DYNACO ST-70 Tube Amplifier

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SOLD

we'll have another one ready soon

Assembled, tested and ready to ship now. This Dynaco ST-70 is not your standard "out-of-the-box" build, as you can see. You'll enjoy smooth and warm, highly detailed, physically and emotionally engaging music, in full color. It's a sound signature you can only get with pure analog tube amplified audio. This amp sounds amazing, and at 70 watts (35WPC) it can easily drive most modern or vintage speakers. Being the greatest selling stereo amplifier of all time (380,000 + sold), the ST-70 has proven itself beyond question, but, they never offered one quite like this.


Photos shown in this listing are of the actual amplifier being offered.

This is a brand new build with 100% brand new parts, assembled, tested and it's ready to ship now.

The Dynaco ST-70 is the quintessential "must have" tube amplifier - this one's on a much higher level. A true dichotomy of sophistication and simplicity, acting together to create a harmonious musical experience far above expectation. It's like a sonic spa.

This classic amp sounds absolutely stunning, powerful and clear with holographic realism. It will also be a beautiful centerpiece for your audio system. This amp literally puts you right at the performance, enjoy the front row seats, drinks are on the house.

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. The Dynaco 70 is, and was always very good, but was subject to being poorly assembled by inexperienced builders, many years ago. These countless "bad" examples turn up for sale in various places and unwary buyers then voice opinions of the Dynaco 70 based on units that not only desperately need service, but were possibly never quite right from the beginning. Even the factory wired models offer little advantage, other than they were likely wired correctly, when they were first sold. After 50 plus years of use, abuse and long term storage, those worn and aged components cannot provide enjoyable or reliable operation. 

I have always found the stock circuit to be the best, they didn't sell over 350,000 of these because they sounded mediocre. Consider this, if you will. If any of the past or previous modified or alternative circuits were really better, wouldn't those have then, or currently dominate the market? Imitation is the highest form of flattery, but when you install a VTA (tubes 4 hifi), Curcio Audio, Triode Electronics or any other driver board or circuit, the amplifier is no longer a Dynaco. Mate this original circuit amp with a quality preamp and some high efficiency speakers and you will be amazed. At 35 watts per channel, it will effortlessly drive even large speakers, with clarity, to levels far beyond what most folks would consider comfortable.

Want to hear what actual owners have to say? Click here to read some of their reviews.

Powered by a massive "made in USA" Dynakit PA-060 (current production) power transformer, which is wound and designed for 120 volt operation. This current production Dynakit transformer does not require a step down transformer. It is designed to operate on today's higher voltages. These new Dynakit transformers were reverse engineered from the original designs using modern technologies, materials and superior insulations. The increased lamination stack allows it to run cooler and provide better regulation. These are super high quality transformers that meet and exceed every aspect of the originals. Modern advancements in materials, combined with traditional methods and better technologies used in their production results in absolutely an superb transformer that produces improved sonics and provides cleaner power. The power transformer is mounted on isolation bushings to stop mechanical vibrations from reaching the chassis.

The new ,current production, Dynakit A470 output transformers are also greatly improved, and made in the USA, like the power transformer. These modern 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 match or exceed the frequency ranges of the originals. These transformers are in one word, exceptional.

I only use genuine USA made Dynakit C-354 filter chokes. These new production chokes are fully encased in a metal housing for excellent shielding and won't leak and goop up your chassis like other brands will.

Output impedance options are 4Ω, 8Ω or 16Ω ohms

The output terminals are standard screw down strips. Photos show the optional Spade Terminal to Banana Plug / Binding Post Adapters installed. Four of these handy and useful adapters are included in this sale.

The Stereo / Mono switch is fully functional, as intended.

The filter capacitor is hand polished to a nice shine, it is a Dynakit 30/20/20/20uF quad cap, rated for 525 volts.

The circuit board is a new production OEM Dynakit board that uses the original Dynaco 6GH8A circuit. Alternative tubes 6U8A and 6EA8 can also be used. 

The Micalex tube sockets on the circuit board are from Belton. 

The resistors are comprised of Allen Bradley and Kamaya carbon composition type. Simply the best type of resistor for retaining the even order harmonics that help give tube audio its rich and lifelike signature sound.

The coupling capacitors are copper foil sealed in oil type from V-Cap (.1uF @ 630 volts). The bypass caps are from MOD, polyester film sealed in oil (.047uF 630 Volts). These "wet" caps have a silky smooth, vast and expressive tone quality and will never dry out.

There are also 2 silver mica (390pF @ 1000V) and 2 polystyrene caps (82pf @ 630V). 

The bias supply is our specially designed upgrade which puts a PCB in place of the old 7 lug terminal strip. This is the exact same circuit, just re-designed for using modern components to provide a quieter and more stable operation. 

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

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

Safety diodes are installed on the rectifier tube socket. The bias pots have safety resistors installed.

An "anti click" capacitor is installed on the power switch for a pop/thump free power on and off.

The gleaming trophy quality chassis is from Dynakit made with mirror polished stainless steel (non magnetic), it is just a work of art.

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 and enjoy listening to, it sounds fantastic. It's a real eye catcher that also performs beyond expectation.

Sale includes the following tubes:

Before using the amplifier, you will need to check and adjust the bias, just to be on the safe side. You will need a voltmeter capable of reading DC Volts / DC Millivolts. Full instructions with diagrams are 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. You should check the bias periodically, about every 80 to 100 hours of use.

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

Shipped nested inside two boxes and insured for full value - signature required*

Not quite what you were looking for? Want something special? We can build it your way, click here to explore this option.

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