Bass Active Electronics - Preamps
Any Questions Or Comments About Bass Guitar Active Electronics, Like John East Preamps, Aguilar, Or Other Types, Installation, Etc. Please Post your Comments Or Questions. Here is Something From Aguilar.
Aguilar DB 680 Bass Preamp Specs:
Dual Parametric Equalization: Two serially arranged active networks. plus/minus 12 db. One EQ is set up from 180 Hz fully variable to 1.2K with fully adjustable bandwidth (Q), and level controls. The other EQ is set up to be fully variable from 1.3K to 7.5 K, again with fully variable bandwidth and level (boost and cut). By arranging the EQs in this fashion we can offer complete flexibility.
Tube EQ: Treble: Tube driven shelving, plus/minus 12db @ 4 K HZ Bass: Tube driven shelving, plus/minus 12 db @ 40 Hz Bass: Tube driven shelving, plus/minus 12 db @ 40 Hz Deep Switch: 2 position tube driven RLC resonant EQ, fixed at 30HZ Bright Switch: Passive RC premphasis @ 5-7 K Hz
Tube effects loop: Tube parallel effects loop with adjustable send and mix control. Left and right returns for stereo effect units.
Output Interfaces: Two 1/4" jack line level output controlled by the master volume control provides unbalanced tube-buffered output for connection to a power amp.
XLR balanced output -- Unlike conventional DI outputs, this balanced configuration allows the player to record directly to tape. No mic-pre is required! The output level has five positions to cover all possible recording and concert situations. They are: -40db pre-EQ, -40 db post EQ, 0db, 2db, and 4 db.
HI and Low 1/4" phone jacks -- These provide individual crossover outputs for full bi-amping capability. Each has its' own front panel level control and the crossover frequency is adjustable from 100 Hz to 1000 Hz.
Input Interfaces: Two selectable inputs: Located on the front panel, selectable by front panel switch or by footswitch.
Auxiliary input: Located on the rear panel. The extra input on the rear panel is useful in a permanent studio or live rack set-up where one needs to access the unit from behind.
Input thru: This is used to send the signal from a bass straight through to the input of another bass head (not a power amp). For example, connecting with a vintage bass amp that you want to record with a microphone, while taking a direct signal from the DB 680.
Optional Footswitch: Allows the player to select input one or two. Also on the footswitch is a master mute control which mutes all signal except signal going to the tuner input (an extremely useful feature in live or studio situations). Retails $100
Tube complement: Two 12AX7A/7025 high-mu twin triodes Three 12AU7 medium-mu twin triodes
posted by bassman @ Saturday, March 25, 2006
11 comments
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11 Comments:
Hello- Any recomendations on what size tone and volume pots should be ,Im putting together an 8 string Active bass
Hello-Thanks for the question.
a good pot would be a 25 k audiotaper pot, not a 250 or 500k pot, they are used on passive electronics. Depending on the maker of your pickups or eq setup, you can buy most of these systems prewired and ready to install-Thanks
Any ideas on a good preamp for my Jazz Bass
Here is a clip from Bestbassgear.com-Its a great preamp
J Retro Preamp Description
The J Retro 01 Bass Preamp is designed to fit directly into standard "Jazz" style basses without modification, including a PP3 battery. Its high quality circuit uses three stacked knobs and includes an active blend circuit plus a 3 band equaliser with bass, variable frequency mid, treble and bright function.
A very gentle built in contour gives immediate colour without detracting from the basic sound of any bass. The active blend circuit prevents the loss associated with many passive basses where, when both pickups are up full, the signal from one pickup feeds into the other and vice versa.
However, a switch is included to allow a passive equal mix of both pickups. A second switch - basic "get-you-out-of-trouble" passive mode is included in case the battery dies in crucial circumstances, but this mode allows lots of useful settings too.
Easy to fit, no routing or modification on most basses.
A standard PP3 battery fits under the plate in the standard cavity in most J-style basses.
J Retro DELUXE
Same as J Retro, but with an added fourth knob for passive tone control. This preamp is made for Fender Deluxe style basses with a side mounted jack.
Technical
VOLUME & BLEND (Knob stack nearest the neck pickup)
VOLUME
The upper knob is the Volume which has two sections under the same knob. A high impedance for the passive path and a low impedance section is used for the active circuitry. When used active, this knob has active circuitry after it so that the feed to your amplifier is a low impedance drive.
BLEND & PICKUPS SWITCH
The lower outer knob is the Blend balance for the pickups. Turn it fully clockwise for the neck pickup alone and fully anti-clockwise for the bridge pickup. The midway position, which has an indent, gives an equal mix of both pickups. The balance between the pickups is continuously variable with progressive level compensation towards the single pickup settings. Important:- The Pickups switch (by the blend) must be set pointing towards the jack for the Blend to function.
BASS & TREBLE (The middle knob stack)
TREBLE (+12dB @ 3 kHz, -12dB @ 1kHz)
The upper knob is the Treble control with boost and cut. The central 'flat' position is indented. The cut settings work on lower frequencies compared to boost to give a deeper sound when the top is rolled off.
BRIGHT (+8dB @ 7kHz)
Pull the Treble knob for the Bright setting.
BASS (+15dB @ 50Hz)
The lower outer knob is the boost only Bass control. The frequency band of boost gets progressively lower as the boost is increased. An indent midway is included to aid the setting of this control.
MID LEVEL & FREQUENCY (The knob stack nearest the jack)
BOOST/CUT (+/- 12dB)
The upper knob controls the amount of Mid boost or cut at frequencies according to the setting of the Frequency knob. The midway indent is the 'flat' position.
FREQUENCY (150Hz - 3kHz)
The lower outer knob is continuously variable and sets the Mid frequencies for boost or cut.
ACTIVE PASSIVE SWITCH (By the jack)
Towards the jack for active, the opposite for passive.
POWER
The PP3 battery is switched on automatically when a mono jack is plugged into the socket.
Alembic F-2B Tube Preamp
The F-2B contains two independant preamp/tone control sections. The amplification is entirely vacuum tube powered. It is normally used as a stereo preamp to interface stereo instruments to power amplifiers. Jacks are provided on the rear for outputs from each channel. In addition a Mono output jack is provided which combines both channels when the F-2B is used with a Mono power amplifier
The F-2B was inspired by the Fender Dual Showman amplifier. In the late '60's, we routinely added preamp output jacks to Dual Showman amplifiers and substituted an external power amplifier for the built-in quad 6L6's, most usually a MacIntosh 75.
The F-2B came about to provide the same preamp functionality in a rack-mounting package, as the Dual Showman was considerably wider than the standard 19 inch rack.
We took the opportunity to make a small improvement in the input jack circuit, while providing identical functionality. Plugging into Jack 1 alone gives full sensitivity, while Jack 2 alone is attenuated 6 dB. If signals are plugged into both jacks simultaneously, mixing resistors combine the signals and give isolation to the two input sources. In the original circuit, the mixing resistors are always in series with the grid of the first stage, and contribute a small amount of Johnson (thermal) noise. Our jacks have additional contacts which completely switch out the mixing resistors when using Jack 1 and the ultimate quietness of the tube is preserved.
As in its predecessor, the instrument signal is amplified by the first stage before any volume control. Without the wide dynamic range provided by the 300 volt supply, the first stage could be easily overloaded by large transients which are characteristic of electric instruments.
The tone control section follows, with a circuit attributed to Tom Walker, wherein the Bass and Treble controls contribute mostly boost and the Mid control provides cut only. While there is no absolutely flat position, the response is reasonably flat with the controls set at 2 - 10 - 2, with the bright switch off. The circuit can be described as interacting, such that the frequencies affected by each control is changed somewhat by the settings of the other controls. Additionally, when all 3 tone controls are turned to 0 then no signal is passed at all. These effects, while not suitable for a music reproduction system, have nonetheless proved highly pleasing for electrical instruments and have been adopted by a wide group of manufacturers.
The Volume control immediately follows the tone control section. The Bright Switch connects a capacitor around the volume control, the value of the capacitor being selected to bypass only the high frequencies. The effect of the Bright Switch is also interactive with the Volume Control, and there is no effect if the Volume control is turned up to 10, and the magnitude of the effect changes, depending on the setting of the control.
The signal loss of the passive tone controls and the volume control is made up by the second stage, also a common-cathode vacuum tube stage. The second stage plate circuit feeds the output jack. Since the output impedance of the tube circuit is fairly high, the power amplifier(s) should be located adjacent to the F-2B so that short connecting cords can be used. While the output circuitry of the F-2B can satisfactorily interface with the vast majority of power amplifiers, the F-2B does not work well if the power amplifier input impedance is lower than 10 K Ohms or if the power amplifier has very low sensitivity.
The mono output on the rear of the F-2B provides a facility to use a stereo instrument with a mono power amplifier. The mixing resistors associated with the mono jack are only connected together when a plug is inserted, thus preserving maximum stereo isolation when using the separate Channel A and Channel B outputs. Another application is to connect the two channels in cascade, by a cable from the Channel A output jack on the rear to the Channel B input jack on the front. The power amplifier is connected to Channel B's output. The signal from Channel A is high enough to drive the first stage of Channel B into distortion. The tone controls of Channel A are used to emphasize those frequencies which will be most distorted, while the controls of Channel B shape the color of the resulting distortion. Channel A's volume control sets the amount of distortion, while the Volume Control of Channel B sets the output level (Master Volume).
The power transformer has taps so that the F-2B can be operated from 100, 120 or 240 volt lines (Mains). It is necessary to open the cabinet and solder the correct tap to the power switch to make the voltage change, however. The Line (Mains) input connector is the IEC (computer type) so the power cord is detachable. The layout of the circuitry and the lead dress to the front-panel components are carefully planned to reject external hum fields. In addition, an internal hum-balance control rejects hum from the AC heater supply. The package is a single unit standard EIA rack mount steel enclosure designed to survive on the road.
hello, i am building a 5 string treble bass. i have 2 emg hz40 pup's, and would like to know what my options for a pre amp are. the hz's are the passive emgs, but would i still be able to use an aguilar onboard preamp?
thanks
Yes, You can-here is some info for you-
Aguilar OBP-1
This preamp uses a musical-sounding unity-gain FET design to provide a clean, transparent sound while freeing the pickups from the loading effect of tone controls. The controls provide up to 18dB of boost-only adjustment. This means the EQ is set flat when both controls are turned all the way down.
This is a hi-fidelity, smooth-sounding preamp that provides a clean, fat sound that’s great for recording. The dedicated 18-volt circuit is designed for maximum fidelity and headroom, and offers a huge amount of bass and treble boost, whether you need to brighten up an old set of strings or add low end rumble for a thick dub reggae tone.
This preamp works well with either active or passive pickup systems, although you will need to wire active pickups as 18 volts to operate the preamp at 18 volts while using the same batteries.
Thanks for the question
where can you find schematics for rewiring an active humbucking pick-up?i just was given a washburn bass,but the wiring is trashed.thanks
Do you mean the complete system or just rewinding the pickups? If its rewinding the pickups,you are far better off just replacing them,if it the system I woul need to know the type and configuration of the bass ,Thanks
Hello I am trying to rewire the entire bass and also look for a good onbord preamp. I have a 4 string bass lace transensor pickups (passive). As i read those pickups works better with 500k pots. can you recomend me wich pream will work better?
I will check on the specs. and post saturday-Thanks
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