ST-70 Series 3

Advanced Classic Tube Amplifier

There is no denying... vacuum tubes are without question, the most sexy, elusive and magical element of all high-end audio gear. One glance at the glowing ember is enough to make an audiophile cry with tears of elation and joy. Tubes aren't as powerful or as clinically accurate as their solid-state counterparts, but there is just something exhilarating about tubes that simply cannot be beat.

Tubes are not like transistors. When you exceed the rail voltage of a solid-state device, the distortion goes from less than 1% to 100% in an instant. The result is clipping or square waves that sound harsh. Tubes never attain the ultra low distortion specifications of their solid-state counterparts. Instead, when pushed hard, the tube naturally rounds out the signal, producing warm-sounding even-order harmonics that are pleasing to the ear.

A good tube amplifier is simple in architecture and does not exaggerate. It works in harmony with the source material and the loudspeaker to produce a sonic landscape with deep natural bass and rich upper harmonics. The Dynaco ST-70 Series 3 follows David Hafler’s original concept while taking advantage of today’s higher resolution parts, 60 years of transformer-building experience, and an accumulation of in-depth circuit design knowledge to produce what may well be the most musically pleasing amplifier ever made.

The Dynaco ST-70 Series 3 delivers the very soul of high fidelity.


After acquiring the Hafler brand, the opportunity came to 'close the loop' and bring David Hafler's original Dynaco brand under the same tutelage. This opportunity cleared the way to have Hafler focus on solid state devices while Dynaco would spearhead tube development.

The ST-70 Series 3 is not a simple remake of the original Dynaco Stereo 70. Early on, we asked ourselves what David Hafler would do if he was alive today and we came to the following conclusion: The ST-70 Series 3 should be the very best amplifier that can be made today using Hafler's finest work as a guide, while using the very best commercially available components. In other words, we did not want to build an amp that required sourcing discontinued tubes, nor did we want to replicate the type of output transformer that may have worked well 50 years ago for the speakers and music of the day. Instead, we wanted to make an amplifier that would have the agility to handle today's musical landscape by capturing subtlety and dynamics, yet when pushed hard could rock a room like a Marshall® guitar amp.

We also wanted the ST-70 Series 3 to be relatively affordable. As soon as we announced the price, the first reaction from the audiophile community was that it was not expensive enough. David Hafler's Dynaco legacy has always been about delivering tremendous value and we saw no reason to shift gears even though the Series 3 has the sound, performance and pedigree of amplifiers that cost significantly more. By making the ST-70 accessible, we believe great sounding audio can be enjoyed by a wider audience and this in turn will spur on the production of even better music as we move forward.


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    High-Pass Filter

    Three position first-order -6dB per octave filter gently rolls off excessive bottom end to add punch and dynamics to the music.

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    Bias Adjustment

    Individual front panel bias adjustment ensures optimal performance or each drive tube by matching the LED intensity.

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    Protective Grill Cover

    Brushed aluminum grill gives a modern look to the vintage-inspired design. Protects the tubes from damage during transportation and adds a measure safety when driven hot!

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    Trim Controls

    Let you adjust the volume of each channel for room design imbalance so that you can optimize the sound at your preferred seating position.

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    Voltage Selector

    2-position 115V or 230V switch allows for use around the globe, features security cover to prevent accidental switching.

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    RCA Inputs

    Gold plated RCA Inputs that won’t tarnish over time provide optimal signal transfer.

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    Impedance Selector

    2-position 4 Ohm or 8 Ohm switch to optimize the output impedance of the ST-70 to best match your speakers.

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    Power Switch

    Rear-mounted access protects against unintended use.

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    IEC Power Connection

    Easily adapts to international power system standards, no need for country-specific power supplies.

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    Speaker Terminals

    No-touch speaker binding posts to meet international standards for safe operation. Allows connection for heavy gauge speaker wire.

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    Audio Output Transformers

    Custom built high-performance audio transformers convert the high output impedance of the tubes to the low impedances required to drive loudspeakers.

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    Output Tubes

    The original EL34 as employed in David Hafler’s famous ultra linear push-pull configuration convert co-phase drive signals to the high power levels to drive loudspeakers.

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    Driver Section

    Classic Williamson-Hafler configuration featuring 12AU7 tubes takes the input signal and converts it to the high level co-phase drive signal necessary to drive the output stage.

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    Power Supply Capacitors

    Extra-large storage capacitors provide clean energy to supply high impulse power and extended low frequencies to deliver explosive dynamics.

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    Power Transformer

    Custom made power transformer is specifically designed to work in conjunction with the solid state rectifiers to supply the high impulse energy to deliver the dynamics for today’s music.


Class AB Quad-triode design


RCA (left/right)


5-way gold binding posts (left/right)

Power Output:

35 watts/channel into 4 or 8 Ohms


User-adjustable bias, selectable high-pass filter


L34/6CA7 output tubes for classic Hafler Ultra-linear response


Selectable 4 Ohm and 8 Ohm speaker loads

Max Power Consumption:

345 watts


17" x 9.25" x 7.5"
(431 x 235 x 190mm)




3 year, transferable


Most Significant Electronic Debuts

Munich High End Show

Dynaco ST-70 Series 3 Amplifier

Well known as the best-selling tube amp of all time, the iconic Dynaco Stereo 70 amplifier has been revamped and redesigned in a Series 3 model in the relaunched Hafler-Dynaco line, now under the auspices of Radial Engineering Ltd. of Canada. Rated at 35Wpc, the new Series 3’s updates and upgrades include the use of more advanced engineering and higher-quality modern parts. In this Class-A push-pull design, 12AU7 dual triode tubes are used in the front end instead of 7199 pentodes. The new power supply has a larger transformer with improved line regulation, increased filter capacitance, and solid-state rectifier. Much attention was paid to overhauling the original output transformers to increase damping and low-frequency control. There’s also a three-position high-pass filter to enable low-end adjustments. Robert Harley had a chance to listen to the new ST-70 (alas, I did not) and reported that it was very dynamic, punchy in the bass (it didn't sound at all like a tube amp in the bottom end), and played quite loudly. David Hafler would have been proud.


Does the Dynaco ST-70 sound like the original?

Yes and no. Yes, in that it retains the David Hafler’s legendary sonic character, but the new design is much quieter, it has significantly better bottom end response, and you will find it to be a lot punchier to adapt to today’s dynamics.

Will you offer DIY kits like the original Dynakits?

No. With today’s litigious society, and the high voltages present inside, we simply cannot afford to risk having someone electrocute themselves. So the ST-70 will only be sold as a completed assembly.

Can I remove the cover?

Yes. This is done using side-access screws to enable you to replace the tubes.

Will replacing the tubes change the sound?

Yes. Each tube manufacturer introduces a particular character to the sound. Trying different tubes is easy to do and fun!

Is the Dynaco ST-70 Series 3 safety approved for insurance purposes?

Yes. Initially, each amp will be individually tested and approved by an inspector for use in Canada and the USA. It will then move to full approval as availability increases for use in other jurisdictions around the globe.

Is the ST-70 made in China like other knock-offs?

No. The ST-70 is made in Canada with hand inserted discrete parts and hand wired cable harnesses.

Can I buy the ST-70 with 100 V settings for Japan?

Not at this time. You will need to use a voltage converter when using the ST-70 in Japan.

At 35 watts a channel, will the ST-70 be loud enough?

Tubes are much louder than their solid-state counterparts. For comparison, a 50 watt Marshall guitar amplifier can be ear-piercing loud when played at full. The ST-70 actually produces 70 watts RMS and if coupled with a pair of efficient speakers, will deliver sufficient output to replicate the feel of a live concert. You will wake the neighbours!

Why are there volume controls on the front panel?

Not all audiophiles have the luxury of setting up a dedicated room. The volume controls should normally be set to full on each channel. Should you have an irregular room, you can compensate by turning down a channel if it appears to be louder.

Can I turn off the BIAS adjustment lights?

No. Lights are good and they will also tell you if you have allowed sufficient time to warm the amp as it will stop drifting when it reaches thermal stability.