Tone Control
In addition to volume controls we offer a tone control option.
In theory this type of control changes the frequency above which the
frequency response is reduced, or starts to rolled off. In practice,
the frequency response curve is more complex (see the curves below).
This style of tone control can only reduce the signal level. It also
works slightly differently in the active and passive modes if you have
an active/passive switch.
In Passive Mode:
The typical Tone Control response is shown below in the passive
mode.
High Frequency Response - TONE in Passive
Mode
Treble roll off position: Black - 100%, Red 66%, Green 33%, Blue 0%
These curves were acquired using a Nordstrand NJ5 pickup connected
with a 10' cable into an Avalon U5 preamp.
The frequency response
at the top end changes depends on the pickup, cable, and loading
amplifier (Since the preamp is bypassed and can
not buffer
the pickup
signals, the frequency change is directly dependent on the pickup,
cable, and loading amplifier).
In Active Mode:
The Tone Control works
in all Z-Modes and in combination with the other active tone controls.
As an experiment, I selected one control setting that produced curves
that were the closest fit to the True passive style treble roll-off
response shown above. I used the same NJ5 pickup, 10' cable, and Avalon
U5 preamp. Below is the frequency response.
High Frequency Response - TONE in Low Z-Mode
Treble roll off position: Black - 100%, Red 60%, Green 25%, Blue 0%
These curves were acquired in Low Z-Mode. It would be easy
to get closer with a 4 band tone control. In this experiment, the
roll-off is not as extreme as it was with the True Passive Treble
Roll-Off but the extreme roll-off (blue line in graph one) can be
simulated by reducing the level of the bass cut while in Low Z-Mode.
The frequency top end changes from about 800 Hz to 16 KHz with only
very minor variations possible due to external loading.
Active style tone controls
Active EQ controls change the relative strength of the response across
a fixed frequency range. The signal level can be increased or
decreased. This is the type of tone control is found
on most bass preamps and getting this type of control is often the
reason for installing
a preamp.
- Features:
- • Natural in all combinations.
- • Flat or unchanged in the center detents so you do not loose
the sound of your passive system.
- • Smooth as they engage giving you control as you first move
the knobs off the center detents
- • Wide frequency ranges for center bands and
• Gentle slopes on the band edges so the tone controls will
not start sounding artificial.
Active 4 Band tone control Response
Active style controls:
We have two active tone control circuits to choose from: the first
can be configured for 1, 2, and 3 bands, or 3 bands with mid frequency
selection; the second is for 4 band active controls.
- The 3 Band Control:
-
• The Bass control is a shelving control.
The signal level can be increase or
decreased by 15+ dB.
The 1/2 variation frequency is at 240
Hz.
• The Mid control center is located at 500 Hz.
The signal can be increased or decreased by 10+ dB.
If a mid band switch is ordered on a system, then the
center band can be moved to 250 Hz or 860 Hz.
The center frequency does not effect the treble and bass controls so
their performance is consistent as the center is moved.
• The Treble control is a shelving control.
The signal can be increased or decrease by 15+ dB.
The 1/2 variation frequency is at 1.92 KHz.
-
- The 4 Band Control:
-
• The Bass control is shelving.
The signal level can be increase or decreased by 15+ dB.
The 1/2 variation frequency is at 172 Hz.
• The Low-Mid control is centered at 200 Hz.
This is a very wide bandwidth control meaning the control
effects a wide range of mid band frequencies.
The signal can be increased or decreased by 10+ dB.
• The High-Mid control is centered at 800 Hz.
This control is not as wide as the Low Mid control
but relatively wide compared to typical controls.
The signal can be increased or decreased by 10+ dB.
• The Treble control is shelving.
The signal can be increased or decrease by 15+ dB.
The 1/2 variation frequency is at 1.92 KHz.
- Our Specifications are a little different than many preamps:
-
• The most important specs for a Bass or Treble control include
the +/- variation range and the frequency at which the level changes
1/2 that amount. You can consider this to be the frequency at which
the tone control effect ends.
Several other preamps list a theoretical peak frequency change point. So
a Bass control might be labeled as 40 Hz instead of specifying the 1/2 max
change frequency points.
We feel the 1/2 max frequency point is a more important real world spec because
it will make much more difference to the player in how the tone control really
feels. For example, the Bass tone control for our 2 band will feel bigger
than the one for the 3 band. The level of max variation is the about same
but the 1/2 max frequency point has been increased for the 2 band version.
• Our Mid range frequency specs are more typical - the center frequency and +/- variation.
Why do we offer both Active and Passive styles for the Treble
control?
The two types of treble controls feel different when you adjust them.
Most players have worked with a passive bass which has a treble roll-off
control (a standard on the Fender bass) and many like the way the passive
tone control rolls off the top end. Other players like the active tone
controls which can boost the signal level.
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