PNP Rangemaster-type treble booster wiring.

[aeromike9]

I have Jack Orman's Multi-Purpose Booster/Buffer PC Board, and want to build a treble booster.  I have built some effects before, but have always followed wiring diagrams.  I am mainly confused on how to hook up the gain pot.  Any help would be greatly appreciated.

[darron]

do you mean this board?
http://www.muzique.com/schem/multi.htm

links to schematics etc. help out to immediately identify what you are after.

if you just want a treble booster that does the same thing, you can just build the single transistor NPN silicon version on the AMZ website and replace C1 with a 0.0047uF cap if you find that's easier than building the original rangemaster part-for-part.


if you want the original germanium mojo: by the looks of it, you'd make the board similar to the silicon transistor booster, but with some very important changes.

1. the rangemaster will be a PNP transistor with POSITIVE ground (IE the positive battery terminal goes to earth rather than the negative one) so you will have to swap the polarity around. you could just use a npn silicon though and keep the ground the same. depends on how much mojo you want to go with?

2. by changing the value of C1 to the small value in the rangemaster (5n, or 4n7 (0.005uf or 0.0047uf)) you will have the treble boost effect rather than a full boost.

3. R5 will be replaced by the 10k volume pot. where the two connection go on the R5 resistor will be the OUTER lugs on the pot, and C2 will connect to the middle lug of the pot.

4. R10 the volume pot will not be used, so the output will come directly off C2 where it would have connected to R10.

5. The bias resistors will need to match the rangemaster, so replace R3 + R4 with 470K and 68k: respectively. if you go with the silicon then keep the values used on the AMZ website.

6. on the rangemaster C2 is a non-polarised 0.01uf capacitor.

7. erm... i think that should cover it?

[aeromike9]

Thanks for all of the great info! This is the schematic to the one I am wanting to build:   http://www.muzique.com/tech/bipolar7.gif
In the schematic, R5 is a 10K resistor, R8 is a jumper, and R10 is the volume pot.  I am just learning how to read schematics, so I am having trouble figuring out how to wire R10.  It looks like one lug is going to the Out1 terminal which is connected to C2 and another to ground, but that is about as far as I can get.

[darron]

oh cool. so you've already got the values you need. the schematic you just liked to isn't really a rangemaster, but it does the same trick (:

regarding the pot, if you were looking at it with the shaft pointing up towards you, the signal from C2 would connect to the lug on the right hand side. the output to the bypass switch and/or output jack would connect to the middle, and earth would connect to the left.

if you try to imagine it, the signal that will go to your amplifier is connected to the middle wiper lug of the pot. as you turn the pot clockwise the wiper moves closer to the circuit's output which is booster. as you turn it anti-clockwise the wiper moves closer to ground which is 0V, so that's a signal mute. anything in the middle will select the volume between the two.'

don't forget to run this circuit off a battery or it's own power supply because the ground is flipped, so if you tried to plug it in with other pedals AND you were using the same power supply between them you'd cause a short. it's not a very power consumptive circuit too which is nice (:

[aeromike9]

Thanks a million for the help darron!  That is exactly the info I needed.

[aeromike9]

One more question. There is only one ground pad on the PCB, so should:

1. The pot be connected to the ground pad on the pcb?  Then where would the jacks be grounded to?

2. Or should the jacks be connected to the pad on the pcb, and the pot grounded to one of the jacks.

Thanks again.   

[darron]

as long as all of your ground meet in the end, it will work.

so you need to connect the grounds together for:

the two audio jacks sleeve's (which will ground to the enclosure too)
the battery ground
the board ground
the pot ground.

(anything else like the LED ground if you have one, switch ground if you have one)

i'd probably have them all star from the input audio jack's sleeve ground.

also, if you want to have the unit turn off when nothing is plugged, wire the battery ground to the input jack's ring instead of sleeve, so a mono plug would short the ring and the sleeve and turn it on when plugged in.

[aeromike9]

Thanks again Darron.  You Rock!!!