# Yamaha Revstar Wiring diagrams



## sjp (11 mo ago)

I am intrigued by the Revstar lineup - to the point where I might just go and buy one. They look like an awesome guitar.

But I am in the middle of a build and it made me wonder how practical it would be to have the same electronics in what I am doing. In particular the "Focus" treble filter and that crazy looking transformer that sits in the circuitry somewhere and feeds off the output voltage from the pickups as far as I can ascertain.

In any case, the range of sounds from the Revstars is really impressive so I wondered if anyone has come across a wiring diagram for them. 

11 second Google yields this:

__
https://www.reddit.com/r/Luthier/comments/gdk9u2

...but I am pretty certain that is at best incomplete.

Answers on a postcard


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## mhammer (Nov 30, 2007)

You might want to check here: Mod Garage: Inside Yamaha’s Dry Switch


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## Wardo (Feb 5, 2010)

Revstar always seemed like a good guitar to me.


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## sjp (11 mo ago)

mhammer said:


> You might want to check here: Mod Garage: Inside Yamaha’s Dry Switch


Thanks, I read with interest, and the linked article about the focus knob.

Maybe I am just blind to it, but neither of them mention the transformer...

"Located on the DPDT switch of a push-pull tone pot, Yamaha's Dry Switch consists of a 330k resistor and a 3300 pF capacitor connected in parallel."


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## mhammer (Nov 30, 2007)

Well, the article is from 2019. Possible that the aforementioned transformer was added to select models since then. I will note that a transformer can be used as an inductor, and placed in series with the signal to cut bass.


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## sjp (11 mo ago)

see over on the right side of this picture. I see a capacitor, a couple of resistors, a volume pot and a 5-way switch and the pull/push tone control. And lurking in the corner is a f*$&ing great transformer. I'm very curious how this is all wired up. If I could get the range of noises out of my build that you could get out of a revstar I would be very happy.


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## sjp (11 mo ago)

@mhammer you make a very good point. Maybe it's not a transformer at all, maybe it is an inductor...


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## greco (Jul 15, 2007)

sjp said:


> but neither of them mention the transformer...


Is it possible that the transformer you rare referring to is actually an inductor?
OOOPS...@mhammer posted before me...


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## sjp (11 mo ago)

@greco yes, I think that's it.






5 Key Differences between Transformers and Inductors | Custom Coils Blog


The transformers and inductors are two important devices used in the electronics. There exists a misconception that these are the same because they look similar in construction and appearance.



www.customcoils.com





For an inductor... "When there is a change in the current that passes through the coil, then a voltage is created, according to Faraday’s Law."

Out on a limb (and borrowing heavily from my undergrad Physics) I am guessing that when in the circuit this inductor will elevate the output voltage. In conjunction with a resistor/capacitor it could really shift the signal.


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## knight_yyz (Mar 14, 2015)

thats actually a super switch and it has a few caps on it as well.


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## sjp (11 mo ago)

@knight_yyz that's the one that was under my first post. There's no inductor in that circuit. I suspect it's an older version.


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## knight_yyz (Mar 14, 2015)

i watched the video and it almost triples the voltage output of the stock pickup. .213 VAC to .585VAC


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## Paul Running (Apr 12, 2020)

.213 VAC to .585VAC will increase the output impedance by a factor of 7.54 in a passive device...it will load-down much easier for the same input device. Is that what you are looking for?


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## benjackcash (5 mo ago)

mhammer said:


> You might want to check here: Mod Garage: Inside Yamaha’s Dry Switch


Thanks for this source man 


Sent from my iPhone using Tapatalk


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## sjp (11 mo ago)

oooh! look! the rabbit hole...









Inductance


Knowing something about it can keep you from doing dumb things.



blackstoneappliances.com


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## mhammer (Nov 30, 2007)

sjp said:


> @greco yes, I think that's it.
> 
> 
> 
> ...


Transformers DO more than mere inductors do, yes. But ultimately, they are coils. Small transformers are often used AS inductors, simply because their primary or secondary coil has the "right" inductance for some purpose.


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## Xevyn (Jul 14, 2021)

sjp said:


> see over on the right side of this picture. I see a capacitor, a couple of resistors, a volume pot and a 5-way switch and the pull/push tone control. And lurking in the corner is a f*$&ing great transformer. I'm very curious how this is all wired up. If I could get the range of noises out of my build that you could get out of a revstar I would be very happy.
> 
> View attachment 431126


Just a note about the new revstars - the first gen revstar's have the dry switch (which is very similar to the bass contour rolloff on the Reverend guitars except without the ability to control how much you can rolloff). With the new Revstar's, only the entry level Element line has the dry switch. The new Standard and Japanese models have the "Focus Switch" which smooths out the treble frequencies and boosts the mids and lows. The pic from the video with the transformer is from one of the guitars with the "Focus switch".

I like the new models but I prefer the dry switch and the neck profile on the gen 1 Revstar's (the newer models have a slightly wider neck that I didn't like as much). I originally was thinking about trading in for one of the newer ones but instead I will be hanging onto my RS502:


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## sjp (11 mo ago)

mhammer said:


> Transformers DO more than mere inductors do, yes. But ultimately, they are coils. Small transformers are often used AS inductors, simply because their primary or secondary coil has the "right" inductance for some purpose.


true that, in fact ANY coil has inductance. Pickups are inductors. 

I've been trying to track down the parts in that picture, especially the inductor/transformer/coil.

There is a post on this forum about half way down by angellahash that seems to list the part number.


https://guitarnuts2.proboards.com/thread/9930/revstar-new-tone-control



VEC4100 G AC1 M86RFA

I've had no luck tracking that down. Googling the whole thing gives exactly one result - which is the post where it's mentioned. So I went looking for transformers and inductors and there are sites like this one...


https://www.mouser.ca/c/power/transformers/?q=4100



I'm not really any closer to finding out what that wiring scheme is, or what part the inductor is. I guess Yamaha consider their circuits proprietary and nobody has yet taken one of the new ones to bits and produced a wiring diagram.


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## sjp (11 mo ago)

here's a better picture from this German site









Test: Yamaha Revstar RSE20, RSS20 & RSP02T


Der japanische Hersteller bewies schon immer ein Händchen für ansprechende eigenständige Designs. Etliche seiner Gitarren sind zu echten Klassikern geworden, allen voran die SG2000, die seit 1976 bis heute zum Yamaha Line-up zählt. 2015 erschien die Revstar-Serie, die vom Design britischer...




www.gitarrebass.de


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## Xevyn (Jul 14, 2021)

You could try contacting Yamaha support for the parts manual or if you want to order the exact parts. They gave me their parts manual a couple years back when I was thinking about buying locking tuners for my RS502. Here's the manual they sent me


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## Paul Running (Apr 12, 2020)

None of those schematics include a transformer and none of the images provide sufficient detail to produce an accurate schematic, without the schematic it's speculation. I don't believe that they are using the transformer as an inductor...how else are they tripling the signal out as noted in post#12.


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## sjp (11 mo ago)

and another... just so they are all in the same place





NGD, REVSTAR Std 2.0


Visited my nearest guitar store a couple of months ago to get a replacement chorus pedal. They had a some demonstrator Revstars in there... had to try the Std 02t and 20, couldn't help myself. Haven't had a 24.75 scale mahogany maple cap guitar with that type of bridge before. Les Pauls have...




www.strat-talk.com


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## sjp (11 mo ago)

angellahash has a go at a wiring diagram in that same forum, but @Paul Running you're right, it's speculative



https://guitarnuts2.proboards.com/thread/9930/revstar-new-tone-control?page=1


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## Paul Running (Apr 12, 2020)

Okay, by their schematic, the transformer is wired as a paralleled inductor.


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## Paul Running (Apr 12, 2020)




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## Paul Running (Apr 12, 2020)

Question is: how is the output almost tripled?


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## sjp (11 mo ago)

Paul Running said:


> Question is: how is the output almost tripled?


Isn't that exactly what inductors do?






Generating High Voltage with an Inductor


A review of inductor basics as related to switching power supplies in generating voltages.



www.bristolwatch.com




.


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## Paul Running (Apr 12, 2020)

I believe that an inductor can generate a momentary spike in voltage at the resonant frequency but not continuously through the entire bandwidth.


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## sjp (11 mo ago)

learning more about what inductors do in AC circuits, their generated signal will lag the input signal by 90 degrees, or a quarter phase. A signal boost plus a phase shift.









AC Inductive Circuits


An Inductor is usually a coil of wire that sets up an alternating magnetic field around it when an alternating current flows through it .Inductance is the property of an inductor that opposes the change in current. It is measured in Henry. Due to this inductance , a back emf is induced in the...




www.electronicshub.org




.


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## knight_yyz (Mar 14, 2015)

Here is the full video


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## mhammer (Nov 30, 2007)

I'm not so sure the schematic Paul shows is accurate. I can't see where the role of transformer in that drawing would increase the amplitude of the output signal. It would certainly alter the *tone*, but as drawn does not seem to impose any noteworthy level shift in the level.

The Les Paul Recording guitar also includes a transformer. However, its role is to turn the low-impedance pickups into a higher-impedance output, such that it can either be used direct into the board (where the normal low impedance is similar to what a voice mic would be), OR it can feed a regular old guitar amp.

To be honest, I'm kinda stumped here.


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## knight_yyz (Mar 14, 2015)

it's meant to be a low to mid boost of 6db. You can really hear it when he turns on the boost with the bridge pickup.


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## Paul Running (Apr 12, 2020)

Okay, now the circuit looks familiar (please excuse the rusty brain). A similar circuit is used in my V2 for midrange boost.


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## mhammer (Nov 30, 2007)

Phil McKnight's decription would suggest otherwise. That's not to suggest you're wrong, because yes cutting mids and bass would indeed reduce overall level. But Phil describes it as a "passive boost", and NOT simply an _apparent_ boost when something affecting level is removed. If the schematic IS accurate, then that would suggest Phil may not "know his gear" as well as he thinks in this particular instance.

I don't say this to throw stones at Phil, or anyone else. Either the schematic is correct and knightyyz is accurate in his description, or Phil misunderstood (perhaps as a result of bad ad copy from Yamaha).


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## knight_yyz (Mar 14, 2015)

to me when he pulls the knob you can hear more mids and bass. So not cutting the mids/bass but boosting those frequencies only. Especially on the bridge pickup. mhammer you mentioned it alters tone and to me you nailed it too because it does alter how the bridge reacts. It is definitely altering the tone by only boosting part of the signal.


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## sjp (11 mo ago)

I've been reading a lot about inductors. Come to the rabbit hole with me...









Frequency-Impedance Characteristics of Inductors and Determination of Inductor’s Resonance Frequency | Basic Knowledge | ROHM TECH WEB


ROHM TECH WEB: Power Supply Design Technical Information Site by ROHM, Providing Basic Knowledge, Technical Information and Design Materials for Power Supply Designing.




techweb.rohm.com





What I found really fascinating about this is that an inductor will have a real variety of effects on the signal and they will differ at different frequencies, which implies they must have really tuned that inductor to the rest of the circuitry - pickups, caps, pots and all (mod at your peril).

What I understood from that site was the fact that the inductor has a resonant frequency which is a function of its physical characteristics (winding mostly). Below that frequency it will act as an inductor, above it a capacitor. Given that a pickup signal will have a really wide range of frequencies, all of these effects will be happening at once.

The one thing that seems immutable is the phase shift of 90 degrees between the input voltage and output current.

None of this really helps me build one - and now I really want to. And I am not sure I can quite explain the mid/low boost which is definitely there in all the sound checks I have watched, and there are many.

One of us has to go and distract the guy at long and mcquaid while someone else grabs one off the wall, whips the cover plate off and draws a wiring diagram. It's the only way we are going to get an answer.


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## sjp (11 mo ago)

Unable to sleep, and unable to put this down, I continued looking at the low pass question and found this...



https://electronics.stackexchange.com/q/25684



_"An ideal inductor would not behave like a capacitor, but in the real world there are no ideal components.

Basically, any real inductor can be though(t) of (as) an ideal inductor that has a resistor in series with it (wire resistance) and a capacitor in parallel with it (parasitic capacitance).

Now, where does the parasitic capacitance come from? an inductor is made out of a coil of insulated wire, so there are tiny capacitors between the windings (since there are two sections of wire separated by an insulator). Each section of windings is at a slightly different potential (because of wire inductance and resistance).

As the frequency increases, the impedance of the inductor increases while the impedance of the parasitic capacitor decreases, so at some high frequency the impedance of the capacitor is much lower than the impedance of the inductor, which means that your inductor behaves like a capacitor. The inductor also has its own resonance frequency.

This is why some high frequency inductors have their windings far apart - to reduce the capacitance."_


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## Paul Running (Apr 12, 2020)

I believe that understanding the effects of the Quality factor of an inductor will help too. If they are using that transformer as a parallel inductor, the Q factor will be low...this may be intentional for a wider bandwidth, at the expense of boost.
So what do you believe is the purpose of this circuit?

There's one for sale on this forum








SOLD - Yamaha Revstar II RSS02T Sunset Burst


This one is less then 2 months old. Very impressive instrument for the price, I own also the humbucker model, love them both but have already a Gustavsson with P-90 so this one available now. Features a custom tailpiece. Its chambered body and carbon reinforced neck were developed using...




www.guitarscanada.com


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## sjp (11 mo ago)

Q is proportional to L / R, so improving it either means increasing inductance (by, say, adding a better ferromagnet in the coil so it stores magnetic energy better) or reducing R (maybe reducing turns? Thicker wire?)

My guess is that they would probably want as wide a range of frequencies as possible, but the audio tests reveal it’s clearly being skewed to lower frequencies. This strengthens the argument in my opinion that this is very carefully tuned to the rest of the electronics in the guitar.

You ask the right question Paul, what’s it for? I think it does triple duty amplifying the signal, acting as a low pass filter and shifting the phase.


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## mhammer (Nov 30, 2007)

The schematic Paul shows indicates an LCR filter - a variable resistance in series with a capacitor and inductor. The typical result of that is a bleeding of spectral content _above_ some point and _below_ some other point. This is precisely what the old Varitone circuit did/does, except that in this instance, there is only one capacitor value, in tandem with a way to vary the resistor. The Varitone has a fixed amount of cut, but switches between different capacitor values to move the focal point and width of the mid-cut around.

Here's Craig Anderton's "Passive Tone Circuit" - an adaptation of the Varitone as a single passive pedal, from his 1980 book, _Electronic Projects for Musicians_. He uses one side of a small interstage transformer as an inductor, with a switch to double/halve the inductance, a rotary switch to select between capacitor values, and moves the variable resistance after the inductor, instead of before the capacitor as in the Revstar circuit. I built one into a pedal, in conjunction with a single FET booster stage, to compensate for the passive loss. I realized that by bypassing the inductor, it would become a treble cut, by bypassing the capacitors become a bass cut, and by bypassing both the caps and inductor, a simple attenuator. So I made that all switchable, turning it into a very flexible tool.

In an older document I got from Dan Torres, he also has a circuit for a bidirectional tone control. One side from the midpoint is normal treble-cut, and the other direction of rotation has a cap in series with an inductor to ground, providing a variable mid-cut. I can credit Yamaha for including such a circuit, in order to make an otherwise standard 2-pickup/two-knob guitar a little more flexible. But credit for the circuit itself has to go to many people before Yamaha.


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## Paul Running (Apr 12, 2020)

Interesting circuit, here's Gibbo's version...early 60s ES-345:








It would be cool to compare the dynamics with the Yammy.


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## mhammer (Nov 30, 2007)

Note that the 10meg resistors effectively bump the corresponding capacitor out-of-circuit. The rotary switch bridges/bypasses the 10meg resistor of the capacitor you _want_ to use, without inducing any switch-popping (as it would if the capacitors were all "hanging", with one end unconnected).


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## Paul Running (Apr 12, 2020)

Gibson has drawn the inductor as a simple, single 1.5H inductor whereas, if the schematic of the Revstar is accurate then, the transformer could be configured as a parallel-aiding or a parallel-opposing inductor...depending upon the phasing connections of the primary and secondary windings of the TFM so, the total inductance will differ in each config.


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## sjp (11 mo ago)

On balance, do you think the schematic of the revstar that angellahash posted in the other forum is correct? Does it at least make sense?


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## Mark Brown (Jan 4, 2022)

mhammer said:


> The schematic Paul shows indicates an LCR filter - a variable resistance in series with a capacitor and inductor. The typical result of that is a bleeding of spectral content _above_ some point and _below_ some other point. This is precisely what the old Varitone circuit did/does, except that in this instance, there is only one capacitor value, in tandem with a way to vary the resistor. The Varitone has a fixed amount of cut, but switches between different capacitor values to move the focal point and width of the mid-cut around.
> 
> Here's Craig Anderton's "Passive Tone Circuit" - an adaptation of the Varitone as a single passive pedal, from his 1980 book, _Electronic Projects for Musicians_. He uses one side of a small interstage transformer as an inductor, with a switch to double/halve the inductance, a rotary switch to select between capacitor values, and moves the variable resistance after the inductor, instead of before the capacitor as in the Revstar circuit. I built one into a pedal, in conjunction with a single FET booster stage, to compensate for the passive loss. I realized that by bypassing the inductor, it would become a treble cut, by bypassing the capacitors become a bass cut, and by bypassing both the caps and inductor, a simple attenuator. So I made that all switchable, turning it into a very flexible tool.
> 
> ...


Holy shit I understood that!!!


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## mhammer (Nov 30, 2007)

sjp said:


> On balance, do you think the schematic of the revstar that angellahash posted in the other forum is correct? Does it at least make sense?


Is that schematic the one that Paul posted here, incorporating the 5-way switch?
If the perceived "boost" IS simply a change in overall level resulting from the spectral content removed or added, then yes. Since the drawing indicates that engaging the transformer/inductor removes/bleeds-off content, however, that implies that engaging the transformer when one pulls the knob "up" is actually the lower output, and not the higher output one.

I'll add, since it appears it wasn't commented on, that the #2 and #4 positions of the 5-way switch, cut out the bass of one, and the other, pickups via the series capacitor introduced. That, plus the "varitone" mid-cut would offer a pleasingly wide range of tones, with little fuss. Clever.

That would be my understanding if the drawing is accurate.


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## Paul Running (Apr 12, 2020)

sjp said:


> On balance, do you think the schematic of the revstar that angellahash posted in the other forum is correct? Does it at least make sense?


Yes, it makes sense. I have not been able to locate an official datasheet for the transformer used in the Revstar...a slight twist to the Varitone config, with the option to switch the inductor in or out of circuit.


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## sjp (11 mo ago)

@mhammer, yes I was referring to the schematic that Paul posted. You noted that _"engaging the transformer when one pulls the knob "up" is actually the lower output"._ That is definitely *not* how the revstar works. Could the wiring diagram have the switch in backwards?


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## mhammer (Nov 30, 2007)

I can't tell which switch position is up or down from the diagram, and wouldn't necessarily assume that the drawing of the connections directly reflects the position of the knob (up or down). It just shows component connections. But looking at it just now, I realized the transformer is always connected. The push-pull switch either bridges the transformer to provide a straight-wire path to ground, or makes the path to ground _through_ the transformer.


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## Paul Running (Apr 12, 2020)

In the early 60s, Epiphone introduced their very limited EA-Professional series (only one was made in 1966). It was a guitar/amp combo in which the Varitone circuit was in the guitar, interfaced to the amp through a 6-conductor cable. Here's the schematic of the EA8-P model:








Publicly, it never caught on.


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## Paul Running (Apr 12, 2020)

After doing a bit of searching, I located a spec sheet for that TFM in the Revstar. Alternative sources indicate an audio line-transformer with an impedance ratio of 6.67:1, centered for 4KΩ to 600Ω-line. It does have a voltage ratio of near triple. however, it would require an active circuit to prevent severe loading of the guitar PUs *if *it's wired as a conventional TFM...last nail for inductor.

*Product : *Signal line-transformer
*Primary Impedance: *4KΩ. s*econdary impedance: *600Ω. i*mpedance ratio:* 6.6°:1. v*oltage ratio:* 2.58:1* 
DCRprimary : *148 Ω. *DCR secondary: *64Ω. f*requency range*: 300Hz - 3.4KHz.


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## AngelLaHash (20 d ago)

The circuit that i drew was from what I could see from the colour wires 

I don't think it's a Booster but more set hi and then brought down low.

IE like what car makers are doing now.. selling you add-on. Heated seats just pay so much a month. It was always a part of the car so isn't really an add-on. 

We can't creat power we can only transform it from one state to another.
I did wonder if I could boost a single pickup with the power from the second one, I am thinking I would have to bring the second pickup more in phase with the first to sound like a boost or I would just get Neck+Bridge.


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## Paul Running (Apr 12, 2020)

AngelLaHash said:


> We can't creat power we can only transform it from one state to another.
> I did wonder if I could boost a single pickup with the power from the second one, I am thinking I would have to bring the second pickup more in phase with the first to sound like a boost or I would just get Neck+Bridge.


An active circuit would produce more effective results...DC power in, to produce more dynamic power out.


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## AngelLaHash (20 d ago)

Paul Running said:


> An active circuit would produce more effective results...DC power in, to produce more dynamic power out.


I only said that to call it a boost when there isn't any power being added is untrue.

Its feels more like a con.

1) this is the sound of the guitar
2) this is the boost

2)this is the true sound of the guitar
1)this is a cut down sound

Car terms. If you push on the accelerate we can go fast. But if we push harder we get a boost. If you just push harder you get the same speed as the boost. Guess more electric car feel to it.


But if you can suggest a replacement transformer as I didn't have a clue on its values just the name . I we recheck the circuit from the images I can see. As the colours make it so nice


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