Dallas Rangemaster Treble Booster LTspice

• One of the first and most influential tone-shaping devices designed to be plugged in front of an amp. Dallas originally made this booster to brighten up darker british amps like the VOX AC30. While labelled as a booster, it definitely has an overdrive quality in its sound. Not long after, it became its own little legend as it was popularized by legendary guitar players like Brian May, Tony Iommi, Rory Gallagher etc. The original Dallas Rangemaster is very hard to come by in real life anymore... • Not really a pedal, as it was designed to sit on top of the amp as an always-on device. This unit has just one knob labelled as "BOOST SET" which for the most part controls the overall output. Other than that it has minimal impact in the sound signature. The captures are done in 0.5 rotational ratio increments of the BOOST SET knob. Settings 0 and 0.5 are not included because the output is practically zero at these settings. • This project was done because I wanted to learn how to do calibrated captures with LTspice and NAM. Calibrated NAM captures enable you to experience an accurate gain response, similar to the real hardware, or the simulated hardware in this case. I chose this classic unit because it's a small circuit, which makes it easy to run complete simulations in a relatively small amount of time and also it's very sought-after and recognizable. As a result of this project, this pack and any of my future LTspice packs will contain calibrated In & Out. • Calibration metadata is already embedded in the NAM files. Details: Input: +7.17 dBu ≙ 0 dBFS | Output: +17 dBu ≙ 0 dBFS You only need to set the headroom of your audio interface's input inside your NAM host. • Slightly technical info: This is the positive-ground version of the circuit, which was featured in the original unit. Today's clones use either negative-ground or a voltage inverter to be compatible with modern pedalboards. The simulation utilizes a PNP OC44 transistor, the same transistor that was in most of the original units (sometimes the OC71 and very rarely the NKT275 were also used). The SPICE model of the transistor was tested and gave back results that match the data that is available in online bibliography. Unfortunately these transistors are very rare to find nowadays, so real-life measurements to verify are almost impossible. The BIAS resistor was set at 3.9kΩ to stay faithful to the original unit. This gave a BIAS voltage of -6.6 V at the transistor's collector. To achieve a BIAS voltage of -7 V, which is the "sweet spot" according to internet gurus, a 4.8kΩ resistor would be needed in this case. In my tests the 3.9k resistor sounded less distorted and with a more trebly voice, which is more of what what this circuit is supposed to do anyway. ⚠️ Note: These captures are (input AND output) CALIBRATED! Preferably use an amp capture with calibrated input after them. If you don't know how to set up calibrated NAM chains watch 2dor's tutorials "𝗡𝗔𝗠 𝗰𝗮𝗹𝗶𝗯𝗿𝗮𝘁𝗶𝗼𝗻 & 𝗰𝗮𝗹𝗶𝗯𝗿𝗮𝘁𝗲𝗱 𝗽𝗿𝗼𝗳𝗶𝗹𝗲𝘀: 𝗾𝘂𝗶𝗰𝗸 & 𝗲𝗮𝘀𝘆 [𝟮𝟬𝟮𝟱]" & "𝗦𝘁𝗮𝗰𝗸𝗶𝗻𝗴 𝗰𝗮𝗹𝗶𝗯𝗿𝗮𝘁𝗲𝗱 𝗡𝗔𝗠 (𝗡𝗲𝘂𝗿𝗮𝗹 𝗔𝗺𝗽 𝗠𝗼𝗱𝗲𝗹𝗲𝗿) 𝗽𝗿𝗼𝗳𝗶𝗹𝗲𝘀" on YouTube OR read the "𝗡𝗲𝘂𝗿𝗮𝗹𝗔𝗺𝗽𝗠𝗼𝗱𝗲𝗹𝗲𝗿𝗣𝗹𝘂𝗴𝗶𝗻 𝘃𝟬.𝟳.𝟭𝟮 𝗶𝘀 𝗿𝗲𝗹𝗲𝗮𝘀𝗲𝗱" blog post on the Neural Amp Modeler website. Of course you are free to experiment! Using the Raw option will also preserve the unit's output that is relative to your input signal or just use whatever levels you like more! The calibrated options will just give you the results that are closest to real life. ⚠️ Note 2: These captures are NOT derived from the physical hardware but from circuit simulation done in a SPICE environment. I just want to be transparent about that and not mislead people. Of course that doesn't mean they can't sound just as good, provided they are done correctly.