Why start with an amp you have to mod, when ours comes fully loaded. If you have the time and the skills, a pair of st70s can be put into decent conditon to do a fine job biamping a pair of speakers. Either option is customizable by the upgrading of specific components such as the tubes that are used. When alls said and done, good tube amps seem to sound more like real life than most solidstate gear. I remember loaning my tweaked out st70 to one of the folks from holmes powell in the mid 80s. Many of you have requested that we develop modules to upgrade the existing dynaco design as opposed to our complete modification package. We like to think of the st70 series 3 as the update that david hafler would have made if he were alive today. It discusses most of the typical and a few atypical problems. Find great deals on ebay for dynaco st 70 and dynakit st70.
Compare the height of the core to the one in your dynaco. Of all the audio manufacturers, both past and present, dynaco is admitedly my favorite. These upgrades really changed the character of the amplifier from slow and soggy to faster, deeper bass, and more detail. A great performer and affordable tube amp is the st70. I used to crank it when i was a teen into his homebuilt corner horn type speakers but havent heard it since.
If your sca80 or st80 is humming more than it used to, then its very likely that the original c9 has lost a lot of its capacitance. Ce manufacturing replacement capacitor is the most common solution, but it is hard to find and expensive. No modifications required, wires have identical color coding as the original unit. In the case of the dynaco st70 for example see attached schematic.
I have a dynaco st 70 that has been in storage for several years and has few hours on it. You can purchase any of our products here from these web pages, making payment with a credit card through paypal, or sending us a money order. This kit will replace the original dynaco driver circuit and printed circuit board, using the excellent sounding 6sn7 triode. I cant imagine it would be different with a vintage st70. This amp was designed to be inexpensive and to get maximum performance for dollar paid. For a generation who adored it, there have been those in following generations who are quite vocal about it, to the point that the only. Not surprisingly, c9 is the main filter cap in both the sca80q and st80 power supplies. It uses a patented circuit of outstanding performance characteristics, along with top quality parts, including the new dynaco superfidelity a470 transformers the finest available. I would like to have it refurbished and updated for electrical components, inputs, and outputs. Pa060 s dynaco st70 upgrade power transformer replacement. There is a difference between the two amps besides the transformers.
You also requested a simple and reliable power supply module. While it was not very powerfull, my friend still claims that st70 was the most musical tube amp he has experienced. Efforts were also made to make the amp more reliable than the original amp. Our famous original dyna st70 rebuild plans from audio basics, july, 1982 article by frank van alstine. The st70 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 st70c3 that graced the pages of the audio amateur about 20 years ago. The ultimate 70 is a ava circuit set for the dyna st 70 chassis that goes far beyo the ava enhanced pure vacuum tube amplifier for your original dyna st 70 chassis. Dyna st70 amplifier suggested modifications parts list.
Legendary dynaco st70 has been relaunched the absolute. Some of you have complained that you want more meat technical information on audio equipment. It was arguably the best selling power amplifier of all time, and is arguably the most maligned such device as well. This new 70 reflects the illustrious history of dynacos involvement with vacuum tube designs as well as the latest advances in vacuum tube.
These amps smoked the dynaco from the beginning of the bandwith to the last and final note. Dynaco stereo 70 series ii amplifier manual keywords. Dynaco dynakit stereo 70 st70 tube amplifier schematic. Discussion in audio hardware started by ampherbal, dec 6, 2014. This is a new, updated, version of the classic, sds labs, dynaco st70 capacitor board. The original dynaco stereo 70 is a true classic that is still regarded with awe by audio enthusiasts worldwide. Im new to the forum having surfed in during my searches for a set of speakers. Some things were not changed like the chassis layout. Introduction this document provides a step by step instruction for rebuilding and restoring the dynaco stereo70 power amplifier. Restoration module this is an exact replacement for the original dynaco pc3 board fabricated from milspec materials.
You could built it yourself or buy one complete but this 35 watt per channel amp changed audio. Another option is to build up the power supply from the various replacement capacitors making. Our st70 kit is one of the best stereo tube amps of all time. The dynaco st70 surely must represent the greatest amplification paradox of all time. They were originally built from 1959 up to the early 90s and according to wikipedia over 300,000 st70s were produced, this is an amazing number of amps, and thanks to this huge volume of these fine amps in the field, an entire industry has sprung up around this. Dynaco st70 series 3 advanced classic tube aplifier. Scan of the dynaco dynakit stereo 70 st70 tube amplifier schematic from the instructions manual.
Our famous original dyna st70 rebuild plans by frank van. I was searching for dynaco amps on audiogon and came across an ad for new dynaco st70 kits. My mouser parts arrived today, and the st70 board went together in about 45 minutes. After having searched this forum i thought it might serve me best to initiate a new thread. Dynaco stereo 70 series ii amplifier manual author. Over the years, we have received may requests asking for service and upgrade help with the longoutofproduction dynaco st70 vacuum tube power amplifier. Id imagine that the venerable dynaco st70 is the most well recognized tube amp in the world. How to repair dynaco pas tube preamp dlab tek tips power supply fix duration. This board is a must for any serious restoration of the dynaco stereo 70 to full stock condition. Most people call it a vta70 vacuum tube audio to distinguish it from the original dynaco st70. This dynaco st70 driver board pc3 has been developed and designed to be a dropin replacement for dynaco 7199 board. Our offerings have the most requested upgrades we sell, built right in.
Dynaco st70 upgrade capacitor board triode electronics. The high end show 2016 in munich marks the relaunch and advanced design of the newest iteration of. I have a dynaco st70 that has been in storage for several years and has few hours on it. New vta st70 page 4 talkin tubes the klipsch audio. I could go on about timbral accuracy and clearer midrange. Over 300,000 of the st70s were produced, and more continue to be built as kits from companies like tubes4hifi and triode electronics. Find great deals on ebay for dynaco st70 and dynakit st70. A custom dynaco st70 kit diy audio electronics from. The el34 output stage is pushpull and the dynakit st70. If the dynaco st70 is great, then the heathkits are world class.
The dynaco st70 series 3 tube amplifier is now finally. Aside from the changes detailed above, the new panordynaco amp is clearly a stereo 70 clone. One of the most frequent failures in the dynaco st 70 is. Dynaco stereo 70 manual stereo power amplifier kit. Dynaco st70 totally restored and upgraded stunning. There have been several iterations of the dynaco st70, including an updated version made in the. Tubes 4 hifi is also known as vacuum tube audio our best known product is the vta st70 pcb modification for the dynaco st70 amplifier, that first appeared in a glass audio magazine article in 1989. 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 tubes4hifi recreates the chassis exactly as it was aside. Here is a very nice example of the venerable dynaco st 70 power amplifier. Dynaco stereo 70 mods, site also known as vacuum tube audio. New dynaco st 70 series ii vs original st70 part i italian version if there is one name in hifi which is synonomous with excellent sound, and at the same time with excellent price, that name is dynaco. 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. Well, if youre still stuck at home selfisolating from covid 19, you might as well be comfortable with the sweet glow of tubes. One of the most popular amplifiers of all time, with over 300,000 of them originally sold, it. Dynaco sca80q gets improved power amplifier section upgrade kit. It uses the 7199 circuit from the original it is not a redesign using the inferior 6gh8. Old dynaco catalogs, big files, beautiful color scans. Dynaco st70 6gh8 6gh8a ecf82 driver board pcb pc3 kit. The heathkits have solid state rectification where the dynaco is tube rectified.
Welcome to everything you wanted to know about our beloved dynaco st70. The kit uses all new parts stainless steel chassis wow. Dynaco st70 modrestore advice needed i recently acquired my fathers old dynaco or dynakit st70 stereo 70 tube amplifier that he used with his. 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. It is being included here to allow the owner to experiment, and. You can also upgrade to sprague coupling capacitors on above. Here at dynakit you will find the right parts to restore, repair or upgrade your original dynaco vacuum tube amplifier. Our famous original dyna st70 rebuild plans by frank van alstine.
I selected the amp because i wanted to try tubes per the advice of this board and a friend of mine had restored about 8 dynaco st70s and said he would do one. Instructions for assembling the dynakit stereo 70 description your dynakit stereo 70 is a complete dual 35 watt power amplifier kit which offers the highest possible fidelity, at low cost and in a compact arrangement. Well, the originals were good amps, but made to meet a price point. From pure original units to mods and improvements that just make these amps so much better. Dynacos first tube amplifier was the mark ii monaural amplifier that pumped out 50 watts of lowdistortion sound. It doesnt get more classic than a dynaco stereo 70. Hard to find parts including dynakit original dropin replacement components typically ship within 24 hours of ordering. This classic tube amplifier used to be the best value on the block. Improved replacement power transformer for dynaco st70.
This board is a must for any serious restoration of the dynaco stereo70 to full stock condition. Discussion in audio hardware started by breakdown7, apr 17, 2012. The sca80 and st80 have the same power amplifier section design. Hello again, am glad that the feedback i am getting from many of you indicates that you are happy with the information and ideas i have been describing. Follow any comments here with the rss feed for this post.
It was introduced in 1959 and was sold until mid1990. The dynakit stereo 70 is a complete dual 35 watt power amplifier kit which offers the highest possible fidelity, at low cost and in a compact arrangement. I put 10 ohm resistors from the cathodes of the 7591s to ground, but i only get. One strange thing im trying to figure out is the bias. The st70 series 3 marks the introduction of a third generation of vacuum tube products bearing the dynaco name.
I bought a stocklooking used dynaco st70 that was dirty and had one bad tube. Comments are closed, but you can leave a trackback. Dynaco stereo 70 series ii amplifier manual created date. I am just finishing up a complete rebuild of my dads old st70. In 1959, dynaco embraced the stereo revolution with the stereo 70. This seems to be a very common problem with sca80s. Over the years, we have received may requests asking for service and upgrade help with the longoutofproduction dynaco st 70 vacuum tube power amplifier.
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