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

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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

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.

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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 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.

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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 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/

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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.

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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.

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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.

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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.

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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.

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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.

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