Q Switch Schematic Wanted

[ralphl]

Anyone happen to have a schematic diagram for adding a Q switch?  
I have an Essence to which I'd like to add the switch. I know I can buy a kit from Alembic, but isn't the whole thing just a common switch with commonly available resistors and caps? Seems like a person could easily build one.
Thanks in advance for any advice or help.

[David Houck]

I don't have a schematic, but I do have an opinion on the idea, since you asked.
 
If you ever plan to sell the bass, the electronics won't be genuinely Alembic if you make your own Q switch.  While you may do a high quality job using mil-spec parts equal to the parts Alembic uses, the buyer won't necessarily know that and will be tempted to pass and find another Essence in the market that hasn't been modified by the owner.
 
I guess I'm a bit of a purist when it comes to Alembics.  There are other members here who disagree with me on this, and I find their opinions reasonable.  We've had discussions on these types of modifications, and others, before.  This particular example is pretty mild; where things really get heated up is when someone wants to put non-Alembic pickups in their instrument, but that's fairly rare.  I think the position that it's your instrument and you are free to do with it what you want is reasonable.  But personally, I'm just a bit of a purist.  If I'm looking at a used instrument, the fact that it's been modified by someone other than Alembic is a significant consideration.
 
But again, the current example is a relatively mild case.  My guess is that you have the ability to do a quality job, and that you would only use the highest quality parts on a par with those used by Alembic, and that the end result would not be measurably different than just ordering and installing the kit.  And of course there is the feeling of satisfaction from doing it yourself.
 
And I suppose that I'm not entirely a purist, since I do consider from time to time modifying my F-2B so that there are input jacks on the rear panel.  (There have been discussions on this as well; and if I recall correctly, the main issue is isolating the jacks from the transformer.)
 
So I've taken some space and some of your time to pretty much not make much of a point at all.

[ralphl]

Not at all, Dave, you bring up exactly the sort of thinking I was looking for. I truly appreciate your comments here and in other posts.
 
If I was really determined to do this myself, I'd just dig in and copy my Series I Q switch and hack at it till I got it. I build little circuits so I am acquainted with what is happening. Not very challenging just looking at the face of it. (Of course, knowing a little about Alembic, I'd probably end up with more questions than answers.)
 
The real reason I posted this question was because Mica has been hard to get a hold of on the phone. And who can blame her?! She is obviously pulled in 42 directions at one time, all the time. When I have gotten a hold of her, she is always extremely kind and takes such time being clear and allowing me to ask questions (Mary too!) and so I feel quite guilty calling frequently. I feel bad about bothering them and interrupting their day with my nit-picky stuff, so I have tried getting as many answers from the forums as possible. Your previous posts have been very educational and easy to read.  
 
But I agree with your main point completely. I will get the components from Alembic and just have to live with the guilt of calling as much as I have to.  
 
Mary and Mica, in advance, sorry for being a pain, but I'm going to get that Q switch one way or another. :-D

[bsee]

I suspect that this would border on some kind of intellectual property rights infringement.  Maybe I'm wrong there, and forgive me if I am.  
 
I would expect nothing but help from Alembic if you were trying to repair a broken Q switch, but I know I wouldn't expect them to do what you ask.  Selling the kit with their design is part of their business, and publishing or otherwise giving it away has to be contrary to their interests.

[ralphl]

I appreciate your conern. Please know I have no desire to steal or sell anything.
The Q switch is exposed so it may be seen in its entirety. It appears to be a commonly  found switch. The values of the components, just a few resistors and capacitors, are not hidden. It appears to me this switch and it's components are wired to the circuit board on the filter potentiometer. The circuit board it is wired to is the more important component, because the switch itself is useless without it. The switch just alters some aspect of the circuit it is attached to. Since the Q switch and its parts are exposed, it is easily backwards engineered (or appears to be as I mention in a previous post).  
Since I am sure this is possible, and Alembic knows that, it is much less a matter of owning the information, but rather about profiting from the information in some way. I am not sure how I could profit from knowing the design of the Alembic Q switch, because I don't know the design of the circuit it is attached to. I don't want to know either.
But I would like to emphasize that I own an Alembic Essence bass and merely wish to add a Q switch. In my last post I clearly state my intentions of purchasing one from Alembic. Considering the nature of the switch itself and my intent to purchase from Alembic, I find your assessment of my original question curious.

[adriaan]

If you ask nicely, I'm pretty sure they'll send you the schematic. But the costs of an 'official' Q switch kit from Alembic are fairly low, and it may help resale value compared to DIY work. It's a great addition - not sure why it is not included in the standard Essence package.

[ralphl]

I have been very nice. I will continue to be nice.
But thank you for the sage and thoughtful advice.

[dfung60]

ralphl -  
 
You actually have touched on the real answer here in one of your own previous comments...  The tonal effect of the Q-switch has little to do with the switch itself, it's the design of the EQ circuit that the switch is wired to.  That circuit is quite a bit different than your normal passive or active EQ circuit.  
 
The EQ circuit is sort of like a low-pass filter with a big difference.  Most simple low-pass filters (active or passive) are engineered to have a specific corner frequency.  When you turn the tone knob, the variable resistor in the pot's value is changing which is shifting the corner frequency around.  Below the corner frequency, things are largely unchanged, and above it, they drop off at some particular rate, usually pretty slowly for passive circuits and often more steeply for active ones.
 
The Q-filter works differently than this.  It's basically laid out like a regular low pass filter, but it's designed to resonate at the corner frequency - it has a peak right before it cuts the higher frequencies off.  The amount of peaking is what the Q-switch is controlling.  In the first position, then tone knob pretty much works like a regular tone cut knob.  In the third position, there's a gigantic peak at the cutoff frequency.  When you turn the tone knob, that peak shifts around making for some pretty unusual tones.  It often sounds a bit like a wah pedal, and that's because it's doing exactly what a wah pedal is doing!
 
So, all the magic here is in the EQ board which has the unusual Q-filter circuit.  The switch is just a switch and resistors.  The resistors are part of the network that sets up the behavior of the EQ circuit and isn't actually in the audio path.  A CVQ knob on a Series II is just a variable resistor where the switch would be which lets you control the amount of peaking in the circuit.  The EQ circuit that a Q-switch or CVQ is connected to is the same circuit.
 
David Fung

[mica]

Hi Russ,  
 
There's no secret about how the Q switch is wired. Here's the information about adding a Q switch to an Essence (or any Alembic Activator electronics system)
 
You remove the 15nF (.015uF) yellow box cap on the outside edge of the board and replace it with an axial 15nF (.015uF) cap that you solder to one lug of the C&K 7201 switch and one of the holes you unmounted the box capacitor from. You can use the existing box cap, but it's sort of a short distance to place the switch away.  
 
Connect a wire from the other hole on the board to the center lug of the switch, and on to the outside lug as well. It's important to cover both lugs with this wire.  
 
When wired like this, you can add a 1Meg resistor connecting the two outside lugs to remove an annoying pop when operating the switch.
 
The C&K 7201 switch is an off the shelf part that we custom order with the longest bushing length they provide and the black finish on the bushing,  paddle, and dress hardware. If you use the standard issue part, you might have to thin the wood where you mount the switch more than we do with our part, so take care in installation and operation.
 
Russ is very nice - we've spoken on several occasions.
 
(Message edited by mica on May 26, 2008)

[ralphl]

Hi Mica,
Yes, the Q switch is straight forward and your suggestions and pointers make it that much easier! Your knowledge and eye for detail are absolutely fantastic. I truly appreciate it! I'll post photos after the addition.
And it is very easy to be nice to anyone I have spoken to at Alembic because everyone I've spoken to is thoughtful, kind, pleasant and extremely nice. And all the good people in the forums, too. Very refreshing!

[David Houck]

Thanks Mica!

[rob_the_fiend]

Mica. Could you provide me with the exakt part number? I can use this in my drawings.
 
I found this PDF when I searced the web:
 
http://www.ittcannon.com/media/pdf/catalogs/Leaf/SW_toggle_7000.pdf
 
(Message edited by rob_the_fiend on May 27, 2008)

[ralphl]

Q switch kit just arrived. When Mary says she's sending something out, she ships quickly! Thanks!
 
It is a cap, a resistor and a switch, single pole, single throw. I thought it would be a double throw (with center position), like my Series I. So, only one level of boost, I assume.
 
Rob, the info on the switch case says, 7101 made by C&K.
 
Any idea what level of boost this kit provides, 3 db? 6 db? Any idea what it might be?
 
A much more important question: Where should the switch located to be Alembic spec?  
 
My luthier, Ron Volbrecht of Nashville Indiana, is a true master and will cut the hole exactly per Alembic directions. Can someone provide me with the specs for the Q switch location on a 2004 Essence?
Many thanks!
Russ

[mica]

There's no specific location for the Q switch on a retrofit - just put it where it makes the most sense  to you. I've sent you the installation instructions to your email address (too large to post). This should help Ron out with everything he needs.  
 
It's an 8dB boost for the 2-position Q-switch.  
 
Sorry, Rob, I don't have that superlong part number handy. That will have to wait for another day.

[rob_the_fiend]

It's okay. Take your time.  
 
The exact model isn't really necessary, but it would be satifying if I could get the renderings as accurate as possible.