Need advice for a bass-cut for my P-Rails

[blackw1re]

Hello y'all,

I got my guitar hooked up with a pair of P-Rails using two 500K log Push/Pulls for Series/Rail/P90/Parallel mode as Volume pots. I use a 500K log pot with currently a .022 uF / 22 nF for tone control. Now the overall sound of this combo is very dark and especially in Series and P90 mode pretty muddy. So I never actually turn down the Tone pot. It came to my mind that I might use the third pot as a bass cut instead of a treble cut. I've found several wiring diagrams including ones with only a cap in series and fancier wirings with 1 MOhm pots and additional resistors, but at the moment I do not have access to 1 MOhm pots nor resistors. So I thought of using a 500K pot in conjunction with a cap.

I have left regular 500K log pots as well as 500K log Push-Pulls.

Is it possible to wire a Push/Pull in such a way, that I can have both a treble and a bass cut depending on the position of the switch? Does anyone have a wiring diagram for that?

If that is not possbile, I am thinking of using the Push Pull like a normal treble cut with the option to engage the bass cut cap in series with the switch. Would this be usable or would this circuit with the treble cap via pot to ground and the bass cut cap engaged cause problems?

If any of these ideas are not feasible, can you guys suggest me a wiring to brighten up my P-Rails? I already tried raising or lowering the Pickups as well as adjusting the screws with no good results for my ears. I also can not use 1MOhm pots, as I can not find a store or online shop in Germany which offers 1MOhm Push/Pulls.

I'd be very thankful for any tipps

Best regards,

Alex

 

[ThreeChordWonder]

Have you fitted treble bleeds to the volume pots yet? One of the consequences of dual, independent volume controls can be that treble gets cut quite harshly even turning down the volume a very small amount.

 

[blackw1re]

Have you fitted treble bleeds to the volume pots yet? One of the consequences of dual, independent volume controls can be that treble gets cut quite harshly even turning down the volume a very small amount.

No, I do not have Treble Bleeds installed. The thing is that the guitar sounds to dark to me with both volumes and the tone on 10. Strangely, when I turn down the volume just a tiny bit, the overwhelming bass gets quiter first and the highs actually stay almost same.

I'll try to attach the current wiring diagram here:

 

[ThreeChordWonder]

I just looked at Seymour Duncan's P-Rail wiring diagrams and although they're both drawn with two tone pots, I can't see why using just one the way you have drawn it should not work.

They do show 0.047 uF caps, however,, and you could try treble bleeds and or a 0.047 uF cap.

If you want to add a bass cut the easiest way is probably to replace the spare tone pot with a push-pull pot, use the push-pull as an on / off or on / bypass switch.

I will have to think about that...

 

[blackw1re]

I just looked at Seymour Duncan's P-Rail wiring diagrams and although they're both drawn with two tone pots, I can't see why using just one the way you have drawn it should not work.

It does work, it just sounds very dark. I used this wiring diagram as a starting point for how to hook up the individual pickup wires:



Except that I have two Volume pots and one master tone now.

They do show 0.047 uF caps, however,, and you could try treble bleeds and or a 0.047 uF cap.

I used a .022 uF on the tone pot because I've read that they have less of a high-cut, which is what I am after. The Problem is that I do not have quick access to resistors. And correct my if I am wrong, but I thought Treble Bleeds have an effect when the Volume gets rolled down, but I would like my guitar to sound brighter in general, preferably with a switch or even with a pot roll, not only when turning the volume down. That's why I asked if it is possible to use a Push/Pull to wire it that in one position it acts as a normal treble cut, but when pulled it acts as a high pass

If you want to add a bass cut the easiest way is probably to replace the spare tone pot with a push-pull pot, use the push-pull as an on / off or on / bypass switch.

With bypass you mean a to use the push/pull as a blower switch to completely disengage the tone pot?

 

[ThreeChordWonder]

On that last point, yes. Either as a blower on the treble and/or on the bass.

 

[blackw1re]

I've stuck with the cap wired to my third push/pull. When the Switch is in normal position, the signal just runs from the tone pot the the jack; when I pull the switch, it runs through a 0.002uF / 2.2nF cap which takes away a small amout of bass. Simple but does the job.

 

[zionstrat]

Switching a tone control from treuble cut to bass cut isn't very hard. I'll watch this thread and see if you don't get there pretty quickly.

But the reason I'm commenting, is a bass cut has a pretty wonderful and specific purpose in my world.. when you have a warm thick fat guitar, a bass cut can thin it out considerably... So you can have your big thick fat Les Paul for Big crunch and then you can thin it back for more articulate stuff. Works great.

On the other hand, if you're starting with a muddy configuration, I'm not sure that a bass cut is the best answer. It means that you are discarding signal that you will never use. As an analogy, we short out humbucker coils all the time to get a thinner sound but if the humbucker tone itself sucks, I would say start with a single coil in the first place.

I've had a few instances where I've had to bypass the tone and volume potentiometer to get a p90 to open up, but that's kind of rare and I don't think the prails fall into that camp.

In your case I would start by looking at potentiometer values and keep in mind that series is one of the most muddy pick up combinations possible.

If that doesn't help, in my book I would say that the body and pickups are just too warm for each other.

On the other hand, muddy might translate to thick and fat. If the bass cut gives you a nice tight overall sound and you reduce the bass cut and find that you've got singing fat solo tones, to go along with the center rhythm tones, I would say you're on to something.

But if the wide open sound is still muddy, it's hard to imagine what you would use it for.

 

[eclecticsynergy]

P-rails are often regarded as very fat and powerful - some would say muddy - when in full series mode.
Being installed in a dark (or even warm) guitar is likely to magnify this.

I would use a DPDT push-pull to put a cap in series on the main output, keeping the tone control as it is.
Even if you don't use it now, you might find a conventional tone control useful once the bass cut is engaged.

I also think treble bleeds couldn't hurt if it's becoming even darker when you roll back the volume.

 

[IMENATOR]

Try an EQ pedal like the Boss GE-7 after the guitar but before pedals/amp then cut some bass and if needed you can compensate the volume drop with the level control. Not the same as your mod but no need to re-wire your guitar, and probable gives you more tone tweak possibilities. Don't forget to lower the bass on the bass EQ controls too, not the same result but helps.

 

[Juanhanglo]

I prefer a bass cut switch. Yamaha uses one on its revstar line.

Use this to your advantage. I do. Sometimes the added bass is useful, sometimes you need to cut it.

Yamaha's bass cut transforms the p90 sound in my rs502t to a more tele like vibe/sound. Its like two different guitars.

I tried the 1 meg pot style years ago, and it was more of an on/off thing than a smooth sweep. It was also on a strat, which never needs any bass cut, IMO.

losing a pot to gain a bass cut is not a viable option for me, hence the switched version.

 

[idsnowdog]

Try 1 meg volume pots.

 

[blackw1re]

Thank you guys for all your replies.

I would use a DPDT push-pull to put a cap in series on the main output, keeping the tone control as it is.
Even if you don't use it now, you might find a conventional tone control useful once the bass cut is engaged.

I also think treble bleeds couldn't hurt if it's becoming even darker when you roll back the volume.

I went for this modification. I've soldered in a third Push/Pull with a Capacitor in Series being engaged when you pull the Knob. This fixed the problem with the incredibly loud bass when the P-Rails are in Series mode and for the P90s. Still though, this mod can obviously not bring back frequencies that are not existent.

In the mean time, I managed to find an online shop in germany, which has 1 MOhm Pots in stock, even as Push/Pulls, so I ordered a bunch of 'em. I also got my hands on a box full of different caps and resistors, so I started to build some treble bleeds in different configurations (Duncan vs Kinman) which I might solder in if the 1 MOhm Pots still don't yield enough highs.

The final solution would be transplanting the P-Rails back into my other Pacifica, where they have been mounted before, as I pretty much liked the P-Rails in that Guitar way more. I'd then just use my two modded 3-Way Mini Toggles to have the Series/P90/Parallel modes available, as I am currently building a completely customized, all-single coil pacifica with noiseless singlecoils anyways to have two guitars, one with singlecoil-ish tone and one with the P-Rails.

 

[eclecticsynergy]

Thank you guys for all your replies.



I went for this modification. I've soldered in a third Push/Pull with a Capacitor in Series being engaged when you pull the Knob. This fixed the problem with the incredibly loud bass when the P-Rails are in Series mode and for the P90s. Still though, this mod can obviously not bring back frequencies that are not existent.

In the mean time, I managed to find an online shop in germany, which has 1 MOhm Pots in stock, even as Push/Pulls, so I ordered a bunch of 'em. I also got my hands on a box full of different caps and resistors, so I started to build some treble bleeds in different configurations (Duncan vs Kinman) which I might solder in if the 1 MOhm Pots still don't yield enough highs.

The final solution would be transplanting the P-Rails back into my other Pacifica, where they have been mounted before, as I pretty much liked the P-Rails in that Guitar way more. I'd then just use my two modded 3-Way Mini Toggles to have the Series/P90/Parallel modes available, as I am currently building a completely customized, all-single coil pacifica with noiseless singlecoils anyways to have two guitars, one with singlecoil-ish tone and one with the P-Rails.

Glad it's working for you. Good to know 1Meg push-pulls are available; I didn't know they even made those.

 

[blackw1re]

Hello girls and boys,

I am now reviving this thread as I got some news. I recently bought myself my first tube amp, a Marshall DSL5. I hooked up my LP-style guitar with the P-Rails in and they are now fully coming to life and sound more balanced and round. Yet I dislike the weight of the guitar and the rather dark sound. So I decided to transplant my P-Rails back into my old new Pacifica, where they have been installed before. I will use measured 1 MPots for both Volume and tone. Or has somebody a better suggestion? I do have quite a big stock of pots available now, ranging from measured 200k up to 1.05 MOhm.

Due to the fact that I had drilled holes in my old Pac, I will reuse these and throw in some On-On-On Switches to have the P-Rails in Series/P90/Parallel mode. I can live without the Rails as I have recently built a totally modded out Pacifica with three DiMarzio Areas, so I am not missing out any Pickup combination.

Coming to my actual question: I recently put a Treble Bleed (1nF Cap + 150k in series a.k.a. Kinman Mod) into my new PAcifica with the Area 61/67s and a 500K vol and 250k tone pot and I freakin love this little modification now. So I decided to solder another one together and throw it into the Guitar with the P-Rails and 1 MOhm pots. Does anyone have a suggestion for the actual values? I've read somewhere that the Resistor should be in the range somewhere between 1/3 and maximum 1/2 of the Volume Pot's value. This formula worked well with a 500K pot used as volume pot for my hum-free single coils. Can anybody confirm this or even has a tried and tested solution for the P-Rails and 1M pots? I am thinking of a 330k resistor with a 1nF cap in series.

 

[blackw1re]

Okay so I finished putting everything together. I used a 1.03 MOhm for the Volume and a 995k for tone. As far as I can say I am really satisfied with the outcome. I really think that those P-Rails needed the higher resistance pots, it is like pulling the blanket off of the amp.

But one thing came out totally unusable: The volume pot with the treble bleed. I went with a 470k Resistor with a 550pf cap in series and it is a desaster. When slowly rolling the volume down to like 9.5, volume drops drastically, treble as well as low end. From there, up to like 3-4 it actually behaves like a regular volume pot, but actually sounding same kind of dull. Only if I am almost at the end, you can hear the treble more present.

I am disappointed because on my other guitar with 500k volume, 150k resistor and 1nF cap it actually works great. Treble is always a bit more present when rolling down.

Should I go lower with the resistance to like 330k? Did I screw up the cap value? Can somebody give me a hint? I think in order to get a better Treble response, I need to try maybe a 1nf Cap. But will this soften the strange taper? I thought the Kinman style circuit does not interfere with the taper of the pots that much..

Update: I finally had the motivation to use some gator clips and hooked up different combinations of Resistors and Caps. I tried a 330k resistor first with 560pF (none of my 680pF caps measure even close to 680pF) cap and a ~1nF cap. I tried both the classic gain (clean) and the ultra gain (distortion) channels in all available pickup combinations (series/P90/parallel):

• The 330k with the 560pF cap still behaved more or less like a regular volume pot to my ears, meaning I didn't get the highs as present when rolled down and the lows also were pretty quiet too soon.
• The 330k with a 1nF brings the highs to where I like them to be when rolling down, but the overall sound became to thin and shrill.
• The 470k with the 560pF cap has a nice low frequency roll-off but the highs tend to get too dull for my taste.
• The 470k with the 1nF cap finally achieved what I wanted to hear. Nice and gradual decrease in lows while treble always a bit more present still, especailly in the upper third of the potentiometer travel. After that, overall volume decreases pretty evenly.

 

[DonP]

Are P-Rails the right pickup for you? Seems like you are trying to pound a square peg into a round hole.