ANNOUNCEMENT
M-125 is currently OUT of stock
All other amps are IN STOCK
You may make a deposit or place an order to get in line
All assembled amps are custom built to order
We are working our way through the queue, please be patient!
ST35 stereo amp |
ST70 stereo amp |
ST120 stereo amp |
M-125 monoblocks |
YouTube videos of our amps |
customer reviews of our amps |
time delay relay |
amplifier parts - transformers & chassis |
 ST70 stereo amp |
 ST120 stereo amp |
 ST35 stereo amp |
 M-125 monoblock |
 these speaker posts are now standard |
NOTE - if you have any questions about any of the 3 amps kits listed on this web page just email me at
send email : tubes4hifi@gmail.com
brand NEW ST70 amplifiers, IN STOCK
ST70 amplifier features:
1. The new STAINLESS STEEL chassis is identical in size, shape and markings to the older original nickel plated steel frame. This upgraded chassis is NON-MAGNETIC and removes any magnetic interference effects of a steel chassis on the audio circuitry. 2. The new USA made power transformer has a higher stack lamination than the original Dynaco power transformer and is rated for 120 volts instead of 115 like the old design. The two tube heater legs are rated for 5 amps each instead of 3 amps each like the old design. This beefed up transformer (which has a bottom plate like the original PA-060 to prevent EMI from the transformer from reaching the audio circuitry) allows the use of KT88 output tubes in place of the EL34 tubes for a slightly different tonal presentation. Four heavy duty neoprene isolation mounts are used to attach the transformer to the chassis. 3. The A-470 output transformers are brand new USA made custom production transformers. They use the same interleaved/layer winding technique as the original cloth lead A-470's and incorporate the same high quality M-6 grain oriented laminations. They are dimensionally accurate to the original design and have a durable heat resistant black epoxy finish. 4. The old stock 30, 20, 20, 20 electrolytic quad cap which had marginal storage capacity for this amp has been replaced by a 80, 40, 30, 20 quad cap for almost double the power storage capacity. 5. The upgraded VTA driver board uses three new 12AU7 or 12BH7 triodes in place of the two mediocre sounding 7199 pentode/triode tubes. Dynaco saved money using a two tube 7199 board design but made some serious compromises in sound quality. 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. This design allows for individual adjustment of each output tube bias. Matched pairs or quads of output tubes are not necessary with this design. 6. The input jacks are gold plated and have a wider spacing to allow for newer design thicker interconnects. 7. The output jacks are modern gold plated 5 way binding posts. 8. The 7 octal tube sockets are modern high quality Celanex sockets with cadmium plated pins. These sockets are very durable and more reliable than the older stock phenolic tube sockets found in the original amps.
Shipping costs will be invoiced separately after your purchase of an amp kit - ~36 pounds for the ST-70 and ~42 pounds for the ST-120.
Kits to the USA are shipped by UPS Ground,Fed Ex Ground, and/or USPS.
Shipments to Canada and other countries outside the USA are shipped by USPS Priority Mail International, UPS, or DHL
Both classic chassis and new style chassis options are available for either ST-70 or ST-120
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your choice of amplifier chassis style, either of above, same price, classic or new, for both ST70 or ST120 amps
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with all parts but NO TUBES |
with all parts and tubes and EL34 output tubes |
with all parts and tubes and 6550 output tubes |
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with NO TUBES |
with ALL tubes & EL34 output tubes |
with ALL tubes & 6550 output tubes |
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(4 larger power supply caps for driver board) |
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 a 21 step attenuator kit to install in place of the unused stereo/mono switch to allow you to use your ST-70 amp without a preamp ! This is a great option if you only have one signal source for your ST-70 like a CD player. The attenuator can also be used WITH A PREAMP. If you turn the control all the way to the right there is complete pass through of the signal with no attenuation or alteration of the signal. You can also use the attenuator as a master level control to effectively reduce the gain of the amp. |
NOTE: This option is only to add the attenuator to an amp kit order and does NOT include shipping |
ASSEMBLED amp |
$45 + $5 shipping = $50 for your EXISTING amp NOTE: price includes shipping inside USA only, for Canada or worldwide, email for shipping cost |
For more information or questions about a KIT or WIRED VTA ST-70 or ST-120 amplifier - - - Email Dan at tubes4hifi@gmail.com
The VTA ST-120 amp kit is IN STOCK
VTA120 amp !!
For those that need a little more power is the Dynaco VTA ST-120.The VTA ST-120 uses three custom wound USA made transformers and is available as a KIT amp or completely ASSEMBLED and tested.
This amp has the same quality components as the VTA ST-70 listed above.
The optional tube set includes three 12AU7 driver tubes and a matched quad of 6550 tubes, along with a 5AR4 or 5U4 rectifier tube
The power transformer has 420-0-420 secondaries and puts about 485 volts on the plates (16% more than the ST70).
The stack lamination on this transformers is about 2.70 inches tall.
This transformer weighs about 4 pounds more than the ST-70 transformer and is rated at 425 milliamps of current flow.
The output transformers have 4200 ohm primaries, 40% ultralinear screen taps and are 3 7/8" tall, 3 1/4" wide and 3 1/8" deep
(about 1/2" taller, 3/8" wider and 1/4" deeper than a stock A-470 output transformer).
Each output transformer weighs about 2 pounds more than a stock A-470 output transformer.
The power storage caps have a higher capacity and voltage rating than the VTA ST-70.
The ST120 is an amazing sounding amp! review and comparison with a McIntosh 275 amp
all ST-70 and ST-120 amp kits come with a heavy duty 16 gauge chassis |
customer photo of ST120 |
"Shipping costs will be invoiced separately ~ 42 pounds by UPS ground"
| VTA ST-120 $1240 + shipping in KIT FORM with all parts but NO TUBES |
VTA ST-120 $1600 + shipping in KIT FORM with all parts and 6550 or KT88 output tubes |
| VTA ST-120 $1690 + shipping ASSEMBLED and TESTED with NO TUBES |
VTA ST-120 $2050 + shipping ASSEMBLED and TESTED with 6550 or KT88 output tubes |
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(4 larger power supply caps for driver board) |
make a $150 deposit to pre-order & hold an amplifier |
| 220/240 volt power transformer for the VTA ST-120 amp kit (add $60 USD) for use in Europe, Australia and other 220/240 volt areas of the world. 8-12 weeks needed to get these. Email me for more information on the 220/240 volt VTA ST-120 amp kit |
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Time Delay Relay
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This is a "time delay relay" board" for tube amps and preamps. The board is 1 7/8 inches wide by 2 1/2 inches long. It takes about 1/2 hour to assemble and is powered by a 6.3 volt AC line taken off V2. When the board is powered up a RED LED lights up to show that the board has power. About 17 seconds after power is applied, a GREEN LED comes on, and the relay kicks in to apply high voltage to your amp. Another nice thing is that if you are in an area that has quick ON/OFF/ON power interruptions the board will automatically reset itself. In other words, if your power goes OFF and then ON again a split second later the board will automatically reset itself and no high voltage will be applied for another 17 seconds. This is only a delay board - you still need a solid state or tube rectifier to plug into the rectifer socket. If you use a GZ34 tube rectifier IMHO you can get by without it. If you use a solid state rectifier like the Weber WZ68, which only has a 3 to 5 second delay, I think it is helpful. It would also be helpful if you have the quick ON/OFF/ON power interruptions. This board is to be used ONLY for solid state rectifiers. If used with a TUBE rectifier, the TDR can cause problems with the normal slow warm up of the tube rectifier and can damage a tube rectifier. If you intend to use a TUBE rectifier ONLY with your amp, you do not need the TDR. If you do use a tube rectifier with the TDR, you should BYPASS the TDR. Instructions are included with the TDR on how to bypass the TDR. This board is a relay switch that will not apply the high voltage power to the amplifier until after the tube filaments are warmed up, the board has a 17 second delay and that can be changed by changing one resistor on the board. This is a very heavy duty industrial relay used for 270vac 3 phase and rated at 8 amps, with 1500v of isolation between the contacts. Similar delay circuits I evaluated for tube amp use had 240v contacts with 1000v of isolation and were physically larger, this is a great addition to your tube amp. It can run on 6vAC or 12vDC. |
| ADD a TDR KIT to your kit amp purchase $35 | ADD a TDR to your WIRED amp purchase $65 |
$35 (free shipping in USA only) |
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Triode/pentode switching kit This kit can be added to any amp driven with the VTA mod PCB to allow your amp to operate in either the normal pentode ultralinear mode, or switch to sweet sounding triode mode. Simply remove the old bias pots and install the switches in the empty 3/8" holes. Note - Kit cannot be installed in a stock amp which still uses the old original bias controls. Comes with all parts and instructions. $30 with FREE First Class mail delivery in the USA. 
Triode/pentode switching kit added to your wired/assembled amp order | $60 |
amplifier parts - transformers & chassis |
Customer Reviews posted on the Internet . . . . . . |
here's a link to a partial view of the build manual
check out our tube preamps here . . .
visit our new "Dynaco Tube Audio Forum"
return to VTA home page
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