Miller Audio

Miller Audio LLC

We Can Fix Your Audio Habit
We Can Fix Your Audio Habit
We Can Fix Your Audio Habit
We Can Fix Your Audio Habit

Introducing the Dyna-70 Ultimate Upgrade Kit for Dynaco ST-70's

The Dyna-70 Ultimate Upgrade comes in two versions-  Manual or Automatic Bias.  For those on a budget, we offer 4 individual bias controls you manually adjust approximately every 3 – 6 months. The optional Auto Bias (AB) system is integrated with our Dyna-70 circuit card, helping to extend tube life and giving an instant visual indication of the health of your tubes.  If an LED does not light, it’s time for a new tube.

Dyna-70 Ultimate Upgrade with Auto Bias (Green LEDs)

The Dyna-70 Ultimate upgrade is based on the 6CA7 / EL34 power tube, just like the original ST-70.  If you have a good set of 6CA7 / EL34 tubes in your original ST-70, they will work just fine with the Dyna-70 Ultimate Upgrade kit.

The Dyna-70 Ultimate Upgrade Kit


No Rectifier Tube

Eliminates a weak point in the original ST-70 design, the single heavily loaded 5AR4/GZ34 Rectifier Tube.

Solid-State On-Board Rectifier

Some Audiophiles claim to prefer a tube rectified sound that can “distort” or "sag" when under load (very desirable in a Guitar amp). With high fidelity sound reproduction the last thing you want is sag induced distortion from your amplifier’s power supply. NOTE: Most new tube amps designed today do not use a Rectifier tube.

"Large Stack" PA-060 Transformer

Use of 6SN7 tubes requires a larger power supply transformer, providing a modest power reserve the original "small stack" transformer could not provide. By eliminating the Rectifier tube, we don't use the 5VAC Rectifier filament Power Supply in the PA-060, offering a modest load reduction on the Transformer, allowing it to run cooler.

"Stacked" Power Supply Filter Design

By pairing the Power Supply Capacitors, we provide proper High-voltage power to B+, Output Transformers, etc. while protecting components from 500+ VDC turn-on voltages. We also increased filtering capacitance by 2 - 3X over the stock ST-70 capacitor design.

Additional Features...

o Automatic Bias Control Module (Optional)
o Manual Bias with Individual bias adjustment for each Power Tube (Standard)
o Metal Oxide Resistors in Power Supply Circuits & Carbon Film Resistors in Audio Circuits

Here in the U.S.A. many people used to build electronic kits. HeathKit, Dynaco and even non-traditional kit electronics manufacturers such as McIntosh, Scott and Fisher let anyone assemble great electronic equipment and save money. Additionally, building kits was relaxing, rewarding and educational.

Miller Audio has developed a high performance audio & power supply upgrade for the ST-70, taking a stereo tube amplifier designed in the late 1950’s, and updating it with 21st century design standards and components. With our design, carefully selected components, and your labor, you get both great sound and value.  However, if you are not comfortable, or don’t have time to build a Dyna-70 Ultimate Upgrade Kit, we’ll do it for you.

OR… trade-in your tired, old ST-70 for a new Dyna-70 Ultimate Upgrade ST-70 amplifier – it’s not as expensive as you might think.  Likely your ST-70 has some rust pits & tarnish on the chassis, the Tube Cage needs painting, the transformers are rusty and also need paint, and the tube sockets are likely loose and worn out. This is the perfect time to restore and/or upgrade your ST-70 with a Dyna-70 Ultimate Upgrade, bringing your ST-70 to like-new appearance and having it sound like it has never sounded before.

Kit Assembly

Kit construction has four steps:

  • 1. Downloading & printing the latest version of the Assembly Manual
  • 2. Assembling and soldering the PC board
  • 3. Wiring the Chassis
  • 4. Mounting the new PC board and completing wiring & final assembly
Dyna-70 Ultimate Upgrade Kit

The kit features all through-hole components; the electronic circuits are built on high-quality, etched 2-layer FR-4 Copper faced Printed Circuit Boards with plated through holes for generous solder contact and easy soldering. The circuit boards have been designed with generous spacing between all soldered points, making assembly easy and reducing solder bridges.

We use quality, trusted name brand components from manufacturers such as Nichicon, United ChemCon, Panasonic, Wima, Solen, Audyn and other name brand components. We source our components from Mouser, Digi-Key, Newark and several reputable U.S. suppliers; you can trust all components are genuine and not counterfeit parts.

Our Suppliers

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