Electronics
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 It has been replaced by a sweepable mid/treble control.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.
The EQ01 is avilable in the Classic Specification and the Custom Specification,
ACG/East Uni – Pre 4K Active/passive 3 band EQ.
A non-filter pre-amp available as an option on all Custom Series basses and the RetroB
Offering a full 3 Band Eq and active/passive switching.
The pre-amp has the following controls.
Stack 1:
Upper ring: Volume.
Lower ring: Blend
This stack works in both active and passive mode.
Stack 2:
Upper ring: Treble cut and boost with pull bright
Lower ring: Bass
Stack 3:
Upper ring: Mid Cut and Boost
Lower ring: Mid Frequency.
Single :
Passive Tone with push/pull active/passive.
Works in active and Passive mode.
Click here for a full run down of the ACG/East Uni-Pre 4K Active/Passive
Uni-Pre – Passive Mode
- Active/Passive mode is selected via the push-pull toggle switch on the tone control.
- In Passive, the active circuit is bypassed and the signal is passed directly to the jack.
When active is selected this brings preamp circuit into operation.
Uni-Pre – Active Mode
- Volume Knob sets the output level for both active and passive paths.
- The Blend Knob sets both the active and passive blend mix for the pickups: ACW for bridge pickup alone and CW for the neck pickup alone. A click midway gives and equal mix of both pickups if they are balanced. Internal Gain Trims, 0-12dBs, allow the pickup levels to be adjusted and/or matched.
- Bass Boost/Cut or Boost only – set according to Jumper Link on circuit board. Controls the level of low end content according to the ‘Bass Window’ settings on the on the circuit board, described later. A centre click is included.
- Treble (Pull for Bright)/Cut knob, controls the higher frequency spectrum according to the setting of the internal Treble Shelf Frequency adjustment. Pull for Bright, adds ‘high end sizzle’ sheen. A neutral setting is provided with a centre click.
- Mid controls the level of Mid Boost/Cut at frequencies according to the setting of the Mid Frequency knob. A neutral setting is provided with a centre click on the upper Boost/Cut knob.
- Tone Roll-off, set CW for no effect. Adjust ACW in order to mellow the treble and fully backed off for the ‘darkest’ sound. Push-pull google switch, pull for the Passive Signal path which consists of the Volume, Blend and Passive Tone. Push in the full Active Signal path.