Dynaco

David Hafler's mission to make tube audio affordable

History

Dynaco was founded in Philadelphia, Pennsylvania in 1955 by David Hafler, a brilliant engineer who had previously worked at Acrosound designing transformer-coupled amplifiers. Hafler's vision was radical: to produce high-quality audio equipment that ordinary people could afford.

The company's business model was equally innovative. Dynaco sold amplifiers primarily as kits, eliminating the cost of factory assembly while maintaining quality through well-designed PCBs and thorough documentation. Customers could save 30-40% by building their own equipment.

The ST-70 (Stereo 70) tube amplifier, introduced in 1959, became the best-selling tube amplifier in history. With 35 watts per channel and a simple, reliable design using EL34 output tubes, the ST-70 sold over 350,000 units over its 17-year production run. It remains the most popular vintage tube amplifier for restoration and modification.

The PAS-3 preamplifier (1963) and FM-3 tuner completed a complete high-fidelity system for under $200—an unprecedented value. Dynaco also produced the Mark III mono blocks and Mark IV mono amplifiers for those wanting more power.

In the 1970s, Dynaco expanded into speakers with the A-25 and A-35, Scandinavian-designed bookshelf speakers that offered exceptional value. The company also produced solid-state amplifiers like the ST-120 and ST-150.

Tandy Corporation (RadioShack) acquired Dynaco in 1983, and the brand eventually faded. However, the ST-70 and other Dynaco classics remain central to the vintage audio hobby, with countless units still in service and an active restoration community.

Key Facts

• Founded: 1955, Philadelphia, Pennsylvania
• Founder: David Hafler
• Business Model: High-quality kits at affordable prices
• Best Seller: ST-70 (350,000+ units)
• Philosophy: High-end audio for everyone
• Legacy: Most popular tube amp ever made

Legendary Products

Dynaco ST-70 (1959-1976)

The best-selling tube amplifier in history. The Stereo 70 delivered 35 watts per channel from four EL34 output tubes in a push-pull ultralinear configuration. Its simple, reliable circuit and excellent transformers made it the gateway to tube audio for generations.

Dynaco PAS-3 (1963-1980s)

The companion preamplifier to the ST-70. The PAS-3 offered multiple inputs, bass and treble controls, and a warm, musical sound that complemented the ST-70 perfectly. The PAS-3X added a cathode-follower output stage.

Dynaco A-25 (1968-1970s)

A bookshelf speaker designed by Seas of Norway. The A-25 used a 10" woofer and 3/4" dome tweeter in a sealed enclosure, offering remarkable bass response from a compact cabinet. It became one of the best-selling speakers of the 1970s.

Dynaco Mark III (1960s)

Monoblock tube amplifiers delivering 60 watts each from a pair of EL34 tubes. The Mark III offered more power than the ST-70 for those with larger speakers or rooms. Often used in pairs for stereo.

Sound Signature

The Dynaco sound is the classic EL34 tube character that has captivated audiophiles for over six decades. The ST-70's 35 watts per channel deliver a warmth and musicality that solid-state amplifiers at any price struggle to replicate. The midrange is lush and present — vocals float in the room with a tangible, three-dimensional quality. Bass is warm and full rather than analytical, and the treble has that sweet, airy quality that makes well-recorded cymbals shimmer rather than splash.

The PAS-3 preamp adds its own tube coloration to the chain, with a richness in the low midrange that makes everything from jazz piano to cello sound incredibly natural. Together, the ST-70/PAS-3 combination creates a sound that is unashamedly musical — these are not reference-accuracy components, they are components that make you want to keep listening. David Hafler understood that the point of hi-fi was to enjoy music, and every design decision in the Dynaco range serves that goal.

Collecting Dynaco

The ST-70 is the most popular vintage tube amplifier in the world, with over 350,000 units produced. Factory-assembled examples are rarer and more valuable than kit-built units, but a well-assembled kit can sound identical. Unmodified examples with original Dynaco-branded transformers and circuit boards command the highest prices, though the ST-70 also has an enormous modification community offering modern PCB upgrades that can elevate its performance dramatically.

The Mark III monoblock amplifiers, delivering 60 watts each, are the power option for those wanting the Dynaco sound with more headroom. The PAS-3 preamp (especially the PAS-3X with cathode-follower output) is the natural companion. The A-25 bookshelf speaker, designed by Seas of Norway, is a hidden gem — one of the best-selling speakers of the 1970s that still sounds remarkably good today. The FM-3 tuner completes what many consider the greatest budget audiophile system ever assembled.

Competitors & Comparisons

Dynaco vs Heathkit: Both kit companies; Dynaco more audiophile-focused

Dynaco vs Eico: Similar market; Dynaco more successful

Dynaco vs McIntosh: McIntosh luxury; Dynaco accessible quality

Amplifiers

• Dynaco - The People's Hi-Fi — Founded in 1955 by David Hafler. Created legendary affordable hi-fi including the ST-70 tube amplifier, PAS-3 preamp, and the iconic A-25 speaker. Made high-end audio accessible to everyone.

Amplifiers

• Mark-III — A tube-powered monaural amplifier delivering 60 watts of rated output, introduced by Dynaco in 1957.
• MK-VI (1975) — High-power stereo tube amplifier from Dynaco, known for robust performance and classic tube warmth.
• PAT-4 (1967) — Solid-state preamplifier from Dynaco with modular design and high-fidelity phono stage.
• PAT-5 (1976) — Solid-state preamp from Dynaco with modular design and low distortion, part of the transition from tube to solid-state audio.
• SCA-80Q (1972) — Dynaco SCA-80Q integrated amplifier with built-in DynaQuad matrix decoder for quadraphonic sound, modular design, and warm musical performance.
• ST-120 (1966) — High-performance solid-state stereo amplifier from the 1960s, known for affordability and modular design.
• ST-35 (1959) — The Dynaco ST-35 STEREO-35 is a classic vacuum tube stereo amplifier from the late 1950s, renowned for its warm sound and pioneering role in affordable high-fidelity audio.
• ST-70 (Stereo 70) (1959) — High-performance tube stereo amplifier that brought high-fidelity tube sound to the mass market.
• ST-80 (1967) — Dynaco Stereo 80 solid-state stereo amplifier from 1967, known for clean performance and reliable design during the tube-to-transistor transition era.
• Stereo 70 (1959-late 1970s) — A vacuum tube power amplifier that became the best-selling tube amp of all time.

Preamplifiers

• PAT4 — A solid-state stereo preamplifier developed as part of Dynaco’s early transition to transistorized audio equipment.

Preamps

• PAS-2 (1960) — Tube-based preamplifier from Dynaco, known for warm sound and modular design.

Speakers

• CAB-1S (1975) — Passive crossover network for bi-amping Dynaco A-25 speakers.

Tuners

• AF-6 (AM/FM Tuner) (1965) — A classic solid-state AM/FM tuner from Dynaco, known for its clean design and integration with ST-series amplifiers.
• FM-3 (1964) — Affordable high-fidelity FM tuner from the 1960s with tube-based design and stereo decoding.

Turntables

• QD-1 (Quadaptor) (1970) — Passive quadraphonic decoder from Dynaco that delivers 4-channel sound from stereo sources using the QS matrix system.

Other Models

• Dynaco - The People's Hi-Fi — Founded in 1955 by David Hafler. Created legendary affordable hi-fi including the ST-70 tube amplifier, PAS-3 preamp, and the iconic A-25 speaker. Made high-end audio accessible to everyone.
• A-25 — A compact, high-performance two-way bookshelf speaker with aperiodic cabinet design and Scandinavian-engineered drivers.
• AF-6 (AM/FM Tuner) (1965) — A classic solid-state AM/FM tuner from Dynaco, known for its clean design and integration with ST-series amplifiers.
• CAB-1S (1975) — Passive crossover network for bi-amping Dynaco A-25 speakers.
• FM-3 (1964) — Affordable high-fidelity FM tuner from the 1960s with tube-based design and stereo decoding.
• FM-5 — Dynaco FM-5 (1959) stereo tuner with tuning meter and volume control — a rare early component from the hi-fi pioneer.
• Mark-III — A tube-powered monaural amplifier delivering 60 watts of rated output, introduced by Dynaco in 1957.
• MK III — A monoblock tube power amplifier released by Dynaco in 1957, designed for high-fidelity stereo systems.
• MK-VI (1975) — High-power stereo tube amplifier from Dynaco, known for robust performance and classic tube warmth.
• PAS 3 — Dynaco PAS-3 (1963–1980s) tube preamp: 4.8 kg, 10Hz–40kHz response, 10V output. Warm, mod-friendly classic.
• PAS 3X — It functions as a two-channel control center capable of both monophonic and stereophonic reproduction. Designed as an update to the PAS-3, the PAS-3X
• PAS-2 (1960) — Tube-based preamplifier from Dynaco, known for warm sound and modular design.
• PAT-4 (1967) — Solid-state preamplifier from Dynaco with modular design and high-fidelity phono stage.
• PAT-4A — A solid-state stereo preamplifier manufactured in the United States during the 1960s or 1970s.
• PAT-5 (1976) — Solid-state preamp from Dynaco with modular design and low distortion, part of the transition from tube to solid-state audio.
• PAT4 — A solid-state stereo preamplifier developed as part of Dynaco’s early transition to transistorized audio equipment.
• QD-1 (Quadaptor) (1970) — Passive quadraphonic decoder from Dynaco that delivers 4-channel sound from stereo sources using the QS matrix system.
• SCA 35 — A vacuum tube stereo integrated amplifier introduced in 1964, available as a kit or factory-built unit.
• SCA 50 — A medium power solid state stereo control amplifier built by Dynaco from 1960 to 1966, noted for its high-quality construction and flexible design.
• SCA 80 — Dynaco SCA-80 (1969–1972) solid-state integrated amp, 40W+40W, 7.2 kg — a compact, reliable performer with flat-path tone controls and dual speaker outputs.
• SCA-120 — A U.S.-made integrated stereo amplifier, noted for 60 watts per channel output and inclusion of a subsonic filter.
• SCA-80Q (1972) — Dynaco SCA-80Q integrated amplifier with built-in DynaQuad matrix decoder for quadraphonic sound, modular design, and warm musical performance.
• ST-120 (1966) — High-performance solid-state stereo amplifier from the 1960s, known for affordability and modular design.
• ST-35 (1959) — The Dynaco ST-35 STEREO-35 is a classic vacuum tube stereo amplifier from the late 1950s, renowned for its warm sound and pioneering role in affordable high-fidelity audio.
• ST-70 — A stereo tube power amplifier that became the best-selling tube amp in history, known for its musicality and accessibility.
• ST-70 (Stereo 70) (1959) — High-performance tube stereo amplifier that brought high-fidelity tube sound to the mass market.
• ST-80 (1967) — Dynaco Stereo 80 solid-state stereo amplifier from 1967, known for clean performance and reliable design during the tube-to-transistor transition era.
• Stereo 70 (1959-late 1970s) — A vacuum tube power amplifier that became the best-selling tube amp of all time.