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Post by treguiers on Nov 15, 2009 21:05:17 GMT -5
OK, Measured the two cells, They're rated at 1.39 and 1.37 volts. Measured the current as you detailed and that came in at 0.42 mA Now the batteries used aren't fresh ones, but i've just literally finished a gig with it and it was working fine. Here's a link to my local electronics store, they don't have the exact one you specified, would any of the others suffice? radionics.rs-online.com/web/search/searchBrowseAction.html?method=getProduct&R=6262349That's the closest one I could find. If that doesn't suffice then I'll order online, but I'll wait til I have the complete shopping list. So do I need a Zener diode? (For Sumgai) As for exaltation, well I am far too ignorant of the subject of electronic to state with any authority the level of his genius. Do I think he's amazing? ABSOLUTELY!
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Post by sumgai on Nov 15, 2009 23:40:47 GMT -5
3g, You exalt not on knowledge alone, or even as a primary criterion, but more as a way of saying "Wow, thanks for your help, it was just what I needed!". I myself usually dole out the occasional +1 for making me laugh out loud. Believe it or don't, some of these jokers on here can actually do that. ;D Also, one can earn a +1 for finding and reporting a link to something new and useful that we've not seen before. But you are welcome to Exalt as you feel the need, you're not gonna get fired for that. HTH sumgai
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Post by JohnH on Nov 16, 2009 0:41:20 GMT -5
treguiers - good, you are getting the hang of this stuff.
Those measurements make total sense, and a 12k resistor should drop the 9V battery supply down into the 3.5V and below range, so the pickup will be happy with either a fresh 9V, (a bit more than 9V), down to one at say 8V.
I do think the cap across the power input is a good idea - otherwise, we could get the up and down swing of current draw from the pickup, changing the supply voltage and affecting the output. A battery with a 12k resistor does not have as much grunt as one without. Not sure, but it is easy and cheap to add the capacitor.
I still think you dont need a zener diode, and I think sumgai thinks so too..
On the JFETs, your shop has quite a selection, and probably most of them will work for a buffer. But out of the ones listed, I suggest a J201, which I have tried with this circuit. They seem to come as a 10 pack.
Ill try to sketch out a diagram of the whole shebang so you can see how it all connects up.
Just one thing to check though - you now have run the guitar both with the mag and the piezo, and maybe just about with both together. Are the sound results and the different tones still sounding like this mixing is going to be a good worthwhile effect? I would think so, but your ears are the key.
John
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Post by treguiers on Nov 16, 2009 4:30:55 GMT -5
Hi John, I've a tendency to use the mag pup for lead stuff and the piezo for more chordal- strummy kind of stuff. When both are on together, it has potential, but the lack of bleed is a drag.
The piezo is considerably louder than the mag. Would increasing the battery voltage(a little bit) of the mag be a good idea to increase it volume?
And now a general message to all you electronics whizzes. I've just completed a knockout strat, which I couldn't have done without your help, and it looks like I'm now set to get my acoustic guitar functioning on a level well above my expectations. Again without you guys, it would never have happened. So thank you. In my enthusiasm for these projects I realize that I may forget that, or that its taken as a given....anyway thanks guys you are doing fantastic stuff.
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Post by treguiers on Nov 16, 2009 17:26:11 GMT -5
A-ha Sumgai, only saw the exalt/smite options now.....it all is starting to make sense!( I wish I could say the same about the electronics! )
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Post by JohnH on Nov 17, 2009 5:10:05 GMT -5
Hi tg
It would be possible to equalise the two output levels, but it leads to a few questions and options.
First, depending how the mag preamp circuit works, there may be a little more volume available at the upper end of its power supply range but only a small amount if any.
Here are the options:
1. Can you not set the volume on the mag Pu at max and the piezo with a reduced setting to balance them?
2. or, A further transistor could be added to act as a booster on the mag Pu before it gets blended.
3. or, The piezo output could be reduced before the blender, so it matches the mag Pu
4. as 3, but add a booster after the signals are mixed to get the level back up again
Some issues to be considered: The type of simple one transistor booster that I would suggest causes the signal to be inverted. ie, not only does it get louder, but the up and down swings get reversed. This makes no difference at all, except when mixing signals, because we could end up with your piezo and mag pu's out of phase, which leads to the question, are they in phase now? ie, when you get some kind of mix of both, and you match the levels using the volume controls, does the bass tend to diminish (as if they are canceling out) as compared to a single pickup? or not?
On my full circuit, by the time I had everything together, the magnetic signal was out of phase with the piezo, so I swapped all the magnetic pickup leads to correct this. But this may be harder for you, since you have probably a sealed unit with its own preamp. Any way, the answer to that would determine whether to pursue option 2 or option 3-4
If this system is leading toward some home-brewed active electronics, how do you feel about making that? (I can help with diagrams) But Its fiddly work even as compared to guitar wiring, and when it doesn't work first time (it won't!) it takes some head scratching. Thats why I was hoping it could be limited to something simple like a single buffer.
What do you run your guitar into for amplification? is it a PA system or a guitar amp?
I'm thinking it might be a very good idea to build this up in steps, starting by getting both pups running off the 9V supply, for which you only need a resistor and a capacitor. Then add a linear pot for blending, and go through a stomp box (do you have a Boss one that you can leave switched off?, so it will act as a buffer - a tuner pedal works well, or a clean booster to help with your solos). Finally, if all is looking well and if required, adding the active parts so it can go straight to a PA.
I usually play my guitar into a stomp box, but last night I checked it again straight into a 15" Behringer active PA speaker - the piezo sounded really good, very much like a Dreadnought even though it is a Strat clone. I just wanted to check again that this circuit approach will work for what you might use it for, and it does!
cheers
John
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Post by treguiers on Nov 17, 2009 10:41:47 GMT -5
Hi John, You asked in option 1: "1. Can you not set the volume on the mag Pu at max and the piezo with a reduced setting to balance them?
Yes I can do this.
Secondly the mag and the piezo are in phase when on together. There's a full bodied sound with plenty of lows when on together.
As regard amplifying the mag pup I only asked cause I like it's sound by itself, but i think if there's going to be inversion problems then I'm perfectly happy as is.
Thee guitar either goes thru a PA system or an acoustic amp(AER compact 60). I sometimes run it thru an "Aphex acoustic Xciter" that to my ears is a DI box with EQ options
What I hoping to do is to get a simple system that operates the mag and piezo as discussed(without the extra amplifiers/boosters). I would gig it for a while and see if there were any areas where mods could be possible.
Further down the line in, as much as is electronically possible I'd love to be able to dial acoustic tones from a macaferri to a martin and some interesting shades inbetween. I have a head full of ideas but I need to get up to speed electronically. Hey John, you don't know me from a bar of soap, yet you are doing all this for me. I really do appreciate it.
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Post by ashcatlt on Nov 18, 2009 1:34:16 GMT -5
I sometimes run it thru an "Aphex acoustic Xciter" This answers a question I had, and I think vindicates me somewhat. The Aphex process has been around a while, and is fairly well documented. It involves hi-passing the signal, distorting it, and then mixing it back with the original. I think that when Sumgai was talking about comb filtering he was thinking of these devices labeled as "acoustic emulators". I think the newer of these use digital algorithms similar to those used in Impulse Response type reverbs, applying a complex filter and some time based information. I wouldn't be surprised, though, if some older or lower budget versions are basically just comb filters. I would be even less surprised to hear that a comb filter would noticeably alter the character of the sound. Comb filtering can be accomplished by mixing a (very) slightly delayed version of the signal back with itself. These delay circuits get complex pretty quick, though. Luckily, an all-pass filter is a pretty simple analog circuit. It's really not a whole lot more components than a buffer. If you were to build one with an adjustable cutoff frequency and mix the result back in with the original, you might (I haven't tried it, but I could "simulate" it, if you're interested) end up with a fairly wide range of tones.
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Post by treguiers on Nov 18, 2009 9:05:12 GMT -5
Hi Ashcatlt, I'm all for tone improvement definitely. I do know enough about electronics to know that when dealing with an acoustic signal, the electronics can get very complex.
Where I'm at at the moment is: one battery source for the piezo and mag pups, a single linear pot to smoothly blend the two signals, leading to a buffer stage for impedance matching.
If it felt that a facility to have an adjustable cut off frequency would produce better tone and it was not to complicated electronically, I'd certainly go for it
Now as for my shopping list: (very open to correction on this one)
A JFET(J201) a 12K resistor a 500K linear pot a 10uf capacitor
Leaving aside what I might need if it is felt the freq cut is an option is that the lot?
Thanks guys
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Post by JohnH on Nov 18, 2009 14:57:32 GMT -5
Almost there, there are a few more bits, so list as follows:
power supply fix : 12k resistor, 10uF capacitor (electrolytic). Just in case you want more voltage to the mag, get a 10k as well. 1/4 W is fine for all resistors.
pot: 500k single linear - I suggest 16mm diameter if you want to mount it on the buffer circuit board
Knob to suit the pot shaft (pot shafts can be knurled, plain round or with a flat)
Buffer: J201, 2x 3.3M resistors, 33k resistor, 2.2uF capacitor (electrolytic), 1.5M resistor EDIT and a 39nF capacitor
Plain insulated flexible hook up wire, two colours if poss for power + and -, screened single-core audio cable - for signal wires
Battery - will you keep the 9V battery in its current place, and get wires into it? or will you need a new box?
Output jack: I assume it currently already has a stereo socket?
If you dont have any, a few aligator clip leads for testing are useful.
What do you want to build the buffer on? I use veroboard (ie copper strips underneath) You cuold build all the buffer on that including soldering the lugs of the pot, then the whole thing is mounted by the pot shaft to the guitar body.
John
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Post by treguiers on Nov 18, 2009 21:44:00 GMT -5
Got my list and going shopping in the AM......
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Post by ashcatlt on Nov 18, 2009 22:36:19 GMT -5
I'm looking for something useful in the all-pass realm, but I'm not that much further than you inthe circuit design realm.
I say buy at least 10 of each of the passive components (resistors and caps), a couple of the transistors and maybe a couple pots too. A few reasons for this:
1) once this thing works you're almost assured to want to build something else.
B) They're cheap.
iii) They can be comined in various series and/ or parallel configs to get different values.
also) Depending what you're doing, you might want to test them for tolerance
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Post by sumgai on Nov 19, 2009 0:54:39 GMT -5
ash is correct, and I'll add one more reason to "double up":
not to mention) The shipping is almost certain to be the same cost.
Until you get to buying reels of 1000 pieces, the weight for these thing is so miniscule.....
If you're about to buy from a place that wants "postage and handling" for each separate item, re-check your spreadsheet, and figure in those hidden fees, you may be surprised. Don't forget to consider any local taxes.
HTH
sumgai
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Post by JohnH on Nov 19, 2009 4:58:33 GMT -5
tg If you find those parts, the next job is to figure out how to build it. I would do it like this, on Veroboard (but you may have another idea) Its a view looking down, as if the board was transparent so the copper strips are underneath. I hope the labels and symbols make sense. The green blobs mean that the copper track under must be cut. The best way to do that is to spin a drill bit of about 6mm in your fingertips, untill it has removed the track at the right hole. Cutting Veroborad is best done my scoring both sides with a Stanley knife, then snapping it over the edge of a bench ans snading the edge. Anyway, if something like that would suit you, then the next step is a overall diagram to hook everything up. As you can tell - I want this to work too! I suggest your first electrical step however is to get the mag pu working via the 12k resistor off a 9V battery, at least as a test. Try it with and without the 10uF cap across the mag pu power input (ie across what were the battery contacts). Note electrolytic caps (two in this design) are polarised, and - and/or + are shown on the can. _ve goes to -ve. cheers John
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Post by treguiers on Nov 19, 2009 10:36:30 GMT -5
Hi John, That looks fantastic. Just waiting to get all the bits from the electronics shop. I've got to gig the guitar this w'end, so it will probably be mon before I start.
Thanks John, you're the MAN!
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Post by treguiers on Nov 19, 2009 20:46:53 GMT -5
Hi John, Just a question about your veroboard illustration. When you make a straight connection between copper strips you use a black line terminated with black dots. On some though it's a black dot surrounded by a white circle. What's the significance of that? With regard to the battery. Is the 12k resistor connected across the mag battery terminals too or in series with one of the battery wires? Is the 12k resistor connected before or after the blender/buffer stage? As the battery is now operating the piezo, the mag and the buffer, will that make the battery life very short? Will the battery be cut off when there is no input jack? As regards to buying in bulk, most of those components come in packs of 5s or 10s or 25s , so I do have more than one of each. All that is left now is to pick up the rest of the components, do the gig on sat( the last note will still be ringing as I rush home to plug in my iron!! then get building(I know, veeeery carefully and slowly!) Again thanks guys, I'd be nowhere near this place without you.
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Post by JohnH on Nov 19, 2009 21:51:02 GMT -5
Hi tg - its just my way of drawing these things, which would not pass muster with any approval authorities!
But a black line with a while blob at one end, represents, in my mind at least, a resistor. Typically I show it like that when it is bridging too short a distance to go flat, so the body of the resistor is vertical with one wire straight down and the other looping up and over and down. Most of the resistors are white rectangles however because they can go flat.
Are you OK deciphering which component is which?, and also, can you read resistor colour codes OK - eg brown red orange = 12,000 ohms etc?
The 12k resistor will go from piezo + battery to mag + battery. I want to add another diagram showng how it is all connected up. Can you describe how the current wires are from each pickup?
Piezo - is the 9V battery built into the control box? can you get to the + and - battery contacts or battery wires to connect to? Is there one cord from it going to the actual piezo sensor, and another that was going to the jack, with this cord comprising an outer braid, and two core wires, one that was for battery connection that went to the 'ring' jack connection, and the other for output
Mag pup - similarly what are the wires that it comes with, again a two core braided wire to connect to a jack?
It would help to have as good a description or sketch as you can that shows how these pups are currently configured, with answers to the above questions if possible.
When you are done, the whole circuit will be completely off if no jack is plugged in. Current drain wont be too much different because I read that the the Fishman prefix preamp (the piezo one), takes about 4mA. The mag pu, as you found out, takes 0.5mA and the new buffer will take about 0.2mA, so overall its less than a 20% extra current drain on the 9V. I reckon it should be good for about 80 hours of run time on a fresh 9V.
If you are waiting to start, you can off course, work on the veroboard module. In fact, you should not put it anywhere near the guitar until it has been proven to work!, which you can do with aligator clips, jack leads etc.
cheers
John
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Post by JohnH on Nov 20, 2009 15:47:36 GMT -5
Further o this, I had a look at the installation guides for the current versions of your two pickups. Could you take a look at these to see if they are the same as yours, or at least with the same basic configuration and wire colours mag Pu - Fishman rare earth humbucker www.fishman.com/uploads/products/documents/63.pdfPiezo PU - Fishman Prefix Pro? www.fishman.com/uploads/products/documents/111.pdfIf these are close, it seems the prefix flips up to get to the battery, so I'm hoping you will be able to wire to it. The mag pu seems to have good access to the battery slot underneath - is that true? I snipped out the pictures showing jack wiring. It seems the wire colours are different - can you confirm? The red seems to be the battery negative in mag but the signal connection on the piezo Also, is that the sort of jack that you have, ie, it has a sleeve connection and three others. Its fine, it means the power gets its own switch within the jack and you could still add a stereo option later.. John
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Post by treguiers on Nov 20, 2009 17:20:49 GMT -5
Hi John, The hours you are putting into this project must be enormous. Here's a link to the fishman prefix that's on my guitar, www.fishman.com/products/details.asp?id=40The rare earth(humbucker. they do a single coil but mine is a HB) is the correct one. I had the innards of my strat out an hour before I was due to leave for a gig last week. So as to not cause too much stress I'm not going at the guitar til after sat(I've a gig with it this sat). After Sat I will take the relevant bits apart(carefully) and answer all your queries. The battery compartment does flip open as in the above illustration. As for a stereo option: i know enough to change a jack! Some of the components will not be available til mon. But I will prep a lot so that come mon I'll have it in my head what to do from start to finish Thanks again John, You're a prince amongst men
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Post by JohnH on Nov 20, 2009 17:40:17 GMT -5
No problem. My interest in this is: I like to design stuff, but cant possibly build everything, so If a idea catches hold, Im delighted if someone else builds it. Also, its interesting to see what other people find useful.
Anyway, back to this. and that older Prefix design looks like good news. The connections are as I thought, but it only takes 1mA. So the total current draw will now be about 1.7mA, so you might credibly get 250 hours out of a new battery.
So Im going to suggest a wiring diagram fro the combined set up, based directly on that Fishman info - then it will be up to you!
Good luck with your gig. We are only rehearsing this weekend so its just fun and a good blast. John
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Post by JohnH on Nov 20, 2009 19:19:17 GMT -5
OK, try this: There's four things to wire together, and with the current pickups having multi-core wires, theres a few choices as to where to take the original wires before redirecting them. On this view, I took the piezo main cord all the way to the jack, as it was originally, keeping the shield and battery negative connection there, but taking the output wire back via a new cord to the blender. That way it keeps your original wire as intact as possible in case you want to revert. Colours match the data that we have, so I hope they make sense. Note the black wire from piezo to mag pup is not strictly required, since it can get its negative supply from ground, but I would put it in so you can do that first and confirm the Mag. works via the 9V, before doing the rest. There'll also be a cord to th epiezo transducer - not shown since that will not change. Good luck, but ask any questions of course. cheers John
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Post by treguiers on Nov 20, 2009 21:20:27 GMT -5
Incredible John. Pure Craft. I can't wait to get started
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Post by ashcatlt on Nov 20, 2009 22:28:14 GMT -5
If you wire the jack so's it uses the (more standard) Ring>Sleeve connection for the battery -, you could end up powering it from a box on the floor - presumably via wallwart, which obviates all question of battery life. Just a thought.
Also, you must post soundclips. I know you're a little ways from having it done, but...
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Post by newey on Nov 20, 2009 22:59:22 GMT -5
Ash said it- soundclips, por favor!
And John- nice work on this. Although the implementation is somewhat specific to tre's pickups, the basic concept is susceptible of more general uses. So, if you would, please repost the diagrams in the Schematics section, so it doesn't get buried here?
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Post by JohnH on Nov 20, 2009 23:31:55 GMT -5
Well its now out of the design office and onto the construction site. Lets see how it works out, then it can be put to bed in the schematics area when its concluded. There's no rocket science here, but still, new puddings need to be proven by eating them!
I think this could be a useful gadget, because it should work equally well blending passive or active sources, or one of each, and then giving an active output. And unlike some other methods, it doesn't significantly load the sources, nor reduce the maximum amplitude you can get from either on their own, then requiring a gain boost. Also, the blending is smooth across the range, not all at the ends of the turn.
On the phantom power idea: One thing I worry about using jack plugs/sockets for this is what happens as you push the plug in, with various terminals being momentarily shorted to others, sparks, thumps and smoke maybe? John
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Post by ashcatlt on Nov 21, 2009 3:32:08 GMT -5
On the phantom power idea: One thing I worry about using jack plugs/sockets for this is what happens as you push the plug in, with various terminals being momentarily shorted to others, sparks, thumps and smoke maybe? John I have to admit to not having built anything like this, but I have followed a few threads on this idea, and I think that a certain minimal amount of current limiting in the power supply can avoid the truly damaging aspects of this. Bumps and thumps happen whether there's DC power or not, and can (and should) be avoided by making sure that the amp end is turned down while the plug is being inserted.
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Post by sumgai on Nov 21, 2009 14:17:39 GMT -5
The first potential issue with a phantom-powered TRS plug is that the ring and sleeve portions will momentarily short out as they slide past the jack's sleeve. Depending on the robustness of the phantom power supply, that momentary shorting may or may not blow the fuse. A good reason to not have the phantom power on at all, when plugging/unplugging the cord in question. Next, it's possible, and likely, that during the plugging/unplugging event, the plug's tip will contact the jack's ring terminal, and the plug's ring will contact the jack's sleeve at the same time. If the phantom-power is on, the power now goes from the jack's sleeve (ground) through the powered circuitry (pre-amp, what-have-you), and back out the ring contact. That ring contact is, at this moment, connected to the amp's input via the tip/center conductor of the cord. That puts a large positive voltage (the phantom power) on the input, which will be amplified down the line until it gets to the speakers - not good! Of course, that's assuming that the circuitry can withstand the reverse voltage. If it's protected by a diode on the incoming power line, then no such thing can occur, and there should be no pops coming out of the speakers. And finally, ash no doubt speaks from experience: whenever phantom-power is in play, always turn the power amp down before plugging/unplugging anything, period. It wouldn't be the first time someone has said "of course I turned off the phantom power", and then suffered a catastrophic pop out of the main speakers. HTH OTOH, I have to wonder.... This implication of ash's first statement is that one can replace the battery with a phantom-power supply. I took that as meaning "one or the other, as you will", not "instead of, sorry 'bout that". Is it possible to have both battery and phantom-power from one TRS jack? sumgai
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Post by treguiers on Nov 21, 2009 15:22:02 GMT -5
Wow guys, Pressure is on!
As regards to sound clips I going to do a before and after as well as all the after possibilities.
I am quite confident to take this project on(particularly knowing I have the support of such expertise!)
At the moment I have to disconnect the 9v battery each time the guitar goes into the case which is a total drag. So the proposed battery situation is a vast improvement over what I got. I use a pa system that has a phantom power facility, but I also use a AER compact 60 acoustic amp which doesn't have phantom.
So all I can say from here is ....I'll keep you posted.
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Post by sumgai on Nov 21, 2009 19:47:22 GMT -5
3g,
Be aware that most PA phantom power is designed for special microphones, and that voltage is almost always 48vDC. If you want to use this, you'll need to do a bit of stepping down in the voltage department.
sumgai
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Post by treguiers on Nov 21, 2009 21:01:31 GMT -5
At the moment, particularly with the kind of hours JohnH predicted as regard to battery life, and the easy access of the battery(with a "battery low" indicator LED), I personally don't see phantom power as a huge necessity for me.
But here's a question: Would it be advantageous to have an canon(XLR) i/p instead of a jack?
My focus at the moment is building John's excellent design. But I would imagine, that with such a blender, any modding of the piezo pre-amp or mag pup will have a huge effect on the overall sound. Much more so than each pup as individuals. Here is where I personally would like to see it go......
But like i said before I just do the donkey work. The scope and possibilities for this design can be much better envisaged by the JohnHs, Sumgais, Ashcatlts and Neweys of this world, than they can by me.
Time to get building.........
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