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Features a dual primary transformer for improved line regulation and 220V/50Hz operation.
Replaces the 5AR4 tube with solid-state rectifiers for reliability and better regulation.
Tripled filter capacitance enhances power supply stiffness and voltage regulation.
Replaces selenium rectifier in bias circuit with solid-state for improved reliability.
Reduced filter inductor value complements increased capacitance, lowering DC resistance.
Limits bandwidth to 20-20,000Hz to improve distortion at frequency extremes.
Moving feedback point to 8 ohm tap reduces distortion caused by imperfect coupling.
Replaces the obsolete 7199 tube with the readily available and better performing 6GH8A.
Uses military-grade epoxyfiberglass PCB and reduces point-to-point wiring by two-thirds.
Connects to a 3-wire grounded wall outlet (120V, 50/60Hz, 15A circuit).
Uses shielded cables to gold-plated phono jacks; requires < 2000 ohm source impedance.
Uses 5-way binding posts for various wire types; maintain phase sense.
Parallels speaker taps for 70W mono operation using 'Y' adapter for inputs.
Details the operational Class A push-pull design, power supply, and bias circuits.
Describes signal flow from input to output tubes, including phase inverter stage.
Periodic bias adjustment using LED indicators and recessed potentiometers for optimal performance.
Set bias when LED pairs are of equal brightness at amplifier idle after 5 minutes warmup.
Note that only one LED may light initially; balance occurs after 5 minutes warmup.
Avoid high preamp volume, stylus drops, arm skids, and extreme tone control use.
Protected by a 3A slo-blo fuse; never replace with higher rating.
Check AC power, power switch, and fuse; replace fuse if blown.
Verify source selection, tape monitor, and cable connections.
Swap cables and tubes to isolate issues between channels.
Indicates a faulty tube; swap tubes to identify and replace the defective one.
Isolate hum/noise source by removing input cables to check preamplifier or cables.
3 years for defects (1 year for tubes) in normal use, excluding abuse or unauthorized modification.
Use amplifier as instructed, provide transportation for service, and present proof of purchase.
Contact dealer or write Dynaco with name, serial number, purchase details, and problem description.
Connect (2) RED '16' ohm taps together for 8 ohm mono operation.
Connect (2) RED '8' ohm taps together for 4 ohm mono operation.
Connect speaker (+) to jumpered RED terminals, (-) to BLACK terminals.
Use a 'Y-adaptor' to combine input signals for mono operation.
Contact SCC for Dynaco authorized parts and service for ST70 II and vintage equipment.
SCC stocks parts for older Dynaco electronics; original part numbers are required for orders.
Out-of-warranty service for older Dynaco equipment is no longer available from SCC.
Dynaco recommends performance-checked pretested vacuum tubes with a one-year warranty.
Features a dual primary transformer for improved line regulation and 220V/50Hz operation.
Replaces the 5AR4 tube with solid-state rectifiers for reliability and better regulation.
Tripled filter capacitance enhances power supply stiffness and voltage regulation.
Replaces selenium rectifier in bias circuit with solid-state for improved reliability.
Reduced filter inductor value complements increased capacitance, lowering DC resistance.
Limits bandwidth to 20-20,000Hz to improve distortion at frequency extremes.
Moving feedback point to 8 ohm tap reduces distortion caused by imperfect coupling.
Replaces the obsolete 7199 tube with the readily available and better performing 6GH8A.
Uses military-grade epoxyfiberglass PCB and reduces point-to-point wiring by two-thirds.
Connects to a 3-wire grounded wall outlet (120V, 50/60Hz, 15A circuit).
Uses shielded cables to gold-plated phono jacks; requires < 2000 ohm source impedance.
Uses 5-way binding posts for various wire types; maintain phase sense.
Parallels speaker taps for 70W mono operation using 'Y' adapter for inputs.
Details the operational Class A push-pull design, power supply, and bias circuits.
Describes signal flow from input to output tubes, including phase inverter stage.
Periodic bias adjustment using LED indicators and recessed potentiometers for optimal performance.
Set bias when LED pairs are of equal brightness at amplifier idle after 5 minutes warmup.
Note that only one LED may light initially; balance occurs after 5 minutes warmup.
Avoid high preamp volume, stylus drops, arm skids, and extreme tone control use.
Protected by a 3A slo-blo fuse; never replace with higher rating.
Check AC power, power switch, and fuse; replace fuse if blown.
Verify source selection, tape monitor, and cable connections.
Swap cables and tubes to isolate issues between channels.
Indicates a faulty tube; swap tubes to identify and replace the defective one.
Isolate hum/noise source by removing input cables to check preamplifier or cables.
3 years for defects (1 year for tubes) in normal use, excluding abuse or unauthorized modification.
Use amplifier as instructed, provide transportation for service, and present proof of purchase.
Contact dealer or write Dynaco with name, serial number, purchase details, and problem description.
Connect (2) RED '16' ohm taps together for 8 ohm mono operation.
Connect (2) RED '8' ohm taps together for 4 ohm mono operation.
Connect speaker (+) to jumpered RED terminals, (-) to BLACK terminals.
Use a 'Y-adaptor' to combine input signals for mono operation.
Contact SCC for Dynaco authorized parts and service for ST70 II and vintage equipment.
SCC stocks parts for older Dynaco electronics; original part numbers are required for orders.
Out-of-warranty service for older Dynaco equipment is no longer available from SCC.
Dynaco recommends performance-checked pretested vacuum tubes with a one-year warranty.
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