"OBP-1" Two band, broad shelving +18 dB at 40 Hz and 4 KHz.
.6" x 1" x 1"
Alex Aguilar's two band on-board preamp sounds great and is
very quiet. It a boost-only circuit, starting from unity gain. Its
design is reminiscent of the old Sadowski preamp.The 18 dB of boost
requires plenty of headroom, 18V is recommended. The circuit can
handle 9-48V. It comes with seperate bass and treble controls however
an EMG dual stacked volume pot can be used if stacked controls
"NS2TMB-183", 18 Volts. Bass; +/-14 dB at 30Hz. Treble: +/-
16dB at10KHz. Mid: +/- 10 dB at 250/500/800Hz switchable, other mid
frequency selections from 250Hz to 1500Hz can be chosen using
different capacitors on the outboard switch. Needs two 9V batteries
Dimensions are: (main module) 0.6" x 1" x 2",
(NTMB3 module) 0.6"x 1" x 1.3"
This is Bill Bartolini's latest and most refined design. It
is quieter and more transparent than anything else out there (108 dB
S/N,THD .003% @ 100Hz) and really sounds good. To quote from the
spec sheet "The (bipolar) +9V/ -9V system allows a completely DC
coupled signal path. There are no capacitors to diminish in any way
the low-end punch, clarity and frequency response of the instrument".
Bill has used wide bands that overlap slightly to avoid the honky
sound of other midrange controls. The 250Hz mid could be useful as a
cut option when recording. Includes a gain trimmer to match output
with your other axes. There are several things to be aware of, the
controls are passive without separate gain stages, there is some
interaction between them (i.e. when you boost the low the mid gets
boosted a bit as well.) The circuit is flat well into the subsonic
range so that you may find your speaker excursion wasting much of your
amp's power unless you filter out below 30Hz. The circuit shifts phase
by 180 degrees which simplifies active/passive switching using a push-pull
pot. There is a tiny offset voltage with the bass boosted which
always gives a "Thunk" when you switch between active and passive
unless you turn things down first.
*note: Bartolini on-board preamps now operate at 9 or 18
volts and are no longer dual rail (+9V/-9V) [M.S.]
"BTC" (Bass and treble on concentric knobs with
Dimensions: 0.3" x 1" x 1.05"
I have used dozens of these in basses, they work well,
they are easy to install and are reasonably quiet (96 dB S/N). They
don't make your bass any better sounding though. The treble shelving
is switchable from 2500 Hz to 3500 to 4500 to 8000Hz via two
micro switches inside the bass. It's a pretty impractical feature
that's hard to evaluate.
"BQC" (Sweepable midrange [300Hz- 3kHz] with concentric
sweep and 12 db boost/cut, concentric bass and treble,switchable
treble shelving) 9V to 27 volts. I recommend 18V power forall EMG
Dimensions: 0.95" x 1" x 2.3"
Cool but unacceptably noisy, the mid band is a bit too narrow to
be useful except as an effect on fretless. You can make wah-wah
sounds with your free hand...
"U-RETRO" - 3 band EQ system with a sweepable mid, dual
input buffers and adjustable gain from 1 to 12 dB for each pickup.
Dimensions: 0.4" x 1.3" x 2.75"
Includes stacked volume and blend controls (blend only works
inactive mode), asymetrical treble control with center detent -
(+12dB @3kHz, -12dB @ 1kHz ) which can be pulled up for "bright"
(+8dB @7kHz), stacked with boost only bass control (+15dB @ 50Hz).>
Mid control; (+/- 12dB) indent at "flat" setting, stacked with
frequencycontrol - (150Hz-3KHz). Also includes active/passive switch
and pickup selector switch for passive mode (switches between rear
pickup and both pickups together). Uses custom plastic element pots, 3
ICs and compact, low noise components on a single epoxy insulated
Very cool but still quite noisy. It colors the sound -treble
gets muted, -bass is bigger and tighter. John is redesigning the
circuit to improve the noise ratio and flatten out the response. Oh,
also themost expensive unit I know of at $250
Note from David (7/2004):
The E-Pro preamp has been
completely revamped since the one I tried and John has addressed all
the issues listed above. I haven't had the opportunity try one since
the redesign and can't comment first hand on the new unit.
"2 AC" Variable10 dB boost with dual buffer, battery
checklight, 9V supply, 3 band eq insert point).
0.5" x 1" x2.25"
The latest design with ultra quiet, audiophile chip
and trimmers for each channel allows you to set boost independantly.
Until WAM starts production of his 3 band EQ section, this unit is
probably superfluous unless you need a buffered blend and variable
Concentric bass and treble with center detents, 18dB boost,6dB
cut, switchable mid boost
Dimensions: 0.5" x .6" x2.6"
I have had this circuit in my bass since the mid-eighties
andit is different from most others in that the shelves are wider and
theslopes flatter. I like it because it really does something
withoutmessing up the volume balance between the strings, when you
boost thebass you're boosting everything between 20Hz and 300Hz
instead of say40Hz to 60Hz as in many circuits. If I need to
fine-tune my sound I'drather do it on my amp anyway. Hand soldered
with high grade,discrete, components using only 2 transistors so
noise should beminimal though I have experienced some RF
interference. The circuitcan be powered with 9V to 48V, I use 18V.
2 band EQ, 3 band EQ: Dimensions: 0.7" x 1.5" x 2.5"
MusicMan 3 Band EQ: Dimensions: 0.7 x 1" x 2.5
I like these now, they work well, The lows are frightening, (MM
lows are probably too low). They have a push/pull volume switch that
activates a "slap contour" which you preset inside the bass, giving
you two distinct sounds. The noise floor is low at -85dB according to
the specifications. The bands are narrow and preset; bass is centered
at 30Hz (25Hz on the Music Man model), mid is 675Hz and treble is up
at 6800Hz. The rather large circuit board uses SMT components and
bulky, plug-in connectors to make it a tricky retrofit (the Music Man
version is smaller). Can not easily be by-passed as you would need to
add a passive volume pot. Runs on 9-18V.