...
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PARTS LIST, CONT. PART VALUE TYPE NOTES MID 2 25kB 16mm right-angle PCB mount pot FREQUENCY 100kC dual 16mm dual pot, right angle TREBLE 2 25kB 16mm right-angle PCB mount pot VOLUME 2 25kA 16mm right-angle PCB mount pot MULTIFILTER 25kA 16mm right-angle PCB mount pot MASTER...
BUILD NOTES DC converter selection There are several brands and models available, all with the same pinout and similar specifications. Here are the DC converters we’ve found that will work in this circuit. BRAND PART # MOUSER # SUPPLY NOTES Traco TEC 3-0923 495-TEC3-0923...
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BUILD NOTES, CONT. Calibration The L5 Preamp has two different calibration trimmers, located on the far-left side of the PCB. To set these, all you will need is a multimeter and a signal generator (which can be a computer or smartphone). Note that all voltages are taken in AC, not DC, since we are dealing with audio signal levels.
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Due to the height of the DC converter and electrolytic capacitors, the components on the switching PCB are mounted on the bottom, the same side as the footswitch. This is in contrast with most other Aion FX projects where the switch is mounted on the bottom of the switching sub-board and the components face up.
SCHEMATIC (INPUT, CH. 1, CH. 2, MULTIFILTER, SWITCHING) Input Channel switching Bypass switching CHANNEL A CHANNEL CH.1 SWITCH CHANNEL LF356 FROM CH.2 INPUT INPUT JACK BYPASS A BYPASS C FROM BYPASS B CHANNEL B OUTPUT JACK 10uF 22pF Channel 1 & 2 Multifilter IC6A RC4558...
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DRILL TEMPLATE INSTRUCTIONS Cut out the drill template on the following page, fold the edges and tape it to the enclosure. Before drilling, it’s recommended to first use a center punch for each of the holes to help guide the drill bit. Ensure that the template is printed at 100% or “Actual Size”.
ENCLOSURE LAYOUT Enclosure is shown without jacks. See next page for jack layout and wiring. Note: The upper pads for the dual-gang gain potentiometer appear to be cut in half. This is intentional! It’s called a plated half-hole or castellated via, and it’s used so that the PCB can lay flat across the pots instead of angling upward for the dual pot.
LICENSE & USAGE No direct support is offered for these projects beyond the provided documentation. It’s assumed that you have at least some experience building pedals before starting one of these. Replacements and refunds cannot be offered unless it can be shown that the circuit or documentation are in error. All of these circuits have been tested in good faith in their base configurations.
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