I've been enjoying an M9 for a little over a year now, and have recently been diving into understanding the rotary eq better, having just bought some very different speakers than I have been using for the past 15 years or so.
I'm curious (honestly, not trying to argue) about referring to it as a Fender style eq. I've seen some comments in past threads here and elsewhere that mention the mids as being cut only, like the classic Fender 3 band. The manual refers to it as boost-only. Yes, it's passive, but that is not an indicator of cut-only, as we're used to on instrument tone controls. I think it really just means that there are no op-amps or other energized components in that portion of the circuit (anyone correct me, please). I've quite happily been running it at noon, because there's a detent there and I didn't clock that portion of the manual until very recently. The way the transients jump out of the speakers, yet lack any harshness is really, really satisfying.
I am a bit unsure of the accuracy of any info on the mid circuit - I wonder if there was a mistake in the copy, because it mentions being a boost only, but also saying that it can remove this band from the signal - that could just be a somewhat vague reference to relative positions on the control.
The bass and high circuits (which are active, unlike the Fender) also seem much more sophisticated than the Fender and I assume (without checking) that the frequency centers are not the same. Boosting and cutting don't just provide a mirror image response curve - there are shelving and H/LPFs working together that are incredibly versatile and usable.
Here's the copy from the manual:
BASS: This control is responsible for the basic mix of low frequencies in the tube pre-amp. The BASS control is an active shelving type control as opposed to a passive style control. This means that a center Q point has been chosen and this control allows you to either boost or cut that frequency. This control differs from the low bands of the Graphic in that it has a broader Q point with a more gentle ramp as opposed to the Graphic’s narrow Q.
The BASS control is actually a gain and frequency control all rolled into one with the Q center at 55Hz and harmonics in both low and high directions are affected because of its broader band nature. As the control is increased past 12:00 there is a 6db per octave rise in gain with the frequency topping out at 321Hz. With 12:00 straight-up representing “flat” (a no boost/no cut setting). As the BASS control is dialed below 12:00, 55Hz and all associated harmonics are reduced and eventually notched completely out of the signal. Conversely, there is a 6db per octave cut beginning at 55Hz going down to 20Hz where the shelving ends with a cut gain of -20db as the control approaches 7:30 (off).
This type of broad band, active rotary control makes it possible to achieve bass characteristics far beyond that of a conventional passive type control. It can increase the low end to an almost absurd level and with a flick of the wrist, dip it to near transistor radio skinniness. Needless to say, with any control this powerful a certain amount of finesse must be applied to achieve musical results. Be especially mindful of this when using the 5 Band Parametric in conjunction with the BASS control.
PULL DEEP: The CARBINE features a pull shift for the BASS control that allows you to choose between two different regions of low end and affects how the control will react.
When the control is pushed in (normal) the bass frequencies are higher and a cut-off is employed so that below a certain point, sub-low frequencies are not part of the mix. This results in a tighter, faster feeling response that is more articulate and will stand out and be heard in a live stage environment. This also works well for recording scenarios where the Bass part needs to sync-up with a complex kick drum line or anytime you need a defined, punchy sound that won’t get lost as the layers of other parts get applied.
PULL DEEP (control pulled out) allows the entire range of low frequencies to pass and fill in the curves creating a warm, rich sound that is foundational for smaller groups. Along with these deeper lows, a subtle enhancement of the super-high frequencies is added to create a round, breathing cushion of air the whole band can ride. Be sure to check out this setting for three-piece Rock or Blues combos and playing R & B styles where you need to add juice to thumbing parts.
MID:
This is the only passive style control in the string of rotary tone controls. This scheme was chosen for its inherently musical blend and for the way the passive style midrange control, with its wide spread and smooth taper, fills in the holes. Unlike the BASS, this control is a boost only, and while it can competently remove this broad spectrum of midrange from the mix, it cannot provide the extreme attenuation of an active style control.
You will find, as we did, that this control works amazingly well for shaping the midrange frequencies with a natural earthiness and character that is a perfect counterpart to its neighbors. It is hard to dial wrong with this more forgiving control as it seems to give you just enough and no more.
For radical and specific scooping of the midrange frequencies for modern R&B and Funk styles, there is plenty of notching power that is infinitely more accurate to be found in the GRAPHIC EQ. Because of this, we opted for the tried and true passive style midrange control that has been working great in all of our amplifiers for decades. It’s hard to improve on a classic.
TREBLE: The TREBLE is also an active shelving style control like that found in the BASS and again, it was chosen for its ability to radically shape the upper harmonic region. Like the BASS, it also has a center Q point with harmonics above and below responding in harmony as it is dialed for either cut or boost.
As the control is increased past 12:00, it produces a 6db per octave rise in gain starting at 723Hz until +20db is reached. From this point, gain remains constant at +20db for all frequencies above 723Hz all the way out to 20Khz. This scheme lends a sweetness of sound while retaining all the necessary cut and focus associated with a traditional passive TREBLE control. As this control is dialed below 12:00, it begins a 6db per octave cut from 3.2Khz to the shelving point at 723Hz, where it continues to attenuate all frequencies above 723Hz until - 20db is reached where cut gain remains constant until the control reaches 7:30 (off). The ability to cut these frequencies more radically makes it possible to obtain incredibly rich and warm old-school R&B and Jazz sounds that rival any recordings of the day.
This active shelving TREBLE control completes the rotary tone control string to create a powerful and extremely accurate network to use as your fundamental platform. It’s no wonder many first time CARBINE players make the comment that just these controls combined with the GAIN create the best tone they have ever heard!
NOTE: As with the BASS control, may we remind you that a control of this type with its increased power should be used with finesse.
In the TREBLE’S case, almost more so, because higher frequencies seem louder to the ear and are generally more painful when set to extremes. Another reason to use care is that high frequencies tend to increase the ambient noise floor when set too high. This is then exacerbated if the ACTIVE MID is combined for added top end boost. Dial with care and music in mind.
