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The Ultimate Tone Vol. 4 Table of Contents and List of Figures |
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Chapter 1: SONIC BOOM Chapter 2: ATTENUATORS Chapter 3: POWER SCALING Chapter 4: SAG Chapter 5: MASTERFUL CONTROL Chapter 6: AMP VOODOO Chapter 7: SUPER SCALERS Chapter 8: G-M-X Chapter 9: Z-M-X Chapter 10: POWER MANAGEMENT Chapter 11: DESIGN PHILOSOPHY Chapter 12: PLUG-N-PLAY Fig. 1-2: Relative phase of sound Fig. 1-3: Sound envelope characteristics Fig. 1-4: Timbre and harmonics Fig. 1-5: Room reflections Fig. 1-6: Audience effect on room sound Fig. 1-7: Fletcher-Munson curves Fig. 1-8: Basic compression and spectral compression effects Fig. 2-1: Speaker efficiency measurement Fig. 2-2: Perceived loudness related to absolute loudness Fig. 2-3: Electrical signal characteristics Fig. 2-4: Other wave shapes and symmetry Fig. 2-5: Duration of sounds Fig. 2-6: Signal phase as absolute and relative terms Fig. 2-7: Phase shift Fig. 2-8: Vector diagram for a pure resistance Fig. 2-9: Voltage stimulus and current consequence for an inductor Fig. 2-10: Vector diagram of inductive current-voltage relationship Fig. 2-11: Current stimulus and voltage consequence for a capacitance Fig. 2-12: Vector diagram of capacitive current-voltage relationship Fig. 2-13: Composite phase relationship for LCR circuit Fig. 2-14: Mechanical parameters and influences over speaker performance Fig. 2-15: Typical electrical impedance curve for a raw driver Fig. 2-16: Frequency response of raw driver Fig. 2-17: Electrical damping of the speaker by the amplifier Fig. 2-18: Damping factor for different tube power amplifier configurations Fig. 2-19: Model of a tube amp output stage Fig. 2-20: Output transformer power bandwidth Fig. 2-21: Electrical model of a dynamic loudspeaker Fig. 2-22: Loudspeaker as both motor and generator Fig. 2-23: Driver compression Fig. 2-24: Loudspeaker magnetic assemblies Fig. 2-25: Real-world verification of “illusionary” sound Fig. 2-26: Speaker attenuator evolution Fig. 2-27: Resistive series attenuator Fig. 2-28: Series-resistance attenuator using power ratios to determine circuit values Fig. 2-29: 100W amp 8O series-resistance attenuator example Fig. 2-30: Loudness for each of the steps in the 100W 8O series-resistance attenuator Fig. 2-31: Designing the series-resistance attenuator using multiple resistance values of the load Fig. 2-33: Transformer attenuation Fig. 2-34: Constant load series-parallel attenuator Fig. 2-35: Output power compared to voltage and current phase relationship Fig. 2-36: Zobel network gets rid of “fizz” Fig. 2-37: Electric fan as reactive load with resistive attenuation to speaker Fig. 2-38: Crippled speaker as load Fig. 2-39: Master-volume amp with no electrical loudness or quiet restrictions Fig. 2-40: Different sized amps for different loudness situations Fig. 2-41: Closed-system options Fig. 2-42: Line output options Fig. 3-1: Loudness perception Fig. 3-2: Transfer curves and operating points Fig. 3-3: Power supply interaction with signal Fig. 3-4: Power Scale essence Fig. 3-5: Simplification of essential control Fig. 3-6: Power supply impedance fallacy with respect to varied voltage Fig. 3-7: Power supply noise rejection by amplifier Fig. 3-8: Capacitive reactance vs. frequency Fig. 3-9: Inherent power supply regulation Fig. 3-10: Current modulations and noise Fig. 3-11: Thyristor characteristics Fig. 3-12: Thyristor regulator circuits Fig. 3-13: SCR-based AC regulator Fig. 3-14: Mosfet AC regulator Fig. 3-15: BJT AC regulator Fig. 3-16: Tube AC regulator Fig. 3-17: IGBT AC regulator Fig. 3-18: DC shunt regulators Fig. 3-19: DC series-pass regulators Fig. 3-20: Integrated circuit regulators Fig. 3-21: Switching regulators Fig. 3-22: Size difference between linear power supply and switching power supply Fig. 3-23: DC switching regulator Fig. 3-24: Conduction control principle Fig. 3-25: Tapped transformer secondaries for two power levels Fig. 3-26: Multi-tapped secondaries for various power settings Fig. 3-27: Multi-tapped primaries for various power settings Fig. 3-29: Multiple transformers with AC regulator Fig. 3-30: Bilateral mosfet AC regulator Fig. 3-31: DC regulators used to control AC Fig. 3-32: Proper way to use a variac for variable power Fig. 3-33: Power conditioner circuits Fig. 3-34: Linear power condition for dedicated amplifier Fig. 3-35: Basic DC regulator Power Scale circuit Fig. 3-36: Intuitive dual-pot Power Scale circuit Fig. 3-37: Choosing the correct pots Fig. 3-39: Tracking regulators with direct control over bias supply Fig. 3-40: Tube bias tracking error with direct-controlled bias regulator Fig. 3-41: Direct-controlled plate/screen voltage and tracking bias regulator Fig. 3-42: Switching regulator for high voltage with linear tracking bias supply Fig. 3-43: Coincident point of Power Scale regulator options Fig. 3-44: Simplest Power Scale regulator Fig. 3-45: Simplest Power Scale regulator with practical refinements Fig. 3-46: Circuit operation and waveforms Fig. 3-47: Setting the range of power control Fig. 3-48: Active current limiting Fig. 3-49: Soft current limiting Fig. 3-50: Capacitor charge currents and turn-on surge Fig. 3-51: Load current vs. Power Scale regulator current Fig. 3-52: Grounding the Power Scale regulators Fig. 3-53: Ideal raw bias supply and alternatives to achieving the ideal Fig. 3-54: Bias supply loading Fig. 3-55: Protecting the bias supply Fig. 3-56: Adding Power Scaling to amps with widely different screen and plate voltages Fig. 3-57: Intrinsic triode within tetrodes and pentodes Fig. 3-58: Plate current dependance on screen voltage Fig. 3-59: London Power’s 700W output stage Fig. 3-60: Waste power in a conventional output stage and effect of changing the screen voltage Fig. 3-61: Mosfet power sharing issues Fig. 3-62: Tracking plate supply regulator for disparate rail amplifier Fig. 3-63: Tracking plate supply operation Fig. 3-64: Signal levels at a high-power level Fig. 3-65: Using preamp volume control to attempt drive compensation Fig. 3-66: Proper drive compensation Fig. 3-67: Overdrive possibilities using Power Scale, Limit and Volume controls Fig. 3-68: Automatic limiting method with Schmitt splitter Fig. 3-69: Automatic limiting with concertina splitter Fig. 3-70: Tracking switch for manual or automatic distortion limiting Fig. 3-71: Power contained in sine and square waves Fig. 3-72: On-off for the Power Scale regulator Fig. 3-73: Fast-transition circuit Fig. 3-74: Integrated instant headroom switch Fig. 3-75: Power Scale boost control Fig. 3-76: Control interaction dependence on settings and pot values Fig. 3-77: Boost and Power Scale controls that are 10× different in value Fig. 3-78: Multiple Power Scale control concept Fig. 3-79: Dual Power Scale controls selected by DPDT Fig. 3-80: Cascading regulators for multiple Power Scale controls - basic approach Fig. 3-81: Detailed approach for two cascaded Power Scale regulators Fig. 3-82: Jfet-controlled fast-transition circuit for dual Power Scale controls Fig. 3-83: Multiple Power Scale selection using relays Fig. 3-84: Multiple Power Scale selection using shunt jfets and mosfets Fig. 3-85: Fast-transition coupling with jfet-shunt-compatible control and three or more Power Scale controls Fig. 3-86: Multiple limit controls in power amp with Schmitt splitter Fig. 3-87: Multiple Limit controls in amps with Concertina splitter Fig. 3-88: Series jfet switches and the correct gate control voltage window Fig. 3-89: LDRs used to select Limit controls Fig. 3-90: Relay-selected limit controls Fig. 3-91: PVA pitfall in audio switching circuits Fig. 3-92: Digital-to-analog converter with current output converted to produce voltage output Fig. 3-93: Current mirror basics Fig. 3-94: Output voltage from input current Fig. 3-95: Current-mode Power Scale regulator Fig. 3-96: Cascoded current-mode Power Scale regulator Fig. 3-97: DAC connected to current-mode Power Scale regulator Fig. 3-98: DAC resolution as number of bits versus steps of output change Fig. 3-99: The pot and programming resistor determine input control of the current mirror Fig. 3-100: Multiple Power Scale controls tied to the current-mode Power Scale regulator Fig. 3-101: “Normalized” control function Fig. 3-102: Linear amplifier as Power Scale regulator Fig. 3-103: Multiple Power Scale controls in the linear amplifier regulator Fig. 3-104: Pure-DC Power Scale approach Fig. 3-105: Amplified follower variation of current-mode Power Scale regulator Fig. 3-106: Eliminating the dead spot at the X-end of the Power Scale control Fig. 3-107: Adding a Master Power Scale control to a relay-switched proportional regulator Fig. 3-108: Adding a Master Power Scale control to jfet-selected multiple Power Scale regulator Fig. 3-109: Master Power Scale added to current-mode regulator Fig. 3-110: Adding a Master Power Scale to the inverted-function current-mode regulator Fig. 3-111: Adding a Master Power Scale to the amplified follower with multiple Power Scale controls Fig. 3-112: Master Power Scale applied to linear amplifier regulator Fig. 3-113: Power Scaling just the output stage Fig. 3-114: Power Scaling the output stage and splitter Fig. 3-115: Power Scaling the output stage, splitter and last preamp stage in typical Marshall or Fender circuits Fig. 3-116: Power Scaling the entire amp Fig. 3-117: Thermal compensation options Fig. 3-118: Plug-and-play connectivity Fig. 3-119: Variable resistance added to cathode and plate circuits respectively Fig. 3-120: Transconductance amplifiers used to compensate signal and bias levels Fig. 3-121: “Practical” plug-and-play option with limited application Fig. 3-122: Connecting bias-modulated tremolo to a Power Scaled amplifier Fig. 3-123: Grid-modulated tremolo for cathode-biased output stage is actually modulating tube bias Fig. 3-124: Triode-pentode switch effect on amplifier characteristics Fig. 3-125: Tube switching for power reduction Fig. 3-126: High-low power switch on Fender “The Twin” Fig. 3-127: Variable cathode resistor in Schmitt to reduce signal output Fig. 3-128: Carvin’s power reduction switch from 1980s models Fig. 3-129: Typical coupling between splitter and power stage, and the impedance change with signal drive Fig. 3-130: Cathode follower easily drives grid with low distortion Fig. 3-131: Normal speaker cone break-up with frequency Fig. 3-132: Transformer core flux density at different frequencies Fig. 3-133: Tube characteristics and how saturation resistance limits drive to the output transformer Fig. 4-1: Internal resistance of a power supply Fig. 4-2: Inherent supply regulation Fig. 4-3: Envelope of an audio signal Fig. 4-4: Change of signal as it passes through the power amp Fig. 4-5: Performance spread caused by imperfect regulation Fig. 4-6: Supply voltage variations in a typical push-pull amplifier Fig. 4-7: Typical SE and high-bias amp supply voltage variations Fig. 4-8: Integrated circuit linear regulator Fig. 4-9: Voltage concerns with linear regulators Fig. 4-10: Typical tube voltage regulator Fig. 4-11: Typical BJT voltage regulator Fig. 4-12: Typical mosfet voltage regulator Fig. 4-13: Vibrator-style regulator Fig. 4-14: Low-frequency BJT transformer inverter Fig. 4-15: SMPS inverter Fig. 4-16: Switching regulator Fig. 4-17: Fan reduces heat-sink size Fig. 4-18: Tube and semiconductor thyristors Fig. 4-19: Typical SCR application as a regulator Fig. 4-20: IGBTs Fig. 4-21: Passive sag added to output stage Fig. 4-22: Passive sag added to complete amplifier Fig. 4-23: Passive sag added to screen supply Fig. 4-24: Active sag control approach using long-loop regulation Fig. 4-25: Sound Craftsman varo-proportional power supply for headroom expansion Fig. 4-26: H.H.Scott 265-A basic power amplifier with dynamic power monitoring Fig. 4-27: Compressor basics Fig. 4-28: Adding compression side-chain to push-pull amplifier Fig. 4-29: “Insert” type compression circuit example from LAB amp Fig. 4-30: Modulating the splitter output using a dual triode Fig. 4-31: Screen modulation problems Fig. 4-32: Mosfet and tube screen modulators Fig. 4-33: Reducing redundancy in the screen modulator Fig. 4-34: Series-pass screen modulator reduces losses compared to shunt approach Fig. 4-35: Adding compression side-chain to SE amp Fig. 4-36: Adding compression to a preamp gain stage Fig. 4-37: London Power Sag Control Kit in B+ line Fig. 4-38: Ground-referenced current limit for fixed-bias output stage Fig. 4-39: Low voltage drop ground-referenced current clamp in fixed-bias output stage Fig. 4-40: Boost amp options for ground-referenced current clamp Fig. 5-1: Guitar sound system built upon a true master-volume approach Fig. 5-2: Tone generators in synthesizer systems Fig. 5-3: Master-volume locations in various guitar amp circuits Fig. 5-4: Ideal transparent amplifier Fig. 5-5: Ideal transparent speaker Fig. 5-6: Alternative method using the PA and monitor system as the output-end of the MV-system Fig. 5-7: Traditional and later metal backline stage setups Fig. 5-8: Clean stage setup with monitor wells and flying PA cabinets Fig. 5-9: Marshall 800 MV amps as examples of “conventional MV” Fig. 5-10: Reducing the conventional MV’s tendency to frequency roll-off over its sweep Fig. 5-11: Ground-referenced MV problem and how to fix it Fig. 5-12: Bootstrapped MV Fig. 5-13: Improved bootstrapped MV Fig. 5-14: Bootstrap MV achieved by cathode-follower reallocation Fig. 5-15: Cascaded bootstrap-MVs allow the implementation of a series effects loop without tone impediment Fig. 5-16: Universal dual-pot post-PI-MV Fig. 5-17: Post-PI-MVs that are NOT recommended Fig. 5-18: Capacitively-coupled dual-pot post-PI-MV Fig. 5-19: Coupling-cap value implications Fig. 5-20: Capacitively-coupled cross-line post-PI-MV Fig. 5-21: Concertina bootstrapped-MV Fig. 5-22: MV for see-saw inverter Fig. 5-23: Seymour-Duncan’s “Juice” control Fig. 5-24: Current-limit used as MV in stacked-Schmitt splitter Fig. 5-25: Electronically controlled splitter current controls headroom and loudness Fig. 5-26: Voltage control of the splitter as a way to reduce output Fig. 5-27: MV-system using full-range amps and cabinets Fig. 5-28: MV-system using guitar amps and cabinets Fig. 5-29: Multiple amps and cabinets Fig. 5-30: Small OT restricts power bandwidth and applicability in a MV-system Fig. 6-1: Early boost circuitry used by Mesa Fig. 6-2: One form of Simulclass Fig. 6-3: Radiotron Designer’s Handbook defines simultaneous class operation Fig. 6-4: Simulclass output stage as originally drawn Fig. 6-5: Corrected Simulclass drawing Fig. 6-6: Triode-pentode switching Fig. 6-7: Tube selection in Mesa-Boogie Fig. 6-8: Power level switch in Trace Elliot 400W bass amp Fig. 6-9: Power tube selection in Fender’s PS Fig. 6-10: Rectifier selection and effect on power supply Fig. 6-11: Voltage reduction by mains-matching tap Fig. 6-12: Attenuated drive to output tubes Fig. 6-13: Comparison of output impedance of small-tube amp and large-tube amp Fig. 6-14: Tube OT with parasitic elements shown Fig. 6-15: Vox’s mosfet output stage with output transformer Fig. 6-16: Typical 50W output stage Fig. 6-17: Reflected plate load impedance and its effect on grid drive and clip points Fig. 6-18: Self bias as “automatic” bias Fig. 6-19: Cathode-bias connection options for EL Fig. 6-20: Basic active-bias arrangement Fig. 6-21: Active bias-balance control from Yorkville Sound Custom 40 Fig. 6-22: Active “cathode bias” that isn’t Fig. 6-23: Current-source tube biasing Fig. 6-24: Active bias control over cathode-biased amplifier Fig. 6-25: Active bias balance in cathode-biased push-pull amp Fig. 6-26: Active balance of fixed-bias push-pull stage via tube screen-grids Fig. 6-27: Primitive approach to sweepable fixed-to-cathode bias Fig. 6-28: Variable RK in sweepable cathode-to-fixed-bias circuit Fig. 6-29: Further improvement of the active swept bias circuit Fig. 6-30: Lamp resistance characteristics Fig. 6-31: Lamp used to control amplitude and thus distortion in an audio-frequency low-distortion oscillator Fig. 6-32: Lamp used to control audio signal amplitude in compressor circuit Fig. 6-33: Lamps as speaker-shunt noise reducers Fig. 6-34: Lamp as speaker protector Fig. 6-35: Stacked-Schmitt splitter Fig. 6-36: Concertina splitter Fig. 6-37: Traditional see-saw inverters Fig. 6-38: Pre-tweed style amp with see-saw middle Fig. 6-39: Pre-tweed revisited with modern-voiced preamp and see-saw middle Fig. 6-40: Method for introducing the sound of aging caps or vintage performance Fig. 6-41: Budget effects loop without send and return controls Fig. 6-42: FX loop with preset return gain but manual send and return controls Fig. 6-43: FX loop with active adjustable return-gain Fig. 6-44 Dual-controls for an effects loop with intuitive switching of direct controls Fig. 6-45: Multi-path preamp where each path has its own loop Fig. 6-46: Multi-voice single-path preamp with individual channel loops Fig. 6-47: Stereo FX loop Fig. 6-48: Dual amp with shared output stage Fig. 6-49: Dual amp selection Fig. 6-50: THD Yellow Jacket tube adapter Fig. 6-51: Conjunctive filter wired two different ways Fig. 6-52: Typical solid-state power amp design where a tube-like output impedance is desired Fig. 6-53: Phil Abbott’s “external amp mod” to achieve SRV tone Fig. 7-1: Unity-gain amplifier is also a power amplifier by definition Fig. 7-2: Typical single-gain-element buffers Fig. 7-3: Conventional non-inverting amplifier using multiple gain elements within a feedback loop Fig. 7-4: Common-grid amplifier, common-base amplifiers and common-gate amplifiers used to achieve non-inverting gain above unity Fig. 7-5: Fractional-gain non-inverting amplifier using attenuator and conventional non-inverting gain stage Fig. 7-6: Fractional-gain non-inverting amplifier using a common-grid stage Fig. 7-7: Fractional-gain non-inverting amplifier using cascaded fractional-gain inverting gain stages Fig. 7-8: Fractional-gain non-inverting amplifier comprised of a voltage follower driving an attenuator Fig. 7-9: Inverting amplifier Fig. 7-10: Conditions that satisfy the presence of only voltage amplification Fig. 7-11: Voltage source characteristics Fig. 7-12: Current amplifier characteristics Fig. 7-13: Currents in various gain elements Fig. 7-14: Current mirror as current amplifier Fig. 7-15: Typical current-mirror applications Fig. 7-16: Input impedance and signal conditions around the current mirror Fig. 7-17: Complementary current-mirror circuit to handle bilateral currents Fig. 7-18: Current amplifier using vacuum tubes Fig. 7-19: AC current amplification with tubes Fig. 7-20: AC current amplification with tubes that does not require a floating load Fig. 7-21: Achieving current gain without power gain Fig. 7-22: Input power “required” versus “absorbed” Fig. 7-23: Typical power stage with voltage input and power output Fig. 7-24: Cathode-driven Super Scaler basics Fig. 7-25: Screen-driven Super Scaler basics Fig. 7-26: Cascaded Super Scalers for higher boost ratios Fig. 7-27: Power-grid tube used in Super Scaler Fig. 7-28: 811A plate and grid curves Fig. 7-29: 812A plate and grid curves Fig. 7-30: 572B power-grid tube used as Super Scaler Fig. 7-31: Methods of balancing hum in filamentary tube output stages Fig. 7-32: SV572-160 Super Scaler Fig. 7-33: Changing power output via output transformer tap selection Fig. 7-34: Adding a line-matching transformer to the output to increase the number of effective taps Fig. 7-35: Looking at the obvious and hidden voltage ratios of a typical output transformer to use as an input transformer Fig. 7-36: “Step-able” boost ratio in cascaded Super Scaler Fig. 7-37: BJT current relationships Fig. 7-38: BJT common-emitter connection Fig. 7-39: Changing the collector load changes the power gain Fig. 7-40: Common-emitter power gain Fig. 7-41: Adding matching transformers to the common-emitter stage to reduce power gain Fig. 7-42: Emitter-follower impedance transformation Fig. 7-43: Common-base power gain Fig. 7-44: Adding an emitter resistance to control gain and raise input impedance of a common-base stage Fig. 7-45: BJT-tube cascode used in Music Man amps Fig. 7-46: Music Man power amp with op-amp front-end shown Fig. 7-47: Open-loop UL with transformer splitter Fig. 7-48: Emitter follower with 1:1 input transformer and 1:2 input transformer Fig. 7-49: Mosfet source-follower output with transformer input Fig. 8-1: Parallel tubes become a composite tube Fig. 8-2: Parallel resistances across a voltage source Fig. 8-3: Series resistances Fig. 8-4: Tube transconductance Fig. 8-5: Bipolar junction transistor transconductance Fig. 8-6: Mosfet transconductance Fig. 8-7: GmX amplifier using tubes Fig. 8-8: GmX tube amp taken to an extreme Fig. 8-9: GmX hybrid amp basics Fig. 8-10: Increasing gm multiplication factor Fig. 8-11: Practical hybrid GmX amp Fig. 8-12: Waste heat and power sharing in the hybrid gmx output stage Fig. 8-13: Cost benefit in other support windings and power supplies by using gmx approach Fig. 8-15: Juggling gmx to reduce VSAT for better efficiency Fig. 8-16: 200W from the 1650T Fig. 8-17: Big power from the 1650W Fig. 8-18: “Traditional” split-winding OT for high-power gmx amp Fig. 8-19: Bridge-style gmx hybrid amp Fig. 8-20: Multi-tier approach to the gmx output stage Fig. 8-21: Intuitive gmx signal sample points that do not work Fig. 8-22: Universal method for interfacing gmx circuitry to cathode-biased output tubes Fig. 8-23: Adding gmx circuitry to individually cathode-biased output tubes Fig. 8-24: Triode-pentode-ultralinear impact on gmx Fig. 8-25: SE amp with gmx Fig. 8-26: 1W-25W SE gmx amplifier Fig. 8-27: Intuitive tube gmx Fig. 8-29: A gmx possibility that isn’t: this is a hybrid amp chain Fig. 9-1: Single-section pots used in ground-referenced and floating circuits Fig. 9-2: Multi-section pot applications Fig. 9-3: DJ source-selection pan-pot Fig. 9-4: Left-to-right panning of a signal in a mixing board Fig. 9-5: Passive balance control for stereo signals using single-section pot Fig. 9-6: Reverb blend and mix controls Fig. 9-7: Effects loop panning controls Fig. 9-8: Selection of direct controls using relays Fig. 9-9: Indirect signal control via remote foot-switch and jfet interface Fig. 9-10: LM3080 transconductance op-amp Fig. 9-11: LM13600 transconductance op-amp with linearizing diodes Fig. 9-12: Transconductance op-amp wired as a voltage-controlled resistance to ground Fig. 9-13: Current and device conditions in the transconductance op-amp configured as a ground-referenced resistance Fig. 9-14: Using multiple transconductance op-amps to alter the levels within a parallel effects loop while accommodating multiple-channel panel controls Fig. 9-15: LAB compressor circuit Fig. 9-16: Direct-current electronically controlled resistance Fig. 9-17: Using a jfet to vary the effective resistance Fig. 9-18: Using a transconductance op-amp to vary the larger electronic resistance circuit Fig. 9-19: Mounting the semiconductor case Fig. 9-20: Discrete transconductance op-amp to handle very large signals Fig. 9-21: Mosfet conduction characteristics Fig. 9-22: Bilateral switch current and voltage limits Fig. 9-23: Bilateral switch turned into a linear resistive element Fig. 9-24: Open-collector output accommodates voltage differences between equipment Fig. 9-25: BJT switch as audio mute, and the limitations to signal control Fig. 9-26: Parallel complementary BJTs as possible linear resistance Fig. 9-27: Parallel complementary BJT open-collector circuit concept incorporating synchronous rectification to take advantage of collector voltage ratings Fig. 9-28: Example output stage in fixed bias and cathode bias Fig. 9-29: Transconductance versus control current for the 3080 Fig. 9-30: Composite electronic-RK circuit with amended values Fig. 9-31: Protecting the output tubes from a zero-bias condition Fig. 9-32: Controlling the bias supply in the swept cathode-bias to fixed-bias circuit Fig. 10-1: Sinusoidal mains voltages Fig. 10-2: Inductive and capacitive loading effects on power factor Fig. 10-3: Effect of abrupt removal of load from power source Fig. 10-4: Lightning and solar flares as electromagnetic noise sources picked up by the mains distribution system virtual antenna Fig. 10-5: Spark gap as spike suppressor Fig. 10-6: Capacitive spike suppression Fig. 10-7: Varistors as non-ideal spike suppressors with unpredictable life expectancy Fig. 10-8: LC and RC filters Fig. 10-9: Line-balancing transformer Fig. 10-10: Steady vs. peak currents and fuse ratings Fig. 10-11: Tube heater start-up and operating currents Fig. 10-12: In-rush current to charge main filter capacitor Fig. 10-13: Thermistor characteristics Fig. 10-14: Thyristor power control approach Fig. 10-15: Bilateral mosfet current-limiter approach Fig. 10-16: Setting up the floating supply with automatic mains range detection Fig. 10-17: Single mosfet in full bridge controls AC current Fig. 10-18: Smooth conduction characteristics of tube rectifier Fig. 10-19: Centre-tapped plate winding discontinuous conduction issue Fig. 10-20: Full bridge with tubes Fig. 10-21: Internal resistance of tube rectifier Fig. 10-22: Mechanically securing rectifier tubes in position Fig. 10-23: Semiconductor junction diode operation and conduction characteristics Fig. 10-25: Leakage currents in solid-state diodes Fig. 10-26: Cleaning up solid-state diode switching noise with inexpensive passive components Fig. 10-27: Alternative rectification scheme with centre-tapped plate winding and solid-state diodes Fig. 10-28: Cross-conduction failure mode when diodes are unloaded, and how to fix it Fig. 10-29: Avoiding cross-conduction failure with full bridge Fig. 10-30: Tube/solid-state switching in B-52 Stealth 100 Fig. 10-31: Three rectification modes using full-bridge supply and tube rectifier Fig. 10-32: AC taps on primaries and secondaries Fig. 10-33: Full-wave bridge over secondary makes taps look like centre-taps Fig. 10-34: Conceptual explanation of tap behaviour Fig. 10-36: Voltage rise problem with replacement of tube rectifier with solid-state diodes Fig. 10-37: Resistive method for voltage restoration is fine with constant load currents Fig. 10-38: Zener diode for voltage restoration Fig. 10-39: Amplified zener and how to use it in cathode-biased amps and fixed-bias amps Fig. 10-40: Buffered proportioning regulator used as voltage restorer Fig. 10-41: Voltage clamping circuit Fig. 10-42: Noise on the DC supply Fig. 10-43: Inrush-limiting resistor does double duty as part of noise suppression filter Fig. 10-44: Tying the chassis ground to the circuit ground Fig. 10-45: Current limiting for high-voltage supplies as an independent circuit Fig. 10-46: Foldback current-limiting characteristic Fig. 10-47: BJT and mosfet safe operating area curves Fig. 10-48: Noise coupling to heater winding Fig. 10-49: Typical reference methods for heater supply Fig. 10-50: Heater noise path within each tube Fig. 10-51: DC-stand-off reference Fig. 10-52: Simple DC heater supplies Fig. 10-53: Simple method for viewing capacitor charge and discharge currents with oscilloscope Fig. 10-54: RC filtering for heater supply Fig. 10-55: Mix of AC and DC heaters in modern high-gain guitar amps Fig. 10-56: Referencing options for DC heater supply Fig. 10-57: Typical ways to wire 6V and 12V heaters on a DC supply, and the option of dual supplies that allows use of dissimilar power tube heater ratings Fig. 10-58: London Power’s DC heater supply method for accommodating 6V and 12V heaters with dissimilar power tube heater ratings Fig. 10-59: Typical voltage regulator circuits for heater supply Fig. 10-60: Heater current regulator Fig. 10-61: Series-string current-regulated heater supply with open-heater annunciation Fig. 10-62: Current-balancing circuit for London Power’s 6/12V DC heater supply using current mirrors Fig. 10-63: Alternative current monitoring approach to Fig. 10-62 using op-amps Fig. 10-64: Power gain at every stage Fig. 10-65: Ultra-simplified power amplifier concept Fig. 10-66: Single-ended tube power amplifier Fig. 10-67: Solid-state single-ended power amplifier variety Fig. 10-68: Typical push-pull tube amp with plate-driven output transformer Fig. 10-69: Obsolete solid-state push-pull form Fig. 10-70: Common solid-state push-pull power amplifier forms Fig. 10-71: Satisfying a class-A signal condition in a SE tube amplifier Fig. 10-72: Satisfying a class-A signal condition in a push-pull tube amplifier Fig. 10-73: Satisfying a class-A signal condition in solid-state SE amplifiers Fig. 10-74: Satisfying a class-A signal condition in push-pull solid-state amplifiers Fig. 10-75: Ideal class-B signal condition Fig. 10-76: Class-AB signal conditions Fig. 10-77: Cathode-bias methods for SE and push-pull Fig. 10-78: Signal condition through the conduction transitions of a cathode-biased amp with shared bias resistor Fig. 10-79: Trying to stabilize the bias point in cathode-biased amps Fig. 10-80: Using a separate power supply between the grid and cathode to stabilize the signal bias condition Fig. 10-81: Achieving a fixed-bias signal condition in a tube amp Fig. 10-82: Amplified-zener as a “cathode bias” form Fig. 10-83: Current source in place of cathode-bias resistor Fig. 10-84: Power supply noise compared to supply noise that appears on the audio output Fig. 10-85: Raw hum balancing of push-pull output stage and issues with UL stage Fig. 10-86: Feedback loop in SE amp helps increase amp PSRR Fig. 10-87: Push-pull power supply noise injection and balance points Fig. 10-88: Improving performance of splitters with further decoupling and larger RC values Fig. 11-1 Over-all format decision tree Fig. 11-2: Active element decision tree Fig. 11-3: Power amplifier topology decision tree Fig. 11-4: Resistor selection decision tree Fig. 11-5: Capacitor selection decision tree Fig. 11-6: Wiring method decision tree Fig. 11-7: Chassis decision-tree Fig. 11-8: Adequate vs. Ample chassis thickness Fig. 11-9: 1645 + 273CX amp Fig. 11-10: 1650K + 272HX amp Fig. 11-11: 1650K + 272JX amp Fig. 11-12: 1639 + 275X amp Fig. 11-13: 1650G + 273BX amp Fig. 11-14: Filter cap differences for the 50W amplifier examples Fig. 11-15: Six 6550 amp Fig. 11-16: Four 6550 amp Fig. 11-17: 811A amp Fig. 12-1: Loudness compensation Fig. 12-2: Typical amplifier chain Fig. 12-3: Follower-type attenuator with added current limiting and DC protection for the speaker Fig. 12-4: Nulling the speaker signal and thus reducing sound output to zero using two amplifiers Fig. 12-5: Waste heat in the null-amp with zero null signal and thus zero attenuation Fig. 12-6: Sine wave power versus square-wave power Fig. 12-7: Power distribution and waste heat during various attenuations Fig. 12-8: Carver commutating output stage Fig. 12-9: Yorkville Sound commutating output stage Fig. 12-10: London Power’s self-cascoding multi-tier output stage Fig. 12-11: Null-amp output stage with optimized supply rails Fig. 12-12: Tube amp load during attenuation Fig. 12-13: Nominal speaker impedance vs. actual impedance curve vs. tube amp loading Fig. 12-14: Adding EQing to provide tonal compensation to attenuated tone Fig. 12-15: Original Super Scaler concept can go louder or quieter Fig. 12-16: Non-master-volume amp driven clean then clipped Fig. 12-17: MV amp driven to point of output clipping Fig. 12-18: Complementary parallel BJT rmx circuit adapted to be high-voltage active load Fig. 12-19: Mosfet bilateral switch modified to be an electronic-controlled resistance Fig. 12-20: Mosfet control voltage reference shift at opposite cycle signal peaks Fig. 12-21: Turning the active load circuit into an active attenuator Fig. 12-22: Floating active attenuator Fig. 12-23: Post-production technique used in recording studios Fig. 12-24: “Embedded” effects sound using front-loaded effects, and the “split” amp with FX-loop Fig. 12-25: Dry-wet multipath stage setup Fig. 12-26: Live post-processing using zmx circuit or null-method Fig. 12-27: So-called “transimpedance” attenuator List of Tables Table 3-1: Variable VS |
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