High pass switch on guitar

[Gabrielinconfident]

I was thinking about tone knobs, which I don't use, and I thought an inverted one (i.e. high pass instead of low pass) would be much more useful to tighten up rhythm tones. Quick search and it's definitely possible. But then it occurred to me: what about a switch? Basically, I’m thinking of a 2-position switch that either cuts below ~150hz, or lets the full signal through. That way, it'd be on for chuggy rhythm, and off for single note stuff, with no need for batteries nor boost pedals. Most amps nowadays have enough gain on their own, it's just the excess low end in the input that makes them flubb. How would that be wired? How would the cap value affect the frequency cutoff?

 

[idsnowdog]

I have been putting this HPF on all of my guitars. I put it on the output jack. It filters out frequencies below 70hz and improves neck pickup clarity. You can also put a passive bass cut on the neck pickup. The signal needs to go to the pot first and then to the switch.

 

[idsnowdog]

You can calculate the frequencies here. A 100K resistor and .01uf capacitor would cut around 150hz.

RC and RL Passive Filter Calculator | DigiKey Electronics

Calculate the -3dB cutoff frequency of RC and RL circuits for both Low and High Pass filters using DigiKey’s passive filter calculator.

www.digikey.com

 

[Gabrielinconfident]

I have been putting this HPF on all of my guitars. I put it on the output jack. It filters out frequencies below 70hz and improves neck pickup clarity. You can also put a passive bass cut on the neck pickup. The signal needs to go to the pot first and then to the switch.

Thank you for the reply. I'm guessing something like the PTB, but universal instead of just neck, and a 2-way switch instead of the 1M pot.

If I do use a knob, does it have to be 1M? My guitars have two knobs, currently 1 vol per pickup including a push/pull split and a Liberator, and finding a 1M push/pull pot isn't the easiest thing. I could live with universal volume + HPF, but I don't want to lose the Liberator nor split.

 

[freefrog]

FWIW, the cutoff frequency won't be the same if the filter is before or after a volume pot.

I've shared a few 5spice sims about that here: https://www.mylespaul.com/threads/on-“anti-mud”-caps-in-series-with-pickups-a-side-note.446786/post-9837538

Also, if a regular tone pot is in the signal path, it's better to wire it before the low-cut / hi-pass series capacitor. It's not for nothing that G&L follows this order in the PTB circuit:

https://www.jocidapark.com.au/circuits/GN2/GL-Tone-Circuit_zps07af1c53.jpg

Just swap the 1M pot of this schematic for a switch and you'll have what you want. HTH...

 

[Gabrielinconfident]

FWIW, the cutoff frequency won't be the same if the filter is before or after a volume pot.

I've shared a few 5spice sims about that here: https://www.mylespaul.com/threads/on-“anti-mud”-caps-in-series-with-pickups-a-side-note.446786/post-9837538

Also, if a regular tone pot is in the signal path, it's better to wire it before the low-cut / hi-pass series capacitor. It's not for nothing that G&L follows this order in the PTB circuit:

https://www.thegearpage.net/board/index.php?attachments/1603225354706-png.299871/

Just swap the 1M pot of this schematic for a switch and you'll have what you want. HTH...

As I mentioned, I don't use tone pots. My guitars came with vol+tone, I've rewired them to be two vols. The switch would likely be connected to the jack, i.e. last thing in the chain, since it's the easiest way to affect both pickups at once.

 

[freefrog]

The switch would likely be connected to the jack, i.e. last thing in the chain, since it's the easiest way to affect both pickups at once.

So, consider what I said: a series cap after volume pot(s) has not the same cutoff frequency than before. But if you start with a 2.2nF (0.0022µF) series cap like in the G&L schematic, it should still give you what you want. If it cuts too much bass to your ears, try 3.3nF, 3.9nF, 4.7nF and so on...

Good luck in your experiments.

 

[idsnowdog]

Thank you for the reply. I'm guessing something like the PTB, but universal instead of just neck, and a 2-way switch instead of the 1M pot.

If I do use a knob, does it have to be 1M? My guitars have two knobs, currently 1 vol per pickup including a push/pull split and a Liberator, and finding a 1M push/pull pot isn't the easiest thing. I could live with universal volume + HPF, but I don't want to lose the Liberator nor split.

I put the HPF last because it is easy to fit a 100K resistor between the two lugs of the output jack. It wouldn't do anything to interfere with the Liberator. Even though putting it last effects all positions you really only notice it in the neck position because the HPF can't filter out frequencies that don't exist at the bridge position.

 

[Gabrielinconfident]

I put the HPF last because it is easy to fit a 100K resistor between the two lugs of the output jack. It wouldn't do anything to interfere with the Liberator. Even though putting it last effects all positions you really only notice it in the neck position because the HPF can't filter out frequencies that don't exist at the bridge position.

Well that's the thing, I’m mostly – mostly! – interested in filtering out low end from the bridge pickup, for metal chugs. Instead of boosting the mids and highs with an overdrive pedal, or use active pups, I wanna be able to plug directly into the amp and passively tighten up the tone for palm mutes. But I still wanna be able to open up the low end for solos, so it doesn't get too ear-piercing on high notes. Modern amps all have enough gain to do that. Effectively, turning the HPF off would work as a lead boost. With an EQ pedal, I’ve found that cutting 100hz does the job. But again, I don't want to have to use a pedal.

 

[idsnowdog]

Well that's the thing, I’m mostly – mostly! – interested in filtering out low end from the bridge pickup, for metal chugs. Instead of boosting the mids and highs with an overdrive pedal, or use active pups, I wanna be able to plug directly into the amp and passively tighten up the tone for palm mutes. But I still wanna be able to open up the low end for solos, so it doesn't get too ear-piercing on high notes. Modern amps all have enough gain to do that. Effectively, turning the HPF off would work as a lead boost. With an EQ pedal, I’ve found that cutting 100hz does the job. But again, I don't want to have to use a pedal.

You need to understand what your frequency range is first. This is easy to do with a graphic EQ. Find your cutoff frequency, then go to the filter calculator. Start with a 100K resistor and the cutoff frequency, and it will tell you the capacitor to use. Then look at this chart to see which capacitors are close, then try substituting different values to see where it moves the cutoff point. This is what I do when I build pedals and amplifiers. https://www.newark.com/uf-nf-pf-capacitor-conversion-table

 

[Gabrielinconfident]

You need to understand what your frequency range is first. This is easy to do with a graphic EQ. Find your cutoff frequency, then go to the filter calculator. Start with a 100K resistor and the cutoff frequency, and it will tell you the capacitor to use. Then look at this chart to see which capacitors are close, then try substituting different values to see where it moves the cutoff point. This is what I do when I build pedals and amplifiers. https://www.newark.com/uf-nf-pf-capacitor-conversion-table

As in my previous message, I have used a graphic EQ (MXR 6-band), and 100hz is the mud freq. Sometimes I cut 200hz as well, but very little. Which is why I was thinking around 150hz. Ideally I would use a variable capacitor to find the exact value, but I don't even know where to find one.

 

[freefrog]

So, consider what I said: a series cap after volume pot(s) has not the same cutoff frequency than before. But if you start with a 2.2nF (0.0022µF) series cap like in the G&L schematic, it should still give you what you want. If it cuts too much bass to your ears, try 3.3nF, 3.9nF, 4.7nF and so on...

Good luck in your experiments.

Below is the electrically induced response of a Duncan humbucker, 500k volume pot, no tone control, before a 2,2nF cap in series @ the output jack (black line = series cap on, vs pink line for the raw response of the pickup without series cap).

This measurement done on a real pickup before my morning coffee is on par with the 5spice sim that I had botched for myself yesterday at night.

If it cuts too much bass, a slightly higher cap value might be preferable. For the record, Rickenbacker mounted series caps of 4,7nF, which is also the value of input caps in Rangemaster style "Treble Boosters".

A resistor can also be mounted in parallel of the series cap to tame its effect, of course. I tend to use trimpots for that. Mileages may vary.

FWIW. HTH.