AMT Analoger ACV-1 User manual

Analoger™ ACV-1
100% Analog Bucket Brigade Chorus Vibrato
Time Warping Modulator
User Manual Revision A
Last Revision 8/3/2022

<2>
Introduction
Thank you for your purchase of the Asheville Music Tools Analoger™
series ACV-1 Chorus/Vibrato & Time Warp Modulator. This pedal,
engineered by renowned analog designer Hawker, features a reissue Bucket
Brigade Delay line to give classic Chorus and Vibrato sounds with the
most natural modulation possible. The onboard Low Frequency Oscillator
and sophisticated control voltage topology guarantee the best sound,
features, and control available in any fully analog modulation pedal
currently on the market. We hope you enjoy many years of use from your
ACV-1 and find it as inspiring and fun to play as we have.
The ACV-1 is a marriage of vintage audio processing techniques and
advanced, high-tech electronics. It is designed using modern, quality
components for uncompromising sound, features, and reliability. We
started with a studio-grade MN3007 BBD, unlike the lower cost MN320x
pedal-grade BBDs found in most stompboxes. We powered it with a clean,
high voltage 15V power supply. Next, we coupled it with a special blend of
two tightly tuned high-Q 5
th
order anti-alias and reconstruction filters, a
compandor with emphasis/de-emphasis, VCA feedback control, a unique
5-amp high current BBD driver, and an analog clock with exponential
modulation technology to obtain unprecedented sound and richness, clean,
precision regeneration, and true fractional delay in a compact footprint.
This is the second in our line of time, phase, and frequency modulation
effects with a synthesizer-inspired control voltage approach. The ACV-1
draws upon Hawker’s decades of experience and expertise designing
modulation and delay-based effects for other companies.
A special thank you to the entire Hypertriangle team, including our sister
companies Asheville Music Tools and Electronic Audio Experiments.
Plus John, Liz, Miranda, Cam, Brad, Hawker and all the other people who
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 market.

<3>
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 ACV-1 uses a recreation of the Matsushita/Panasonic MN3007 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 BBDs can do what digital 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 chorus have such great feeling
vibrato. 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.

<4>
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 perceive this difference as incorrect. Early digital delays like the
Lexicon PCM 41/42 did use a variable clock using a different, now
obsolete, process, but these are 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, so 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
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 including the clipping, feedback network, clock stability,
modulation wave shaping/curves (exponential or linear, etc.) that are all
important to get that great analog delay 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/

<5>
About the Firemen and the ACV-1 Artwork
Our pedal artwork pays homage to Hawker’s past pedals and classic
modular synthesizers. The lines and boxes around function blocks lend
themselves to classic modular synthesizer layouts, which were organized
by function. You may notice the use of synthesizer terms such as “LFO,
VCO, CV” and very literal function knob names rather than the more sonic
based names of guitar pedals (FEEDBACK and TIME rather than
Regeneration and Manual for example). This helps the user see the logical
function blocks and signal flow to understand what is happening without
obscuring the meaning.
The feet used in our artwork, you should know that to start time warping it
is just a step to the left, and then time will be fleeting. Let’s do it again!
The schematic drawing was adapted from the original Panasonic sketch of
the BBD internals. It shows the bi-phase clock and capacitor storage to the
output. The careful observer will note that each clock pulse moves only
half the buckets forward preventing them from colliding with the next
stage, and hence the two clocks fire at different times to move half the
signal and part of the output signal is one clock behind the other part.
The firemen used in our artwork and literature come from the 1990s
Panasonic data books and an applications note released for their and
Digikey’s marketing. On the cover and back of this book was a picture of
firemen in a bucket brigade line. This represents the BBDs function of
passing the sound from one capacitor or “bucket” to another many times
before it is sent out by varying the clock, thus delaying the sound.

<6>
Set up
Use only a standard, 9VDC REGULATED, center-negative power supply
rated for at least 200mA, from a reputable vendor for all your Asheville
Music Tools effects. 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 ACV-1 may draw over 200mA when engaged. 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 ACV-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: ACV-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 ACV-1 to the effects send/return of
your preamp, power amp or mixing console. You may also use
the ACV-1 to replace the existing preamp if connected to just the
return. Use this way in buffered Bypass mode only.
•DI (Direct Input): The ACV-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.

<7>
Getting Started
Let us explore the range of controls on your ACV-1.
Connect your guitar or other instrument to the INput jack. Connect an
amplifier, 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 150mA of power and connect it to the 9V DC input.
Be sure to power up the ACV-1 BEFORE turning on your amplifier to
prevent speaker pop and the potential to damage your speakers or
headphones.
To start, set the ACV-1 to the Home position and take a step to the left.
This will produce a basic chorus sound, shown in the graphics to the right.
Set TIME, RATE, AMOUNT,
MIX & TONE to be straight
up 12:00 position.
Set FEEDBACK knob fully
counterclockwise (7:00).
Set the EXP switch
clockwise to RATE and set
the PHASE and LFO
switches to the up position. This
represents wet and feedback in phase
and a triangle LFO shape.
There is no way to damage the ACV-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 ACV-1.

<8>
Operation
The ACV-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 AMP Module. Let us look closer at these modules.
DELAY MODULE
TIME: The TIME knob adjusts the center
delay time from ~3ms to ~60ms (more
using LFO and control voltages). If you
modulate the delay time while playing,
you will also notice a pitch change as the
signal currently captured in the BBDs is
spit out faster or slower, therefore
compressing or expanding the delay time.
Between about 9:00 and 3:00 produce
chorus sounds. Further CW becomes more
of a slap back, while CCW more flanging or comb filter.
PHASE SWITCH: selects whether the delayed sound mixes and feeds
back in phase or out of phase. This difference is most pronounced with
shorter settings of the time knob or higher amounts of feedback. With
shorter time and lots of feedback this can produce a very vocal like quality
similar to a talk box. It is also more pronounced on bass notes than higher
pitch notes.
FEEDBACK: The FEEDBACK knob affects how much post TONE signal
is fed back into the buckets. It equates to the regeneration knob on a flanger
and creates deeper time-based peaks in the signal. At longer delay times it
acts more like a delay feedback control providing multiple repeats. At
extreme settings it may go into self-oscillation providing drone tones that
are affected by the time 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.

<9>
LFO MODULE
The Low Frequency Oscillator (LFO) module is a modulation source for
animating the delay time and phase as well as for bending the pitch of the
signal. Unlike traditional chorus or vibrato units, our LFO provides sine
wave and square options and uses exponential modulation for musical and
balanced movement, the way the ear and brain want to hear it. In the
synthesizer world this is the familiar Volt/Octave tracking used for pitch
and frequency. Our modulation is symmetrical around the TIME setting,
changing above and below it. This means that as you reduce the LFO
amount the pitch and time will stay centered, where you have it, and not
shift offset with the AMOUNT setting (requiring TIME to be adjusted) as
with traditional modulation devices.
RATE: The RATE knob adjusts the
speed or rate of modulation from about
0.10Hz to 15Hz (wider range via control
voltages). Lower settings provide a slow
whoosh or a rhythmic pitch shift.
Medium speeds provide a chorus or
vibrato effect while faster rates provide a
gargle or, bubble sound.
AMOUNT: The AMOUNT knob controls the depth or
range of pitch movement at the speed of the LFO, or the amount of effect.
Use low amounts for subtle shimmer and larger amounts for vibrato or
octave or greater pitch shifts or spaceship warbles.
LFO SHAPE SWITCH: Selects a triangle wave (up), slewed square wave
(middle), or a sine wave (down). Use triangle wave for traditional gradual
ramped chorus type modulation, square waves for rapid pitch jumps and
sine for a smooth continual movement vibrato or flange sound.
Be sure to read the control voltage section for information on this module
with expression pedals or control voltages.

<10>
AMP MODULE
The AMP modules provide wet and dry signal blending as well as tonal
control of the ACV-1 wet signal.
MIX: The MIX knob provides a
cross-faded wet/dry mix between the
delayed wet and clean tone. A 1:1
mix, providing the deepest comb
notches, is at about 11:00 and not
12:00. It may be easier to find this
with shorter delay times. When
turned fully CW the ACV-1 will produce vibrato effects similar to a
rotating speaker.
Note: If you are applying a sustained steady pitch to the ACV-1 and have the MIX knob
set near 12:00 you may find that the direct and delayed signals alternately will reinforce
or cancel each other as the DELAY TIME is varied. This is a normal result of mixing a
steady pitch with a delayed replica of itself. This phase cancelation is the chorus/delay
equivalent of “standing waves” in a reverberant room.
TONE: The TONE knob is a continuation of Hawker’s highly acclaimed
ADG-1 tone control that has been re-voiced slightly higher for the ACV-1.
It is a modified, non-symmetrical, “tilt type” filter with a soft curve and
center flat position. It provides both high pass and low pass control with a
knee around 740Hz. It is placed after the bucket and INSIDE the feedback
loop and will bring out or dampen the delayed mix allowing it to become
more present or fit under your playing. Extreme settings of this will
accentuate the feedback amount and cause self-oscillation.

<11>
CONTROL VOLTAGE or EXPRESSION SECTION:
Using the EXP knob and an external EXPression pedal or control voltage
with your ACV-1 will greatly increase the dynamic playing and tonal
possibilities as well as expand the control range beyond the extent of the
front panel knobs alone. Use a standard 10-50K linear expression pedal
that uses the +5V voltage supplied on the ring jack and outputs the control
voltage on the tip or use a 0-5V external CV voltage from a Eurorack
module, Synthesizer, DAW, or similar source.
CAUTION: Voltages over +5V or below 0V may damage your ACV-1.
Use only standard 0-5V control voltages. If your expression pedal has a
trim knob, you may find it helpful to use this feature to reduce the range of
the expression pedal to less than a full knob sweep to make it easier to dial
in the exact sound you seek.
Please note: In order to give a wider playing capability with expression
inputs, the control setting selected by the EXPression switch will reduce
the knob range and setting slightly. Think of it as turning the knob to -1.
The EXP controls are additive with their corresponding knob in that the
EXP input is added to the knob. For full control voltage range set the knob
to the most counterclockwise (CCW) setting, however using both you may
get delay times, feedback amounts, LFO rate or amount beyond those that
can be achieved using just the knob. Unlike the ADG-1, the ACV-1 time is
additive like the rest of the controls. Delay times beyond the normal TIME
knob position will produce an aliased or ring modulated sound.
Use only your fingers, a plastic screwdriver, guitar pick or similar plastic
device to turn the 4-position EXP rotary switch. Never use a metal object
that could damage the shaft. If you use this feature frequently, we have
included a knob (C&K part # 297F02000). Note this knob will turn the
shaft but there is not enough shaft length through the enclosure to
permanently secure the knob to the shaft and it may fall off. Do not glue
the knob to the shaft or your ACV-1 will not be serviceable.

<12>
FOOT SWITCHES
BYPASS FOOTSWITCH: Turns the effect on or off. The LED is lit
when engaged and will modulate to the LFO rate in a triangle wave shape
regardless of LFO switch shape. A switch inside the ACV-1 is user
selectable for true bypass or buffered bypass.
TRUE BYPASS / BUFFERED BYPASS:
If you carefully remove the 4 screws holding the cover on to the back of
your ACV-1 you will see a bypass setting switch underneath the jack board
on the edge of the PCB. This is the ONLY user accessible option on your
ACV-1.
Do not adjust any of the carefully calibrated factory set trim pots.
Use the switch, on the left side of the jack board, to select true bypass
(Default – switch to the outside of the enclosure) or buffered bypass
(switch towards the inside of enclosure). In true bypass when the effect is
not engaged the input is coupled directly to the output and does not pass
through any electronics. If you have loading, tone or noise issues from long
cable runs select buffered bypass to use the internal JFET as a simple
buffered output with approximately 4K ohm output impedance. Buffered
bypass may have a slight gain loss depending on the impedance match.
This is normal.

<13>
Technical Overview
Utilizing over 350 carefully selected components, the entire ACV-1 is
designed for a 100% analog signal chain. We began with a classic chorus
architecture using an Xvive™ MN3007 reissue BBDs and a step-up boost
power supply to power our premium audio-grade op amps and high-
tolerance, non-microphonic capacitors, providing performance, temperature
& voltage stability, low noise and maximum headroom.
We then implemented a vintage-style compandor with emphasis/de-
emphasis coupled with two discrete transistor, 5th-order discrete, anti-
aliasing and reconstruction filters to provide a familiar character with
superior clarity, noise reduction, and dynamic feel. The feedback circuit
uses a voltage-controlled transconductance amplifier as a VCA, to provide
classic, warm regeneration tone while offering an accurate method of
dialing in the perfect controllable amount of deep notch cancellation effect.
The input preamplifier consists of a discrete, high impedance, JFET input
stage that can also be used as an always-on buffer. When engaged, the
preamplifier circuit provides impedance matching and gain for optimal
signal to noise ratio. It contains some limiting to provide character from hot
signals and prevent transients from overloading the delay section.
The analog clock, modulation, oscillator, and even the switch logic are all
fully analog. Our VCO, with temperature compensated exponential
modulation, drives the BBD at extremely high current to eliminate artifacts
and provide a clear tight sound and gain consistency. An assignable
expression input increases the flexibility and control available to the user.
The ACV-1 is designed using a multi-layer PCB with dedicated split power
and ground planes for low noise and cross talk. The power input is fully
protected from reverse polarity and over-voltage conditions. Our MHz
range, step up, high voltage power supply is designed to eliminate sources
of noise and radio frequency interference (RFI/EMI) and the I/O is
designed to protect from electrostatic discharge (ESD) spikes to ensure
carefree operation in any studio or performance environment.

<14>
Specifications:
•Type: 100% Analog signal and control path
•Delay Time: 3.1ms - 59ms. 1.9ms - 95ms with LFO and to 155ms
with external Control Voltages
•Feedback: 0 to near infinite. Capable of self-oscillation using tone
or EXP input coupled with knob position.
•Rate: LFO RATE, from 0.1Hz to 14Hz (28Hz with CV control)
•Amount: LFO depth control from OFF to 60% of TIME sweep
•Mix: Center 50%. Adjust from full wet to full dry
•Tone: ~740Hz center tilt filter. Center = Flat to 0.3dB
High +5dB to -10dB, Low +4dB to -7dB.
•Phase Switch: 180° phase shift of wet signal and feedback signal.
•LFO: Selectable Triangle, Sine or slewed Square wave
•Expression Switch: 4 position rotary selects Time, Feedback,
Rate or Amount external control. All controls are additive to the
front panel knob adding extended range. TRS jack usable with CV
or Expression pedal, (CV range is 0-5V). Ring supplied current
limited 5V output. Control input on Tip.
•Bypass Footswitch: effect on/off user selectable True Bypass or
JFET Buffered (Accessible by removing ACV-1 Cover)
•Power: 9VDC @ <150mA. 70-90mA typical. Up to 250mA start
up. Standard pedal center negative 2.1mm x 5.5mm barrel.
•Input impedance: >1MΩ
•Output impedance: 1KΩMax (5k max for buffered bypass)
•Max input level: +14.25dBµ (4.0V RMS)
•Max output level: +14dBµ (3.9V RMS)
•Noise Reduction: 2:1 broadband with 10dB HF emphasis
•Genuine Hammond™ die-cast aluminum enclosure,
•Dimensions: D=4.95” (12.5 cm), W=3.75” (9.4 cm), H=2.25” (5.8
cm)
•Weight: 15oz (425g)
Note: All specifications subject to change at the whim of our overloads.

<15>
Presets:
Let’s try out some sound ideas for the ACV-1 using it to Warp Time. So
with a bit of a mind flip, you’ll be into the time slip where nothing can ever
be the same. Remember kids, since analog products have some variability,
the exact knob setting may be slightly different from those shown below.
Classic Chorus: It's so dreamy, fantasy
free me. All knobs, except feedback, near
12:00. Phase and LFO switches up.
Adjusting the time knob to the right will
achieve a more drippy 80s chorus, try
adding some feedback to this. Or stepping
to the left a more 90s tight shimmery chorus
sound. Now from there...
It’s just a tweak to the left :As we dial
the time to the left the chorus gets tighter
and more shimmery. Add some tone to
enhance the sparkle. Adjust the time to the
thicken sweet spot and try flipping the
phase switch.
Step the feedback in right: Now add
some feedback until you get a tight
resonant sound ala Flanging.

<16>
Put your hands on the switch: Flip that
phase switch and you will take off to
another dimension, with voyeuristic
intention, giving expressive vocal sounds.
Try the LFO with sine wave for smoother
modulation. This sound is more pounced
on lower notes.
Dial the modulation in tight. Reduce
the rate and increase the amount control to
get deep flanging tones. You might even
be able to find that Big ol’ jet airliner to
carry you far away. Sounds awesome with
some fuzz before the ACV-1.
It’s the LFO’s thrust that really
drives you insane :Now it’s time to go
crazy on the LFO and waveshape and see
what you can come up with until you're
spaced out on sensation, like you're under
sedation.
Let’s tweak the time warper again .
Keep going with it. See what you can come
up with now. Well I was walking down the
street just a-having a think and I came up
with this bubbly ghost chomping goodness.

<17>
Shirley don’t call me Leslie. If we
remove the dry signal, we get a vibrato
sound like a rotating speaker. Try this one
with an octave pedal in front for some
great organ sounds. It’s a big rotating
Doppler effect, but that’s not important now.
Feeling Slap Happy and I came up with
this Good ol’ classic Chickein’ Pickin’
Goodness. Produce a great slap back sound
and maybe even add some feedback for a
drippy meandering dance. Use an
expression pedal to get crazy long ring mod
delays.
Drippy Reverberant Chorus :Let’s try
that original chorus sound again but this
time we add some feedback, muted sounds
to take a walk down the path to ambiance.
With this preset time meant nothing, never
would again.
Clouds of Mercury : And for our final
number this dear fantasy land of hollow
happy warbles. It's astounding, time is
fleeting, and madness will take its toll.
Now go take off and do the Time Warp
Again!

<18>
Tools To nspire Your Creative Muse
Proudly Designed, Manufactured, Machined & Assembled in the
mountains of Western North Carolina
Changelog
Revision Date Notes
Rev A 08/03/2022 Production release
Rev 1 05/25/2022 Prototype manual
Visit our website for more information, mods, hacks, and presets.
www.AshevilleMusicTools.com