SSS wiring question

[frets]

My opinion, despite the loading factor of a 250k vs. a 1meg blend pot, in this circuit, as in many, the tone is affected. I believe there was a reason behind his 1meg pot selection.

[newey]

Yes, YogiB, good to see you again and thanks for the correction as to the blending. I also did not look at the wiring, assuming Phostenix' diagram was correct. Never assume . . .

[cem]

All this information made me dizzy:)

Also looking at the orientation of the blend pot as currently shown in the diagram (i.e. noting that full output of the blended pickup is with the control fully clockwise, "on 10") we know that (as with blending in the centre position of an Les Paul) a log taper is not ideally suitable and linear taper would be better.

So this means that i can use this pot, right?

shop.fender.com/en/intl/parts/amp-controls-electronics/500k-dual-linear-potentiometer/0041266000.html



I have to make sure because it is an amp pot. This is the cheapest and fastest solution for me.

If i get this pot and modify it as Retread has described(making each end no-load), it won't effect the tone in any way when it is off(turned to either extreme), correct?
Wouldn't i need 2 detents for ease of use? Otherwise it will be a bit hard to know at which point the no-load zone ends. Could that be modified as well?

[newey]

Still can't see your link to tell you if that is the correct part

[cem]

Hahah. So that's the reason why i wasn't getting any answers for this one.

EDIT: I can't send the link no matter what i try so i will write the name:

Fender 500K DUAL LINEAR POTENTIOMETER


FEATURES

500K dual linear taper potentiometer

1/4" solid-shaft design

Accepts set-screw mounting amplifier knobs

Mounting washer and nut included

Used on Vibro-King® Custom, Dual Professional™ and Prosonic™ amplifiers (1994-present)

[newey]

OK, that sounds like it should do. And you don't have to use an amplifier knob, 1/4 inch is a fairly standard US size for knobs using a set screw. Any US Telecaster knob, for example, will fit (note that import-style knobs are typically 6mm, which is slightly smaller than 1/4 inch. However, these can be drilled out to 1/4" with a 1/4" drill bit, if it's a metal knob).

However, since this is designed to be mounted through a amp faceplate, the shaft is likely not long enough to go through a wood body. Pickguard mounting should be OK, as I mentioned earlier.

[reTrEaD]

May 27, 2020 15:54:53 GMT -5 cem said:

500K dual linear taper potentiometer

Linear taper sounds like a poor choice to me.

A dual ganged pot with one element having an audio taper and the other having a reverse-audio taper would be somewhat better. But in my opinion, a 'true blend' pot would be best.

I wouldn't worry about modifying it for no-load. I'd just omit the connections to ground.

[Yogi B]

May 27, 2020 7:36:43 GMT -5 reTrEaD said:

If the blend pot is a 'true blend' pot as ChrisK described it, the elements are unlike what we normally see. From fully CCW to center on one element there is essentially no resistance. From center to fully CW the resistance increases slowly when we begin the clockwise rotation and more rapidly toward the CW end.

The other element works in a similar fashion, but from the CW end of the rotation.

That's what we'd all probably want a dual-gang blend pot to do, alas that's not what any pot I know of does. ChrisK's blend pot has what datasheets tend to call the M & N tapers, they do have zero resistance over half their rotational range but when the resistance does start increasing it does so linearly. See his original post: Blend and Pan Pots

Because of this, the center detent position should be "both on".

With the assumption that the pot's taper is as you described above I would agree -- but such as it is, unfortunately linear, and linear taper being the same in both forwards and backwards directions, the option of a "both off" centre is as equally plausible.

• Centre "both on":
  
  

  		Blend Control
  		Fully CCW	Centre Detent	Fully CW
  SuperSwitch Position	#1	N- to Hot (N off)	N- to Gnd (N on)	N- to Gnd (N on)
  	#5	B+ to Hot (B on)	B+ to Hot (B on)	B+ to Gnd (B off)

• Centre "both off" (via a switcheroo of 'hot' and ground connections to the blend pot):
  
  

  		Blend Control
  		Fully CCW	Centre Detent	Fully CW
  SuperSwitch Position	#1	N- to Gnd (N on)	N- to Hot (N off)	N- to Hot (N off)
  	#5	B+ to Gnd (B off)	B+ to Gnd (B off)	B+ to Hot (B on)

Due to the linear taper both options will work equally well (or equally badly) so it's mostly a question of user preference, options are.

However one thing that might be worthy of note is that -- because only a small amount of added series resistance is needed to affect the blend amount near the fully blended-in end of the range -- the "both on" variation will have the largest apparent change near the middle of rotation where you may end up fighting with the centre detent, whereas the "both off" variation avoids that by putting the majority of the blend at the outer edges of rotation.

To be honest, I haven't looked carefully at the switching.

A closer look at the switching was required to answer my question: "Why do we need a dual gang pot for a simple parallel blend control?". If the wiring didn't put the neck & bridge in series (as in positions 2, 3 & 4, with the S1 Down), we could most likely get away with needing only a single gang pot.

May 28, 2020 8:40:22 GMT -5 reTrEaD said:

May 27, 2020 15:54:53 GMT -5 cem said:

500K dual linear taper potentiometer

Linear taper sounds like a poor choice to me.

A dual ganged pot with one element having an audio taper and the other having a reverse-audio taper would be somewhat better. But in my opinion, a 'true blend' pot would be best.

As above, a 'true blend' pot is linear. Also I'm not quite sure what you're planning with the A/C taper, but as to further clarify my response to to newey regarding blend orientation, for a simple blend control with one end of rotation being both pickups blended out and the other end being full blend, both gangs should have the same taper. Here's a greatly oversimplified diagram mashing positions 1 & 5 together:

Firstly, looking at the bridge pickup and its half of the blend pot, which we'll assume has a reverse-audio taper 500k, at 50% rotation the pickup has 450k in parallel with it (wiper to terminal 1) and 50k in series with it (wiper to terminal 3). Moving on to the Neck pickup with the same taper and rotation position, thus the same 450k of resistance between wiper and terminal 1 in parallel and the same value of 50k in series with the pickup albeit just on the ground-side instead.

I wouldn't worry about modifying it for no-load. I'd just omit the connections to ground.

Looking at the above diagram, can you see why that wouldn't work? However I agree in principle, the pots don't need to be no-load, removing the connection to ground on the bridge blend gang and the connection to the volume pot input from the neck blend gang would remove the loading of the pot. On the other hand, it also means that with the blend turned fully down the blended pickup won't be fully off and will still provide a path between output and ground i.e. still load the other pickup(s). Is that audibly different to if the blended pickup were truly disconnected? And even though I'd say probably not, no-loading the pot removes that doubt.

[reTrEaD]

May 27, 2020 7:36:43 GMT -5 reTrEaD said:

for a simple blend control with one end of rotation being both pickups blended out and the other end being full blend, both gangs should have the same taper.

What is the purpose of that? It just looks like a (rather poor) dual volume control unless another pickup is also connected to the output.

[Yogi B]

May 28, 2020 13:36:15 GMT -5 reTrEaD said:

What is the purpose of that? It just looks like a (rather poor) dual volume control unless another pickup is also connected to the output.

The diagram shows what would happen if positions 1 & 5 of the 'Strat mode' were combined together. I don't intend to represent any actual switching state, but rather simultaneously illustrate how each gang of the blend pot is connected to the relevant pickup. In actuality:

For position 1, B+ is disconnected from the pot, instead connected directly to the output.

Whereas, in position 5, N- is disconnected from the pot and instead connected directly to ground.

[cem]

At this point i have no idea what you guys are talking about lol. But it feels like you guys are getting somewhere. 

Could anyone tell me a dumbed down version of all these in simple english when you guys come to a consensus?

[Yogi B]

May 28, 2020 14:16:24 GMT -5 Yogi B said:

May 28, 2020 13:36:15 GMT -5 reTrEaD said:

What is the purpose of that? It just looks like a (rather poor) dual volume control unless another pickup is also connected to the output.

The diagram shows what would happen if positions 1 & 5 of the 'Strat mode' were combined together. I don't intend to represent any actual switching state, but rather simultaneously illustrate how each gang of the blend pot is connected to the relevant pickup. In actuality:

For position 1, B+ is disconnected from the pot, instead connected directly to the output.

Whereas, in position 5, N- is disconnected from the pot and instead connected directly to ground.

reTrEaD is this better?

---

Drawing that out like above was at least useful for furthering the "do this without needing a dual-gang pot" branch of thought. What if the blend pot was a push/pull (or similar), e.g. when down the blend pot functions only as the neck blender for positions 1 (and 2); and when pulled it acts as the bridge blend instead. Spitting the blend function as such also has the advantage of allowing you to quickly toggle between the unblended selection and a preselected blend amount. In simplified form, that would look something like this (assuming log taper pot and thus max blend at "0"):

(Note that the lower pole of the DPDT isn't strictly necessary and only serves to avoid the shunting of pickups which would otherwise occur in some cases.)

[newey]

Could anyone tell me a dumbed down version of all these in simple english when you guys come to a consensus?

Yes, and we're getting closer to that consensus. Why are we getting so technical here? Because, as we said from the beginning, this is a fairly complex scheme and we want to be sure it works the way you want it to. We want you coming back later and saying "You guys rock!" as opposed to "You guys suck!".

As for consensus, I'm on board with YogiB's idea here:

What if the blend pot was a push/pull (or similar), e.g. when down the blend pot functions only as the neck blender for positions 1 (and 2); and when pulled it acts as the bridge blend instead. Spitting the blend function as such also has the advantage of allowing you to quickly toggle between the unblended selection and a preselected blend amount. In simplified form, that would look something like this (assuming log taper pot and thus max blend at "0"):

This approach solves several issues. First, parts availability and cost; a DPDT push/pull (or perhaps a push/push) is cheaper and more readily available nearby you than some fancy blend pot you need to order from Fender. Second, the wiring is more straightforward. Third, as YogiB said, you could "preset" one blend setting and just hit the pot to switch to that. And, the change can be easily worked into the original Phostenix diagram.

[reTrEaD]

May 28, 2020 16:28:22 GMT -5 Yogi B said:

reTrEaD is this better?

Yes, but actually what made it better was going back through the thread, reading what you previously posted and looking more carefully at the wiring diagram.

Thanks for being patient with me while I was being quite thick.

[cem]

Yes, and we're getting closer to that consensus. Why are we getting so technical here? Because, as we said from the beginning, this is a fairly complex scheme and we want to be sure it works the way you want it to. We want you coming back later and saying "You guys rock!" as opposed to "You guys suck!".

Hey, you guys already rock though:)

This approach solves several issues. First, parts availability and cost; a DPDT push/pull (or perhaps a push/push) is cheaper and more readily available nearby you than some fancy blend pot you need to order from Fender. Second, the wiring is more straightforward. Third, as YogiB said, you could "preset" one blend setting and just hit the pot to switch to that. And, the change can be easily worked into the original Phostenix diagram.

Awesome. I like this idea as well and i am really excited!!!

[Yogi B]

I'm about half way through drawing an updated diagram, but I've just realised something odd about the placement of the 2 & 4 positions in 'series mode' (with the S1 down): they seem swapped. To clarify, the positions do produce the selections that Phostenix details, I just think the design should have those two positions reversed.

Consider position 2, for which the specified selection is (B + M) × N -- while this is partly composed of the standard Strat position 2 of B + M, lets think about the actual voltage output.\begin{aligned}
V_2
&= \frac{V_b \cdot Z_m + V_m \cdot Z_b}{Z_b + Z_m} + V_n \\[1.5em]
&\text{(assuming }Z_b = Z_m = Z_n = Z\text{)}\\[1.5em]
&= \frac{(V_b + V_m) \cdot \bcancel{Z}}{2 \bcancel{Z}} + V_n \\[1.5em]
&= \frac{V_b + V_m}{2} + V_n
\end{aligned}That is, the neck pickup contributes twice the amount of the other two pickups to the overall output. Conversely in position 4 the bridge pickup would be contributing double that of the other pickups. As I opened with, this seems backwards to how we would normally expect those positions to fall, i.e. position 2 should sound closer to the lone bridge pickup than the neck pickup, and vise-versa for position 4.

I haven't checked this assertion with an IRL test as the only guitar I think I could test this with is currently in a state of awaiting upgrades, but my Tillman SPICE simulation file seems to agree with the rough calculation above.

If others would concur with my reasoning, then I'm pretty sure the 'series mode' 2 & 4 positions can be swapped without affecting the ordering of the standard Strat selections.

[JohnH]

hey Yogi,
If you are doing a new Yogi version of a Phostenix Strat X2, I'll throw in 2c worth.

There are a couple of (A + B) x C combos. But I think they don't have the hum-cancelling (B+N) x M, which I reckon is the most useful one. It's noise-free, powerful, but not muddy (neither are the others), due to inductance only 1.5x single.

On blending, I've never found a parallel blending solution that gives a more interesting tone than just fully blended, or just one single. But series blending is very interesting right through the sweep. A 250k linear pot with a track section removed at at mid turn can do that with no loss.

[Yogi B]

May 30, 2020 8:59:08 GMT -5 JohnH said:

hey Yogi,
If you are doing a new Yogi version of a Phostenix Strat X2, I'll throw in 2c worth.

I wouldn't really say I'm doing a properly new version, just a refinement: correcting the issue I noted in position 3, rearranging the series mode selections, and swapping out the blend control. Though one further thing that may also be worth doing is making the bridge bendable into the N + M position, just to make things more symmetrical (and add another way to get B + M + N).

There are a couple of (A + B) x C combos. But I think they don't have the hum-cancelling (B+N) x M, which I reckon is the most useful one. It's noise-free, powerful, but not muddy (neither are the others), due to inductance only 1.5x single.

Though I agree, I don't see that happening without a major redesign, due to how the bridge and neck pickups have one lead permanently connected to ground and hot respectively. If I were designing a 'me' version M × (B + N) may be something I'd incorporate, but I think my priority would be swapping out the other two in favour of B × (M + -N) and N × (M + -B).

On blending, I've never found a parallel blending solution that gives a more interesting tone than just fully blended, or just one single. But series blending is very interesting right through the sweep. A 250k linear pot with a track section removed at at mid turn can do that with no loss.

For me the question of series or parallel blend kinda boils down to a question of how close the coils are in proximity to each other, for example: series blend in the form of a spin-a-split on a humbucker (or maybe a faux-humbucker formed from B×M or N×M) makes more sense, the coils are relatively tonally similar so the hotter/heavier sound of series verses single coil provides a larger variation in tone; whereas for pickups further apart like B and N, I'd want the tonal difference due to positioning be more evident, without it being clouded by increased output.

In any event, I'm now wondering about some scheme where position 3 has a blend between B+N and M, the blend mode being togglable between parallel and series, but that's probably a different diagram for a different day.

---

May 30, 2020 3:19:10 GMT -5 Yogi B said:

I'm pretty sure the 'series mode' 2 & 4 positions can be swapped without affecting the ordering of the standard Strat selections.

Okay, this should do it (and I also hope that truth table makes sense):

[cem]

Yogi B thank you so much for this:) The truth table is clear to read as well. Great job!!!

Although i'm pretty sure it works, if anyone can verify the diagram it would be awesome. Because if my guitar tech couldn't make this work, i wouldn't be able to know if it's his fault or the diagram's.

Also, i would like to ask a couple more questions:

So a regular, vintage strat has one 250k volume and two 250k tone pots. We can say the same thing about this diagram as well, 250k s1 switch, 250k tbx pot and regular 250k pot for blend. Does this mean when the blend pot is off, this wiring makes the guitar sound closer to the vintage/regular strat wiring as oposed to Strat X-2 Plus wiring which doesn't have the additional 250k blend pot?

Does the blend pot effect the tone in any way when not in use?

[cem]

Can anyone vet this diagram for me please

[cem]

Bump

[cem]

Bump

[newey]

Sorry that no one has gotten back to you on this, cem. Real work intrudes today, but I may get the chance to have a look over the weekend. Part of the delay is that I haven't memorized the S-1 switch logic, so I have to dig up the S-1 data to be able to trace the wiring out.

[cem]

Thank you so much newey. More power to you:) (Is this an old expression? I have never heard it being used but i found it in the dictionary lol)

[newey]

More power to you:) (Is this an old expression? I have never heard it being used but i found it in the dictionary lol)

I don't know where that expression comes from, but it is generally used in the sense of meaning "Do whatever you want to do, I think you're crazy but I won't interfere"

So, in English, you might hear someone say: "I'm going to enter the Boston Marathon!", someone else relies "Hey, more power to you".

Younger folks now will typically just reply "Whatever" instead.

[Yogi B]

Jun 11, 2020 5:08:35 GMT -5 newey said:

Part of the delay is that I haven't memorized the S-1 switch logic, so I have to dig up the S-1 data to be able to trace the wiring out.

Okay, so what can I do to make my "D"s and "U"s clearer or more obvious?

---

May 31, 2020 9:52:37 GMT -5 Yogi B said:

Though one further thing that may also be worth doing is making the bridge bendable into the N + M position, just to make things more symmetrical (and add another way to get B + M + N).

cem is this something you'd be interested in?

I forgot that I'd mentioned this, but having had a proper think I reckon this can be done with only minor modifications, but will unfortunately force the use of the simpler but less elegant push/pull wiring which will result in shorted coils in some circumstances, however this scheme is already less than perfect in that regard.

[cem]

it is generally used in the sense of meaning "Do whatever you want to do, I think you're crazy but I won't interfere"

Wait i didn't mean that lol. There is an expression in Turkish which roughly means i hope your hard work feels easy or i hope you have an easier time while doing the work. That's what i meant if that makes sense. I didn't know more power to you was a sarcastic expression. Well, good to know:)

cem is this something you'd be interested in?



I forgot that I'd mentioned this, but having had a proper think I reckon this can be done with only minor modifications, but will unfortunately force the use of the simpler but less elegant push/pull wiring which will result in shorted coils in some circumstances, however this scheme is already less than perfect in that regard.

Being able to get N+M+B on both 4th and 2nd positions would be nice. But can you tell me more about the drawbacks? What do you mean by push/pull wiring?(using another push/pull pot and getting rid of tbx?) And what are shorted coils? Do i have that problem in some circumstances on this current diagram as well?

[Yogi B]

Jun 12, 2020 3:18:10 GMT -5 cem said:

Being able to get N+M+B on both 4th and 2nd positions would be nice. But can you tell me more about the drawbacks? What do you mean by push/pull wiring?(using another push/pull pot and getting rid of tbx?)

I mean a change to how the blend push/pull is wired. The TBX control is unaffected by this and can stay.

And what are shorted coils?

A shorted (or shunted) coil is when both ends of a pickups coil are directly connected to each other. Why does that matter? Well, if the ends of the coil are connected that means we have a loop and a path for current to flow through the pickup. The reason this is potentially bad is because of the laws of electromagnetic induction, specifically Lenz's law which states that an induced current flows in the direction that opposes the change in flux that drives the induced current. So the theory is that this will slightly damp the vibration of the strings altering the tone and potentially reducing sustain. See: Shunting Coils - 'Beware the Tone-Sucker'!

In cases where the shorted coil is in very close proximity to the selected coil, this can also have a more direct effect due to capacitive and inductive coupling between the coils, see: Damping caused by the unused coil when splitting a humbucker & Avoiding capacitance from unused portion of coil with a tap. However the coils are far enough apart on a regular Strat that we needn't worry about this particular issue.

There is also a question of if having the yards of extra wire in the coil connected to the circuit, but not in a way that it produces output, acts as an antenna for noise; and whether this is worse with one end disconnected (a hanging coil), or with both ends connected but shorted together.

Because of these potential issues, we tend to try to avoid shunting coils in diagrams, but that isn't always possible, and in those cases practicality usually beats purity. (Shunted coils are acceptable if they are necessary to achieve a certain set of switching selections, or by allowing them we can greatly simplify the wiring.)

Overall, don't worry about it. Yes, shunted coils will probably have some small effect on tonality, sustain & hum, but they should all be minor in comparison to effects from other variables.

Do i have that problem in some circumstances on this current diagram as well?

Well yes, but as I say don't worry about it!

For example, in Strat mode position 5 (Neck only) the middle pickup is shunted. Looking at my diagram:

• Firstly follow the black M- wire it connects to the upper-right common terminal of the superswitch, in position 5 this is connected to the green wire that is grounded on the back of the TBX pot.
• If we then follow the yellow M+ wire, we see it connects to the upper-left common terminal of the superswitch, in position 5 this is connected to centre-right terminal of the S1 switch via the grey wire. As we are in Strat mode the S1 is up and thus grey wire is connected to the green wire on the terminal above -- this wire is ultimately grounded along side the other on the back of the TBX -- completing the loop.

[cem]

I see. Even though it bugged me at first that the shunting occurs in one of the most useful positions of a strat(5th), after reading the shunting coils thread, i think the difference would be almost inaudible so i am okey with that.

By the way, the tbx pot finally arrived so i took my guitar to my guitar tech immediately. He said he would be able to do it in 2 weeks. So Yogi B, if you update the diagram this week he could maybe use that instead. If not that's okey since the current diagram is good enough for me.

In the meantime it would be awsome if this diagram was vetted. I hope newey finds the time to do it this weekend.

Fingers crossed:) I hope everything goes well.

Also, he said he had never done a no-load pot mod before. I can easily find a video for that i think but for this particular diagram, which end does he have to cut in the pot in order to make it a no load? Because in the diagram when the pot is at 10, it is off if i am not mistaken. Which is how i like it to be, like a reverse pot. Does that change the end that he has to cut?

[Yogi B]

Jun 13, 2020 5:13:17 GMT -5 cem said:

I see. Even though it bugged me at first that the shunting occurs in one of the most useful positions of a strat(5th), after reading the shunting coils thread, i think the difference would be almost inaudible so i am okey with that.

Just to let you know that isn't the only place that there is a shunted coil it is just probably the easiest to explain. The middle is also shunted in Strat position 1 too. And if I remember correctly the rest are dependent on the position of the blend control so get more difficult to explain.

So Yogi B , if you update the diagram this week he could maybe use that instead.

Righto. It's only a couple of changes: eliminating half the p/p switching and adjusting terminals 4 & 5 of the lower-right superswitch throw.

Also, he said he had never done a no-load pot mod before. I can easily find a video for that i think but for this particular diagram, which end does he have to cut in the pot in order to make it a no load? Because in the diagram when the pot is at 10, it is off if i am not mistaken. Which is how i like it to be, like a reverse pot. Does that change the end that he has to cut?

Correct about it being off at 10. Therefore it is the same end as you would cut for the more common use as a no-load tone pot, so it should be the same as you find any guide -- but just to be clear, roughly the position shown below: