On the JS II "Deep/Hard Switch"...

[fronobulax]

Reference the above diagram that was drawn from inspection of an unmodified 1971 JS II. I'm starting this thread because there seems to be some doubt as to just what the switch does electrically and thus does in terms of sound. There is no doubt in my mind what is happening electrically but that is because I am comfortable with mathematics beyond calculus, have spent time professionally doing digital signal processing and have not forgotten all of my high school physics. While I certainly expect to misstate something I will find it easier to accept my mistake if you can couch it in terms familiar to high school physics since we really are dealing with basic science here.

The far right shows the output as controlled by the PU selector switch which is irrelevant to this discussion. To the left of that are the tone and volume potentiometers. The former shunts high frequencies to a capacitor and hence to ground. The latter shunts some potion of the signal to ground. Thus the tone control varies between allowing high frequencies through and cutting them. The volume control just cuts the output level. For the discussion of the switch these are irrelevant.

On the left are the pickups. Since the bridge pickup is simpler, it will be discussed first. The output goes from the pickup to a resistor (and then to the controls). In general the higher the resistance at this point in the circuit the "darker" the tone. Resistance here reduces high frequencies and dynamic range. So with this resistor the bridge pickup will have less treble, dynamic range and output compared to the "raw" bridge pickup.

The toggle places the neck pickup in one of two modes. In one mode the output goes through a resistor and the results are the same as for the bridge PU. Compared to the "raw" output, the output has less treble, dynamic range and output. Note that the value of the resistance is different for the neck and bridge pickups so they will sound different above and beyond the differences due to placement.

In the other mode, the output goes through a capacitor which effectively shunts high frequencies to ground. So the effect of the switch in the other position will be less treble, compared to the "raw" pickup.

So there really should be no mystery about what the switch does. In one position the neck PU should sound very similar to the bridge PU. In the other position the treble is seriously cut. For most people whether this is a good or a bad thing depends upon their reaction to the Guild humbucker and their personal preferences in tone. If you don't like the humbucker then nothing is going to make it sound any better. If you like the humbucker then this gives a larger tonal range to play with.

Lots of room for confusion because the circuit is a treble cut - it is taking something away, but the marketing literature says "Bass Boost" which suggests adding something (which is normally impossible with passive circuitry). More confusion because folks assume it does what the switch does on an S-100 (which is either a coil tap or a phase reversal but I'm not sure).

I believe the circuit is the same for all humbucker equipped Guild basses, which would be the Starfire and JS after 1970 plus a few stragglers in 1970 and the reintroduced M-85 which occurred circa 1971.

I know the circuit is not the same as the circuit that was used on Bisonic equipped Starfires from mid-1967 through 1970 when the PU was "upgraded" to the humbuckers.

 

[mavuser]

Thanks for taking the subject to the next level. I will contribute more to this thread after the new year when I have more time and more information on the issue.

But I can say now I had been curious as to what exactly the "deep hard" switch does, thank you for clarifying that-i am not questioning that any further and to be candid I am not the electrician or mathematician that Frono and many (or most) others here appear to be.

but my real interest in the subject and discussing it here is much broader- regarding the tone and overall sound of the humbucker itself, with and/or without the deep hard switch...across the board.

i am really only talking about the neck pickup in my posts, unless i make specific mention otherwise, just to be clear. in all instances.

it seems to me there is one blanket reputation for the "sludgebucker," yet from what I have read and my limited personal experience, it seems to sound different on different basses, possibly with the DH switch coming into play, not sure. but with or without the DH switch my point is MY BASS sounds alot better than the reputation it has here.

i am NOT comparing it to the Bisonic. that pickup sounds unreal and is in a class of its own. i think we all agree on that. its apples and oranges...and if 99 percent of the people in the room prefer apples then it is what is and speaks for itself. That is a rare and expensive bass and you should all consider yourselves lucky to have one.

BUT there has to be some middle ground between a hagstrom bisoninc and a puddle of sludge. Again, the Guild humbucker is indeed that puddle of sludge...sometimes. but other times, it is much more in the middle of the road, or even closer to "that sounds pretty good" ...more like a Fender or standup sound. someone on this forum even describes a JS bass w/humbucker sounding a bit like a banjo, and i understand what they mean.

the previous mention of the green capacitors vs. non-green capacitors should be mentioned here again. maybe there is something there sonically? i havn't got a clue. and I am uneducated in the subject. then there is the semi-hollow vs. the solid body, the maples and mohoganys. and the guts like i said. i think amps make a big difference too, but the discrepancy in tones im hearing together with the things i am reading are significant enough to remove amps as enough of a variable to come into play.

At the Guitar Center near me, I played a 1972 mahogany/walnut Gibson EB-0 with one humbucker in the neck. it had the textbook Gibson humbucker tone. big, fat, and flat sounding. still though, it shook the floor and sounded so different than what i am used to hearing. i thought it sounded totally cool. at this time i had already been previously familiar with a video of Catherine playing a maple sunburst Starfire 2 with humbuckers. I dont know what year that bass was made. I dont know which pick up she was using, my guess is the neck pick up. i dont know if that Starfire 2 has a DH switch , and if so, if she had it engaged or not. based on what i know to this exact moment my guess is it was the neck pick up without the DH switch engaged, if it had one. but i really dont know.

I do know that the Gibson EB-0 sounded enough like the Starfire 2 describe above, for me to start shopping for a Guild JS-1 with a humbucker. it did not take me long to find one. at significantly less than half the price of the Gibson at the Guitar Center, in equal condition or better, also made in 1972, i snuck out of Rumbleseat.com at hundreds less than i have even seen one for on ebay. supposedly the bass i got was turned in by the original owners daughter.

anyway when I got it in the mail, i found the one mode (i guess with the DH switch engaged) had ALL KINDS of bass-super loud, strong, sloppy tone just all over the road. "THIS" i told myself "is the SLUDGEbucker they are all talking about" just...wow. it sounded a little like the Gibson and Starfire, but maybe 3 times louder/stronger than the Gibson for sure, and much muddier. all kinds of swamp thunder sludge, whatever you want to call it. in that regard more removed from the Gibson and Starfire humbucker sound I had heard.

But then in the other mode (with the DH switch "off"...i guess) just the complete opposite. my first thought was "this bass has been modded." super tight, warm and punchy. much closer to the Fender basses which feature a "split single coil in humbucking position" (ok...).
more neutral third parties comments include "it sounds kinda like a stand up" and "that doesn't sound like the Gibson bass at all" and "hey that sounds pretty good." i find those all to be quite the compliments considering i have essentially zero bass skills at this point.

anyhow, there comes a point where you stop asking questions and enjoy what you have. We all know Guild had several variations of what appeared to be the same instruments or amps. I think i got lucky with my bass and simply want to inform others here that there may be more to the humbucker than just the "sludge." or maybe i just like the humbucker a lot more than most. i am familliar with the Bisonic enough, i have heard one of the best players i know of play it extensively...at this point for it to have turned me off to the humbucker. but it hasn't. I think my bass sounds fantastic and there are a few others that have posted similar details on their JS basses here as well. Yet most of the banter on the humbucker is regarding the sludge and its low desirability. There seems to be a gap in the information in my opinion, but I am no expert. I can tell you my bass sounds about 800 times better than that Gibson and cost less than half the money, without using the DH switch. I will rarely, if ever, use the DH switch, as far as i can see right now.

On my bass, the DH switch also increases the volume and/or gain significantly. to go from one mode to the other, I MUST turn the gain and/or volume down on my amp. If i don't things will break both inside the amp and out. my walls might crumble and the neighbors will likely call the police.

also just to be clear, the tones i get on my JS1 are a result of the tone pot turned all the way off (zero) and the volume turned all the way up (10), i adjust the amp as necassary. I think it sounds best that way. most like the stand up or vintage sound. it sounds good with a little color too, but i like playing with the tone all the way off.

 

[fronobulax]

i am NOT comparing it to the Bisonic.

I think the vast majority of folks who don't like the Guild humbucker are comparing it to the Bisonic. Why settle for mediocrity when greatness is within reach? In my personal case, I bought the Starfire for emotional reasons (not sonic ones) about six years after the JS but once I did the JS hardly ever got any playing time. That said, since everything about tone is subjective, I will try and keep the Bisonic out of my comparisons, at least for purposes of your discussion.

BUT there has to be some middle ground between a hagstrom bisoninc and a puddle of sludge. Again, the Guild humbucker is indeed that puddle of sludge...

Sludge is the neck PU with the tone dialed down to zero and the deep/hard switch in the deep (treble cut) position.

Non-sludge begins with flipping the switch the other way.

the previous mention of the green capacitors vs. non-green capacitors should be mentioned here again. maybe there is something there sonically?

Again, the color of the capacitor has absolutely no effect on its electrical properties. When capacitors are color coded to indicate their value that color coding is usually in the form of dots and not the color of the casing. So if you think the color has anything to do with the sound then we are going to have to agree to disagree.

If, however, I have missed something and the capacitor values did change and the color somehow indicates that change did occur then yes, the capacitor value will have an effect on the sound. The value of the capacitor will effect which high frequencies are attenuated and by how much. Changing the capacitor attached to the switch will change just how much treble is cut when the switch is engaged. One extreme in capacitance will almost certainly cover the sound in sludge. The other extreme will have a minimal, and barely noticeable effect. We could put this to bed if you could actually read and report the value of the capacitors :wink:

then there is the semi-hollow vs. the solid body, the maples and mohoganys.

I happened to play the GSR SF I bass with a NOS humbucker for a few moments through my own amp. The sound had more in common with my JS than it did with my Starfire (no surprise) but it did sound a little different from the JS bridge PU which could have solid vs hollow or the location in the "sweet spot" or both. I am hard pressed to explain how the type of wood of a solid body directly effects any pickup (or solid vs. hollow, for that matter) but people claim that it does. My best guess, assuming they are correct, is that the construction affects the string vibration in subtle ways which, in turn, affects what the pickup picks up.

Catherine playing a maple sunburst Starfire 2 with humbuckers. I dont know what year that bass was made. I dont know which pick up she was using, my guess is the neck pick up. i dont know if that Starfire 2 has a DH switch , and if so, if she had it engaged or not. based on what i know to this exact moment my guess is it was the neck pick up without the DH switch engaged, if it had one. but i really dont know.

If it had humbuckers then it was most likely 71 or later and it had the DH switch.

As a tangent, the GSR SF basses and the 70's vintage basses have the same humbuckers but I do not know whether the PUs in the 90's reissues were the same humbuckers or different ones.

As another tangent, at some point it is the player's hands that determine the sound and a world class bassist is going to get the sounds they want out of any instrument, sometimes in spite of the pickups. Just a thought.

But then in the other mode (with the DH switch "off"...i guess) just the complete opposite.

My experience as well - the switch makes a dramatic difference.

anyhow, there comes a point where you stop asking questions and enjoy what you have. We all know Guild had several variations of what appeared to be the same instruments or amps. I think i got lucky with my bass and simply want to inform others here that there may be more to the humbucker than just the "sludge." or maybe i just like the humbucker a lot more than most.

As noted above refusing to compare the humbucker to the Bisonic can generate a lot more positive comments about the humbucker. Most folks think it holds up very well against a Gibson, for example. As for variations on the PU and associated electronics anything is possible with Guild but I'd place my bet that nothing changed that would effect the tone.

On my bass, the DH switch also increases the volume and/or gain significantly.

Interesting. Not my experience. I can dial my amp in so that changes I make on the controls on the bass keep the volume within an acceptable range of variation. But switching basses definitely forces me to change things if I want to keep the perceived sound levels constant. My amp does have limiting and compression but I hardly ever see the light that says it is engaged.

 

[mavuser]

To clarify further and simplify my point, I realize I may be in the minority both on this forum and beyond- in being a fan of the Gibson Humbucker.

The Guild Humbucker is a different story. It sounds waaaay too good to be so "love or hate" among Guild enthusiasts.

I am very curious to hear a Guild bass w Humbucker that does not have a DH switch at all. Perhaps I already have

 

[fronobulax]

I am very curious to hear a Guild bass w Humbucker that does not have a DH switch at all. Perhaps I already have

I think the only such instrument that left the factory without one would be the new GSR SF Bass. If I am wrong then I would expect the oddball to be a JS I since the specs for a JS I varied and were even sometimes different from the corresponding JS II.

 

[hieronymous]

Let me preface by saying that I have no electronics knowledge whatsoever.

My impression of the switch is that one setting is actually a bass-cut, similar to the "baritone switch" on Gibson EB-2 basses. That's why people mistake it for being a bass-boost, when actually the position with the strong bass frequencies is the default. So the "hard" setting cuts some of the deep lows, resulting in a more "Fender-like" sound as opposed to the "Gibson-like" sound of the "deep" setting.

The interesting thing about the neck pickup on the Guilds is that the bass-heavy position also has a treble-cut? So bypassing the switch would allow the full-range of frequencies to be heard. That's what I'm thinking of doing, though I guess the next question is, do you want to hear the full range of the pickup?

Re: volume level compared to Gibson - the '60s Gibson "mudbucker" is an extremely powerful pickup, with very little high-end frequency output - very little midrange frequency output either IME. I'm not sure about the '70s ones - those were moved closer to the bridge, whereas the '60s ones are right up by the neck. I have had two '60s Gibson basses, and to me those are absolutely the highest output, most bass-heavy pickups I have ever played. My early-'70s Guild M-85 neck pickup has a little bit more articulation/midrange response.

If I have time I will try and make soundclips of the positions with my M-85 - the problem being that it is strung with flats so there isn't a lot of high-end content.

 

[mavuser]

A semi-hollow instrument definately has an acoustic resonance, to some degree, that a solid body doesn't have. But if everything else were the same they would sound a lot like each other, besides that "hybrid resonance." I also think the maple and mohahany starfires sound different to my ears, from what I have heard.

Which is actually not much when it comes to either of them having a Bisonic. I'm lucky to hear Catherine's live. Other than that I have Jack and Mellowgermans videos. Hence the reason for the exclusion of the Bisonic here. In the big picture, most people don't have a Bisonic or can't afford one to compare their bass to. Or maybe just cant find one. Some of us just aren't worthy of it. Like buying a Ferrari when you don't have a license to drive, or a garage to park it in. So if leaving the Bisonic out of it results in some honest positivity for the humbucker, then we are pretty much on the same page. I think it's fair to say the Bisonic loyalty together with the bonafide sludge mode, and the paralell to the Gibson EB has overshadowed the better half of the Guild Humbucker.

One discrepancy though, is most of the aforementioned Bisonic loyalty vs. Humbucker is with regard to Starfire owners. Much of the input here, and referenced, is from 70's JS owners.

I thought it would be constructive to discuss the same pickup in different basses, with the switch in both positions, and incorporate the Gibson. Which I think we have done rather successfully!

 

[fronobulax]

My impression of the switch is that one setting is actually a bass-cut, similar to the "baritone switch" on Gibson EB-2 basses. That's why people mistake it for being a bass-boost, when actually the position with the strong bass frequencies is the default.

One of the reasons I am so anal about phrasing is because so much of the discussion about this switch depends upon whether you are talking electronics or sound and whether you consider the switch in the up or top or bass side position to be normal or whether the "default" position is down, bottom or treble side. I've had people tell me both positions are normal and give reasons for their choice.

Let's call position A the one where the signal goes through the resistor and position B the one where it goes through the capacitor. Sound wise, moving from A to B will appear to boost the bass. The sound change from B to A is less distinct to me but if you wanted to call it a treble boost I wouldn't argue.

Electrically it is incorrect to use the word "boost" because it is a passive circuit and nothing is being added, only subtracted. Electrically B is a treble cut compared to A. I don't have good words to describe A compared to B besides "different".

To the extent that the "raw" output of the PU is considered Normal then the A position is closest to "raw".

So the closest thing to "raw" without modifying the wiring would be the switch in the A position and the Tone control maxed out at the treble end. If you like that and want more then clipping out the resistor controlled by the switch and/or changing the tone pot would be the the things to try.

 

[fronobulax]

A semi-hollow instrument definately has an acoustic resonance, to some degree, that a solid body doesn't have. But if everything else were the same they would sound a lot like each other, besides that "hybrid resonance." I also think the maple and mohahany starfires sound different to my ears, from what I have heard.

To be clear, whatever the sonic differences are between the various woods and solid vs. hollow, those differences will be observable even if there are no pickups involved. Those differences effect the vibrational characteristics of the strings and will be present even if the pickup is not "sensitive enough" to capture them.

One discrepancy though, is most of the aforementioned Bisonic loyalty vs. Humbucker is with regard to Starfire owners. Much of the input here, and referenced, is from 70's JS owners.

There are several members who either have Bisonic equipped JS basses or have replaced the factory humbuckers with Dark Stars.

I thought it would be constructive to discuss the same pickup in different basses, with the switch in both positions, and incorporate the Gibson. Which I think we have done rather successfully!

I suspect the preference for the Bisonic has stifled any serious discussion of the merits of the humbucker on its own. You are to be commended for sticking up for it.

There are a couple folks with JS basses that still have the humbuckers. I can only recall one person who had a Starfire with humbuckers and I think they sold it. There are several folks with solid body M-85s with humbuckers. But for the most part, it was the Bisonic Starfire that put Guild basses on the map so they get a lot of the talk.

 

[hieronymous]

So to me this is a fascinating thread - I know that some are content to just "poo-poo" the sludgebucker but at this point I'm stuck with them and willing to look for the positive, or at the very least trying to discern the "facts" - of course, we know how subjective "tone" can be! I am going to play off of some of frono's comments to try and set up my experiment, which I will post separately.

One of the reasons I am so anal about phrasing is because so much of the discussion about this switch depends upon whether you are talking electronics or sound and whether you consider the switch in the up or top or bass side position to be normal or whether the "default" position is down, bottom or treble side. I've had people tell me both positions are normal and give reasons for their choice.

Agreed - if we aren't careful, then we just end up with vague, arbitrary statements. I know next to nothing about electronics (I wish my dad had taught me but in hindsight it was his joy to work on my instruments). I like to think that I have a fair amount of experience as a bassist, both live and in the studio, though much of my studio experience is in the past 10 years with computer-based recording. And after ten years or so of participating in bass guitar forums I know that things can get slippery when we try to talk about music!

Electrically it is incorrect to use the word "boost" because it is a passive circuit and nothing is being added, only subtracted.

Again, agreed - this is a totally passive circuit so we should only use "cut" since nothing can be boosted.

Electrically B is a treble cut compared to A. I don't have good words to describe A compared to B besides "different".

This is what I want to address with actually recordings (see my next post).

Let's call position A the one where the signal goes through the resistor and position B the one where it goes through the capacitor. Sound wise, moving from A to B will appear to boost the bass. The sound change from B to A is less distinct to me but if you wanted to call it a treble boost I wouldn't argue.

To the extent that the "raw" output of the PU is considered Normal then the A position is closest to "raw".

So the closest thing to "raw" without modifying the wiring would be the switch in the A position and the Tone control maxed out at the treble end. If you like that and want more then clipping out the resistor controlled by the switch and/or changing the tone pot would be the the things to try.

This is where I start to get confused! I want to be very clear about what position A and position B are. I will provide more detail in my next post and try to be consistent.

So there we have it for now. I have the raw materials ready for my next post - please be patient with me, I think it will be worth it!

 

[hieronymous]

OK, I'm ready to start with the experiment! Let's get warmed up with an image:

OK, now that we have that out of the way, here's what I did: With ProTools LE 8.0.1 I recorded my M-85 II fretless in each position. I played both fingers and pick, but for the sake of this demo I just included fingers, with my thumb resting on the corner of the fretboard. I recorded each position - the neck pickup soloed in each "suck switch" position, then with both pickups in each position, then just the bridge pickup. I also used the EQ section of a mastering program called Ozone (the link is version 5, I'm still using Ozone 3) to capture a snapshot of the EQ curve of one of the notes. I also have a screenshot of the two switch positions next to each other for another (albeit less accurate) visual.

So first, here are the soundclips. Position A is with the switch up (towards the bass side), Position B is with the switch down (towards the treble side) - I think this matches Frono's terminology in previous posts in this thread.

neck pickup in A position

neck pickup in B position

both pickups with neck in A position

bridge pickup

So far so good - use your ears to listen to the various positions in relation to each other. My subjective impressions from just playing the bass since I got it were that 1) the A position is much bassier than the B position, and 2) the neck in position B and the bridge by itself sound really thin.

Then I decided to take a screen shot of some of the soundclips in ProTools:

The top is the neck in the A position, the bottom in the B. Edit: I incorrectly stated that amplitude and frequency were combined in the waveforms - I was informed that the size of the signal is displaying amplitude, so the B position is louder, though as the spectrum analyzer snapshots below show, there is less of the deep 70 Hz frequency.

Next I used the EQ section of Ozone to take "snapshots" of the low A being played at the 5th fret of the E string. In this first image, the purple curve is the neck pup in the A position and the yellow curve is the neck pup in the B position:

The lowest frequency is several decibels lower in the B position, while the midrange from about 200 hz and up is higher. You can really hear it in the soundclips. Personally, I'm not too fond of the midrange sound in this setting, which is part of why I hesitate to have the capacitor taken out of the circuit.

In this second image, the purple curve again is the neck pickup in the A position, and the white curve is both pickups with the switch in the A position:

With both pickups, you retain the bass, but still get increased midrange/treble response, though there's still not a lot of treble.

Ideally I would provide snapshots of each position, each note even! But I didn't get that far. This will hopefully help illustrate the differences between the two settings of the suck switch. There is still a lot of work to be done, but this is a start.

 

[fronobulax]

Thank you! I will comment more later but will say one thing now. I have often used "thin" to describe the B position except when I have not been playing the JS for a while. If I pick it up after a period of neglect and the switch is in the B position then the tone is fine and thin is never the first word that leaps to mind. This suggests to me that in my subjective experience the sound in the A position is so dominating that it becomes the standard of comparison whether it is deemed good or bad.

Fascinating.

 

[Zelja]

Reference the above diagram that was drawn from inspection of an unmodified 1971 JS II. I'm starting this thread because there seems to be some doubt as to just what the switch does electrically and thus does in terms of sound. There is no doubt in my mind what is happening electrically but that is because I am comfortable with mathematics beyond calculus, have spent time professionally doing digital signal processing and have not forgotten all of my high school physics. While I certainly expect to misstate something I will find it easier to accept my mistake if you can couch it in terms familiar to high school physics since we really are dealing with basic science here etc

Frono, I am going to have to disagree with a good portion of your circuit analysis. I base this mainly on my many hours spent dealing & mucking around with guitar & amp circuits - I also have an Electrical Engineering degree. Note, I have little experience with these basses but coming to some conclusions based on the circuit as drawn only.

Some basics first before I go into the Deep/Hard switch. Maybe some of this could be too basic but hopefully it will help someone and also give some background to the discussions that follow. Skip to the sections with headings if it is all too simple.

Firstly the switch seems to be drawn wrongly if it is a 2 position switch - the contact should be shown connected to either to top or bottom pair of terminals. As drawn, it would indicate that the circuit is open in the middle position (switch effectively not closed to either pair of terminals) which would effectively make it a mute switch. A very minor quibble though.

Now the pickup - it has it's own electrical properties such as internal DC resistance, inductance & impedance. When looking at the circuit though, it is best to look at it as a multiple frequency AC voltage source. When a string is plucked, a current is in fact generated but that is seen as a voltage, with respect to ground, at the output of the pickup.

Volume control - is a potentiometer (or pot)- a variable resistor. Between the two outer legs you have it's full resistance at all times, e.g. 500k ohms. The middle leg is the "variable" resistance part which changes with respect to the other two terminals as the shaft is turned. When wired as a volume control it acts as a voltage divider. One end is connected to ground & the other end is connected to the input signal (from the pickups generally). The middle leg is connected to the output. The voltage to the output is reduced depending on the resistance of the middle wiper with respect to ground. E.g. if the pot is set such that the resistance on the middle terminal is 300K Ohm then the voltage seen as the output is : Vop = 300/500 x Vin = 0.6 Vin.

The Tone control pretty much works as you say. It also uses a pot but in a different way to the Volume control. As shown on the diagram, it uses only two lugs of the pot & is wired as a variable resistor in series with the capacitor which goes to ground. Now a capacitor allows certain frequencies to go through & blocks others depending on it's size. The smaller the cap value the more low frequency signals are blocked & so only higher frequencies pass. If the tone pot is set to 0 Ohms (0 on your tone dial), then all the high frequencies that the capacitor will allow to go through it are shunted to ground as that is the path of least resistance for these frequencies. As a result only the lower frequency signals are passed to the output signal. As the tone pot is increased, you increase the resistance before the cap, making it harder for all the high frequencies to be shunted to ground, hence more highs manage to get to the output & you get a brighter tone. When the pot is on full (say 500k resistance), then most, but not all, of the highs get to the output as very little is shunted to ground.

The Deep/Hard switch.

In the other mode, the output goes through a capacitor which effectively shunts high frequencies to ground.

Nope, the capacitor is not wired to ground - it is in series to the volume control. The way it is wired allows the higher frequencies to pass through to the volume control (& hence output) & blocks the lower frequencies. Hence, when the cap is in circuit, that would be the "Hard" position with the brighter tone. Reverend & some others use this type of thing as a basis of their Bass Contour or Bass Cut controls - signal goes to the output via a small cap with a pot in parallel with the cap. When the pot is set to 0 ohms, the cap is completely bypassed & the full signal goes to the output. When the pot is on full resistance (generally 2M Ohms, the cap is almost fully in play & lots of the bass is blocked from going to the output & a thinner sound results. In between pot values vary teh overall tonality between the two extremes as you would expect.

The series resistors.

The output goes from the pickup to a resistor (and then to the controls). In general the higher the resistance at this point in the circuit the "darker" the tone. Resistance here reduces high frequencies and dynamic range. So with this resistor the bridge pickup will have less treble, dynamic range and output compared to the "raw" bridge pickup.

Ok, disagree with some of the conclusions here. Note, that anything connected after a pickup is a load on the pickup. Note also that the lower the load the more highs are lost. This is why on most humbucking pickups (which generally have less highs than single coils), 500K pots are used, while generally 250K pots are used on single coils.

Initially I was stumped as to why the 220K & 150 K pots are in the circuit but I think I have it sussed. As drawn, they form a voltage divider with the volume/tone pots. For the sake of clarity if we ignore the tone pot& cap (get's complicated as it is is a frequency dependent voltage divider) the total resistance seen by the neck pickup is 220K + 500K (I'm guessing this) so - 720K. So even when the pot is full up the signal from the neck pickup as seen by the output will be attenuated as follows: Vop = 500/720 X Vin = 0.69 Vin.

So what is the point of this? I believe it is an attempt at volume balancing for the two modes. When the Hard switch is engaged, the cap is in the circuit & a significant bass cut occurs which would also cause & be heard as a volume drop. So when set to the "Deep" position, there is no cap in the circuit & all the frequencies pass through equally - this would cause a volume increase compared to the "Hard" position, so to counter this, the resistor is added, forms a voltage divider & reduces the voltage to the output & hence decreases volume. I'm am surmising that the smaller resistor on the bridge pickup is used so as to drop less voltage/volume on that pickup (Vop = 500/650 x Vin = 0.77Vin) as generally you get more volume in the bass position than in the bridge position for the same pickup spec. So this is another attempt at volume balancing between the bridge pickup & the neck pickup in the two neck modes.

Based on all this if you bypass the "Deep/Hard" switch & the resistors (connect pickup output directly to the volume pot), you should get more output signal from the bass & hit the front of your amp harder. You will probably also get a touch more brightness as voltage dividers cause some loss of highs (notice that you often lose highs when you turn the volume down on a guitar).

So, does all the above sound plausible based on your actual experiences with the bass?

More confusion because folks assume it does what the switch does on an S-100 (which is either a coil tap or a phase reversal but I'm not sure)

The S-100 etc uses a phase switch so it only has an effect when both pickups are selected.

 

[Happy Face]

please remind me why it is there in the first place. Do I recall something about the desire to emulate the "ticky-tock" sound or something?

For me I believe it is academic since the accursed switch was pulled out if my JS before I bought it.

 

[fronobulax]

The Visitor From the Future should take my previous comments with a shaker of salt until I absorb and react to Zelja's comments, which show some definite signs of being more correct than mine, if only because I elected to analyze parts in isolation for simplicity and that does not seem to have been the best choice. The Visitor From the Future should know that sometimes I like run on sentences. I do think my next useful contribution probably involves mapping out the switch once and for all although I am sorely tempted to try and recreate the circuit as I understand it in an analog circuit simulator.

As for why it is there....

For me the JS is the least versatile of my basses in terms of the variety of sounds/tones it can produce. If I want a varied sound palette the Starfire and the Pilot both have it beat. But it does produce some specific tones than no other bass in the stable can produce but for me those tones are exactly the tones with the switch in the "bassyist" position which I believe (but see above) is what would be lost of the switch were removed.

 

[chazmo]

Whatever it does, fix it in software.

Sorry, I couldn't resist. I know my brain works rather differently than you crazy 'leccies! Jamie, you *haven't* forgotten all your high school Physics?! I know I have. A looooong time ago.

Jamie, good on you for trying to map this circuit. Sadly, all I could think of was how good it'd be if capnjuan were still here to chime in. Sounds like zelja and heironymous are putting you on the right course though.

 

[Zelja]

But it does produce some specific tones than no other bass in the stable can produce but for me those tones are exactly the tones with the switch in the "bassyist" position which I believe (but see above) is what would be lost of the switch were removed.

Frono, I'm pretty sure I'm correct & you won't lose the "bassyist" tone with the switch bypassed as I reckon with the cap in the circuit , that that is the "Hard" position.

There is a really easy way to test this, no soldering or destruction involved. First get yourself a lead or two with some crocodile clips at either end:

- Open the control cavity cover of the bass & put the bass into the neck potion with the Hard switch position activated. Play.
- Now clip the two crocodile clips on either end of the capacitor only. You are effectively taking it out of the circuit. Play. I bet that that it now sounds similiar to the "Deep" mode but probably a bit louder as there is no voltage divider in play - try flicking the switch back & forth. You will be basically seeing the difference between having the 220K resistor in the circuit & out of it.
- You could also try putting the clip on either side of the 220K Resistor & you should hear a volume increase compared to when you take one of the clips off. If you have two leads with crocodile clips you can keep the one on the cap & add the one on the resistor. You should now hear no change between the two positions (you will hear the click of the switch when changing over though) as the switch is effectively bypassed & out of the circuit..
- You can bypass the switch totally as well with one lead by putting one clip on the switch terminal connected to the pickup & the other clip on the switch terminal going to the volume pot. The simplest & easiest way to (semi-permanently) take the the switch out of the circuit is too solder a wire between these two switch terminals - very easily reversible, no parts to store, no holes to cover - you are just left with a switch that does nothing.
- You can also test the effect of the 150K resistor on the bridge pickup by connecting a lead across the resistor. Once again I'm expecting a slight volume increase when the lead is connected & hence the resistor is out of the circuit.

Give it a whirl - should take 5 minutes.

 

[fronobulax]

Give it a whirl - should take 5 minutes.

*snicker*

It will take me five minutes to find a screwdriver, make a safe place to work on the bass, and move the Christmas Tree so I can get to my amp... We won't even mention whether it will take me less time to find some alligator clips or just buy some more.

However, since I want to map out the switch correctly once and for all, this will be easy to accomplish at that time so as long as we can wait several days...

 

[Zelja]

*snicker*

It will take me five minutes to find a screwdriver, make a safe place to work on the bass, and move the Christmas Tree so I can get to my amp... We won't even mention whether it will take me less time to find some alligator clips or just buy some more.

Sorry Frono but my estimate only includes taking the cover off, doing the test & putting the cover back on. It does not take into consideration the finding/buying of tools, clearing of space, moving Christmas trees, watching motivational videos, visualization and/or deep breathing exercises. :lol:

 

[mavuser]

OK, I'm ready to start with the experiment! Let's get warmed up with an image:

OK, now that we have that out of the way, here's what I did: With ProTools LE 8.0.1 I recorded my M-85 II fretless in each position. I played both fingers and pick, but for the sake of this demo I just included fingers, with my thumb resting on the corner of the fretboard. I recorded each position - the neck pickup soloed in each "suck switch" position, then with both pickups in each position, then just the bridge pickup. I also used the EQ section of a mastering program called Ozone (the link is version 5, I'm still using Ozone 3) to capture a snapshot of the EQ curve of one of the notes. I also have a screenshot of the two switch positions next to each other for another (albeit less accurate) visual.

So first, here are the soundclips. Position A is with the switch up (towards the bass side), Position B is with the switch down (towards the treble side) - I think this matches Frono's terminology in previous posts in this thread.

neck pickup in A position

neck pickup in B position

both pickups with neck in A position

bridge pickup

So far so good - use your ears to listen to the various positions in relation to each other. My subjective impressions from just playing the bass since I got it were that 1) the A position is much bassier than the B position, and 2) the neck in position B and the bridge by itself sound really thin.

Then I decided to take a screen shot of some of the soundclips in ProTools:

The top is the neck in the A position, the bottom in the B. Edit: I incorrectly stated that amplitude and frequency were combined in the waveforms - I was informed that the size of the signal is displaying amplitude, so the B position is louder, though as the spectrum analyzer snapshots below show, there is less of the deep 70 Hz frequency.

Next I used the EQ section of Ozone to take "snapshots" of the low A being played at the 5th fret of the E string. In this first image, the purple curve is the neck pup in the A position and the yellow curve is the neck pup in the B position:

The lowest frequency is several decibels lower in the B position, while the midrange from about 200 hz and up is higher. You can really hear it in the soundclips. Personally, I'm not too fond of the midrange sound in this setting, which is part of why I hesitate to have the capacitor taken out of the circuit.

In this second image, the purple curve again is the neck pickup in the A position, and the white curve is both pickups with the switch in the A position:

With both pickups, you retain the bass, but still get increased midrange/treble response, though there's still not a lot of treble.

Ideally I would provide snapshots of each position, each note even! But I didn't get that far. This will hopefully help illustrate the differences between the two settings of the suck switch. There is still a lot of work to be done, but this is a start.

I'm not sure how much more I can contribute to this thread, but I will add that none of those audio clips sound like my bass. I'd also like to thank each of you for contributing. Fascinating indeed!