DYNACO STEREO 70 (ST-70) Tube Amplifier


SEE HOW TO BUY ONE where can I buy a new Dynaco or Dynakit Tube Amplifier. Get a new tube amp here. Factory wired

$1,299.00 + $130.00 Shipping


The greatest selling amplifier of all time. This is the special order ST-70. The base price shown is without upgrades, options or tubes.  

These ST-70 Amplifiers have a 3-4 week production period, as each unit is specially built, customized to your liking. It takes some time to order and receive the components, and of course time for building and testing the unit. There will usually be a few orders to complete before I get to your build anyway. The component varieties, brands and features I offer are proven top performers. You can "pick and choose" with confidence and I will build you a great sounding ST-70 ampIf you need one now, please check to see if one is "ready-to-ship".

The photos shown are of previous units, to provide visual examples. Generally speaking, most units look very similar when completed, but your specific unit will have all the special features you have chosen.  

A Special Dynakit ST-70 One-Off Retro Audiophile Build

STANDARD BUILD FEATURES:


OPTIONS & TUBES

ST-70 TUBES (tubes not included)

The ST-70 amplifier uses the tubes listed below

You are not required to purchase tubes with the amplifier. Your amplifier will still be fully tested, but it will ship without tubes, unless you purchase tubes with it. If you want to order tubes with your ST-70 amplifier, view the ST-70 tubes page.


SHOP FOR TUBES FOR THE ST-70

OPTIONS / UPGRADES

The standard build includes 1% metal film resistors. We offer several options for upgrading to better resistors. The resistors are very important to the sound quality, as well as contributing to the reliable operation of the amplifier. Upgrading to carbon film and carbon composition type resistors will make the amplifier sound its best, since they contribute to the "warmth" and allow passage of even order harmonics. Even order harmonics fit into the western musical scale and are more pleasing to the ear.

The standard build includes CDE 940 series capacitors. We offer several options for upgrading the capacitors for your ST-70 amplifier build. The capacitors are critically important to the sound quality, as well as contributing to the reliable operation and overall the appearance of the amplifier. Although the standard CDE 940 caps sound great, they cannot compete with the Amtrans or V-Cap capacitors. 

There are several options available for upgrading the tubes sockets for the driver tubes on the PCB.

The standard build includes the standard screw terminals, these give use all three of the 4Ω, 8Ω and 16Ω (Ohm) terminals. The amp can be upgraded with barrier block terminals. I offer spade screw terminal to banana plug / binding post adapters to make things neat and easy. This allows you to keep all three of the 4Ω, 8Ω and 16Ω (Ohm) terminals, but with an easier way to attach speaker leads.

The stereo to mono switch is optional. If you want the stereo  / mono switch included, see the ST-70 options page and request this option with your order.

The amplifier uses the original bias circuit and bias set adjustment pots. 

See the Upgrades and Options for the ST-70

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

about the ST-70

The circuit board I use is a new OEM Dynakit board. This board uses the original 6GH8A circuit developed by Dynaco in response to the 7199 tube going out of production entirely back in 2007. Alternative tubes 6U8A and 6EA8 can also be used with this board. These tubes are equivalent to a 7199 but have a different pinout. The 6GH8A revision was a simple matter of rerouting a few traces to accommodate the different pin arrangement of the 6GH8A tube. 

I have always found the stock circuit to be the best sounding. They didn't sell over 350,000 of these because they sounded mediocre, this is a rather conspicuous fact. 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. Be aware, when you install a VTA (tubes 4 hifi), Curcio Audio, Triode Electronics or any other driver circuit, the amplifier is no longer a Dynaco.

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. A great deal of research and engineering went into making these new transformers match or exceed every aspect of the originals.

I only use genuine 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 the old design could. The C-354 is varnish dipped for moisture resistance, improved electrical insulation and reduced vibration.

The filter capacitor is a 30/20/20/20uF 525V rated part by Dynakit. It's made in USA, hand polished to improve appearance.

I use a custom designed PCB style bias supply which uses Nichicon or Kemet 100uF / 100V electrolytic caps, audio grade film capacitors and metal film resistors for super quiet, stable and reliable operation. This uses the original bias circuit but the PCB allows for the neat installation of better performing, modern  components.

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

Carefully and expertly wired by hand using only Kester 63/37 eutectic solder for superb connections. 600V rated 22 AWG stranded wire throughout.

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

An "anti click" capacitor is installed on the 6 amp rated power switch to provide a thump / pop free power on and off.

The beautiful "trophy quality" chassis is made with mirror polished stainless steel (non magnetic) and is truly a work of art.

The included cover has a lightly textured finish, in Original Brown or Satin Black.

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

Manuals, biasing instructions and initial set up printouts / diagrams all included. Email and phone support provided if needed. 

Be sure to check out the "ready-to-ship" units, they're assembled, tested and ready to go

ST-70 Dimensions:

ST-70 / V-Cap Tone & MOD capacitors / Carbon Comp resistors



Dynakit ST-70 / Upgraded Resistors & CDE 940 Capacitors (covered)



Dynakit ST-70 / PRP metal film resistors / Mundorf MCap ZN capacitors



Dynaco ST-70 / AMRG Resistors / AMCY capacitors



A One-Off Dynaco ST-70 "Super NOS" Build



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