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

[hagmeat]

The deed is done. Hagmeat came over yesterday & the mods were carried out.

It was a bit difficult to leave the resistors in & just bypass them (it's tight in there!!) so both the 220K on the "Deep" side of the switch & the 150K going from the bridge pickup were removed & replaced with a shunt (used some resistor leads). Also took out the cap, placed a 150k resistor across it neatly, soldered them together in parallel & placed it back into the circuit - the "hard" position. Result, as previously described, were more volume in all positions & more beef in the hard position, but less beef (i.e. brighter) than in the "Deep" - this position sits somewhere between the Neck in "Deep" mode & the bridge position.

In summary the standard wiring was actually doing the following:
- Neck in "Hard" position - massive bass (& hence volume) cut
- Neck in "Deep" position - substantial volume cut, probably some slight loss of highs as well
- Bridge position - substantial volume cut, probably some slight loss of highs as well

^^^^^^
I couldn`t have said it better. Thanks again Zelko, you`re a champion !

 

[Zelja]

^^^^
No probs mate, glad you are happy with it.

 

[fronobulax]

I'm not going to go out on a limb and try and analyze this myself, but I note some similarities between the mod documented in this video and the Deep/Hard circuit.

 

[Zelja]

^^^^
Well they both use a cap to brighten the sound but under different conditions and in different ways.

The so called treble bleed mod allows more high end to get through to the output than the rest of the attenuated signal as such the overall tone stays brighter. A portion of the overall signal is fed to the output (how much depends where the volume knob is set) plus a good deal of the highs are also allowed through un-attenuated. This is to counteract the effective loss of high end as you turn the pot (due to a number of factors including cable capacitance, input impedance of the amp etc, I think). The intent of the treble bleed mod is to give a similar tone (balance of highs/lows) as the volume is turned down.

Now as stated in previous posts, on the JSII, with the resistor in series with the Volume pot (in the neck PU on the "Deep" setting & the bridge PU at all times), it is the same as having a volume pot that is always turned down & to about 4 on on the neck PU as tested by ear! Maybe this is part of the reason these PUs are described as muddy?

In the "Hard" switch position on the JSII, all of the signal is fed through a cap & as such a lot of the bass/mids do not get to the output.

 

[fronobulax]

See this link. Our hieronymous posted his work there as well. Slightly different set of comments but mostly wanted people to know the contents were similar.

 

[mavuser]

I just want to add if anyone is interested there is a nice looking 1972 black JS-1 on ebay right now. I am unaffiliated with the seller but as I have stated, a fan of the instrument. Compared to mine and what I paid for it, i think the starting auction price + shipping is reasonable. Even the BIN could be justified, or very close to it. The biggest differences in my bass and this bass is this one has the chrome sting cover, (presumably) unmodified rosewood saddles, and the original hardshell case (with 2 broken latches). other than that condition looks similar and they are both 1972. looks like a good deal if someone wants to get in the game with a JS-1, I was happy I did. cheers.

http://www.ebay.com/itm/111021640911?ssPageName=STRK:MEWAX:VRI&_trksid=p3984.m1423.l2661

 

[fronobulax]

Adding the drawings now that LTG can host. Both were made by "inspection" of my '71 JS II, unmodified from the factory.

Visitor from the future should note that much of what I said up until @Zelja's post was wrong. Don't believe me.

Drawn by my college roommate who was always a better bass player and went on to get a degree in Electrical Engineering and design medical equipment.

Drawn with my stepfather, also a EE, who finished his career dealing with microwave ommunications.

 

[lungimsam]

Thanks, Frono!

 

[Rambozo96]

Adding the drawings now that LTG can host. Both were made by "inspection" of my '71 JS II, unmodified from the factory.

Visitor from the future should note that much of what I said up until @Zelja's post was wrong. Don't believe me.

Drawn by my college roommate who was always a better bass player and went on to get a degree in Electrical Engineering and design medical equipment.

Drawn with my stepfather, also a EE, who finished his career dealing with microwave ommunications.

I am far from an EE and more of a tinkerer/warranty voider at best but it seems to me the “deep” selection is with that cap in series with the neck pickup which would probably filter out some highs whereas the selection with the resistor would just attenuate the signal before the volume and tone controls. I don’t know why Guild felt the need to run resistors in series with the pickups unless it made for an unpleasant tone “wide open”.

 

[Rambozo96]

Err well guess I was incorrect in my sentiment. I remembered SD made a post about running a cap in series with the hot wire of a pickup but it seems that the opposite is true that it would reduce the muddy nature of the neck pickup which for example a Gibson EB bass is infamous for. Can’t get it right all the time I suppose.

 

[fronobulax]

I am far from an EE and more of a tinkerer/warranty voider at best but it seems to me the “deep” selection is with that cap in series with the neck pickup which would probably filter out some highs whereas the selection with the resistor would just attenuate the signal before the volume and tone controls. I don’t know why Guild felt the need to run resistors in series with the pickups unless it made for an unpleasant tone “wide open”.

[edited]

The Deep/Hard switch.
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.
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.

 

[Guildedagain]

Is this one of the longest running threads here?

Fascinating to be reading so much about this while totally digging the crap out of my JS2 on a daily basis.

I sprayed out the scratchy pots, finally, and wow!

I gained some volume. The pots went dead quiet.

Tone and construction on this bass are unmatched, and I've had many basses over the years.

Here are some super detailed shots of my JS2 electronics, you can read the chiclet cap numbers/values/maker. Btw, they are not "lime green" but more "forest green".

Pics from pot cleaning day.

Pot date code 304-7205 = Stackpole pot 5th week of 1972.

Stackpole pots as found in vintage Strats.

The cap maker I E C is elusive, who is it?

 

[lungimsam]

I am interested in getting one and this thread is very interesting and informative.
I have read other threads about this bass and am glad to say some people do like the Guildbucker.

Now we just need you owners to upload some sound clips for us to hear. I am interested in hearing the bridge pickup with the volume and tone knobs all the way up. Played thru clean channel with fingers, not pick.

 

[hieronymous]

This is all I can contribute (I think I grabbed this from an eBay ad) - I don't think this pic is in this thread but I might have missed it:

The deep-hard switch on my '71 M-85 II became a Q-switch when my bass was Alembicized, and it's fretless so my sound clips aren't necessarily representative...

 

[mavuser]

Tone and construction on this bass are unmatched, and I've had many basses over the years.

Here are some super detailed shots of my JS2 electronics, you can read the chiclet cap numbers/values/maker. Btw, they are not "lime green" but more "forest green".

definitely I agree on the quality and tone of the bass! all (vintage) Guild basses are that way!

the lime green cap I observed was for a Hagstrom Bisonic neck pickup in the solid body JS bass, with no suck switch or deep hard switch (no switch at all).

the forest green caps are observed in semi hollow SF basses w Hagstrom Bisonics, as well as Humbucker equipped JS basses (just not Fronos, among others presumably). But again, "anything goes" is a much better description when discussing the evolution of Guild bass circuitry in the 60s-70s. some Bisonic pickups even had 2 magnets, while others had one.

 

[Guildedagain]

There must be sound clips, but to me the bridge pickup isn't where the bass shines. It's on the neck pickup, and to me the real magic happens at 5 or below on the tone knob.

 

[SFIV1967]

The cap maker I E C is elusive, who is it?

No idea if the "I E C" is even a manufacturer. There are a few like IEC Electronics Corp. but they were contract manufacturers not a capacitor manufacturer. Often those Polyester or Mylar capacitors had only the values on them. Probably made in Taiwan or Japan at that time.

Ralf

 

[lungimsam]

No i mean isolated sound clips. Can’t hear what I need when its in da mix.

 

[fronobulax]

The obsessive moderator is going to suppress the veer and move the Bisonic discussion elsewhere.

The request for isolated JS II sound clips is still open

 

[Guildedagain]

I'll see if I can do something.