Shift Line A+ Flex

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Page last updated Mar 21, 2026

Pricing and availability

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Price

Average Price: $280

Standard/Professional

$199

$500+

Price Tier

In the Bass Preamps category, Shift Line A+ Flex is priced in the Standard/Professional range. This is quality gear at a fair price point, suitable for beginners, hobbyists, and pros alike.

Budget

Standard

High-end

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Description

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The A+ Flex is a tube bass preamplifier aimed at players who prefer the classic East Coast sound.

Here at Shift Line, we've always been particularly fascinated with bass-focused devices. Our product lineup includes the Olympic preamp with its "California sound", so the introduction of the East Coast-style Flex preamp was just a matter of time. We're extremely happy to introduce the new device, as the Flex can significantly expand your sound palette.

The A+ Flex is a fully analog preamp based on the 12AX7 tube. The device allows for soft compression and characterful harmonic saturation while also giving you control over your instrument's tonal balance and volume. The Flex has three outputs (main, balanced and THRU) allowing you to set up multiple independent signal chains. Additionally, you can use the device as a drive pedal or toneshaper due to its bypass switch.

Product specs

Brand	Shift Line
Model	Flex
Year	2021 - 2025
Made In	Russia
Categories	Preamps
Pedal Format	Standard

FAQs

What type of power supply does the Shift Line A+ Flex require?: The Shift Line A+ Flex requires a standard 9V DC power supply, with a minimum current of 200mA, which is typical for many pedalboard setups.
Is the Shift Line A+ Flex suitable for live performances?: Yes, the Shift Line A+ Flex is designed for both studio and live performance settings, offering versatile tone shaping and a robust build that can handle the demands of gigging.
Can the Shift Line A+ Flex be used with electric guitars as well as bass guitars?: While primarily designed for bass, the Shift Line A+ Flex can also be used with electric guitars, providing unique tonal options for guitarists looking for bass preamp characteristics.
Does the Shift Line A+ Flex feature an XLR output?: Yes, the Shift Line A+ Flex includes an XLR output, allowing for direct connection to mixing consoles or audio interfaces, making it ideal for both live and studio applications.
What are the main tonal characteristics of the Shift Line A+ Flex?: The Shift Line A+ Flex is known for its rich, warm tones and versatile EQ options, making it suitable for a wide range of musical styles from rock to jazz.

Videos

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Philip Conrad

TUBE Bass Pre ⚡️ [Shift Line A+ Flex]

Philip Conrad

Ламповый Басовый Преамп A+ Flex by Shift Line — подробный обзор

Real Bassist

A+ by Shift Line Flex | Tube preamplifier for bass guitar

Shift Line

A+ by Shift Line Flex with Pavel Paukov

Shift Line

Обзор Shift Line Flex

Bassberserk

Shift Line A+ Flex Demo

Erik Arkö

A+ Flex by Shift Line

Nikita Demchenko

A+ Flex (tube bass preamplifier) by Shift Line

ShurSoma

Reviews

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Owner Insights

We analyzed real musician discussions from forums and Reddit to find what players love, question, and tweak about Shift Line A+ Flex.

Features and functionality

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The Shift Line A+ Flex includes two mid-boosts at 400Hz and 600Hz, providing versatility for different tonal preferences without cutting mids.
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The bass EQ on the A+ Flex is set at 40Hz, beneficial for users incorporating a high-pass filter in their setup.
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Comparisons

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The Shift Line A+ Flex offers more tonal range compared to the SushiBox Finally DI, providing noticeable mid boosts and earlier breakup at lower gain settings.
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The A+ Flex is described as an Ampeg B-15 in a box, with what appears to be a Baxandall tone stack for high and low shelving EQ.
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Build quality

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The A+ Flex is a compact DI box, smaller than both the Phil Jones PE-5 and the Sansamp, with a robust build and a 12AX7 tube.
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Use cases and applications

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The A+ Flex is favored by players who avoid scooped tones and require a robust mid-range presence, especially useful in non-slapping bass styles.
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