- Build Rating
A couple of firsts for me with this build:
-First time using a drill press. I love it. Should have gotten one sooner.
-First time hand-finishing a bare aluminum enclosure. I wanted a brushed aluminum look, so I just went straight in wet sanding with 120 grit sandpaper, moving the enclosure back and forth across the sandpaper until the surface looked uniform. It's not perfect and it wasn't a fast process, but I'm happy with the results. In the future I might build a little jig to help guide the enclosure across the sandpaper in a straighter line. A clear coat or some other form of protection may also be a good idea to keep the finish looking fresh.
-First time adapting a full circuit schematic to vero from scratch. I started with the PedalPCB RangeFinder as a base because of the lower parts count compared to other charge pump Rangemaster circuits. I modified the input cap switching slightly and replaced the fixed 68K bias resistor with a 100K trimpot.
The input capacitors are wired in series lug to lug on the rotary switch. Starting fully CW with the full-range setting (100n), each position CCW adds a new capacitor in series to achieve the desired input capacitor value (two 100n in series for 50n, etc.). The cap combinations translate to 100n, 50n, 24n, 12.75n, 7.5n and 5n. I like the 5n and 7.5n settings the most since I like bright and bitey guitar tones, but these are all very usable. I found the 100n input cap in combination with an already distorted amp to give me somewhat of a fuzz-type of tone. I'm usually not into fuzzes but to me this sounds quite pleasing. Very thick and organic.
It would have been a good idea to breadboard the circuit before committing to the vero layout because after putting it all together, there was quite a bit of power supply noise in my signal, whereas with a battery it was almost dead quiet. I was able to fix it for normal use cases with some additional power filtering; that's the little vero add-on by the DC jack. 47R series resistor on the +9V line followed by parallel 220u and 100n caps to ground, and an additional 100n cap to ground on the -9V pin of the charge pump.
There's also some whine coming from the charge pump, thankfully only really noticable with high gain on the amp. I'm using a TC1044SCPA. Pins 1 (boost) and 8 (V+) are jumpered, which I thought should put the oscillating frequency out of audio range but apparently that's not enough. The whine gradually changes its frequency when I manually press on the charge pump and reverts back to the previous pitch when I let go. It also is dependent on the supply voltage. Using a depleted battery lowers the frequency of the whine. I have not tried replacing the charge pump yet with another model - ICL7660S or LT1054CP for example. Maybe it's also just the proximity of the power and signal lines due to the cramped vero layout. Further testing necessary!
ALL THAT ASIDE, I'm absolutely loving the tones I get with this. I've mostly been playing an SSS strat into the clean and crunch channels of my Marshall DSL100H, gain on the amp as well as the pedal cranked, tone and master controls to taste. It gives me just the right amount of grit and bite for classic hard rock rhythm tones on the clean channel, and searing lead tones on the crunch channel.
I tried a small variety of transistors (P30, MP20B and MP42B) from as low as 24 hFE up to 122 hFE, and from 20 uA to 76 uA leakage current measured with the R.G. Keen transistor testing circuit. They all sounded fine. I settled on a P30 with 73 hFE and 21 uA leakage. Unfortunately the P30 transistors were the noisiest of the bunch but they also sounded best to me. These appeared to have slightly better high frequency response - which would explain the extra noise as well. The MP42B were a little harsh and the MP20B fell somewhere in between. I didn't do any blind tests, so take those findings with a grain of salt. As I said, in the end they all sounded fine and biased "correctly" regardless of gain and leakage.
I found no correlation between leakage current and noise. The MP20B all had leakage around 75 uA but were the quietest. The P30 had leakage from 20-30 uA but were the noisiest.
As for biasing: I recorded a bunch of tests with collector voltages from -4.5V to -7.8V. I found single coil guitars benefited from being biased slightly hot at -7V to -7.2V, while humbuckers sounded best anywhere between -4.5V and -6V due to increased headroom and thus better clarity of the signal. Keeping the collector voltage the same while adjusting the base voltage from -1V up to -1.3V seemed to give more bottom end and a generally fuller tone, while going from -1V to -0.8V thinned out the tone. In all my tests, I preferred the base voltage at -1V. Veering too much from that bias point seemed to make it sound less rangemastery.
All in all, this is a simple but very effective circuit. I'm glad I spent a good amount of time comparing different bias points to find my personal preferred settings, and I would encourage anyone to do the same. You may not like this circuit biased to the "correct" Rangemaster voltages, but biased differently it may very well be a different story. I will probably build another one of these at some point in the future with external bias controls. This will definitely get you the most out of this circuit, especially if you're playing both single coil and humbucker guitars through it.
-First time using a drill press. I love it. Should have gotten one sooner.
-First time hand-finishing a bare aluminum enclosure. I wanted a brushed aluminum look, so I just went straight in wet sanding with 120 grit sandpaper, moving the enclosure back and forth across the sandpaper until the surface looked uniform. It's not perfect and it wasn't a fast process, but I'm happy with the results. In the future I might build a little jig to help guide the enclosure across the sandpaper in a straighter line. A clear coat or some other form of protection may also be a good idea to keep the finish looking fresh.
-First time adapting a full circuit schematic to vero from scratch. I started with the PedalPCB RangeFinder as a base because of the lower parts count compared to other charge pump Rangemaster circuits. I modified the input cap switching slightly and replaced the fixed 68K bias resistor with a 100K trimpot.
The input capacitors are wired in series lug to lug on the rotary switch. Starting fully CW with the full-range setting (100n), each position CCW adds a new capacitor in series to achieve the desired input capacitor value (two 100n in series for 50n, etc.). The cap combinations translate to 100n, 50n, 24n, 12.75n, 7.5n and 5n. I like the 5n and 7.5n settings the most since I like bright and bitey guitar tones, but these are all very usable. I found the 100n input cap in combination with an already distorted amp to give me somewhat of a fuzz-type of tone. I'm usually not into fuzzes but to me this sounds quite pleasing. Very thick and organic.
It would have been a good idea to breadboard the circuit before committing to the vero layout because after putting it all together, there was quite a bit of power supply noise in my signal, whereas with a battery it was almost dead quiet. I was able to fix it for normal use cases with some additional power filtering; that's the little vero add-on by the DC jack. 47R series resistor on the +9V line followed by parallel 220u and 100n caps to ground, and an additional 100n cap to ground on the -9V pin of the charge pump.
There's also some whine coming from the charge pump, thankfully only really noticable with high gain on the amp. I'm using a TC1044SCPA. Pins 1 (boost) and 8 (V+) are jumpered, which I thought should put the oscillating frequency out of audio range but apparently that's not enough. The whine gradually changes its frequency when I manually press on the charge pump and reverts back to the previous pitch when I let go. It also is dependent on the supply voltage. Using a depleted battery lowers the frequency of the whine. I have not tried replacing the charge pump yet with another model - ICL7660S or LT1054CP for example. Maybe it's also just the proximity of the power and signal lines due to the cramped vero layout. Further testing necessary!
ALL THAT ASIDE, I'm absolutely loving the tones I get with this. I've mostly been playing an SSS strat into the clean and crunch channels of my Marshall DSL100H, gain on the amp as well as the pedal cranked, tone and master controls to taste. It gives me just the right amount of grit and bite for classic hard rock rhythm tones on the clean channel, and searing lead tones on the crunch channel.
I tried a small variety of transistors (P30, MP20B and MP42B) from as low as 24 hFE up to 122 hFE, and from 20 uA to 76 uA leakage current measured with the R.G. Keen transistor testing circuit. They all sounded fine. I settled on a P30 with 73 hFE and 21 uA leakage. Unfortunately the P30 transistors were the noisiest of the bunch but they also sounded best to me. These appeared to have slightly better high frequency response - which would explain the extra noise as well. The MP42B were a little harsh and the MP20B fell somewhere in between. I didn't do any blind tests, so take those findings with a grain of salt. As I said, in the end they all sounded fine and biased "correctly" regardless of gain and leakage.
I found no correlation between leakage current and noise. The MP20B all had leakage around 75 uA but were the quietest. The P30 had leakage from 20-30 uA but were the noisiest.
As for biasing: I recorded a bunch of tests with collector voltages from -4.5V to -7.8V. I found single coil guitars benefited from being biased slightly hot at -7V to -7.2V, while humbuckers sounded best anywhere between -4.5V and -6V due to increased headroom and thus better clarity of the signal. Keeping the collector voltage the same while adjusting the base voltage from -1V up to -1.3V seemed to give more bottom end and a generally fuller tone, while going from -1V to -0.8V thinned out the tone. In all my tests, I preferred the base voltage at -1V. Veering too much from that bias point seemed to make it sound less rangemastery.
All in all, this is a simple but very effective circuit. I'm glad I spent a good amount of time comparing different bias points to find my personal preferred settings, and I would encourage anyone to do the same. You may not like this circuit biased to the "correct" Rangemaster voltages, but biased differently it may very well be a different story. I will probably build another one of these at some point in the future with external bias controls. This will definitely get you the most out of this circuit, especially if you're playing both single coil and humbucker guitars through it.
