Dynaco st-70 vta octal driver board

Efforts were also made to make the amp more reliable than the original amp. It uses octal tubes, which are right in line with the lovely classic sound of the dynaco. The series ii had a nice metal plate covering the driver board. Dynaco dynakit st70 vacuum tube stereo amplifier vta st 70 octal driver board. The older st70 design had one bias control for each channel whereas the vta board has a separate bias control for each of the four output tubes. Tubes4hifi vta st70 35 wpc stereo tube amplifier kit. In fact, there are tens of thousands of the original dynaco tube amplifiers still in use around the world. The red jacks on the front were added to make it easier to use your meter probes.

Including our custom made transformers, which are made to original specs right here in the usa. Bolt the new populated circuit board into the chassis. The making of the vta amp and dynaco st70 amp driver board covers. 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. Triode usa dynaco st70 tube diy amp kit triode electronics. For those that need a little more power is the dynaco vta st120. Dynaco was a bit a head of some of the other kit builders from that era as their kits had less construction required using preassembled circuit boards, which the builder had to do less wiring to make the amps run the first time verses some of the other kit builders which involved a complete point to point wiring.

Dynaco dynakit stereo 70 instructions for assembly pdf download. In a vta st70st120 tube amp kit, the vtatdb replaces the 3 lug terminal strip. An 80, 40, 30, 20 uf main power supply electrolytic cap. The upgraded vta driver board uses three 12au7 or 12bh7 or 6189 or 5963 or 5814 triodes in place of the two. If im reading the schematic correctly, they act as the current sources for the v1 and v3 of the driver board, and are out of the signal path. Dynaco mkiii mods diy canuck audio mart hifi and audio. This board shouldnt be doing to the amp what it is doing. Rca blackplate nos 12au7 driver tubes in vta70 driver board. The layout was changed to use the contemporary components and 6gh8a tubes. Vta tube amp kits those are 6sn7 octal driver tubes.

Dynaco st70 with vta driver board kit instruction manual. This design allows for individual adjustment of each output tube bias. The older st 70 design had one bias control for each channel whereas the vta board has a separate bias control for each of the four output tubes. All parts needed for a complete upgraded dynaco st 70 type kit except for the tubes. Antique radio forums view topic basket case dynaco st70. Dynaco upgrades lets talk audio and diy 2channel home. Sds labs and triodeelectronics power supply boards. If the dynaco st70 is great, then the heathkits are world class. Pa060s power transformer nearly twice the lamination stack size of the original, a470s output transformers. The total capacitance on the original dynaco st 70 amp was 90 uf. C11 replacement 15 pages amplifier dynaco stereo 80 owners manual. Vta st120 with ccs driver board amp kit assembly manual. A simple led bias meter and supply for the dynaco st70 and.

Dynaco shows a short black wire to the nearest 6550 tube socket for ground. There are biasing instructions in the user manual for each output tube mentioned. Up for buy it now is the dynaco vta stereo 70 in kit form using all new parts. As well as our upgraded dynaco st70 heavy duty stainless steel chassis, triode usa dynaco st70 driver board ef86 or 6au6 model, or no driver. Dynaco dynakit st70 vacuum tube stereo amplifier vtast70. Note the location of input and output resistors on the circuit board and unsolder. In addition, we offer an array of new select dynakit classic vacuum tube. Here at dynakit you will find the right parts to restore, repair or upgrade your original dynaco vacuum tube amplifier. Over 300,000 of the st70s were produced, and more continue to be built as kits from companies like tubes4hifi and triode electronics. Recently, i got bitten by the nostalgia bug and picked up a pair of old factorywired dynaco st70s in pretty nice condition. Bob latino st70 kit project audiokarma home audio stereo. If the dynaco st 70 is great, then the heathkits are world class. Output tube changes the original triode electronics board design manual included modifications to this board and to the amplifier to allow using other output tubes in a st70. I was searching for dynaco amps on audiogon and came across an ad for new dynaco st70 kits.

Vta tube amp kits sturbridge, massachusetts facebook. Dynaco mkiii mods diy canuck audio mart hifi and audio forum. The driver tubes were also relatively new zenith labeled uncarbonized 7199s, of unknown american manufacture. The 7 octal tube sockets are high quality celanex sockets.

There are no recycled parts from an original dynaco st 70. Its likely that i mixed something up on the triode driver board. I traced the circuits on both to figure out which resistor goes where, but still may have goofed somewhere. You might want to consider the vta driver board from tubes4hifi. The total capacitance on the original dynaco st70 amp was 90 uf. 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. The vtatdr may also be easily retrofitted to any vta st70st120 tube amp kit. This board also contains an on board bias supply for the output tubes.

The tubes4hifi recreates the chassis exactly as it was aside. Very happy with the vta driver board noval version. Triode, usa customer service mf 9am4pm ct 18007743201 email us anytime. Tube stereo octal relay a stepped interface amplifier vta driver circuit board driver circuit board rc a stepped interface dynaco stereo amplifier telemotive e5507 circuit board octal relay driver circuit vero octal relay driver circuit board rc dynakit st70 st 70 interface dynaco. Dynaco saved money using a two tube 7199 board design but made some serious compromises in sound quality. There are no recycled parts from an original dynaco st70. The driver board is covered by one of our vta driver board covers which. In the original build manual they do instruct the builder to twist each of the four tabs on the can. 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.

Simply remove the old bias pots and install the switches in the empty 38 holes. Depending on condition consider replacing the octal sockets for the rectifier, and output tubes. Improving signal to noise ratio on the dynaco mark iii. This a drop in replacement for the original dynaco st70 pc3 driver board but with modern epoxy fiberglass pcb.

Nov 30, 2012 the c24x choke in the vta st 70 is rated at 240 milliamps and runs cooler. Clearly, these are superb tubes to use in a reference dynaco st 70. In a stock st70 the board replaces lugs 5, 6 and 7 of the 7 lug terminal strip. Comments are closed, but you can leave a trackback. Dec 02, 2006 i have the vta mod dynaco st70, and a freind of mine has the mk3s also vta, as far as i am concerned it is the best dynaco upgrade ever, and it doesnt take a rocket scientist to install. Triodepentode kit as used on the vta st70 pictured above. In a stock st 70 the board replaces lugs 5, 6 and 7 of the 7 lug terminal strip. Tubes4hifi vta st70 35 wpc stereo tube amplifier kit usa. The original st 70 used the 7199 tube as the driver. Making the vta and dynaco st70 driver board covers youtube. This phenolic material was not very heat resistant and the board would many times turn black from heat under the.

The st 70 represents a very desirable package for the modifier as it lends itself to a large number of modifications from the most simple to the most complex, witness the ar st 70 c3 that graced the pages of the audio amateur about 20 years ago. I ordered the boards and components as a kit and sourced the coupling capacitors from mouser. As well as our upgraded dynaco st70 heavy duty stainless steel chassis, triode usa dynaco st70 driver board ef86 or 6au6 model, or no driver board, and our triode usa dynaco st70 upgraded capacitor board. The c24x choke in the vta st70 is rated at 240 milliamps and runs cooler. This phenolic material was not very heat resistant and the board would many times turn black from heat under the 7199 tube sockets. Also, if youre trying to go 100% sand free, then you cant use the vta board on your st 70. On the other hand, i would strongly recommend a power supply upgrade at the same time you do an input board. Replacement power supply rev e hardware 18 pages amplifier dynaco sca80 assembly manual. I have the vta mod dynaco st70, and a freind of mine has the mk3s also vta, as far as i am concerned it is the best dynaco upgrade ever, and it doesnt take a rocket scientist to install. I have never worked on a dynaco mark iii or any dynaco tube amp using octal driver tubes and never listened to one with a octal driver tube so i have no opinion on how it sounds. Follow any comments here with the rss feed for this post. Kathys estate sales since the early 1970s providing clients with the highest level of service available throughout the portland metropolitan area eurotubes we are into tubes.

After a few emails with bob, i ordered one of his st70 kits with all the upgrades. The next major difference between the amps was the driver section. Pa125m power transformer 1 a125m output transformer 5 celanex octal tube sockets 4 ground lugs 1 550 volt rated quad cap 2 c24x chokes 1 scm supplementary cap module 1 set of esl. They sounded smooth and a bit flatter then the tubes4hifi st70, which sounded crisper and the way i would describe it as a faster amp. Vta driver board kit rebuild pages amplifier dynaco pat5 assembly manual. Dynaco st70 help talkin tubes the klipsch audio community. Now you can build your own st70 on a new type 304 stainless steel chassis frame with. Dynaco st70 6gh8 6gh8a ecf82 driver board pcb pc3 kit dyna. The upgraded vta driver board uses three new 12au7 or 12bh7 triodes in place of the two mediocre sounding 7199 pentodetriode tubes. This unit was ultimately upgraded by me using roy mottrams vta octal driver assembled board.

Tubes4hifi vta70 driver board for dynaco st70 assembled. Id imagine that the venerable dynaco st70 is the most well recognized tube amp in the world. The triode board can use any common tubes, and i think that is what makes it a good design. Tubes4hifi vta70 octal driver board for dynaco st70 assembled. The original st 70 simply had the driver board exposed to the air not good if someone accidently pours liquid onto your amp like at a party. This a drop in replacement for the original dynaco st 70 pc3 driver board but with modern epoxy fiberglass pcb. Tubes4hifi vta70 driver board for dynaco st70 assembled ebay. Dynaco st70 power supply board the board replaces the large multi section electrolytic capacitor and the bias supply circuitry in dynaco st70 amplifier. An all triode vta driver board made of milspec epoxy fiberglass. Legendary dynaco st70 has been relaunched the absolute. Now you can build your own st 70 on a new type 304 om 5934079. Huge assortment of octal driver board and related listings. In a vta st 70 st 120 tube amp kit, the vta tdb replaces the 3 lug terminal strip. I shrunk wrapped the bias wiring and pins on the octal sockets attached to front of the.

Dynaco dynakit st70 vacuum tube stereo amplifier vtast70 octal driver board. This entry was written by admin, posted on may 29, 20 at 3. The vta triple triode board, however, features a better phase splitterinverter design with ccs constant current source. It was introduced in 1959 and was sold until mid1990. Now you can build your own st 70 on a new type 304 stainless steel chassis frame with. New dynakit st70 advice page 3 steve hoffman music forums. Using biaset is a relatively safe way to set the bias on dyna amps with a digital meter, and some of the latest production dyna boards offer. In a vta st70 st120 tube amp kit, the vtatdb replaces the 3 lug terminal strip.

New dynaco st 70 series ii vs original st70 part ii. The original dynaco stereo 70 is a true classic that is still regarded with awe by audio enthusiasts worldwide. Hopefully under the chassis is a capacitor board and maybe a bigger choke. This is the new octal version that uses 6sn7 tubes, and has a. This is the new octal version that uses 6sn7 tubes, and has a ccs constantcurrentsource for the phase splitter for perfect balance. Wap2 mono preamps to see how they work using the octal plugs. My dynaco mkiiis are the dynakitparts version and i use the high gain tubes4hifi driver boards which use three 12at7s. On one of the dynaco st70s, i installed a new 6gh8 driver board instead of dealing with the rare 7199 issue, and i designed a small 3.

This kit may be added to any vta board driven dynaco st 70 to allow your amp to operate in either the normal pentode ultralinear mode or at the flick of the switch in the sweet sounding triode mode. The st 70 used two 7199 tubes, but yes, the pots with the blue shafts on the original st 70 would be to set the bias for the output tubes. The markiiis used a different tube set in the driver and i think thats the primary difference. This kit may be added to any vta board driven dynaco st70 to allow your amp to operate in either the normal pentode ultralinear mode or at the flick of the switch in the sweet sounding triode mode. Dynacovta st70 new custom built st70 35wpc tube audiogon. Quad cap the 30, 20, 20, 20 uf quad cap on the original st70 has been replaced with an 80, 40, 30, 20 uf cap on the vta st70. It is being included here to allow the owner to experiment, and. A custom dynaco st70 kit diy audio electronics from. Id imagine that the venerable dynaco st 70 is the most well recognized tube amp in the world.

Hard to find parts including dynakit original dropin replacement components typically ship within 24 hours of ordering. Dynaco st70 with cloth leads on output transformers. This is probably the most intricate custom version of our vta st70 amp created to date. The making of the vta amp and dynaco st70 amp driver board. Dorey design group ddg dorey design group is a fullservice web design, open source programming, and marketing firm located in portland, or. Quad cap the 30, 20, 20, 20 uf quad cap on the original st 70 has been replaced with an 80, 40, 30, 20 uf cap on the vta st 70. Dec 27, 2016 recently, i got bitten by the nostalgia bug and picked up a pair of old factorywired dynaco st70s in pretty nice condition. The must have added those when the took out the octal sockets that were on the front. Reconnect all wires to the new circuit board as follows. Up for buy it now is the vta stereo 70 in kit form using all new parts.

Mine was an old version, and the current documentation is for the new board, with a different layout on the pcb. These amps smoked the dynaco from the beginning of the bandwith to the last and final note. Now you can build your own st70 on a new type 304 om 5934079. I am happy with the product quality and the performance of the vta driver boards.

The latest production dyna transformer for the st70 has a larger stack and is designed for the current 120 volt line power. New 6sn7 octal driver use for dyna mk3, vta m125s or vta m70s. New dynakit st70 advice steve hoffman music forums. The st70 used two 7199 tubes, but yes, the pots with the blue shafts on the original st70 would be to set the bias for the output tubes. Unscrew the input board from the chassis and remove. Dynaco st70 modified from stock with vta70 octal driver flickr. For driver tubes in this amp you may use any 12au7, 12bh7, 5963, 5814, 6189 or the mullard cv4003. Triodepentode kit as used on the vta st 70 pictured above. This dynaco st 70 driver board pc3 has been developed and designed to be a dropin replacement for dynaco 7199 board. I then had the urge to try this schematic on a pair of heathkit w7s.

Looks like a tubes4hifi vta octal driver board, upgraded power transformer, and some kt88s. Dynaco vta st70 stereo tube amplifier for sale canuck. One of these tubes has been replaced, for reasons which will be discussed further in. Dynaco st70 rewire and refresh techtalk speaker building. Also, if youre trying to go 100% sand free, then you cant use the vta board on your st70. Over 300,000 of the st 70s were produced, and more continue to be built as kits from companies like tubes4hifi and triode electronics. This dynaco st70 driver board pc3 has been developed and designed to be a dropin replacement for dynaco 7199 board. After using it for a few months and ironing out some hum issues by isolating the transformers to eliminate mechanical vibration, replacing the driver tubes, etc. My uncle had the stereo 120, pat4 preamp, fm3 tuner, and a25 loudspeakers. The vta driver also uses less feedback for noticeably better sound than the old design.

Clearly, these are superb tubes to use in a reference dynaco st70. The vta tdr may also be easily retrofitted to any vta st 70 st 120 tube amp kit. This is very important as if the grid drive is reversed, it will turn your st70 into a power oscillator damaging not only your amplifier, but your speakers and likely your hearing in the process. One of these tubes has been replaced, for reasons which will be discussed further in the section on the driver board. Number and unsolder all wires from the driver board. The kit uses all new parts stainless steel chassis wow. Latino says the original driver board was made of an inexpensive phenolic material with open solder traces on the bottom of the board. All connections to the board are marked with the original number markings on the top and bottom silkscreen layers.