Question Cutlass HSS journey (wiring question)

[milosjak]

Hey guys,

I'm following up on my journey with BFR Cutlass HSS, in quest to find a bridge pickup that's as dynamic as the stock singles on it.
So far, aside from stock ceramic humbucker I tried the BKP Riff Raff, and now the humbucker-sized P90, the BKP Nantucket.

This Nantucket is insane. It feels hotter and more alive than the Riff Raff even though it should be lower output than the humbucker.
If you might be trying to achieve something similar to me, give a humbucker-sized P90 a try.

I'm still fresh with it, so we'll see if, after the honeymoon phase I decide to swap the whole pickguard for SSS configuration in the end.

Now to the question: I shared the SSS wiring diagram with my luthier, as I was thinking since I'm switching from a humbucker to the P90 which is technically a single coil that it should be wired as per SSS diagram. However I hear considerably more noise on it compared to the singles. The noise is also present in bridge+middle position.
I did a little test, where I pull out the battery and listen for what happens until the output dies. On singles, the moment I plug out the battery, there's an obvious hum that pops up. When I do the same with bridge P90, the existing noise maaaaybe increases a hair but that's it.
Is it wired wrong? Is the pcb on HSS different than SSS and perhaps I shouldn't have followed the SSS diagram?

Thanks!

 

[beej]

Nice! I also wanted a bit of a change ... put the humbucker from a Luke III in there.

It sounds to me like the Nantucket isn't wired to the Silent Circuit. The bare (shield) should go to 'G' on the pads. But the Black (ground) should probably be wired to the PHA pad, next to where the ground of the middle is wired. (Not sure what your tech did.)

If it is wired correctly, you may just pick up more noise from that pickup, in which case you'll want to adjust the trimpot of coil A so it adds more cancellation. You may have to play with this a bit ... worst case, you could move the middle coil to the coil B Silent Circuit (from the A), and then adjust A for ideal cancellation in the bridge.

 

[milosjak]

Nice! I also wanted a bit of a change ... put the humbucker from a Luke III in there.

It sounds to me like the Nantucket isn't wired to the Silent Circuit. The bare (shield) should go to 'G' on the pads. But the Black (ground) should probably be wired to the PHA pad, next to where the ground of the middle is wired. (Not sure what your tech did.)

If it is wired correctly, you may just pick up more noise from that pickup, in which case you'll want to adjust the trimpot of coil A so it adds more cancellation. You may have to play with this a bit ... worst case, you could move the middle coil to the coil B Silent Circuit (from the A), and then adjust A for ideal cancellation in the bridge.

Aaaah, that's actually a great idea. I'll check the wiring as well, but the tech did follow the musicman provided schematic. I think you're on to it. It must be currently set to a minimum as it was previously wired for a humbucker.

When it comes to the pickup, if you don't feel like the LIII pickup is working out for you think about a p90. It's definitely a different voicing than the singles still, but now I feel like it can keep up with how alive the singles sound.

 

[Iperfungus]

Hi there!
P90s are hotter single coils: more windings on a single coil --> more output --> more noise, compared to standard single coils.
That's normal for a P90s to be noisier than a standard single coil pickup.

That being said, as beej wrote, you've the two options:
1) wrong wiring: P90 is not connected to silent circuit --> adjust wiring
2) correct wiring: the P90 needs some more hum cancellation compared to single coils

Good choice: P90s are awesome pickups.
They just are like wild mustangs...

 

[milosjak]

Yeah, so a bit of an update on this one, in case anyone knows what might be going wrong. I went a bit back and forth with my tech, and it seems like we still can't figure it out.

To reinstate what I said already, we originally followed the SSS wiring diagram. All was fine, except for the fact that the neck and the bridge were both controlled by the same trimpot. The one that controls noise reduction. So I went back to him to ask him if he can reverse the placement on the middle and bridge, so that bridge humbucker becomes controlled by a single trimpot and the middle and neck by the other. However, originally he didn't move the ground wires, saying, the ground is all the same it doesn't matter, let's just move the live wire position, and so we went with it.

After further testing I realized that at that point neither the middle nor the bridge pickup have any noise cancelation any more. I thought it must've been the fact that we didn't switch the grounds and that the circuit is somehow dependent on having the ground wires be as per the original SSS diagram, but with the switch positions for middle and bridge, like I said before.

He did switch around the ground wires, however the middle and neck seem to be still without noise cancelation.
He is out for a vacation and is coming back the day after tomorrow, so I'll catch up with him then and see what the issue might be, and to test it further, but I don't get what is going wrong here.

Why would there be an issue with having middle and bridge connections switched around on the pcb?
Any help is very much appreciated, while I wait for my tech to come back to work.

Thanks!

 

[DrKev]

(Assuming the silent circuit here works in a similar way to the older silent circuits) the pickups are grounded through the silent circuit. Also note that there are two circuits because the stock singles are not all same polarity and wind (because the middle is RWRP and needs a silent circuit of appropriate phase to cancel its noise). This all means the ground connection matters and the stock single coils need to go to where they were originally.

The bridge pickup will therefore share the silent circuit of the neck pickup (assuming the bridge pickup is the same magnetic polarity and wind direction as the neck pickup).

 

[milosjak]

(Assuming the silent circuit here works in a similar way to the older silent circuits) the pickups are grounded through the silent circuit. Also note that there are two circuits because the stock singles are not all same polarity and wind (because the middle is RWRP and needs a silent circuit of appropriate phase to cancel its noise). This all means the ground connection matters and the stock single coils need to go to where they were originally.

The bridge pickup will therefore share the silent circuit of the neck pickup (assuming the bridge pickup is the same magnetic polarity and wind direction as the neck pickup).

Interesting... OK, I'll get it reverted for the neck and middle. I don't understand why the bridge wasn't silenced. Perhaps the just had to switch the wires around between the circuit and the switch.

 

[beej]

Actually ... that is a great point Kev. The polarity will have to be reversed on the other SC. My bad there.

There is a trick you can use to get two different adjustments off the same silent circuit- wire the weaker one (single coil) through a small trim pot, before soldering to the pad. Set the maximum level of cancellation on the SC for the higher output pickup. Then, dial in the small trimpot to adjust cancellation for the weaker pickup.

 

[milosjak]

Actually ... that is a great point Kev. The polarity will have to be reversed on the other SC. My bad there.

There is a trick you can use to get two different adjustments off the same silent circuit- wire the weaker one (single coil) through a small trim pot, before soldering to the pad. Set the maximum level of cancellation on the SC for the higher output pickup. Then, dial in the small trimpot to adjust cancellation for the weaker pickup.

You mean to add my own extra trimpot, is that what you're suggesting? Sounds interesting.

 

[beej]

Shoot, that's not right either. Let me clarify. I wrote this without properly thinking about it.

On the old Silent Circuit, the trick that would work is using trimpots between the Yellow wire and ground. (Grounding the Yellow wire defeats the silent circuit.) So you could use a gang of trimpots to tune the output strength for each switch position (a value of 500k is good), using one set of switch poles.

You find a position where the hum is optimal on the Silent Circuit, then increase it a bit (clockwise). Then, use the trimpots to dial it in for each pickup. I can't take credit for this idea- it was Dudley Gimpel's. I have done it and it works well, though it's a bit messy to wire up.

So, on the new SC, the layout is obviously different. But, the PCB has a set of pads labeled "SCM" that you short to defeat the Silent Circuit. What I'm thinking is that you could try a trimpot wired between these pads and it could work the same way. I have not tried this, but it's worth a shot. (I will try it on my Cutlass next time I take it apart.)