Wiring for hot-rodding a precision.

[danlea]

Hey fellas,

I've attached a schematic I've drawn up for a hot-rodded p-bass. It's a Fender Japan with a Seymour Duncan SPB-2 (hot precision) and I'm getting it routed to add a STK-J2 (hot stack jazz) at the bridge, making it rather like the backup Squire Precision Special I've loaded with the same (only the jazz is single coil). Anyway, I'll get to the point. I never dial down the precision, so that doesn't need an individual control, but I do need a volume control for the jazz and want a master volume for fading in and out where necessary. I almost always have the tone control fully in, occasionally dialling it down either half-way (once in a while) or completely (once in a blue moon). I plan on sticking in a mini-switch for this, and as they only have on-off-on toggles in Maplins (£2, just up the road from me) and I'd rather not order a more expensive three-way on-on-on switch from the internet and have to pay postage, I've implemented a slightly round-about way of controlling the treble leakage. Switch centred (off) is no cut (~250k), down is moderate cut (~23k) and up is proper dub.

Aside from this, it's exactly as the recommended Seymour Duncan wiring, [i]except[/i] for the lack of a pot, or even a dedicated resistor for the p pickup since the pickup is already loaded with both the Jazz and master volume pots I figure another would only serve to cut the output further - in fact I'm considering changing the pots to 500k for this reason, but Seymour Duncan don't say anything about using higher values for any of their bass pickups, or for any configuration.

Ok, enough from me. Any thoughts?

Dan.

Edited August 10, 2008 by danlea

[DHA]

[quote name='danlea' post='259558' date='Aug 10 2008, 09:41 PM']Hey fellas,

I've attached a schematic I've drawn up for a hot-rodded p-bass. It's a Fender Japan with a Seymour Duncan SPB-2 (hot precision) and I'm getting it routed to add a STK-J2 (hot stack jazz) at the bridge, making it rather like the backup Squire Precision Special I've loaded with the same (only the jazz is single coil). Anyway, I'll get to the point. I never dial down the precision, so that doesn't need an individual control, but I do need a volume control for the jazz and want a master volume for fading in and out where necessary. I almost always have the tone control fully in, occasionally dialling it down either half-way (once in a while) or completely (once in a blue moon). I plan on sticking in a mini-switch for this, and as they only have on-off-on toggles in Maplins (£2, just up the road from me) and I'd rather not order a more expensive three-way on-on-on switch from the internet and have to pay postage, I've implemented a slightly round-about way of controlling the treble leakage. Switch centred (off) is no cut (~250k), down is moderate cut (~23k) and up is proper dub.

Aside from this, it's exactly as the recommended Seymour Duncan wiring, [i]except[/i] for the lack of a pot, or even a dedicated resistor for the p pickup since the pickup is already loaded with both the Jazz and master volume pots I figure another would only serve to cut the output further - in fact I'm considering changing the pots to 500k for this reason, but Seymour Duncan don't say anything about using higher values for any of their bass pickups, or for any configuration.

Ok, enough from me. Any thoughts?

Dan.[/quote]

Hi Dan,

I am not sure that your circuit diagram is correct? If you explain in words what each switch position does and how then I may understand.

Dave

[danlea]

Ok. Given that the amount of treble cut is inversely related to the resistance in series with the capacitor, I've put in three options. In the off position, the resistance is simply that of the permanently wired in resistor (~250k - the figures in the schematic are minimum resistance specs of the resistors I'll be buying and they come in 240k, not 250k). This is the standard full spectrum tone setting of most basses. In the down position (A) the other resistor is added in parallel, giving a resistance just below it's own value. In the up position ( the resistor is shorted, giving effectively zero resistance and the full treble cut.

I'm pretty sure that bit's fine, I'm not really certain about how the loading of the pickups affects the tone and output. If I were to follow the Seymour Duncan wiring for P-J blend and master exactly I'd be replacing the p pot with a resistor as it doesn't need to change, but I can't see that this resistor would then actually be doing anything useful, so have left it out.

Dan.

[Cernael]

I see the ground, but whence do you take it to the hot?

[DHA]

[quote name='danlea' post='259800' date='Aug 11 2008, 11:19 AM']Ok. Given that the amount of treble cut is inversely related to the resistance in series with the capacitor, I've put in three options. In the off position, the resistance is simply that of the permanently wired in resistor (~250k - the figures in the schematic are minimum resistance specs of the resistors I'll be buying and they come in 240k, not 250k). This is the standard full spectrum tone setting of most basses. In the down position (A) the other resistor is added in parallel, giving a resistance just below it's own value. In the up position ( the resistor is shorted, giving effectively zero resistance and the full treble cut.

I'm pretty sure that bit's fine, I'm not really certain about how the loading of the pickups affects the tone and output. If I were to follow the Seymour Duncan wiring for P-J blend and master exactly I'd be replacing the p pot with a resistor as it doesn't need to change, but I can't see that this resistor would then actually be doing anything useful, so have left it out.

Dan.[/quote]

Should be fine and will not do any harm so "suck it and see"

Dave

[bnt]

[quote name='danlea' post='259558' date='Aug 10 2008, 09:41 PM']I've implemented a slightly round-about way of controlling the treble leakage. Switch centred (off) is no cut (~250k), down is moderate cut (~23k) and up is proper dub.[/quote]
- with the switch centred, what is the effect of the 240KΩ resistor and the capacitor in the circuit?

In general, using 500kΩ pots will give a slightly brighter sound, since they place less of a load on the pickups.

Edited August 13, 2008 by bnt

[danlea]

[quote name='bnt' post='261817' date='Aug 13 2008, 06:51 PM']- with the switch centred, what is the effect of the 240KΩ resistor and the capacitor in the circuit?[/quote]

The 240kΩ resistor provides the maximum resistance setting, i.e. as if you had a 240kΩ pot there turned all the way up, which is the standard setting. The switch being centred (off) means there is no parallel route to the capacitor. The effect of switching either the 24kΩ resistor or the direct path in is to reduce the overall resistance, just like turning the pot down.

As long as no-one notices anything stupid I missed then I'll go ahead with it and I'm sure it'll be fine. The only issue then is the value of the switched resistor - exactly what tone I want from the mid-setting, but that can easily be changed to suit.

Dan.

Edited August 13, 2008 by danlea