Jay Turser Surfmaster -- Passive tone/EQ switches

[thunderaxe]

Hi all,

First-time poster here. I recently purchased a used Jay Turser Surfmaster:




As you can see it is based on a Jazzmaster body, but with 3x P-90 pickups and a 5-way strat-style blade switch, and it has three switches on the top. I've surmised that these are essentially passive tone or EQ switches. I found a thread on another forum where someone posted about the guitar: 

www.harmonycentral.com/forums/topic/1638137-jay-turser-surfmaster/

They included this crude diagram of the wiring:



I've opened up the guitar and confirmed the accuracy of the diagram, at least for the switches and the master volume and tone pot.

It's the switches that are confounding me a little though. I had already studied that diagram and done some googling to get a sense of what capacitors and inductors wired the way these are, might be expected to do and concluded that they were, essentially, a treble cut, bass cut, and mid cut. But then when I plugged it in to my amp and tried them out they didn't sound like I expected at all. So here's my expectation and experience of each switch:

All switches are in parallel like a tone control and thus I assume are shunting certain frequencies to ground

Top switch: 2A223J (0.022uf) cap in series with inductor to ground.

Expectation: a mid cut/scoop, will thin out the thick mids of the P90 pickups and produce more of a scooped, strat-like sound.

Experience: Instant mud. Cuts all the high frequencies like turning a tone knob all the way to 0. The least useful of all the switches. I might have expected this from the capacitor alone but I expected the inductor to prevent the high frequencies from getting shunted to ground.

Middle switch: Two 2A222J (0.0022uf) caps in parallel (=0.0044uf together) to ground --

Expectation: a subtle (due to the very low capacitance value) treble cut, like turning the tone knob down a little. 

Experience: a very nasally midrange sound like a half-cocked wah pedal. are the caps producing a resonant peak at their cutoff frequency the way certain low-pass filters do?

Bottom switch: through inductor to ground.

Expectation: a subtle bass cut, thinning out the low end of the P90s but keeping the mids and highs intact.

Experience: a massive volume cut and thinning out of the sound. This one is actually the most useful, it does help in getting a theoretically more classic single-coil sound.


Can somebody help me figure out what the circuits are actually doing to create the sounds I'm hearing and what I might do to make them more useful?

[gckelloch]

The problem is likely the metal covers and the inductor. The eddy currents from the metal covers further reduce the high-end of the already high-end reduced high inductance Steel core P90s, and the inductor is likely not low enough impedance to allow the much reduced high-end to be significant, so you mainly get bass when the inductor & 22nF cap is engaged. The 2x 2nF cap = 4nF. That creates a strong midrange peak with a P90. The peak freq is higher when more of the P90's are in parallel, but the high impedance of the P90s decreases peak level progressively more above ~1kHz.

If you don't want to spend much money, I'd first replace the P90 covers with plastic. Figure out how to wire the switches so you have just the inductor going to the tone knob in parallel with the pickups on one switch to get marginally brighter tones as the knob is turned down. Wire one of the 2nF caps on another switch in parallel to ground for a potentially useable midrange boost that will increase in freq when the inductor switch is engaged and the tone knob is turned down. You could then use the 22nF cap as a typical tone knob cap on the last switch, or use it or the other 2nF cap in series with the pickups for bass reduction, but there will be bass reduction anyway when the inductor switch is on and the tone knob is down, and you'll be able to hear the resonant peak better. A lower capacitance cable may be of use for the brighter tones.

UPDATE 06/21: a better option might be to use one switch to bypass all the tone options with a ~500k R on it. You could then wire the inductor to the tone knob on one side of one of the remaining switches and the 22nF cap on the other side to the tone knob. Wire a 2nF cap on one side of the remaining switch for a mid-boost in parallel with the other switch. That would be pretty cool, and you can set up the tone routing b4 engaging it with the first switch. I have a similar setup on one guitar.

BTW, make sure the P90 covers are actually metal b4 replacing them. Changing to plastic won't make much difference if they are chrome-plated plastic.

[stevewf]

Here's YouTube video interview of a guy at a gig with his 3 Surfmasters. He mentions that all three of them behaved differently, right out of the box. With that in mind, I'm not surprised to learn of yet a fourth variation. Got a soldering iron?

[thunderaxe]

Yeah I've seen that video too, it sounds like some of his might have had broken wiring. The fact that my guitar perfectly matches the diagram posted by the person from the thread above makes me think this is the standard wiring for these guitars.

I don't have a soldering iron but I have friends who do and I am looking to mod this into something more useful. My current idea is to add a reverend style bass contour knob next to the volume and tone. The standard way to do it would be with a capacitor in series but I'm wondering if I could use the inductor in parallel that's already in there but control it with a knob rather than a switch so I can dial in the amount I want. Unfortunately I don't have any good way of measuring the inductor, I have a multimeter but it doesn't measure inductance.

I'm also open to more suggestions on what to do with the switches, I really appreciate the ideas in the first reply.

[gckelloch]

Jun 24, 2023 19:44:54 GMT -5 thunderaxe said:

Yeah I've seen that video too, it sounds like some of his might have had broken wiring. The fact that my guitar perfectly matches the diagram posted by the person from the thread above makes me think this is the standard wiring for these guitars.

I don't have a soldering iron but I have friends who do and I am looking to mod this into something more useful. My current idea is to add a reverend style bass contour knob next to the volume and tone. The standard way to do it would be with a capacitor in series but I'm wondering if I could use the inductor in parallel that's already in there but control it with a knob rather than a switch so I can dial in the amount I want. Unfortunately I don't have any good way of measuring the inductor, I have a multimeter but it doesn't measure inductance.

I'm also open to more suggestions on what to do with the switches, I really appreciate the ideas in the first reply.

Wiring the inductor in parallel from one side of one of the switches to the tone knob will reduce bass (and shift the resonance up) as the knob is turned down. Might be too much all the way down, but you can wire a 5~10k R in series with it if you want less bass loss.

Other options: use one of the switches to engage the bridge or neck P90 for all possible pickup combos, or use it as an OoP or HOoP switch for the middle P90, assuming the switches are DPDT.