Dynakit Stereo 70 Tube Amplifier (6GH8A version)

Enjoy the rich smooth tones of analog audio and even order harmonics that only vacuum tube amplification can produce. It reveals musical qualities with fantastic realism and depth you may have never imagined possible. This amplifier brings the legendary original design up to date, and then some.

Your favorite music can sound even more beautiful. Choose from standard components or step up to one of our premium component selections designed for audiophile level performance. The ST-70's naturally high impedance (470K) makes it compatible with virtually any solid state or tube preamp.

You simply won't believe that you are listening to a Dynakit, but you'll sure be glad that you are. This is truly an Audiophile Grade Tube Amplifier

It is fairly safe to say that most people today have no idea of just how wonderful a Stereo 70 amplifier is capable of sounding like. Isn't it the great smooth sound and sweet tones produced only from tube amplification what you seek? Like a musical time machine, this amplifier will take you back to when tubes ruled it all. But there's even more to consider here. All of the components used in this amplifier have greatly improved characteristics over the ones available and used 50 years ago. That makes the sound quality of this amp even better than it would have been then, as a new one 50 years ago. Take a good close look. This Stereo 70 offers superb sound, high build quality, safe and reliable operation, great looks.

    ORDERING OPTIONS:

    • Choose from our available tube sets
    • Available with a Bias Balance Control Upgrade by Dynakit

    We can always use your preferred brand of tubes and components, don't hesitate to ask.

         Our Standard Tube Set: 

        • 2 NOS 6GH8A tubes by RCA, GE or a Mullard variant (as per availability), tested and matched. 
        • (4) NessTone EL34/6CA7 tubes, our standard grade output tubes. Hand selected and tested here in the USA and then identically matched by their plate current test results using the ROE computerized testing system. 
          • (1) Groove Tubes 5AR4/GZ34 rectifier tube. 

          The Premium Tube Set:

          • (2) NOS Premium 6GH8A (RCA or G.E. or Mullard Variant) L-2 tested for noise & microphonics, test matched
          • (4) Mullard EL34 New Production - L-2 tested for noise & microphonics, plate current matched
          • (1) Genalex - Gold Lion U77 / GZ34 - L-2 tested 

          An Audiophile Tube Set:

          • (2) NOS Premium Brand or Mil. Spec 6GH8A - L-2 tested for noise & microphonics, test matched
          • (4) GOLD LION KT77 / EL34 - L-2 tested for noise & microphonics, plate current matched by the manufacturer
          • (1) NOS 5AR4/GZ34 - (RCA, Mullard, GE, Amperex, Sylvania, etc., as available)  L-2 tested

           

          Details and Features 

          • Mundorf MCap ZN Capacitors - 600v - 5% - .22uf & .1uf for Improved Bass Response
          • Cornell Dubilier Silvered Mica Dipped Capacitors - 390pf @ 1000v & 82pf @ 500v Rated - 5%
          • PRP Audio Grade Resistors - High Resolution - 500v Rated - 1% Accuracy - Ultra Low Noise 
          • Genuine Dynakit PC-3 "B" Circuit Board - Made Specifically for 6GH8A Driver Tubes
          • Bias Circuit - Upgraded 100uf Capacitors / Flameproof Metal Oxide Resistors
          • Dynakit PA-060 Power Transformer (120v Windings) - No Voltage Reducer Needed - Note the taller Lamination Stack
          • Dynakit A-470 Output Transformers - (4,8,16 Ohm Taps) - Grain Oriented Laminations - Interleave Wound - Made in USA
          • Dynakit C-354 Shielded Power Supply Filter Choke - (1.75 Henries, 62 Ohms, 10%) - Made in USA
          • Brand New High Quality Tube Sockets
          • 600v & 1000v Alpha Wiring Used Throughout the Entire Amp 
          • Genuine Dynakit Multi Section Filter Capacitor - Factory Correct Values 80/40/30/20uf - 525v Rated (an upgraded version is available for an additional cost)
          • New Dynakit Stainless Steel Mirror Finish USA Made Chassis (Non-Magnetic) - Beautiful Museum Quality Look (dimensionally accurate to the original)
          • Dynakit Perforated Steel Cover / Cage - USA Made with a matching badge
          • Flashback Prevention Safety Diodes Installed at the Rectifier Tube
          • Additional shielding on under chassis components to help reduce EMI / interference
          • Careful wire routing to reduce movement & electromagnetic signal interference (EMI)
          • Assembled With Alpha Fry 60/40 rosin core solder - for the Very Best Quality Connections
          • Power Transformer Isolation Bushings - Prevents the Transfer of Mechanical Transformer Hum to the Chassis
          • Silver or Gold Plated RCA Input Jacks - Wider Spacing for Larger Modern Input Cables 
          • Original Screw Style Speaker Output Terminals - Full Function  (4,8,16 Ohm + Common/Ground) (options available for banana plugs for additional cost, ask us about this option)
          • New heavy duty power cord
          • Heavy Duty Rubber Feet with Steel Bushings - 


          Assembled with Great Attention to Detail Using High Quality Parts - 48 hr Minimum Burn in and Thoroughly Auditioned / Actual Listening Tested. Operates From a Standard 120 VAC Wall Outlet - No Voltage Reducer (Variac) Needed - Designed & Built for Today's 120v+ Voltages. 

          6 month limited warranty - see details below

          Arrives With Bias Preset * - Just Install the Tubes - Simple To Do - Instructions are Included (recommended to recheck and reset upon first use due to varying AC currents in different locations)

          Front Preamp Sockets are Wired for Bias Set Only - Reduces Audio Signal Interference (Dynaco PAM or similar preamps that use these sockets will not work with this configuration. Contact use if you intend to use a preamp which require the use of these sockets. Our Dynakit Bias Balance Control Upgrade cannot be installed if the front sockets are configured for preamp power use)

            Vintage Vibe - Modern Reliability - The Beautiful Sound of Tubes

            Okay, so, how does it sound? - “Magical” - this is not your average Dynakit Stereo 70 folks. With our standard components or further enhanced with our premium components this amp is very musical with highly detailed voicing and plenty of solid, clean wonderful bass. This amp is absolutely dead quiet - no hum, no buzz, no hiss. It sounds like it is supposed to, like you want it to. If you're in search of that "golden age of audio" sound combined with “stunning looks”, you've just found it. This ST-70 delivers dramatically improved sonics as the result of being built with technologically advanced components and high-end parts.

            We buy the kits direct from Dynakitparts.com, then add our own upgraded features and components to further elevate the performance of the amplifier. In addition to giving you a beautiful and unique look, you get a truly spectacular sounding amplifier.

            We can always use your preferred brand of components, don't hesitate to ask. We want to help you get it the way you want it. Click Here to Contact Us

             

            This Dynakit Stereo 70 Uses The Genuine Dynakit PC3(B) Circuit Board - Made Specifically For Using 6GH8A Tubes - No Tube Adapters Needed! We use Mundorf Capacitors and PRP Audio Grade Resistors for Superb Sound.
            "I hand build each of these amps like I was going to keep them myself, forever. " - Kenny R.


            The Optional Dynakit Bias Balance Control

            This is an upgrade option, it's an additional secondary bias control circuit that equalizes the bias current between each pair of output tubes. Bias is adjusted as usual first using the original 10k bias pots. Then the balance is adjusted, this is for equalizing the current between each pair of output tubes. These secondary balance adjustments are made using the additional balance pots and adjusters which are installed conveniently behind the front octal sockets. The adjuster is very discreet and is accessible at the center holes of the already existing front octal sockets. Full easy to follow bias setting instructions are included.

             

              1. Set the bias initially using the original bias adjusters

              2. Set the balance using the additional adjusters located in the center of the front sockets

              3. Bias is now set and equally balanced -
              add this bias balance upgrade by using the dropdown menu when ordering your amplifier

               

              The Dynakit Transformers: 

                  Two new Dynakit A470  "ultralinear" output transformers are powered by a massive new Dynakit PA-060 power transformer, these are as good as you can get. These outstanding transformers are new production, made in USA by Dynakit. The PA060 power transformer and two A470 output transformers are wound for modern day voltages, a major factor to consider here. The original (vintage) transformers are inarguably excellent, but they were designed to operate on 117 volts (think 1950's). Today's household AC current is often near 125 volts or even higher, 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 transformers. Alternatively, you can just plug one of those old amps in and proceed to cook the components into oblivion! These modern Dynakit transformers operate cooler, produce less distortion and easily outperform vintage transformers in every category. These are Dynakit transformers, they were reverse engineered from the original designs using modern technologies and superior insulations. The increased lamination stack on this power transformer allows it to run cooler and provide better regulation too. These wont buzz or hum like the originals often do either. These are super high quality USA made transformers that meet and exceed every aspect of the originals. There's more......if there were some sort of "magic" in cloth covered leads, Dynakit would have certainly insisted on using them. The truth is, there's simply no magic in cloth covered lead wire, period, it is simply inferior. This is not a guitar amplifier, this is Hi-Fi folks, in 2021! In any comparison, these new transformers are better than those old originals, no offense intended. Modern advancements in materials, combined with traditional methods and better technologies used in the production of these transformers has resulted in absolutely superb transformers that produce improved sonics because of their cleaner power. They operate quieter and run cooler than the originals too. They provide less distortion and increased reliability, they're just better. Like I said before, this is not a 50 year old amp and is not pretending to be one. This is a modern amp based on a very successful 50+ year old proven design.
              -
                  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 simply 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.
              -

              Great job, well done Kevin! (Kevin DeVaney is the owner of Dynakitparts.com)

               

               The 6GH8A Tube:

              The 6GH8A like the 7199 tube is a vacuum tube combining both a pentode and triode in a single glass envelope. Each section has a separate cathode and is electrically independent, the pentode is used for the input stage, and the triode as a phase inverter. Using the updated Dynakit PC-3 board made for 6GH8A tubes, this tube can now be used with exceptional results. Amplifier makers like HH Scott, Harman Kardon and Eico, among others, have used the 6GH8A since back in the late 50's.

              "I find no audible difference in the 7199 and the 6GH8A so long as both tubes are of equal quality. Good quality tubes are essential for the overall sound quality simply because they are a part of the circuit, the circuit can only sound as good as it's parts will allow. Good circuit design is critical, the Dynaco circuit is genius." - Kenny R.

              The 6GH8A, also no longer in production, appears to be in abundant supply and very affordable. Like all tubes, some brands and build styles offer both sonic and reliability advantages over cheaper, inferior made tubes. This amp comes with 2 NOS RCA, GE or a Mullard variant (as per availability) 6GH8A tubes, tested and matched.

              So, are you still thinking using 6GH8A tubes is questionable?

              View this scan of an original Dynaco Series 2 Tube Amplifier manual, these amps came direct from Dynaco with 6GH8A tubes! A great Read and full of information.

              Here is a quick look at an important excerpt from that Dynaco document: "The original ST-70's single tube (7199) is out of production and unavailable. The ST70II uses, instead, the 6GH8A. Since this tube has been extensively used in high frequency applications, availability is excellent. It works exceptionally well in this application, yielding better consistency and lower distortion. (TECHNICAL NOTE: Though most tube manuals do not list a spec for the 6GH8A, extensive testing by Dynaco of large numbers of 6GH8A tubes has revealed noise floors that are, on average, lower than modern production 7199's. The 6GH8A is NOT a drop-in replacement for the 7199 tube as pinout for the two tubes is different. Do not attempt to interchange them. The printed circuit board material......................." (read more)

              This Dynakit Stereo 70 Uses The Genuine Dynakit PC3(B) Circuit Board - Made Specifically For Using 6GH8A Tubes - No Tube Adapter Needed!

               

              Included with your shipment: 

              Warranty Information Documents (printed on paper)

              The manuals, instructions, pictorials, diagrams, schematics and supplemental documentation are all included on a CD-ROM.

              Each unit is custom, a hand built, made to order unit. Your unit will look identical but wire color and routing may be slightly different from unit to unit, these are hand built custom units. Turnaround time is 3 weeks or less. (most of the time is simply awaiting parts arrival and shipping/travel time). Once purchased, you will be kept informed of your orders progress with occasional email messages direct from funtastic vintronics.com. We want you to know things are under way and going as planned. Prepayment in full is required and includes shipping. The price is comprehensive, meaning no additional fees or surprise charges will occur.  Shipping price also includes shipping insurance for full value. Straightforward simple business here. 

              Unpacking your shipment:

              Tubes, fuse and Fuse cap are removed for shipment - numbered and boxed, all packed carefully for secure shipping Tube installation instructions with a numbered easy to follow pictorial included.

               *bias will be pre-set but due to variations in AC wall voltages the bias should be checked and adjusted for your location before using the amplifier. 

               

              This item is covered by a warranty:

              warranty is limited - warranty is for 6 months from the date of purchase, warranty coverage is offered the original purchaser only. Proof of purchase is required to file for an RMA.

              RMA is for warranty work only, it is not for a refund. Issues from abuse, misuse, neglect or external damages are not covered. Signs of tampering or repairs by anyone other than funtastic vintronics voids all warranty coverage.

              Damage from moisture of any kind, electrical surges, lightning and static electricity are not covered. Coverage is limited to replacement of any original components which have failed under normal operating conditions. Faulty components will be replaced with no charge to you for parts or labor. Vacuum tubes/valves are not covered by warranty. Damage caused by faulty tubes is not covered by warranty.

              Shipping both ways is the responsibility of the original owner/purchaser of the unit. You must request an RMA number prior to making any warranty claim. Your RMA must be approved prior to shipping. Please follow appropriate packing methods to prevent shipping / transportation damage. We strongly suggest insuring your shipment for the replacement value of the item being shipped.