Transformer inside guitar??

[A13X]

There must be more than meets the eye, right?

Okay, I have had many a wiring cavity open, but have never seen what looks to be a transformer inside. I’m sure others with more experience have, and I’m hoping someone can explain to me what is going on in this circuitry.

Guitar is a Yamaha Revstar RSS02T with dual p90’s, passive circuitry.
That “transformer” is brought into the circuit via a push pull tone pot. It’s advertised as a boost by Yamaha.
In my use case I find the resulting tone terrible and have no need for it, so I’m also looking for some other ideas on what to utilize that push pull pot for.

 

[SRHmusic]

It's probably a cheap audio transformer intended to change the output voltage, but it will also raise the output impedance. Maybe you can add in a step change in the he time cap or something simple instead.

There was a thread on this or a similar Revstar(?), over at TGP last year. The second post has links to some modifications.

Revstar RSS20 schematic?

Any schematics for this guitar available? A facebook link was posted in another thread but it seems dead. Or at minimum I can't access it since no facebook login for me. Next stop is Yamaha customer service but I thought I'd check here too. thanks

www.thegearpage.net

 

[archetype]

Sweetwater says: "Yamaha has equipped this Revstar with their proprietary “focus” switch that shifts your tone’s resonant frequency and supercharges your pickup’s power."

Per 'Net info, the primary is 500 Ohms and secondary 2.43 KOhms. I assume the transformer replaces the previous resistor/capacitor filter and is used for bass rolloff. It certainly is a monster big transformer for something that passes less than 1 Volt.

Do an Internet search and you can find all sorts of wiring alternatives. Many are on competing forums, so I can't link to them here.

 

[memorex]

It's not really a boost. I've seen the schematic, and it looks like it's used as an inductor in the tone control circuit. The schematic indicates there's a switch to bypass it. Some of the versions of Revstar use it with a rotary switch of different cap values that makes it like a Gibson Varitone. I used to have a Gibson ES345 Stereo with the Varitone, which while useful, was also a tone-sucker. I found that adding a mini-toggle switch to lift the ground side of the inductor effectively took the Varitone out of circuit, and then the guitar sounded like an ES335.

 

[A13X]

It's probably a cheap audio transformer intended to change the output voltage, but it will also raise the output impedance. Maybe you can add in a step change in the he time cap or something simple instead.

There was a thread on this or a similar Revstar(?), over at TGP last year. The second post has links to some modifications.

Revstar RSS20 schematic?

Any schematics for this guitar available? A facebook link was posted in another thread but it seems dead. Or at minimum I can't access it since no facebook login for me. Next stop is Yamaha customer service but I thought I'd check here too. thanks

www.thegearpage.net

Awesome, thank you for the explanation and the idea!

Sweetwater says: "Yamaha has equipped this Revstar with their proprietary “focus” switch that shifts your tone’s resonant frequency and supercharges your pickup’s power."

Per 'Net info, the primary is 500 Ohms and secondary 2.43 KOhms. I assume the transformer replaces the previous resistor/capacitor filter and is used for bass rolloff. It certainly is a monster big transformer for something that passes less than 1 Volt.

Do an Internet search and you can find all sorts of wiring alternatives. Many are on competing forums, so I can't link to them here.

I’ll definitely check it out. Almost everyone I’ve ever interacted with in this particular forum is incredibly kind and knowledgeable so I rarely go elsewhere.

I love the tone of this guitar so I really don’t NEED to change the wiring as I just never use the pull position on that pot, but the tinker(er) in me says to do something useful with it

 

[A13X]

It's not really a boost. I've seen the schematic, and it looks like it's used as an inductor in the tone control circuit. The schematic indicates there's a switch to bypass it. Some of the versions of Revstar use it with a rotary switch of different cap values that makes it like a Gibson Varitone. I used to have a Gibson ES345 Stereo with the Varitone, which while useful, was also a tone-sucker. I found that adding a mini-toggle switch to lift the ground side of the inductor effectively took the Varitone out of circuit, and then the guitar sounded like an ES335.

I came up short when looking for a schematic. I probably just moved right past it.

 

[sammy1974]

Switch it on and it automatically does a second chord inversion.

 

[Peegoo]

Hohner, Reverend, and other makers have incorporated inductors like this in their passive guitar circuits, calling them bass contour, mid-shift, etc. Torres Engineering used to sell a kit of parts that contained the inductor and other jellybean components to retrofit into any guitar. They called it a mid cut.

 

[A13X]

Hohner, Reverend, and other makers have incorporated inductors like this in their passive guitar circuits, calling them bass contour, mid-shift, etc. Torres Engineering used to sell a kit of parts that contained the inductor and other jellybean components to retrofit into any guitar. They called it a mid cut.

The concept is pretty awesome, and my hats off to whoever came up with it however long ago. That’s the kind of outside-the-box thinking that has brought electronics so far. Unfortunately, I just can’t get a tone I like out of it. The pups lose all clarity, and without it they already push my amp to its sweet spot. Although, If I’m being honest I’m extremely basic in what I like for tone. I enjoy the dance with the tubes 90% of the time and the other 10% I dial down the volume for a pure clean tone.

 

[Peegoo]

The concept is pretty awesome, and my hats off to whoever came up with it however long ago. That’s the kind of outside-the-box thinking that has brought electronics so far. Unfortunately, I just can’t get a tone I like out of it. The pups lose all clarity, and without it they already push my amp to its sweet spot. Although, If I’m being honest I’m extremely basic in what I like for tone. I enjoy the dance with the tubes 90% of the time and the other 10% I dial down the volume for a pure clean tone.

It totally depends on the caps used and how they interact with the choke. I have an early-80s Hohner TE Pro (their version of the Telecaster) that came with a midrange control. It made the guitar sound muddy as soon as it was rolled back from 10. I tried a few different changes and I got close, but the stock Lawrence pickups sounded great all by themselves so I took it all out of the circuit.

I have two Reverends with the bass contour control and their scheme works really well. It's super useful.

 

[hopdybob]

maybe its something like Bill Lawrence his Q filter? much smaller
Q filter

https://www.wildepickups.com/cdn/shop/products/IMG_1150_1024x1024@2x.JPG?v=1547412161

 

[Nicko_Lps]

Bah.
Rookie size transformer. We all know tone is in the "iron" size.

 

[P-Nutz]

Maybe it could transform me into a better player?!

 

[Nicko_Lps]

Maybe it could transform me into a better player?!

If that works, i have 2 heyboer's in my cabinet waiting... A 100 watter and a 40 watter.

Could be like 10kg of steel, ill be Jimi Hendrix in a couple of minutes. Broken back in the next 10 minutes

 

[philosofriend]

If you wire an inductor in the place of the capacitor in a standard tone control, the pot will dial in a passive attenuation of the bass frequencies. In a normal tone control, the capacitor wastes some of the treble by sending it to the ground. An inductor can do the same thing, except it will be dumping bass. I had this circuit on a guitar decades ago. It worked best when it wasn't doing very much (which come to think of it describes a normal tone control a lot of the time).

When you put capacitors and resistors in the circuit the Q can become so low that it often sounds like a soggy mess (can anyone say "varitone"?) I know some people like the varitone, but not enough to keep it in production.