AMT Analoger AFG-1 User manual

Analoger™ AFG-1
100% Analog Bucket Brigade Flanger
A Whooshless Resonant Comb Modulator
User Manual Revision A
Last Revision 05/16/2023

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Introduction
Thank you for your purchase of the Asheville Music Tools Analoger™
series AFG-1 Flanger: a Whooshless Resonant Comb Modulator. This
pedal features a reissue Bucket Brigade Delay line to deliver classic
Flanger and Chorus sounds with the most natural modulation possible. The
synthesizer-inspired control voltage topology provides an extended range
of functionality and precision not available in most flangers. The AFG-1
draws upon renowned analog designer Hawker’s decades of experience
creating modulation and delay-based effects. We hope you enjoy many
years of use from your AFG-1 and find it as inspiring and fun as we have.
The AFG-1 is a 100% analog effect, built with over 380 high-quality
components to combine vintage audio processing techniques with
advanced, high-tech, electronics. At its core is a high headroom, 256 stage,
reissue MN3009 Bucket Brigade Device. True sine-wave exponential
modulation and a selectable response dynamic envelope detector modulate
its VCO based delay clock. It contains tightly tuned, discrete, high-order
filters and a compandor with emphasis/de-emphasis to keep the noise floor
low while imparting an animated feel. The VCA-based feedback control
offers warm regeneration tone and a controlled method of dialing in deeply
notched comb filter effects. A JFET input stage and input preamplifier
optimizes the signal-to-noise ratio and allows for tone shaping and
harmonics enhancing overload at higher settings. The whole ensemble is
powered by a protected and highly regulated 15V power supply for
carefree operation in any stage or studio environment.
A special thank you to the entire Hypertriangle team, including our sister
companies, Asheville Music Tools and Electronic Audio Experiments. Plus
John, Liz, Rosser, Miranda, Brad, JohnTone, Hawker and all of the other
people who have contributed. This design was truly a team effort, and it
was a joy to work with every one of you to bring this pedal to fruition.
We hope you enjoy many years of use from your AFG-1 and find it as
inspiring and fun to play as we have.

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Hawker’s Log: What is all this Flanging stuff anyway?
History, Artwork, the Whooshless Wonder, and Flanging versus Phase Shifting
The AFG-1 flanger has a rich history. It is probably my favorite delay-
based sound, and is the fourth flanger I have designed for commercial
release. This flanger came about by adding the features that I felt were
lacking in my previous designs, while building onto the Analoger format.
The AFG-1’s graphic
pays homage to both
the tape flanger of
yesteryear and the
comb filter frequency
response it produced.
Flangers are based on modulating a very short delay line from 0.2ms-10ms.
Early flanging was done by grabbing or controlling a tape recorder’s take
up reel “flange” or motor to be slower than a second unit that was tracking
in sync. The first tape was then combined with the second to create a comb
filter effect. Frequencies half the delay time were canceled out, while
frequencies the same as the delay time were enhanced. Since 50Hz-1 =
20ms, and 2KHz-1 = 500µs we can see that to cancel these frequencies we
require a delay time of 10ms – 250µs. This is in the range of the AFG-1
and a typical guitar, bass or synth note. One difference in tape flanging is
that the 2nd tracking tape has its own fixed delay. For this reason, a tape
flange can do “through zero” flanging easily where the 1st delay may be
faster or slower than the static 2nd delay. To do this in analog not only adds
a potentially undesirable pre-delay, it requires twice as many parts adding
to cost and complexity. Thus, the AFG-1 is not a TZ flanger.
The AFG-1 has some unique features. It utilizes sine wave and bipolar
additive modulation as well as phase summing options, unlike traditional
flangers. More uniquely, it contains a clipping drive circuit and an
envelope follower. The drive circuit came about because I have often used
distortion before a flanger to increase harmonic content. I added an
envelope follower because I often played my flanger with an expression

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pedal, moving my feet in tandem with my picking, and felt an envelope
follower would even better capture this dynamic responsiveness.
In the AFG-1, the time/freq can be modulated by the LFO and by tracking
the user’s playing dynamics. Using the envelope on its own removes the
sometimes-objectionable whoosh of traditional LFO based flangers when
not playing. This adds an articulated effect that effectively turns the FREQ
knob to the right or left based on your playing. It can produce deep “out-of-
band” sounds or aliased dive bombs of long delay times depending on the
direction and amount of envelope. The three carefully tuned ENV settings
adjust the response timing for playing styles and situations anywhere
between fast finger picking to melodic ambient strummed soundscapes.
So what is the difference between Flanging and Phasing? Reviewing: In a
flanger all notes are delayed the same amount. The flanger cancels
frequencies that change depending on the delay time. This happens at
harmonic intervals of the delay time. The key difference is that, within a
flanger’s circuit, all frequencies get the same delay time.
Phasers:A Phaser, also known as an all pass-filter, shifts frequencies
above the cut off frequency by 90 degrees. They are in pairs of stages to get
180 degrees, which will cancel out a signal. This cut off is based on a fixed
frequency and not time. Therefore, it has a known delay at one frequency
only; other frequencies have a different delay time, and phase shift, thus are
delayed differently. The resulting comb filter looks different, and is not
harmonically related, as shown below.
More reading at:
https://www.soundonsound.com/sound-advice/q-whats-difference-between-
phasing-and-flanging

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Hawker’s Log: About BBDs
I am often asked what gives analog delay-based effects their characteristic
sound. The reason for me is different than I see others usually mention.
A BBD (Bucket Brigade Delay) works by storing a momentary snapshot in
a capacitor isolated by a FET network. It passes this sample from one
capacitor to the next via a bi-phase clock until it reaches the output. These
samples are like water in a bucket brigade line, passing the audio from one
“bucket” to the other until it reaches the “fire” at the end. BBDs were
originally designed for distance measurement with radar. When the radar
signal was sent out, a copy was delayed through a BBD and compared to
the reflected signal. By sweeping the time until the reflection cancels out
the delayed sample, the delay time, and thus distance, is measured. Early
digital oscilloscopes, like the Tektronix 2440, also used them as temporary
storage since Analog to Digital converters of the time were too slow. CCD
cameras still do this today for the same reason. Today they are used almost
exclusively for audio processing in delay, chorus, and flanger effects.
The AFG-1 uses a recreation of the Matsushita/Panasonic MN3009 PMOS
BBD from Xvive™. The MN300x series BBDs use a higher voltage for
superior clarity, noise, headroom, and distortion compared to the MN320x
NMOS types typically found in most stompboxes. However, the MN320x
BBDs are capable of wider delay times with a faster clock. The reissue
BBDs sound very close to the Panasonic parts but are more transparent and
have a lower noise floor, though with less animated character. In addition,
the sound does not vary over delay times as much as their predecessors did.
Perhaps the biggest reason analog BBD based delays can do what digital
counterparts often cannot is due to Fractional Delay, often referenced as the
Doppler Effect. Since the clock moves continuously, delay time moves
smoothly and unfixed by incremental steps. That is why analog choruses
and flangers tend to feel more natural. The ear is very sensitive to this and
perceives this as distance and movement. This trick is how movies pan
sound or make you think a bullet just whizzed over your head. Most digital
delays simply cannot do this.

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With a fixed clock frequency, they can only take a sample step every 48 or
96KHz and step at that increment. This only simulates fractional delay and
is not true fractional delay. The ear can hear the difference, and so the brain
will process this difference as incorrect. Early digital delays like the
Lexicon PCM 41/42 did use a variable clock using a different, now
obsolete, process. However, these were the exception, not the rule. Most
digitally controlled analog delay based modulation that use a processor-
generated clock do not use steps small enough for true fractional delay.
Therefore, while they may use a BBD, the modulation does not sound as
natural as some picosecond step clocks or true analog modulation.
In addition, BBDs have some other “artifacts” that give them their unique
sound. The transfer characteristics, gain, noise, distortion, and frequency
response vary depending on the bias voltage and clock frequency making
the sound change as the delay time changes. They also do not put out the
entire signal at the same time. Half the signal is a ½ clock behind the rest
of the signal, yet combined at the same time, making for a strange, smeared
mixing of the signal samples slightly out of time.
Other components in a BBD circuit are also responsible for the signature
sound of analog delays. BBDs require companding and emphasis/de-
emphasis networks to improve the signal to noise ratio, but these add phase
changes, limiting and an animated “breathing” compression character to the
sound. The design of the filters affects the frequency response, peaking or
ringing, and potential aliasing or ring modulation. There are many more
parts of the analog design often overlooked in digital recreations that affect
the sound as well. This includes the clipping, feedback network, clock
stability, modulation wave shaping/curves (exponential or linear, etc.) that
are all important to get that great analog sound.
For more reading about BBDs check out these great websites:
https://www.electrosmash.com/mn3007-bucket-brigade-devices
https://www.premierguitar.com/articles/25035-behind-the-bucket-brigade
https://pedals.thedelimagazine.com/bbd-chips-the-magic-behind-analog-delay-
pedals/

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Setup
For all Asheville Music Tools products, use only a standard, 9VDC
REGULATED, center-negative power supply from a reputable vendor.
For the AFG-1 the supply should be rated for at least 200mA. Vintage style
rectified & filtered, but unregulated, supplies are not acceptable for use
with this product. We like the Truetone™ One Spot® and similar products.
When using other pedals in your signal chain, we recommend an isolated
power supply.
The AFG-1 may draw over 200mA on power up. Use caution if using multi
output supplies with 100mA outputs. Use the higher current outputs
when using this type of supply. Never use a higher voltage with this
product. There are no sonic benefits, and you risk damaging the pedal and
voiding the warranty. The pedal will not turn on if it detects an overvoltage
supply or high ripple from an unregulated supply. Our products do not use
a conventional 9V battery due to the high current draw.
Your Analoger™ Series Pedal ships with a clear plastic protector over each
of the knobs. Feel free to peel it off if its presence shows on the knob top.
The AFG-1 has a flexible bypass making it able to be used in various
configurations for guitar, synthesizer, or line level applications, including:
•Standard pedal use: AFG-1 connected into an amplifier input,
with or without other pedals. You may use the pedal in either
Buffered or True bypass mode in this configuration.
•Insert Effect:Connect the AFG-1 to the effects send/return of
your preamp, power amp or mixing console. You may also use
the AFG-1 to replace the existing preamp if connected to just the
return. Use it this way in buffered Bypass mode only.
•DI (Direct Input): The AFG-1 can be used to line match to a
mixer or DAW input for the correct drive and signal conversion
from the guitar’s high impedance out to a console or DAWs low
impedance line in. It can also be used as a buffer placed before
other pedals. For best results use with 10K or higher line input.
Not suitable for 600ohm input impedance of some classic
consoles. Use this in buffered Bypass mode only.

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Getting Started
Let us explore the range of controls on your AFG-1.
Connect your guitar or other instrument to the INput jack. Connect an
amplifier, other pedals, mixer, or DI box to the OUTput jack. If you have
an expression pedal (or 0-5V control voltage source like a synthesizer
output), connect it to the EXPression input.
Use a 9V regulated 2.1mm, center-negative, power supply, capable of
providing at least 200mA of power and connect it to the 9V DC input.
Be sure to power up the AFG-1 BEFORE turning on your amplifier to
prevent speaker pop and the potential to damage your speakers or
headphones.
Let’s start with a basic flanging sound to familiarize ourselves with the
AFG-1. First, set the knobs to the Home position shown in the graphic
below, and engage the foot switch.
Set FREQ, AMOUNT &
ENVELOPE to be near
straight up or 12:00 position.
Set FEEDBACK knob to the
right at about 2:30.
Set the DRIVE and RATE to
9-11:00. Set the PHASE
switch to the up position and
ENV switch to the middle. EXP
switch clockwise to RATE.
This represents a classic Flanger sound.
There is no way to damage the AFG-1 through knob settings so feel free to
have some fun exploring how each control works There are some hidden
tricks, gotchas, and advanced possibilities, so once you are done having fun
read on to learn more about the AFG-1.

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Operation
The AFG-1 is laid out in homage to modular synthesizers with three main
modules. They are the DELAY Module, the LFO (Low Frequency
Oscillator) and the Drive/Envelope Modules. Let us look closer at each
of these modules.
DELAY MODULE
FREQ:The FREQ knob corresponds to the
MANUAL knob on a traditional flanger and
adjusts the center delay time from ~0.5ms to
~14ms (more using LFO and control
voltages). As you turn the knob CW you
decrease the delay time which corresponds to
higher pitch comb filter sound. Between
about 7:00 and 10:00 produces chorus sounds,
while past that is more flanging territory.
PHASE SWITCH: selects whether the delayed sound mixes and feeds back
in phase or out of phase. The up or “JET” position produces traditional
flanging sounds with the feedback and delayed sound in phase with the dry
signal. The middle “SWIRL” position is the most subtle mode. It sets the peaks
of feedback out of phase with the delayed and dry signal similar to the reverse
feedback knob on one of Hawker’s previous wood sided effect designs. Finally,
the down or “PHASE” position sets both the feedback and delayed signal out
of phase with the dry signal. This produces deeper bass and a more vocal sound.
This is similar to the ODD position of the classic A/DA Flanger or the TYPE
switch in Hawker’s previous classic black and silver mini-flanger design.
FEEDBACK:The FEEDBACK knob affects how much signal is fed back
into the buckets. On traditional flangers this is called “regeneration”. Feedback
creates deep time-based peaks and notches in the signal. At extreme settings it
will go into self-oscillation, providing drone tones that are tuned by the FREQ
knob setting. Try it out, get lost. Come back after and read the next section.
Be sure to read the control voltage section for information on this module with
expression pedals or control voltages.

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LFO MODULE
The Low Frequency Oscillator (LFO) module is a modulation source for
animating the FREQ (delay time) and providing movement to the notches
and valleys of the comb in the signal. Unlike most traditional flangers, our
LFO provides exponential, true sine wave, and octave symmetrical
modulation (instead of Hz symmetrical) for musical and balanced
movement, the way the ear and brain want to experience it. In the
synthesizer world, this is the familiar Volt/Octave tracking used for pitch
and frequency. Modulation is symmetrical around the FREQ setting. Use
FREQ to set the center point of the modulation and the LFO will move
equal fractions of an octave above and below this FREQ setting.
RATE: The RATE (AKA SPEED) knob
adjusts the speed or rate of modulation
from about 0.01Hz to 8.3Hz (wider range
via control voltages). At minimum the
sweep is almost imperceptibly slow.
Lower settings provide a slow whoosh or
a rhythmic pitch shift. Medium speeds
provide a chorus effect, and faster rates
provide a gargling, bubbly sound.
AMOUNT: The AMOUNT knob controls the depth or range of pitch
movement at the speed of the LFO, or the amount of modulation. Set
AMOUNT low for a deep jet plane whoosh or subtle shimmers. Set
AMOUNT higher for chorus, octave jumps or wild pitch shifts and
spaceship warbles. This is slightly different from the WIDTH knob on
traditional flangers, which is a pan control between MANUAL control and
LFO control. Instead, it adds the modulation on top of the FREQ setting,
rather than panning between the two, and thus provides for more total
range and wider control beyond just the FREQ panel knob setting.
Be sure to read the control voltage section for information on this module
with expression pedals or control voltages.