Dynaco ST-70 Amplifier - special audiophile build (PCX)
Dynaco ST-70 Amplifier - special audiophile build (PCX)
Dynaco ST-70 Amplifier - special audiophile build (PCX)
Dynaco ST-70 Amplifier - special audiophile build (PCX)
Dynaco ST-70 Amplifier - special audiophile build (PCX)
Dynaco ST-70 Amplifier - special audiophile build (PCX)
Dynaco ST-70 Amplifier - special audiophile build (PCX)
Dynaco ST-70 Amplifier - special audiophile build (PCX)
Dynaco ST-70 Amplifier - special audiophile build (PCX)
Dynaco ST-70 Amplifier - special audiophile build (PCX)
Dynaco ST-70 Amplifier - special audiophile build (PCX)
Dynaco ST-70 Amplifier - special audiophile build (PCX)
Dynaco ST-70 Amplifier - special audiophile build (PCX)
Dynaco ST-70 Amplifier - special audiophile build (PCX)
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Dynaco ST-70 Amplifier - special audiophile build (PCX)

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Brand New Dynaco ST-70 Amplifier

SOLD

Contact us to discuss details, payment / ordering options and pricing.

This and other models of the 70 series amps are available and are built to order. Turnaround time is approximately 30 days from order date.

Dynaco ST-70 / Dynakit Stereo 70 Tube Amplifier customized "audiophile grade" build
Includes premium tubes and the black protective metal cage/cover.

This "muscled up" amp sounds absolutely stunning, it's dead quiet and crystal clear, it will be a beautiful centerpiece for your audio system.

The classic push-pull design of the ST-70 is a proven success. If you have not had the pleasure to hear a Dynaco 70 built right, with all new high quality components, then you simply cannot hold a fair opinion of the capabilities and enjoyable listening experience this amp offers. By virtue of the advancements in technologies, the modern components are considerably better than those which were available back when these amps were wildly popular in the 60's and 70's. The Dynaco 70 is, and was always very good but was often subject to being poorly assembled by inexperienced builders. These countless "bad" examples turn up for sale in various places and unwary buyers form and voice opinions of the Dynaco 70 based on units that not only need service but were probably never quite right from the beginning. Even the factory wired models offer no serious advantage other than they were likely wired correctly, when they were first sold. The components on the factory wired units were the same, good for the time, but
not so great by modern standards. After 50 plus years of use and long term storage, those aged components cannot provide reliable and accurate operation. The capabilities and performance of today's modern components brings out the true sonic genius of this legendary amp and kicks it up to a different level. Pair this amp with a quality preamp and some high efficiency 4 or 8 ohm speakers and you'll be amazed. At 35 watts per channel, it will effortlessly drive even large speakers to levels beyond what most consider comfortable.

Powered by its massive "made in USA" Dynakit PA-060 power transformer, which is wound and designed for 120 volt operation, there is an important factor to consider. Those original (vintage) Dynaco PA060 power transformers are considered most excellent, but remember, those were designed to operate on 115-117 volts (think 1950's). Today's household AC current is often near 125 volts, so the use of a "step down" or "bucking" transformer is necessary to reduce the voltage down to a safe operating level for any vintage amp having its original transformer. Simply plugging one of those old amps into a wall socket with today's higher voltage will cook the associated components into oblivion! Voltages increase exponentially once they reach the transformer and the relative components are not capable of sustaining this increase. (simply adjusting to a lower bias setting on an old 117V amp does NOT solve the problem). The modern Dynakit transformers on this amp do not require a step down transformer, they are designed to operate on higher voltages, they run cooler, produce less distortion and easily outperform vintage transformers in every category. These new Dynakit transformers were reverse engineered from the original designs using modern technologies and superior insulations. The increased lamination stack allows them to run cooler and provide better regulation. These are super high quality transformers that meet and exceed every aspect of the originals. In any comparison, these new transformers are better than those old originals. Modern advancements in materials, combined with traditional methods and better technologies used in their production has resulted in absolutely superb transformers that produce improved sonics and provide cleaner power. Again, they operate quieter and run cooler than the originals, they provide less distortion and increased reliability, they're just better. The power transformer is mounted on isolation bushings to stop mechanical vibrations from reaching the chassis.

The new A470 output transformers are also greatly improved, like the power transformer. These modern version
output transformers are interleaved/layer-wound and incorporate the high quality M-6 grain oriented laminations like the original design, because that is a good design. These use better quality wire with better insulation, the primary is wound the same as the original A470 using the same number of turns on the same number of sections. These are made using the same patented Dynaco winding method, and made on the same core size and material type as the originals. These transformers are in one word, exceptional.

Output is set up for using 4, 8 and/or 16 ohm speakers.

The Stereo / Mono switch is fully functional as intended.

The filter capacitor is a standard Dynakit 30/20/20/20 rated for 525 volts.

The circuit board is a new OEM Dynakit board. This board uses the original Dynaco 6GH8A circuit. Alternative tubes 6U8A and 6EA8 can also be used. The tube sockets on the circuit board are NOS parts from Cinch. The resistors are comprised of KOA & Amtrans AMRG Carbon Films, Riken & Kamaya Carbon Compositions. Ohmite High Voltage Epoxy Molded, Metal Glaze-Metal Oxide Power Resistors ranging in tolerances from 1% up to 5%.

The Aluminium foil paper in oil capacitors are "Golden Black" AMCY series by Amtrans (Japan) (.1uF @ 6300 volts & .047uF 630 Volts) There's 4 silver mica (82pF @ 500V & 390pF @ 1000V). The two 100uF electrolytic capacitors on the bias supply are from F&T (Germany), the two 10K resistors are by Amtrans / AMRG, the two .02uF film caps are JB brand. Translated into English, this amp sounds fantastic and performs beyond expectation.

The RCA inputs are gold plated for improved contact and corrosion resistance, the inputs are spaced slightly wider
apart, making more room for today's larger connectors.

Carefully and expertly wired by hand using only Kester 63/37 eutectic solder for superb connections. 20 AWG, 22 AWG and 18 AWG stranded and solid core wire throughout.

Safety diodes are installed on the rectifier tube socket for added protection.

An "anti click" capacitor is installed on the power switch.

The gleaming trophy quality chassis is from Dynakit made with mirror polished stainless steel (non magnetic) and it is just a work of art. Custom chrome knobs are installed on the bias pots. (NO, those are NOT volume controls)

The amp sits proudly on 4 oversized rubber feet for improved chassis ventilation and has a great looking stance.

This is a high quality, custom built, hand assembled amplifier you'll be proud to own, enjoy listening to, and never
have to make an excuse for.

  • (4) EL34 / 6CA7 Power Tubes (testing at 90% each)
  • (1)  GZ34 / 5AR4 Rectifier Tube
  • (2) 6GH8A / 6U8A driver tubes


Bias is recommended set at 1.56 VDC using 120-125 Volts of AC. Before using the amplifier, you will need to check and adjust the bias due to variances in AC power from my location to yours. You will need a voltmeter capable of reading DC Volts / DC Millivolts. Full instruction with diagrams are of course included. This is a very simple and straightforward procedure and part of owning virtually any tube amplifier. AC voltage can actually vary from outlet to outlet so set the bias using the outlet you intend on operating the unit on / from. Anytime you relocate the amplifier or change tubes you need to check the bias and adjust it for a correct setting. Failure to keep bias set properly can result in tube failures.

Manuals, instructions, diagrams are all printed and included. Email and phone support is provided as needed.

  • 1 year warranty on the transformers, 6 month warranty on everything else (excluding tubes) Warranty information can be viewed here
  • Manuals, instructions, diagrams are all printed and included. Email and phone support is provided as needed.
  • Contact information will be provided with the manuals and paperwork associated with each unit.
  • No other items or cables seen in the listing are included unless specifically stated.
  • You get both the amplifier pictured and the preamplifier pictured - all tubes pictured are also included
  • Shipped nested inside two boxes and insured for full value - signature required*
  • Properly packed - Promptly Shipped - FedEx Only
  • No P.O. Box delivery


*All insured shipments require a signature at time of delivery.
If you cannot be home or have someone there to sign for your shipment please contact me first for delayed or alternative shipping options. Delivery changes are not possible once shipped.

Inspect your delivery immediately, damage reports must be made within 24 hours to file a damage claim or damage return. Thoroughly document (use both photographs and written observations/comments) damages and save ALL of the packaging. Failure to comply, may and usually, results in denial of a claim.