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Message: [QUOTE="Bombastus, post: 91860, member: 2178"] Passive guitar volume controls change more than signal level because the pickup, potentiometer, cable capacitance, and pedal input form one connected electrical network. Turning the knob down can therefore change both how hard a transistor is driven and the spectrum arriving at it. The distinction matters with old-style boost and fuzz circuits because many present a much lower input impedance than modern amplifiers. A passive pickup reacts to the load. Half volume is not simply the full signal made quieter. [HEADING=2]The guitar volume knob changes the source itself[/HEADING] A passive pickup behaves as a frequency-dependent source with resistance and inductance, while the cable adds capacitance and the guitar controls add their own resistive loading. The familiar upper-mid or treble resonance comes from those parts interacting, not from the pickup alone. Moving the volume pot changes the network. Measurements and models of [B][URL='https://research.aalto.fi/en/publications/acoustics-and-modeling-of-pickups/']pickup and volume-control interaction[/URL][/B] show that the guitar volume control can damp the pickup's resonant peak as well as reduce output level, so the source feeding the pedal changes its frequency response as the knob moves. Pedal input impedance then decides how strongly the next stage participates. A very high-impedance input takes relatively little current from a passive pickup and leaves more of its natural resonance intact, while a low-impedance input loads the pickup harder and can flatten or shift the response. Vintage Fuzz Face circuits sit at the end of this relationship. Their input impedance can fall to only a few kilohms, far below the roughly one-megohm input common on modern guitar gear. Roll the guitar volume back into such a circuit and several things happen together. Signal amplitude falls. The guitar's source impedance and pickup resonance change, and the first transistor receives a different drive condition. [HEADING=2]Cleanup is not a germanium switch[/HEADING] Lower input level obviously matters because a nonlinear transistor stage clips less when you stop hitting it as hard. If amplitude were the entire story, though, a buffer placed between guitar and pedal would preserve exactly the same cleanup curve after the guitar knob was turned down. It often does not. A buffer presents the guitar with a high input impedance, then feeds the following pedal from a much lower output impedance. The pedal no longer loads the passive pickup directly. Part of the old guitar-to-pedal interaction disappears even while the buffer passes the changing signal level. This is why some vintage-style fuzzes become brighter, harsher, less responsive, or simply different when a buffered tuner, wireless system, active pedal, or other low-output-impedance device sits in front. The issue is circuit interaction, not a blanket rule that buffers damage tone. Pickup-simulator networks exist for the same reason. Designers can deliberately place resistance, capacitance, inductance, or a transformer between a buffer and a sensitive fuzz so the circuit sees something closer to the electrical source it was designed around. Germanium often gets credit for cleanup because famous germanium fuzzes and boosters made the behavior desirable and obvious. Silicon circuits can also clean up from the guitar volume when their topology, bias, input loading, and gain structure support it, while a germanium circuit designed around a buffered high-impedance input may react quite differently. [HEADING=2]Pedal order can rewrite the guitar knob[/HEADING] A direct guitar connection gives a sensitive transistor stage access to the pickup's changing source impedance. Put another device in between and the first pedal may now see the output impedance of a buffer, preamp, compressor, tuner, wireless receiver, or active pickup instead. Active pickups make the contrast especially clear because their built-in electronics provide a lower output impedance than traditional passive pickups. The following pedal receives a source that is less affected by its own input loading, so a circuit famous for passive-pickup interaction may lose part of the behavior players associate with rolling the guitar down. Treble-bleed components across a guitar volume control alter the result again by allowing more high-frequency content to bypass part of the potentiometer as volume falls. A pedal can therefore appear to clean up with extra sparkle on one guitar and become noticeably darker on another before any transistor difference enters the equation. Great Eastern FX describes strong volume-knob cleanup as part of [B][URL='https://goldmidi.com/community/threads/great-eastern-fx-has-debuted-the-transformer-boost-pedal.77258/']the Transformer Boost's germanium response[/URL][/B], but the useful lesson extends beyond one device. The 2N1175 contributes to the gain stage, while the guitar, cable, pedal input, bias, and anything earlier in the chain help decide what signal reaches it. Testing cleanup is more revealing when you keep the whole front end consistent. Use the same guitar, cable, pedal order, and pickup setting, then compare how the sound changes across the guitar volume travel rather than judging the transistor material from one full-volume chord. Move a buffer ahead of the pedal afterward and repeat the test. If the cleanup character changes even at comparable signal levels, you are hearing the surrounding electrical relationship at work, not a mysterious property locked inside a germanium can. [/QUOTE]

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