Complete Triode USA Dynaco ST-70 DIY Tube Amp Kit.
All parts needed for a complete Upgraded Dynaco ST-70 Type Kit except for the tubes. Including our custom made transformers, which are made to original specs right here in the USA: PA-060-S Power Transformer (Nearly twice the lamination stack size of the original), A470-S Output Transformers, C354 Choke. As well as our Upgraded Dynaco ST-70 Heavy Duty Stainless Steel Chassis, Triode USA Dynaco ST-70 Driver Board (EF86 or 6AU6 Model, or "no driver board"), and our Triode USA Dynaco ST70 Upgraded Capacitor Board.
What's so special about our Dynaco upgrade boards? The object of our upgrade boards is to provide a replacement for the original boards that would result in a perceptible improvement in sound quality and overall performance. These Dynaco upgrade 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, 6BL8/ECF80, 6U8/ECF82, or 6AN8, are capable of. The manual includes information on adapting the amplifier to different output & board tubes, adjusting resistor & capacitor values if desired, plus a comprehensive Troubleshooting Guide. 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. Our 6AU6 version of the board is also available but does not support 6922, 6DJ8, 7308, or 6CG7.
Our Kits are a great choice if you really want to learn more about how your amplifier operates, too. You see, unlike many other Kits, you are not totally locked in to only certain components, nor are you stuck with unchangeable circuit values which limit the versatility of your amplifier and further modifications. There are no "big secrets", you don't need permission from a "guru" to change or tweak it, the manual has instructions for about every change you could imagine making. Instructions are included for triode connecting the output tubes, which will give you a taste of hi-end triode-itis for the cost of 4 resistors, about $1. So, you've got a choice..you can just plug in & play, or you can do your own experimenting if you'd like to, learn a lot and become your own neighborhood Dynaco guru. And you won't break the bank doing it, either. The stock board and parts kit includes, metal film resistors, polypropylene capacitors, which do just fine..but if you like you can modify many component values and try different or exotic parts and tweak to your heart's content. The board sounds fine even with the off the shelf, current production tubes, and special grading and matching is not absolutely necessary. It is a good example of what can be done with the original type of circuit with improved components, and makes a good case for the virtues of simplicity and short signal path in audio design. 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 7199,6GH8,6BL8/ECF80, 6U8/ECF82 or 6AN8 are capable of. Comes without tubes, see our "Tubes for Dynacos" link at bottom of page for them. The board manual includes information on adapting the amplifier to different output & board tubes, adjusting resistor & capacitor values if desired, plus a comprehensive Troubleshooting Guide.
Online instruction manual with step by step build instructions. The sonic upgrade will be immediately noticed from a stock Dynaco st70 type amp. With our board you are not captive to one design. It was made with the experimenter in mind. The driver board manual has the instructions to modify the board to use different tubes and part values, so later you are free to try different things that might sound better in your system.
Our ST70 Dynaco Upgrade Cap Board Replaces the original aluminium can capacitor and increases capacity from the original 30-20-20-20 to over 500uF's, using high quality capacitors which are bypassed by metallized polypropylene caps for superior high frequency response. This board gives the amp the bass definition that the ST70 original lacked. Amp can be used with a 5AR4/GZ34 tube rectifier or solid state diode plug-in unit (sold separately), or just wire some diodes to the socket. It also replaces the bias supply capacitors & diode as well.
Kit also includes: High Quality Cliff Tube Sockets, AGC Fuse Holder, Power Switch, Gold Plate Binding Posts, Gold Teflon insulated RCA jacks, Bias Test Point Jacks, 10k Precision Electronics (PEC) bias potentiometers, off-board resistors included 10ohm biaset resistors (1V biaset), cloth wire, chassis, choke, and more! Everything to build a working amp in one place...
For our international customers you can also order the kit with our PA-521-S 120/240v export power transformer instead of the PA-060-S for an extra $35.00. Use the drop down menu to order.
The kit is sold with everything you need to put it together except tubes. The driver board requires 2x EF86 or equivalent (or 6AU6 for the other version of board) tubes, and one of either 12AU7/ECC82 (or equivalent), or 12BH7 or ECC99. The power section of the amplifier requires four EL34/6CA7 tubes. If you will be using a tube rectifier (recommended) you will also need a 5AR4/GZ34 Tube. If you will be using a solid state rectifier let us know so we can adjust the cap board values for a higher voltage rating. We sell a octal plug in solid state rectifier if you want this option. With our kit you can have hours of tweaking and reconfiguring this amp to best suit your system and needs. Different driver configurations, driver tube types, output tube types, and triode connection, all can be used, and are explained. This is an amp you won't get bored with. We are very proud to offer you this amp, and thanks to our customers, whose feedback and suggestions helped make this happen. We look forward to hearing about how you have customized, and what tweaks you have done to your amp.
We now offer the kit "without a driver board option", in case our Upgrade Dynaco driver board doesn't suit your needs, or you have an old original Dynaco board you want to press back into service. 35WPC (17.5WPC wired in triode).
"WITH TUBES" Option Includes: EH 6CA7 Matched Quad, Sovtek GZ34/5AR4, EH 12AU7, & EH EF86 x 2pcs.
Check out our Brand New, Fully Revised Instruction Build Manual!! ST-70 Build Manual
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