This is your guide to the standard electronics options available for all ACG Custom and Über basses.

ACG Pre-amps

I use ACG Dual Filter  and East Tone UK pre-amps exclusively in all of my basses.

I first approached John East while building my first basses. I started out using his J-Retro and BTB01 pre-amps. However, what I really wanted was a filter-based pre-amp, so I asked John repeatedly if he was going to make one.

After some pestering, John admitted he couldn’t see himself designing a filter pre-amp within the foreseeable future at that time, and one way to get what I was looking, for was to commission the design myself. This news lead to the design and production of the ACG EQ01 Dual Filter pre-amp. (This would be the only pre-amp in ACG basses until the release of the EQ03.)

The EQ02 – a retail version of the EQ01 – quickly followed then the EQ03 which launched in 2012. After 7 years of customer feedback and experience, I decided a new pre-amp was needed to take the pre-amp in a more focused direction. Once again, the only man for the job was John and with his expert input, the DFM pre-amp launched in 2014. The DFM is now my flagship dual filter pre-amp and is only available in ACG instruments.

ACG DFM pre-amp

The introduction of the Dual Filter Modular pre-amp represents a change in direction for the ACG filter pre-amps. The goal with the previous versions has been to make a pre-amp that was as versatile as possible. Having gone down the path of trying to be all things to all players for a number of pre-amp versions I decided it was time to produce a more focused pre-amp to produce the sound I want to hear from ACG Basses.

The new Dual Filter Modular pre-amp is the result of several months work with John East.

Changes made to the pre-amp from the EQ03.

The lowpass filter range has been reduced by an octave. This allows much better resolution within the pot rotation giving a greater degree of control specifically in the mid region. It also reduces the amount of top end in the circuit.

Introduction of the Attack Boost feature. When selected via internal dip switches this feature is activated by the push/pull on the bridge filter stack. When pulled out you get a boost of a very narrow band of frequencies  in the 8 kHz region and the level of the boost can be set with the internal trim pot.

The high pass filter which has been a feature of all the previous pre-amp has now been dropped. It has been replaced by a sweepable mid/treble control. Lower ring sets the frequency with the upper ring controlling gain.

  • Click here for a full run down of the ACG DFM

    The Dual Filter Modular pre-amp is available in 4 different configurations.

    DFM 4K

    Stack one: Volume/Blend.
    Stack two: Low-pass filter for the neck pickup plus push/pull switch to activate the low mid boost. The lower ring is the filter frequency, with 41 detents. The upper ring is the overshoot peak level.
    Stack three: Low-pass filter for the bridge pickup plus push/pull switch to activate the upper mid boost or Attack Boost. The lower ring is the filter frequency, with 41 detents. The upper ring is the overshoot peak level.
    Stack four: Sweepable mid/treble.

    DFM 4K/AP

    Same features as the DFM 4K but with a passive tone control in lieu of stack four, the sweepable mid/treble.
    The single pot passive tone features a push/pull active passive switch. The tone control works in both active and passive modes. Passive is a full bypass even when the battery dies the passive section will still work.

    DFM 5K

    Same features as the DFM 3K with the addition of:
    Stack four: Sweepable mid/treble.
    Single five: Passive tone with active/passive on the push/pull

    When the active/passive/tone pot is added, the volume/blend continues to work in both active and passive modes. When the bass is put into passive mode, the filter stacks have no effect on the sound. The passive tone pot can be used to shape the sound in both passive and active modes. The passive section completely bypasses all active sections in the pre-amp, so even without power the bass will continue to work in passive mode.

    Note: When the DFM 4K/AP or the 5K/AP are used with the MC range of pickups the passive mode operates as normal. However should you lose power, the bass will no longer produce any sound. This is because the ACG IB1 board that connects the pickups to the pre-amp requires power to mix the pickup signal. So, if the battery dies there will be no output from the pickups.

    The push/pull switches on stacks 2 and 3 activate a low-mid and hi-mid boost/attack boost that is independent of the filter positions and work globally so both can be active at the same time. Internal dip switches allow you to chose between two frequency settings on each stack. There are also trimpots to adjust the level of the boost from very subtle to a very pronounced boost.

    Details on the frequencies and levels, and how to set them can be found in the instruction bundle at the bottom of the page.
    The DFM pre-amp is now standard on all Custom and Über range basses in whatever configuration best suits you requirements. The EQ03 has now been discontinued.
    Instructions for the DFM can be found at the link below.

Both the EQ01 and SEQ are available in Custom ACG basses, but with the release of the DFM I strongly recommend that you choose the DFM for your bass.

ACG/East P-Retro pre-amp

Our non filter pre-amp available as an option on all Custom Series basses.
The pre-amp has the following controls.

Stack 1:
Upper ring: Volume.
Lower ring: Tone.
This stack works in both active and passive mode.

Stack 2:
Upper ring: Dual Boost
Lower ring: Frequency
This stack works in active mode only.

Mini toggle switch: Active/Passive selector.

  • Click here for a full run down of the ACG/East P-Retro Pre-amp

    • Active/Passive mode is selected via the toggle switch.
    • Volume knob push/pull switch inactive in passive mode.
    • In Passive,the active circuit is bypassed,and the signal from the Volume is passed directly to the jack.

    When active is selected this brings stack 2 into operation.

    • Volume knob switch pulled up,activates a bright function.
    • The Volume and Tone work as normal but their output feeds the active circuitry, which in turn feeds the jack.
    • When the Boost knob is in its centre click,there is some additional gain with a flat response.
    • Turning the Boost knob CW from its centre click, boosts the mid spectrum according to the Frequency knob setting.
    • Turning the Boost knob ACW from its centre click, boosts the bass and treble spectrums combined, with overall balance set by the frequency knob.
    • Pulling the Boost knob actuates an internally pre- set Deep boost.
    • Deep boost switch with four frequencies, set via internal switches.
    • Deep boost level set via internal preset trimmer.

    This pre-amp is combined with a 4 way rotary pickup selector giving the following options.

    • Bridge
    • Bridge and Neck in parallel
    • Bridge and neck in Series
    • Neck
ACG EQ01 filter pre-amp

The EQ01 pre-amp is the predecessor to the EQ03 and is available on request in Custom Basses and for purchase directly.

The EQ01 features two low-pass filters, one per pickup and a global high-pass filter just like the EQ03, affording you the ability to EQ each pickup independently, however it does not have the mid boost options, or detents on the filter stacks.

The EQ01 is available in two configurations; the 4K and 5K. The 5K has the addition of a passive tone pot. This is not the active/passive switch used in the EQ03; the pot works the same way as a tone pot on any passive bass.

ACG EQ01 4K: £200.00
ACG EQ01 5K: £210.00

Supplied with wired jack socket. Internal controls. Gain adjustment for each pickup. Treble path selection. A trim pot which allows you to choose which pickup supplies the feed for the high pass filter. Lower ring needs a knob with 8mm internal diameter. Upper ring needs a knob with 6mm internal diameter. Knobs can be bought from East UK.

UK postage insured special delivery is £7.00
Rest of the world insured trackable delivery is £13.00

Please get in touch at sayhello@acguitars.co.uk if you would like to make a purchase.

ACG SEQ filter pre-amp

The SEQ pre-amp has been discontinued.

Below are download bundles, including installation instructions for the current two versions of the ACG pre-amp, and the previous versions.

DFM  |  SEQ  |  EQ01  |  EQ03