Signal paths - bass/treble controls with Q's & filters

[terryc]

Having looked at 'Factory to Customer' forum there a few basses with mutiple tone shaping controls so here is my question to all and the people at Alembic.
Does the signal path go from the PU's to the bass & treble controls then to the Q controls/switches and tone filters or is it the other way around and does it affect the tone in either wiring arrangement.
Could a switch be used so you can select either bass/treble controls or the Q/filter arrangement or both on at once, series or parallel(I bet that will be noticed to anyone deciding on their next custom!!!!)
Trouble is it may begin to look like a strip on a mixing desk!!
Thoughts anyone?

[David Houck]

I seems to me that the choice of signal path would affect the tone.  However, I've only had one cup of coffee this morning and it's hard for me to visualize the shapes of the frequency curves.
 
For instance, if the filter is first and you back it off a bit and then the filter is followed by the treble control which you then boost, then depending on where the filter is set, you would be boosting frequencies that are being rolled off.  (If I remember correctly, the roll off is 8dB per octave.)  In the opposite configuration, you would be rolling off frequencies that had been boosted.  I think in those two examples the shapes of the resulting curves would be different.
 
If I remember correctly, the East Meets West setup has the filter first and then the bass and treble controls.  But my memory is not highly reliable.
 
My guess is that on a custom order you could have it routed either way; and it would also be my guess that if you wanted a switch added to change the routing, that would be possible.

[terryc]

Obviously you own one of these basses with the said configuration..do you think it is overkill to have so many control options..bass & treble AND the filters..it sounds like by your explanation that it is lose one lot gain another..I suppose the circuit switching would be useful.

[David Houck]

I have a bass with Europa controls, but not one with East Meets West controls.  Whether it is overkill or not depends on each individual's preferences; and it can also depend on how that individual intends to use the instrument.  For instance, for a bass that is primarily going to be used on stage, it might be more practical to have the quick change switches of a Europa; but for studio work it may be more useful to dial in a more precise tone with the bass and treble controls instead of switches.
 
After my first post I had a second cup of coffee and thought about it some more and decided that I have no idea how much difference there would be having the bass and treble controls before the filter rather than after.  The series/parallel switch could be interesting; but I have no idea how useful it would actually be.  And the either/or switch might be useful; however if the bass and treble controls are at 0 (middle, no boost or cut) then they are essentially off, and if the filter is all the way open with no Q switch boost then it is essentially off.  The either/or switch would then just reduce to one flip of a switch a choice of two settings that might otherwise take two or three movements to complete.

[adriaan]

It would seem to make even more sense (at least to me) if the two would work in parallel, and the two signals were blended after the fact. But then why is there no blend pot?
 
As there is little point in being able to boost frequencies that have already been cut, and also that the filter can be used more in the sense of a colour additive, I would guess that the bass/treble controls come before the filter.
 
Anyway, EMW is different from the Europa/Rogue packages in that it has cut/boost pots instead of switches, so it is more flexible. On the other hand, I'm not sure whether it uses the single preamp that we associate with the Epic/Orion package, or the dual preamp that you get with a Europa/Rogue.
 
Ah, questions, questions ...

[gare]

Terry
No, it's not overkill. I have an Excel with the EMW electronical pkg. It's actually quiet handy..used judiciously.  
Set your sound using the filter and Q switch, tweak it more with the amp. Then use the active treble and bass controls to make adjustments on the fly as needed without loosing your original sound.  In small increments of course, otherwise it has the tendency to overdrive most preamps.
Gary

[keith_h]

I also have the EMW package in my fretless Orion and love it. Like Gary I set my tone controls to the mid-point detent and then adjust the filter to the sound I want. After this I adjust the bass and treble controls to get the overall tone I require for a song. Yes, it is quite easy to overdrive the rig's preamp by turning everything all the way up.  
 
I took a look inside and see one pot for the volume. There is a pot on the filter but it has been taped over. I assume it is a volume control but has been set to the appropriate level for the preamp in the bass. In any event tape means don't touch so I will leave it alone.
 
I can't tell whether the tone or filter comes first as all of the wiring goes to the preamp board.  
   
Keith

[bob]

For the electronics we're discussing here, I don't believe it matters whether the tone controls are applied before or after the filter. For any given frequency, boosting by X and then cutting by X gets you back to the same place as doing them in the reverse order. If the filter were more of a brick wall, then it would be different, but I'm pretty convinced in this case the changes are simply additive.
-Bob

[bigredbass]

Here's where my being pretty ignorant electronically as to what goes on 'under the hood' comes in handy.
 
If I dialed in a tone with the bass and treble cut/boost, THEN ran it through the Q . . .
 
 . . . it just seems like that would sound different than setting a tone with the Q and tweaking it with bass and treble cut/boost. . .
 
. . . since in each case I was dealing with a different tone where I handed it off from one to the other.
 
If I ran a bass through a rack to a parametric THEN through a SuperFilter, I KNOW it would sound different than running it through the SuperFilter, THEN thru the parametric.
 
Or is it just me?
 
J o e y
 
(Message edited by bigredbass on January 23, 2006)

[gare]

Keith
I saw the tape in mine too..aren't you dying to peek underneath it ?  
 
I'll have to go along with Bob, at least the perceived effect is additive.

[gare]

Its not just you Joey.
If it runs thru the filter first, which is basically at low pass filter. Once set, it would restrict the 'program material' to a certain frequency range. At that point the active controls can not boost or affect frequencies already removed by the filter at it's cutoff freq.. IE: if you set up for a low thumpy sound by setting the cutoff low, the treble control would only act like a 'presence' control since most of the highs have been filtered out.
Dat make sense ?
G

[David Houck]

But Gare; Bob's arguement seems to make sense also.  In your example if you reverse the ciruit so that the treble control is first followed by the filter which is as you said once set, isn't the treble control still going to act like a presence? .  Both Bob's and Joey's arguements seem to make sense to me!
 
Why is there tape on the trim pots???

[keurosix]

2 Cents:
I have to agree with Bob. Both Q filter and Bass & Treble controls affect the final sound regardless of order because the output is mono. There would be no way to separate the different controls from the signal path without ripping and tearing (ouch!), so they are in effect working interactively. It would be nice to be able to insert one before the other or vicea versa, but that would only be possible after the signal exits the guitar, like in Joey's comparison. However, the Bass and Treble control could be looked at as broad overall sound controllers, and the Q filter could be seen as a fine-tuning enhancer, or Character control. The effect is similar to Series 1 or Signature electronics where 2 filters work together to enhance the overall sound. Example: A broad (high filter setting to allow more freq through) low-boosted Bass Q filter combined with a tighter (low filter setting for a mid range peak) highly boosted Treble Q filter setting. For this custom circuit, you actually would get 3 variables with the Bass & Treble acting as 2 Broad sound modifiers, and the Q filter acting as a fine-tuning enhancer. Hummm..
Maybe I WILL consider this for my next custom order!
Kris

[bob]

The filter does not remove frequencies above the cutoff setting - it just rolls them off at some fixed slope (12 dB per octave for the low pass on the instrument, I think). Meanwhile, a typical shelving tone control (ignoring the slope where it kicks in) cuts or boost everything above/below some fixed point, by a fixed number of dB, often by a max of about 8-10 dB or so.
 
So you just take the two curves, for the filter and tone control effects, and for any given frequency, add up the two values to figure out what the resulting output will be. The order doesn't matter.
 
Now... I will grant that in reality, you may hear some differences if you take a signal that is already down 24 dB, and try to boost it by 8 dB (for example), rather than boosting it first and then rolling it off with the filter. But this is only relevant if noise/distortion/low signal losses/etc. are creeping into the picture. And in practical terms for these instruments, the filter slope is really only relevant for a very small number of octaves anyway, so we aren't losing that much. We discussed this in the process of designing the circuit for my custom, and the bass/treble pots are the very last thing before the output jack.
 
It may also be worth noting that this is really only relevant for a treble control anyway, given that the usual bass control will operate well below the lowest cutoff frequency of the filter. And in the treble region, the sharp Q spike you can get with the filter is likely to dominate your tone anyway (though again, a treble control will still raise or lower that and everything around it).
 
I'm not quite sure I understand the comment, because the output is mono. That isn't what determines whether the effects are simply additive. However, in practical design terms, it is certainly simpler to apply bass/treble switches or pots, after summing the output from the two pickups and possibly filters. This way you only have one signal to modify, though of course if you wanted separate bass/treble controls for each pickup, you would need extra circuitry and could it before or after the filters.
 
Why is there tape on the trim pots???

[the_8_string_king]

My custom Europa has 6 tone controls per pickup; each pickup has a filter, a 4/8/12 db Q switch, another toggle that chooses between filter off/filter on without Q/filter on with Q, bass and treble knobs (+/- 12 d) and a mid-range quick change toggle (+/- 6 db).
 
I'm frankly ignorant of most the technicalities. But I do know from experience that for me, these controls are worth having, and are not overkill. They work extraordinarily well.
 
The treble boost works when the filter has the treble filtered out; but it isn't as strong as it would be without the filter.
 
The fact is that it IS sometimes useful to use the treble boost while the filter and Q are emphasized elsewhere. The filter is the primary tone control. I'll often use it (and the Q) in say the lower mid range... so I CAN'T (simultaneously) use it in the treble range.
 
Having a stereo bass with individual processing, and where each pickup has an eq AND a versatile filter and Q system is the ultimate.
 
It works VERY well, clean sound, quiet, and very efficient.
 
As one of those people you mentioned with multiple tone-shaping options, I thought I'd give you my input. If you're interested in further input, I have some pretty cool ideas as far as having a simple and compact but extremely versatile combination eq and filter/Q system -based on my custom and my Elan with Europa electronics.