aion Ephemeris User manual

EPHEMERIS JFET BOOSTER 1
PROJECT NAME
EPHEMERIS
BASED ON
EFFECT TYPE
PROJECT SUMMARY
DOCUMENT VERSION
Xotic EP Booster
A hybrid JFET/BJT boost circuit loosely based on the preamp section of the Echoplex EP-3 tape delay.
JFET boost/preamp 1.0.0 (2023-11-24)
BUILD DIFFICULTY
Easy
Actual size is 2.3” x 1.86” (main board) and 1.78” x 0.86” (bypass board).

EPHEMERIS JFET BOOSTER 2
TABLE OF CONTENTS
1Project Overview 7Drill Template
2Introduction & Usage 8Enclosure Layout
3-4 Parts List 9Wiring Diagram
5Build Notes 10 Licensing
6Schematic 10 Document Revisions
INTRODUCTION
The Ephemeris JFET Booster is based on the Xotic EP Booster, a one-knob boost first released in 2009
that is loosely based on the preamp section of the Echoplex EP-3 tape delay. There have been some
minor changes to the circuit throughout production, but we traced one in 2023 to ensure that we had
the most accurate representation of the circuitr.
In addition to the gain knob, the original EP Booster also has a DIP switch on the inside with two
additional settings. In the stock circuit, the minimum gain setting is +3dB above unity. One of the DIP
switch settings adds a resistor at the output that essentially just turns down the volume and sets the
minimum gain position at unity gain instead.
The second mode disables a treble-cut filter. This could be called a treble boost, but in practice it
provides something more like a flat response while the stock mode has a slight cut above 3.2kHz for a
vintage-sounding warmth.
The Ephemeris moves the treble cut to a front-panel control, and replaces the fixed resistors at the
output with a true volume control. The gain and volume controls are somewhat redundant, but at high
gain levels it’s possible to get the second transistor to clip, so different combinations of gain & volume
can yield different tones. You can still dial back to unity gain as well, so the pedal can be used as a tone
enhancer or buffer.
We have also ported the “Bass” switch from the earlier version of the EP Booster, and added a third
position which cuts bass a bit, inspired by the original EP-3 preamp. More on this in the build notes.
USAGE
The Ephemeris has the following controls:
• Gain sets gain of the JFET stage.
• Volume sets the volume level at the output.
• Bright (toggle switch) disengages a hi-cut filter between the stages.
• Bass (toggle switch) selects the frequency range of the filter, with Low and Hi settings as well as an
in-between Mid.

EPHEMERIS JFET BOOSTER 3
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.
View parts list spreadsheet →
PART VALUE TYPE NOTES
R1 33k Metal film resistor, 1/4W
R2 1M Metal film resistor, 1/4W
R3 4k7 Metal film resistor, 1/4W
R4 8k2 Metal film resistor, 1/4W
R5 1k Metal film resistor, 1/4W
R6 15k Metal film resistor, 1/4W
R7 1M Metal film resistor, 1/4W
R8 10k Metal film resistor, 1/4W
R9 100R Metal film resistor, 1/4W
R10 10k Metal film resistor, 1/4W
R11 10k Metal film resistor, 1/4W
R12 390R Metal film resistor, 1/4W Power supply filter resistor.
RPD 1M Metal film resistor, 1/4W Input pulldown resistor. Can be as low as 1M.
LEDR 10k Metal film resistor, 1/4W LED current-limiting resistor. Adjust value to change LED brightness.
C1 47n Film capacitor, 7.2 x 2.5mm
C2 22n Film capacitor, 7.2 x 2.5mm
C3 1uF Electrolytic capacitor, 4mm
C4 10uF Electrolytic capacitor, 5mm
C5 OMIT Can use 10uF here and leave C6 empty. See build notes.
C6 1uF Film capacitor, 7.2 x 3.5mm Can omit and use 10uF for C5. See build notes.
C7 3n3 Film capacitor, 7.2 x 2.5mm
C8 OMIT Can use 10uF here and leave C9 empty. See build notes.
C9 1uF Film capacitor, 7.2 x 3.5mm Can omit and use 10uF for C8. See build notes.
C10 47uF Electrolytic capacitor, 5mm Reference voltage filter capacitor.
C11 100uF Electrolytic capacitor, 6.3mm Power supply filter capacitor.
C12 100n MLCC capacitor, X7R Power supply filter capacitor.
D1 1N5817 Schottky diode, DO-41
Q1 2N5457 JFET, N-channel, TO-92
Q2 2N5088 BJT transistor, NPN, TO-92 Can substitute BC549C (rotate 180 degrees).
GAIN 10kC 16mm right-angle PCB mount pot Reverse audio (reverse log or antilog) taper.
VOLUME 50kA 16mm right-angle PCB mount pot Audio (log) taper.
BRIGHT SPDT on-on Toggle switch, SPDT on-on

EPHEMERIS JFET BOOSTER 4
PARTS LIST, CONT.
PART VALUE TYPE NOTES
BASS SPDT on-off-on Toggle switch, SPDT center off
IN 1/4" stereo 1/4" phone jack, closed frame Switchcraft 112BX or equivalent.
OUT 1/4" mono 1/4" phone jack, closed frame Switchcraft 111X or equivalent.
DC 2.1mm DC jack, 2.1mm panel mount Mouser 163-4302-E or equivalent.
BATT Battery snap 9V battery snap Optional. Use the soft plastic type—the hard-shell type will not fit.
FSW 3PDT Stomp switch, 3PDT
ENC 125B Enclosure, die-cast aluminum Can also use a Hammond 1590N1.

EPHEMERIS JFET BOOSTER 5
BUILD NOTES
C5/C6 and C8/C9 capacitors
The EP Booster uses 10uF capacitors (C5 and C8) as signal couplers immediately after both the JFET
and transistor stages. We recommend keeping electrolytic capacitors out of the signal path wherever
possible. This PCB includes space for an alternate film capacitor (C6 and C9) in each of these positions,
in which case C5 and C8 can be omitted entirely.
Due to the low source impedance, 1uF is more than enough to pass all useful bass frequencies. However,
if you want to stick as closely as possible to the original circuit, use 10uF for both.
Bass switch
The original EP Booster (Rev. 1) had an internal switch to add bass. Overwhelmingly, players felt like the
switch didn’t actually do anything, and this was our experience in prototyping as well. We recommend
using 1uF for C3 and 10uF for C4. The original values are 10uF for C3 and 100uF for C4.
The 22n setting (middle position) is an addition to our version of the circuit, inspired by the original EP-3
unit that used this value in one of the variants.
Volume knob
The Rev. 2 circuit replaced the bass switch with a +3dB Boost switch. This is actually a slickly-marketed
volume cut, since the +3dB setting is equivalent to the stock Rev. 1 circuit. We have replaced this with a
full volume knob so that the circuit can get down to unity gain. Just note that
Transistor substitutions
The EP Booster uses the BC849C for Q2, which is the SMD equivalent of the BC549C. The Ephemeris
PCB uses the USA E-B-C convention, so we recommend using the 2N5088 or 2N5089. If you do want to
use a BC549C, just make sure to rotate it 180 degrees from the silkscreen.
Q1 is a MMBF5457, which is the SMD version of the 2N5457. These are available from Aion FX
mounted to through-hole adapters and will perform identically to the ones used in the original.

SCHEMATIC
EPHEMERIS JFET BOOSTER 6
GND
1M
1N5817
100uF
10kC
50kA
GND
+9V
100n
VA
2N5457
2N5088
1M
33k
47n
GND
4k7
10k
10k
390R
GND
47uF
GND
VB
1uF
GND
GND
8k2
VA
10uF 1uF
1k 15k
3n3
GND
1M
VB
VA
10k
GND
10uF
1uF
100R
GND
22n 10uF
IN
OUT
RPD
D1
C11
GAIN
1
2
3
VOLUME
1
2
3
C12
Q1
Q2
R2
R1
C1
R3
R10
R11
R12
C10
C3
R4
C5 C6
R5 R6
C7
R7
R8
C8
C9
R9
BRIGHT
2
3
1
BASS
2
3
1
C2 C4
GND

EPHEMERIS JFET BOOSTER 7
DRILL TEMPLATE
Cut out this drill template, 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 this template is printed at 100% or “Actual Size”. You can double-check this by measuring
the scale on the printed page.
Top jack layout assumes the use of closed-frame jacks like the Switchcraft 111X. If you’d rather use
open-frame jacks, please refer to the Open-Frame Jack Drill Template for the top side.
LED hole drill size assumes the use of a 5mm LED bezel, available from several parts suppliers. Adjust
size accordingly if using something different, such as a 3mm bezel, a plastic bezel, or just a plain LED.
0 1 2
CM
0 1
INCH
x: -0.65, y: +1.71 x: 0.65, y: +1.71
ø9/32” ø9/32”
x: -0.65, y: +0.41
ø1/4”
x: 0.65, y: +0.41
ø1/4”
x: 0, y: -1.20
ø15/32”
x: -0.775, y: -1.20
ø5/16”
CENTER (0,0)
125B
ø3/8” ø1/2”
0.385”
0.625” 0.625”
ø3/8”
OUT DC IN
VOLUME GAIN
BRIGHT BASS
FOOTSWITCHLED

EPHEMERIS JFET BOOSTER 8
ENCLOSURE LAYOUT
Enclosure is shown without jacks. See next page for jack layout and wiring.
125B

EPHEMERIS JFET BOOSTER 9
WIRING DIAGRAM
125B
IN +VGND N.C. N.C. OUT
PCB
IN
GND +V +V JACK GND JACK
OUTIN
GND GND PCB
OUT
Shown with optional 9V battery. If battery is omitted, both jacks can be mono rather than one being stereo.
Leave the far-right lug of the DC jack unconnected.

EPHEMERIS JFET BOOSTER 10
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. However, not all the
modifications or variations have necessarily been tested. These are offered only as suggestions based
on the experience and opinions of others.
Projects may be used for commercial endeavors in any quantity unless specifically noted. No
attribution is necessary, though a link back is always greatly appreciated. The only usage restrictions
are that (1) you cannot resell the PCB as part of a kit without prior arrangement, and (2) you cannot
“goop” the circuit, scratch off the screenprint, or otherwise obfuscate the circuit to disguise its source.
(In other words: you don’t have to go out of your way to advertise the fact that you use these PCBs, but
please don’t go out of your way to hide it. The guitar effects industry needs more transparency, not less!)
DOCUMENT REVISIONS
1.0.0 (2023-11-24)
Initial release.