Guild TRIOCT (whhhaaaaaaat??)

[Mark Hammer]

I thought it was a beat-up iPhone...  

wtf? ....is that a crude hex pup then?....nevemind, re-read it.

I think you might be right, Rob.      Facetious?  Moi?? 

When I said in another post that it looked like it was "whupped with an ugly stick", I meant it.  The epoxy covering is lumpy and uneven, and clearly NOT moulded.

Was it supposed to replace an existing pickup?  That's a very good question, and one I never thought about until now.  There would have certainly been enough guitars at that time that, strangely enough, would have come without a bridge pickup.  There would have also been a somewhat broader array of pickup profiles and form factors available then than now, when you consider all of those oddball form factors from the assorted Japanese, Italian, German, and other manufacturers.  It wasn't all PAF, Strat, and P90 shapes in those days.  So, while imaginable, I'm not guessing that the plan was to simply re-use the existing screw holes for the pickup the guitar came with.

The pickup is low profile enough that one could have situated it between body and strings over a wide range of locations, perhaps with a bit of foam or surgical tubing or other flexible material to raise it up to an appropriate height, if need be.

I've not investigated enough to know whether the pickup is one coil per string, or something else.  It certainly has enough room for more than one coil, and I can't recall any hum when I last tried it out at least 8 years ago (can you imagine an octave divider that WAS sensitive to hum?  Yeesh!  ), so maybe there are two coils per string.  Ya got some iron filings, Dino?

[digi2t]

I've had time to put down the Mutron, and have finally delved into the belly of the beast. These are my PRILIMINARY schematics of the Trioct. I broke it down into sections, since there's just too much for me to handle in one drawing. I would have loved to throw this down as one drawing, but I'm not that talented. Besides, the "String Amplification" section is simply copy/paste, six times.
I'm not sure if I've named each section correctly, and my notes on the transistors can surely be ameliorated, so take them with a pinch of salt. All comments, recommendations, suggestions, observations, etc. are welcome.









Like I said, it's the first draft, I've yet to sit down and retrace, but I figure it'll give you guys some fat to chew.

EDIT: I just thought about it, I should really do a video of this puppy in action (forehead slap!). I'll see if I can jig up the hex pup on one of my axes, and do a demo. Sorry guys.

[Gus]

power supply looks like a standard regulated emitter follower.  Is there a missing connection in the 2n2907 emitter section?  I will check the circuit when I have some time.  A 317 circuit should work.

The output section looks wrong as drawn I would guess the output of the gain stage would go to the collector of the 2n5133 gain stage maybe both .1uf in parallel for .2uf from the collector and does the 100pf go from base to ground?  
The footswitches look like they ground out the signal from the volume wipers that are driven by the amps in the audio mixing section to turn off the sections.

Looking at the amp section is G connected to C as shown in the schematic?  The 82k not being connected to G and being used as a summing resistor to the normal amp in at C and out at J makes more sense to me.  That node is at lower gain and would be a "cleaner" signal.

I will think about the amp section schematic

Check the connections for the .1uf cap going to the 2n404. 

[Gus]

Did you get a chance to check the output section?
Did the C and G trace out like the edited diagram?

[digi2t]

Did you get a chance to check the output section?
Did the C and G trace out like the edited diagram?

Gus... you are SUCH a task master!

Yes, I've been working on it this morning, between stirs of my world famous spaghetti sauce. The above schematics have been modified.

power supply looks like a standard regulated emitter follower.  Is there a missing connection in the 2n2907 emitter section?  I will check the circuit when I have some time.  A 317 circuit should work.

I think I've got it right now.

The output section looks wrong as drawn I would guess the output of the gain stage would go to the collector of the 2n5133 gain stage maybe both .1uf in parallel for .2uf from the collector and does the 100pf go from base to ground? 
The footswitches look like they ground out the signal from the volume wipers that are driven by the amps in the audio mixing section to turn off the sections.

The 100p was in the wrong place, and the power feed was wrong, but the rest looks right.

Looking at the amp section is G connected to C as shown in the schematic?  The 82k not being connected to G and being used as a summing resistor to the normal amp in at C and out at J makes more sense to me.  That node is at lower gain and would be a "cleaner" signal.

Corrected.

Check the connections for the .1uf cap going to the 2n404. 

Right call, again. Moved to the right place.

Like I said before, I need to fine tooth this sucker again. Wouldn't surprise me if I find other places where my eyes deceived me.

[Gus]

Tracing a build like this can be hard on the eyes.

The two .1uf(.2uf)make more sense going to the collector at the output section

Interesting circuit might be able to use Si for the Ge they don't look like they add tone they look to be an low threshold AC coupled switch.  Also the 100K with the "brighten up" cap .01uf is to make this edge sensitive
The  section that goes to E has a little lowpass added .1uf and 510K
To D you have a highpass .1uf and 100k and then the diode
Note in the audio mixing section The amp with the E input also drives the amps with the F and D input

[digi2t]

I just did a little experiment.

I plugged my guitar (bridge pup humbucker) into one of the six string circuits. Ground to ground, and tip feeding the circuit. Surprisingly enough, it works. Mind you, all six strings are now feeding one circuit, rather than a circuit per string, but it works nonetheless. I don't recognize any appreciable difference between the hex pup, and my humbucker, playing single string lines. This makes me wonder how critical the hex pup construction really is.

I have a crapped out GK-2 pup. Think I'll try and see if the coils from it will work to feed the string circuit.

[PRR]

> power supply ....a missing connection in the 2n2907 emitter section?

Not sure what you are asking.

Because digi2t is still working on "connections", and not "systems", some of the paths are not drawn for on-sight understanding.

If I were to plan such a thing, without a mess-o-wires in front of me, I'd draw more like this:



Now the 2N2907 is some sort of "constant current" thingie.

More strictly the current depends on the input voltage, but not the output voltage. It presents a very high dynamic impedance to the 2N2222, lifting its voltage gain from small to ~~500, and improving PSRR.

There are other ways to do this, maybe with the same parts-count, but that's how they did it and nothing wrong with it.

EXcept.... the observed numbers do not work out. 1N750 is a 4.7V Zener. Add 0.7Vbe for 2N2222, the Base should be 5.4V. Multiply by 3k3+1k8/1k8 voltage divider, output should be 15V, not 19V. Mis-copied resistor value? Drifted resistor? Drifted 1N750?


Agree that a LM317 could be used. The raw voltage is mighty close to '317's rating. A short on the output (shorts happen, especially when hands are inside the box) "could" toast the '317. The D40D4 and 82 ohms is pretty robust. The "improved performance" of the '317 may not improve anything. (Assuming the 15V/19V discrepancy can be resolved.... not that 4V more is bad, but if it's drifty it's liable to get worse.)

[PRR]

Ah... if "N750" is a draw-library generic Zener and not an actual 1N750, then it might be a real-common *6V* Zener, which makes the 19V happen and gives excellent tempco.

[digi2t]

Ah... if "N750" is a draw-library generic Zener and not an actual 1N750, then it might be a real-common *6V* Zener, which makes the 19V happen and gives excellent tempco.

Nailed it Paul. I "assumed" the 1N750, since the only thing I could se was 1N75... due to how the diode was soldered in.  Not that I'm fond of exploratory desoldering, but in this case, it revealed itself to be a 1N754A diode. 6.8vdc zener. Schematic corrected.

Houston, we have 19 volts.

[Gus]

I was getting about 15 VDC in the sim I made with the 4.7VDC zener and guessing how the circuit was connected.  The first posts of the circuits when I first replied were different than what is posted now.

The about 38VDC and the PNP connection at the 82ohm makes sense to help have a more +VDC for the base drive (a NPN EF needs to have the base voltage "higher" than the emitter). A simple regulator circuit can operated a little more efficiently with a PNP pass device

I was thinking if a 317 was used to have the unregulated only a few more volts than the 15VDC or 19VDC

Some of my early posts might not make sense because the schematics have been changed after some of my posts

A thread from another forum about a hexpickups first and last posts
http://www.groupdiy.com/index.php?topic=48856.20

[digi2t]

Some of my early posts might not make sense because the schematics have been changed after some of my posts

Gus, don't worry about it. Like you said, you're going by what I post.

Quite frankly, it's great that you all take the time to look at it, and comment. Your eyes are much more trained to look at this stuff than mine, so your comments help guide me somewhat insofar as corrections are concerned. That, and your analysis helps with comprehension of the circuit too.

Thankfully, the corrections made to date are corrections that I won't have to do later. 

[liquids]

I just did a little experiment.

I plugged my guitar (bridge pup humbucker) into one of the six string circuits. Ground to ground, and tip feeding the circuit. Surprisingly enough, it works. Mind you, all six strings are now feeding one circuit, rather than a circuit per string, but it works nonetheless. I don't recognize any appreciable difference between the hex pup, and my humbucker, playing single string lines. This makes me wonder how critical the hex pup construction really is.

I have a crapped out GK-2 pup. Think I'll try and see if the coils from it will work to feed the string circuit.

From a glance, since the circuit is the same for each string - especially the filtering - it seems that it's not aimed at improving tracking (of, say, the sub octave?!) by a higher LPF cutoff for the high string, but a lower LPF cutoff on the low strings.  So it would make sense that effectively, it's not that much different....
The probable purpose of the hex pickup for this particular unit was probably to allow 'chord' sub-octave and rectified octave up (assuming that is what it is at a preliminary glance...?).  In that case, playing single string lines wouldn't affect tracking....and is synth like in the sense of a monophonic moog-style synth, and/or what I think most people tend toward with this kind of effect.

However, the individual per-string circuit allows for chords.  That is kind of hammond-like, or allows some of the digital & current ehx type of potential - if you want to strum.  I personally find that playing some open 6-string chord and having it be like a multi-voice thing kind of...overkill.  But if you think hammond or polyphonic synth - harmonics controlable - intervals become rather powerful, and playing intervals (beyond standard power chords), or bass note + interval kind of chord play - like a jazz guitarist might be playing chords - that ability takes on a unique force and is probably where these capbilities shine.

Whether one likes the sound - then, now, and/or compared to what was available at the time of production and what is available now - is personal preference.  =)

That hex pickup might be all the cooler if you looked into harry bissel's muffy III (enter Mark Hammond's great posts on direct-waveform synth stuff that harry's system is founded on).

[PRR]

Working through.

Would help to have part-designations for easy pointing-to.

In String Amplifier, one transistor sure makes more sense as PNP than NPN.

Also the circled 0.1u+510K makes no sense alone, and may be one of the other 0.1u+510K networks, copied thrice.

I make no sense out of the lower-right maze. It has input but no output?

[digi2t]

Working on it.

Right again on the PNP. It's a 2N5139. Positioning of the transistor is not conducive to easy reading of the part number.

Lower right has corrections, and I'll apply "Q" designators to the transistors. As you say, it hard to point to "that" transistor.

[armdnrdy]

I suppose you would like me to fabricate a pick up for this thing? 

[digi2t]

I suppose you would like me to fabricate a pick up for this thing? 

Yes. For yesterday. Please.

Are you done yet?



Seriously though, from the limited testing I've done so far, it seems pretty open to what pickup would be required to make it work. First things first though, I have to get the schematic straight.

[Mark Hammer]

Are you regretting your little trip to Ottawa, now? 

[digi2t]

Are you regretting your little trip to Ottawa, now? 

Not a chance! The salsa was delicious! 

[liquids]

I suppose you would like me to fabricate a pick up for this thing? 

Do you genuinely make hex-style pickups, etc?