Rangemaster

The Rangemaster is kind of a Treble Booster, it was invented to push the high frequencies while cut off the muddy in distortion low frequencies, and as a pre-amp to add gain to the following tube amp. By accident it has some side effects, what makes it the real Rangemaster. This page tries to de-mystify this magic stomp box.

Properly set up with the gain of the following amp, you get a bell like clean sound at low volumes with little distortion and a midrange frequency fully distorted sound at maximum volume on guitar. This is one of Rory Gallagher's specialities in guitar sounding. But other's like Brian May and Richie Blackmore used treble boosters as well. Rory didn't use a footswitch to set level of distortion, he used the volume knob on his strat. The original Rangemaster works best with Fender Guitars and VOX or Marshall amps, but the germanium transistor was very noisy.

The Rangemaster is very simple in construction, a perfect DIY project for a musician who is able to handle a soldering iron.

Simulation Schematic

This is not the original Dallas Rangemaster circuit, but has same effect. My recommandation for transistor is the low noise BC109C. The bias should be corrected by variing R6 to get the voltage at collector

	9V * (10+5) / (10+10+5) = 5.4V.

Explaination: The DC current I(R7) = I(c) = I(R8) if the gain of Q3 is huge and thus the I(b) is small against I(c). For maximum peak-to-peak AC voltage and symetrical clipping the DC voltage U(ce) must be eq. U(R7), so for DC bias analysis Q3 can be replaced by a resistor with same value as R7. Now we a have voltage splitter 2 x 10k + 4k7, and can compute the DC voltages as done above.

Treble Boost

Settings: VOLUME: 8 (R3=R4=125k), TONE: 10 (R2=250k)
Result: The resonance of the pick up is at 10 kHz.

TONE Control

Settings: VOLUME: 8 (R3=R4=125k), TONE: 0 (R2=0)
Result: The resonance frequency is lowered to around 400 Hz.

Midrange Boost

Settings: VOLUME: 10 (R3=0,R4=250k), TONE= 10 (R2=250k)
Result: The resonance frequency is lowered to 1.2 kHz.
Comment: the resonance frequency can be altered by changing of C3

Silicon vs. Germanium

Power Supply

Treble Coil - the Noiseless Rangemaster Alternate

When I switched over to the great soundig "VOX ToneLab", I had to find out the build in Rangemater effects sucks, because it only filters the sound like a simple high pass filter, it doesn't interacts with the pickup like rangemasters do. Of course you can use a Rangemaster with ToneLab, but you'll get back the noise and need of a power supply.

So I looked around for an alternative, preferrable passive and noiseless. And there's no need for any gain because the ToneLab has plenty of it, specially with the build in TubeScreamer effect, what sound's great to me.

What can be filtered with capacitances can be filtered with inductances as well. Instead of cascading the pickup with the capacitance, put an inductance coil in parallel to the input of the ToneLab or any high gain amp. Like with rangemaster it has to be the first device in the chain.

But where to get such an inductance coil? If you have a closer look to the simulation circuit of the coil on the right, you'll find out it looks like a simple guitar pickup! It should have same or more inductance and resistance than the pickups you're using in your guitar, to not make the sound too thin. Take an old Humbucker to start with. Remove all metal like screws and magnets if possible. And now you have only one problem left if placed near a power suppy: Hum. Put the pickup into a small steel case, preferrable permalloy (mu metall), and use humbuckers, and fix the pickup or fill the case with wax from a candle.

This devices is passive, you do not need a power supply or battery, it's reliable and the best of all: it's noisless, and if properly shielded it does exactly what I was looking for. It doesn't sound exactly like the Rangemaster, for me it's even better. You can lower the volume at guitar and get that bell like sound. This works with all passive guitar circuits, I tried it with fender and gibsons, and call it treble coil.

Treble Coil Prototypes

Below are shown some prototypes I tested so far.

The small sandwich is a P90 coil without magnets and screws wrapped with a permalloy foile (0.05 mm) with single side glue, the coil sounds great to me but the shielding is not sufficient especially for a single coil pickup.

The roller is a humbucker in single coil size packed with to halfes of permalloy housing for small signal audio transformers, 1 mm wall thickness, and filled with wax from a candle. This works best in shielding, but for me the humbucker is a bit low in resistance and inductance and makes the sound a bit too thin.

A full size humbucker in a 1 mm wall thickness permalloy housing, sounds great and is well shielded.

Links

• Guitar electronics page by Helmuth Lemme thanks for the Pick Up parameters
• collection of vintage and new-design effects here you can get the orignal Rangemaster schematics

These Rangemaster pages are created and maintained non commercially by Volker Grupe (created 3.Apr.2005, last update: 16.05.2005)