Dynaco st70 driver boards

Introduced in 1959, the st70 was available as a kit dynakit intended for assembly by the purchaser or as a complete factorywired unit dynaco. Dynaco mark iii poseidon board vs original dynaco 6ana. These boards were wired at the factory, tested and packaged with the unassembled chassis. St70 baseline2 dynaco sca35 st35 tube amplifier upgrade. This is my attempt to document the differences between the original dynaco design of the mark iii amplifier using the 6an8 vs a new design diytube poseidon driver board using a 12ax7 and 12au7 or. I compared it to a scott lk150 in the past before the upgrade the lk150 stock sounded much clearer and more transparent. Our newest version of the ef86 board has been slightly revised to accept 6922, 6dj8, 7308, and 6cg7 in the phase inverter. The original dynakit circuit design is retained throughout and features a modern engineered symmetrical layout constructed from high quality 0. Take your st70 amps from 1960s performance to 2019 performance,it will sound 10x better and run cooler. Mapletree audio design sr70a special red driver module. To save a few bucks, literally, dynaco went with a triodepentode circuit, so that. I already modified the st70 with the sds cap upgrade, so i am no longer using the quad cap, but to install the new vta driver board, im going to need my can cap replacement to be wired in a similar fashion.

The original dynaco driver met these needs with a single pentode gain stage at the input, followed by a simple splitload phase inverter to drive the output stage. He also sellls a 60 watt mk111 version on a single st 70 chassis. A simple led bias meter and supply for the dynaco st70 and. Most of the boards shown here have not been professionally made, but rather ill be custom etching them for you on a oneoff basis. The st70 used four el34 output tubes, one gz345ar4 rectifier tube, two 7199 input driver tubes, two output transformers, one power transformer, and a preassembled printed circuit board pcb containing the driver circuit. This has proven to be more than enough to handle current flow of the vta st70 at any volume level.

Restoration module this is an exact replacement for the original dynaco pc3 board fabricated from milspec materials. Dynaco st70 amp here we have an extra clean original dynaco st70 tube amp, with cloth transformer leads,nos dynaco branded 7199 driver tubes. Lets just say i used the board on a few dynaco s and i was happy with the results as compared to other mod boards and stock boards i tried. The triode usa dynaco st70 boards emulate the simple but highly effective due to the short signal path and single gain stage original dynaco circuit, but with lower hum, noise, distortion, and a wider voltage swing across heavier loads, than a 7199,6gh8,6bl8ecf80, 6u8ecf82 or 6an8 are capable of. One of the most frequent failures in the dynaco st70 is the original quad electrolytic capacitor. Dynaco never gave a parts layout on their pc3 driver board for the st70. Here is my dynaco stereo 70 with curcio audio engineering modified boards that i put together in the early 90s. Mapletree audio design sr70a special red driver module for dynaco st70 installation instructions rev.

I to have many dynaco mods from the top of the line curcio to a welborne labs circuit to a get this puke vanalstine that i had bought used. Unlike the original, all wiring on the sr70a is pointtopoint with connections to the amplifier made to turret terminals. This board uses the 7199 tube which is the original design. Either of these tubes is relatively low cost and readily available. Here at dynakit you will find the right parts to restore, repair or upgrade your original dynaco vacuum tube amplifier. It is on kind loan from a member who bought it used online and repaired it. I needed to replace the quad capacitor, which i did today, and thought id take a photo before i put the cover on. Jun 28, 2016 the first thing i did was to look for a suitable replacement driver board.

Triode usa tube amp kits transformers tubes dynaco. Most were kits and 90% of the ones i have seen were assembled by amateurs that did a terrible job of wiring and soldering. The vta st70 has 464 uf of total capacitance to run the amp. Mark3mark2 upgrade driver board with parts one dynaco mark 3mark 2 upgrade board with parts and instructions. Dynaco upgrades lets talk audio and diy 2channel home. Welcome to canuckaudiomart, a classifieds site for used audio and hifi. It uses the longtailed pair phase splitter in a true differential amplifier configuration. This new 70 reflects the illustrious history of dynaco s involvement with vacuum tube designs as well as the latest advances in vacuum tube technology. I also will entertain doing new designs if i have access to the component in question. I just got a one of the dynaco st70 upgrade driver boards from the vta70 and i was very happy with both the performance and customer services from the folks at vacuum tube audio. Dynaco st70 with vta driver board kit rebuild assembly manual. He sells new kits and turnkey st70s with an updated driver board and power supply, and trannys newly built to original specs, except for the mains tranny which is heavily upgraded.

Previous owner hand upgraded it but could not get it working. Dynaco st70 6gh8 6gh8a ecf82 driver board pcb pc3 kit. Get the best deals on dynaco when you shop the largest online selection at. Dynaco s solidstate kits were different from the popular heathkit products and dynaco s own vacuum tube kits because of their preassembled circuit boards. It was introduced in 1959 and was sold until mid1990. I tried a few different driver boards and my ears told me that using the tubes4hifi vta driver board designed by roy mottram made a big difference in sound quality over what i could get out of these older original dynaco st70s. The layout for both the components and wire connections are clearly identified by either a round or square solder pad on both sides of the board. This driver board came with great quality components, as well as great instructions on how to assemble the kit. Perhaps the most famous and enduring modification to the dynaco st70 was created by roy mottram of vacuum tube audio vta.

A custom dynaco st70 kit diy audio electronics from. In this kit youll get one pcb and one matched pair two tubes of nos 6gh8a. Dynaco st70 with vta driver board kit instruction manual. This dynaco st70 driver board pc3 has been developed and designed to be a dropin replacement for dynaco 7199 board. Overall i am in love with the new sound of my st70. We now have a killer mic preamp project with our new st70 ef86 board. Triode usa tube amp kits transformers tubes dynaco upgrades. The board uses a cascoded 12au7 into a long tailed pair phase inverter. Multiple boards receive discounts and can share a custom etching charge.

They also never listed the parts that were on the driver board in the. Well known as the bestselling tube amp of all time, the iconic dynaco stereo 70 amplifier has been revamped and redesigned in a series 3 model in the relaunched hafler dynaco line, now under the auspices of radial engineering ltd. The original dynaco st70 was sold with a perforated sheet metal cage that covered the transformers, tubes, and the driver board. Here you will find all the boards you need to restore your small dynaco amplifiers, and upgrade them with new power supply boards, which include the popular efb modification that provides greater power output, lower distortion, and extended tube life. The kits that bob latino sells do not include the cage, but you can get them from other dynaco parts suppliers. Tubes4hifi vta70 driver board kit for dynaco st70 ebay. Gillespie designs pc10a replaces the obsolete, increasingly hard to find, and expensive 7199 driver tube with either a 6gh8a or 6u8a. Its not unusual for folks to run these amps without the cage because it looks cool, i guess. Stereo 70 driver board 7199 board replacement modules a. Unlike the st70 which had the driver board separate from the output tube sockets, the st35 has the driver and output circuits on one circuit board.

The vta 70 is unquestionably the best circuit ever put in a dynaco st70 period. I stuffed this one with prp audio resistors and 715p coupling caps. An input signal produced by a test cd or function generator is applied to the amplifier input and the output of the driver board is measured at the output tube grid resistors r4, r5, r10, and r11. No ones heard it yet, so hard to have any opinions. Driver boards for dynaco st70 our newest version of the ef86 board has been slightly revised to accept 6922, 6dj8, 7308, and 6cg7 in the phase inverter. I have done a search and did not come up with anything. I tried a few different driver boards and my ears told me that using the tubes4hifi vta driver board designed by roy mottram made a big. Joe curcio makes great replacement driver boards for the st70, both one with the original 7199 circuit hell sell you an. This upgrade to the original st70 was first introduced in 1988. May 09, 2016 the st70 series 3 marks the introduction of a third generation of vacuum tube products bearing the dynaco name.

The original st70 simply had the driver board exposed to the air not good if someone accidently pours liquid onto your amp like at a party. Dynaco continued to follow david haflers lead by producing simple, reliable, easy to manufacture and assemble electronics with the best usermanuals in the industry. My uncle had the stereo 120, pat4 preamp, fm3 tuner, and a25 loudspeakers. Triodepentode switches to allow the amp to run in two modes of operation 11.

It follows the original wire hole layout, but it was modified to use widely available 6gh8 6gh8a 6kd8 ecf82 tubes instead of the obsolete and hard to find 7199 tubes. Stereo 70 driver board 7199 board replacement modules. There is a single bias control for each pair of tubes which is not optimal. Given that it is 60 years old, one can forgive the rust and dust. Tubes4hifi vta70 driver board for dynaco st70 assembled. An all triode vta driver board made of milspec epoxy fiberglass. In 1969, dynaco became a whollyowned subsidiary of tyco, inc. Worse, direct replacements are both expensive and offer no. The vta 70 is unquestionably the best circuit ever put in a dynaco st70 period whats so nice about the board is the fact you have a separate bias pot for.

Triodeelectronics and sds labs power supply boards are an upgrade for the original aluminum can capacitors. The driver tubes were also relatively new zenith labeled uncarbonized 7199s, of unknown american manufacture. Increases in total amp capacitance over and above the the anemic 90 uf total on the original dynaco st70 do help the original st70 amp play better. Review and measurements of dynaco st 70 audio science.

Also popular are rebuild kits with newly engineered driver boards that one can use to improve an existing st70. Dynaco st70 series 3 advanced classic tube aplifier. Anyone here do any upgrading of their dynaco s themselves using the sds labs cap boards andor the various driver boards available. I had modded an st70 with the triode driver and power supply cap boards. The original st70 used the 7199 tube as the driver. New dynaco st 70 series ii vs original st70 part ii. R20 and r22 are located on the quad cap as in the original circuit. Making the vta and dynaco st70 driver board covers youtube. Theres probably been more written about the dynaco st70 than about any other single piece of hifi gear, and the marketplace is probably have been more full of variations on that circuit than just about anything else on the market over the years from the early audio research amp to the van alstines to the sonic. In addition, we offer an array of new select dynakit classic vacuum tube. Dynaco st70 6gh8 6gh8a ecf82 driver board pcb pc3 kit dyna. Number and unsolder all wires from the driver board. Resistors of 33k or lower need to be at least 1 watt rating and resistors 18k or lower need to be 2 watts.

The dynaco stereo 120 was the first powerful 60 wattschannel transistorized stereo power amplifier in wide production. Forty years of technological progress allows us to bring you lower distortion and greater efficiency, along with protection circuits that make your amp nearly bulletproof. Yes, they are no longer true dynaco amplifiers because the driver board has been changed. This board is a must for any serious restoration of the dynaco stereo70 to full stock condition. The more popular dyna circuit boards are also available though triode electronics. A new updated st70 can be had from bob latino in the states. For a few years after, david hafler remained as an advisor to the company before starting the hafler company in 1977.

Our newest version of the ef86 board has been slightly revised to accept 6922, 6dj8, 7308, and 6cg7 in the phase inverter position as well as 12au7, 12bh7, and ecc99 that were previously supported. The making of the vta amp and dynaco st70 amp driver board covers. Once teh 7199 or the 7247 driver boards aer replaced, they really are no longer a true dunaco amp, but are upgrades, or ven totally new designs, with newer, better circuitry and passive components. While there are many driver boards available for the dynaco st70, most follow the same common formula. Same exact size, parts layout, and hookup connections as the boards above. Dynaco st70 6gh8 6gh8a complete stuffed driver board pc3. Best seller and best performing modification for 30 years now. Recently, i got bitten by the nostalgia bug and picked up a pair of old factorywired dynaco st70s in pretty nice condition. All connections to the board are marked with the original number markings on the top and bottom silkscreen layers. The dyna boards have been professionally made and ill be passing this savings on to you. Of couse we also sell the replacement aluminum can capacitors as well. The driver output circuit boards are separate for left and right. I have recently acquired a dynaco st 70 amp that i plan to pair with a bottlehead foreplay preamp i am going to build. Top vented cover, original textured dark brown color.

Note the location of input and output resistors on the circuit board and. Hard to find parts including dynakit original dropin replacement components typically ship within 24 hours of ordering. Clearly, these are superb tubes to use in a reference dynaco st70. The original may be left in to cover the hole in the chassis. Vta70 driver board bare pcb for dynaco st70 amplifier. This a drop in replacement for the original dynaco st70 pc3 driver board but with modern epoxy fiberglass pcb. Tubes4hifi vta70 driver board for dynaco st70 assembled ebay. The dynaco st70 amps were available in either factory built or in kit form. Limited production black textured covers with black dynaco nos label are now available. Diytube mark iii poseidon driver board driver board designed by shannon parks over at. They are made back in 80s in ei tube factory, under philips licence and with some of genuine philips materials. I initially used kimber coupling caps but have switched to audiocap theta bypassed with the russian ft1 teflon, which is a few steps up. The next major difference between the amps was the driver section.

Search the internet and there are at least 10 different boards available to replace the original. Dec 02, 2006 anyone here do any upgrading of their dynaco s themselves using the sds labs cap boards andor the various driver boards available. The new power supply is infact identical in most respects to the old except in the area of supply decoupling on the driver board, refer to the driver schematic for the values. The amp above shows one of the new driver boards available. Its developed and designed to be drop in replacement and it follows original wire hole layout, but its modified to use widely available 6gh8 6gh8a 6kd8 ecf82 tubes instead of obsolete and hard to find 7199 tubes. A custom dynaco st70 kit id imagine that the venerable dynaco st70 is the most well recognized tube amp in the world. Tubes4hifi vta70 octal driver board for dynaco st70 assembled. Tubes4hifi vta70 driver board bare pcb for dynaco st70. One of these tubes has been replaced, for reasons which will be discussed further in the section on the driver board.