Dyna 70 Upgrade (DIY kit)

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  • Regular price $449.00


The AVA enhanced pure vacuum tube amplifier for your original Dyna ST-70 chassis.

Over the years, we have received may requests asking for service and upgrade help with the long-out-of-production Dynaco ST-70 vacuum tube power amplifier. The Ultimate 70 is a AVA circuit set for the Dyna ST-70 chassis that goes far beyond the original Dynaco design.

The audio circuit has been carefully engineered for the widest controlled bandwidth and stability under all conditions. We think you will love the Ultimate 70 as it is just simply lovely sounding. It takes every last bit of grain away from your records and CDs, but takes nothing else away at all. The highs just float. Transparency, detail, definition, range, and dynamics are wonderful. It's got a mid range to die for and bass extension and control you would not believe possible at this power and price. The sound stage is huge, the depth is pure reality, and the emotion of the music is all there, like you have never heard before.

Rebuild kit

This rebuild kit allows a kit builder to enjoy the Ultimate 70 at a lower cost. This moderate skill level kit is ideal for those who still enjoy the satisfaction of building electronics. With the do-it-yourself rebuild kit, the AVA input-output jack set, new output tubes, and new rectifier tube available as extra-cost options.

You need a wired and working Dyna ST-70 to start with, complete with functioning transformers, rectifier tube, and output tubes. We provide you with two new 6GH8A tubes to replace the original 7199 tubes. Replacement output and rectifier tubes are available as an option in the event that you don’t have the tubes or are not sure about the quality of the tubes.

The kit rebuild replaces the entire Dynaco supplied audio circuit, quad filter capacitor, and bias supply. Most old problems will be thrown away along with the old circuits. Instructions for bias adjustments and basic troubleshooting are included in the manual. All the parts are through hole (no surface mount parts), and the PC card is solder masked and silk-screened on both sides to make it easy to build.

An optional AVA input-output jack set provides heavy duty 5-way binding posts for your speaker connections and new gold plated input jacks that are spaced further apart than the originals, allowing modern cable ends to fit better.

Rebuild kit plans

If you would like to build the Ultimate 70 rebuild kit but are not sure of what is involved, we will provide the construction plans free of charge via a PDF file upon request. The plan includes parts lists, wiring layouts, step-by-step instructions, and all of the general advice and wiring guidelines. You can learn what tools and skills are required, the complexity of the project, and the thoroughness of our guidance.

Rebuild kit PC boards

And If you are a real do-it-yourselfer, you can purchase just our bare PC Ultimate 70 bare circuit board with the plans and furnish all of your own parts.

The Dyna 70 Upgrade is also available as a factory rebuild.