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welcome to our dealer in Massachusetts - Bob Latino

Bob sells and supports our amplifier kits and ready-built amplifiers!


ST70 stereo amp

ST120 stereo amp

M-125 monoblocks

customer reviews of our amplifiers

time delay relay



ST70 stereo amp

ST120 stereo amp

M-125 monoblock

NOTE 1 - if you have any questions about any of the 3 amps kits listed on this web page just email me at send email : Bob01605@aol.com If you want to talk by phone I can email you my phone number for a call. NOTE 2 - to purchase any amp kit on this web page just let me know by email send email : Bob01605@aol.com with the following info: 1 - Which kit? (ST70, ST120, or M125) 2 - Do you want a complete tube set? (ST70 or ST120 only) 3 - Do you want both capacitor upgrades? (ST70 or ST120 only) 4 - Do you want the stepped attenuator kit? (on ST70 or ST120 only) 5 - Do you want the TDR (time delay relay)? (on ST70 or ST120 only) 6 - Your USA or Canada ZIP code to figure shipping charges. Payments can be made by cashier's check, money order, or via PayPal. Payments by cashier's check or money order will receive a $25 discount on a SINGLE amp kit (ST70 or ST120) or a $50 discount on a PAIR of M125 kits. All wired and tested amps are custom built and shipped out about 2 weeks after receipt of payment.


brand NEW ST70 amplifiers, in KIT or ready to go!

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. 
   Eight quality Sprague 716P "orange drop" coupling caps are included with the board.
 
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.

9. Includes two triode/pentode switches to allow switching between these two modes of operation. 
   The switching may be done while the amp is running to compare the two sonic presentations.


 

"Shipping costs will be invoiced separately after your purchase of an amp kit - 36 pounds for the ST-70 and 45 pounds for the ST-120.
Kits to the USA shipped by UPS Ground or USPS Priority Mail. Shipments to Canada by USPS Priority Mail International ONLY.
Shipments to areas other than the USA and Canada will be shipped with a tracking number by USPS Express Mail International ONLY. "


$719 + shipping IN KIT FORM
with all parts but NO TUBES
$839 + shipping IN KIT FORM
with all parts and tubes and EL34 output tubes
$909 + shipping IN KIT FORM
with all parts and tubes and KT88 output tubes
$1035 + shipping WIRED with NO TUBES
$1155 + shipping WIRED with ALL tubes & EL34 output tubes
$1225 + shipping WIRED with ALL tubes & KT88 output tubes
240 volt operation add $35 to KIT amp price
add capacitor upgrade for $45 (4 Power supply and 4 hand matched Russian K40-Y PIO coupling caps)

A 21 step, stepped 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 may 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 may also use the attenuator as a master level control to effectively reduce the gain of the amp.
$50 added to any ST-70
or ST-120 KIT amp
$75 added to any ST-70
or ST-120 WIRED amp

$50 + $5 shipping = $55
for your existing amp



all ST-70 and ST-120 amp kits come with a heavy duty 16 gauge chassis


ST70 amp kit assembled by Bob

the internal wiring with the Triode/Pentode switches


For more information or questions about a KIT or WIRED VTA ST-70 or ST-120 amplifier - - - Email me at Bob01605@aol.com



VTA120 amp !!

For those that need a little more power is the Dynaco VTA ST-120.
The VTA ST-120 is a 60 WATT PER CHANNEL amplifier built on the same ST-70 stainless steel chassis as the amp pictured above.
The VTA ST-120 uses three custom wound USA made transformers and is available as a KIT amp or completely WIRED and tested.
This amp has the same quality components as the VTA ST-70 listed above. The optional tube set has a GZ34 rectifier,
three 12AU7 driver tubes and a matched quad of KT88 tubes.
The power transformer instead of 360-0-360 secondaries like the ST-70 has 420-0-420 secondaries and puts about 485 volts on the plates
(pin 3) of the output tubes. The ST-70 puts about 420 volts on the plates. The stack lamination on this transformers is about 2.70 inches tall
- my ST-70's power transformer stack is about 2.05 inches high. 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!! Check out this
review and comparison with a McIntosh 275 amp


"Shipping costs will be invoiced separately - 45 pounds from zip code 01566 by UPS ground"

VTA ST-120 KIT with NO TUBES > $909 + shipping

VTA ST-120 KIT with all tubes > $1099 + shipping
VTA ST-120 WIRED and TESTED amp with NO tubes > $1305 + shipping VTA ST-120 WIRED and TESTED amp with all tubes > $1495 + shipping

add capacitor upgrade for $45 - (4 Power supply and 4 hand matched Russian K40-Y PIO coupling caps)

240 volt power transformer for the VTA ST-120 amp kit (+$50 USD) for use in Europe, Australia and other 240 volt areas of the world.
This transformer must be special ordered and will cause a delay of about 4 weeks before I can ship out your VTA ST-120 kit.
Email me for more information on the 240 volt VTA ST-120 amp kit.



21 step attenuator as shown above.
$50 added to ST-120 KIT amp
$75 added to ST-120 WIRED amp


Time Delay Relay

This is a "time delay relay" board" for tube amps and preamps.
The time delay allows the tube filament heaters to come up before any high voltage is applied. The time delay is nominally about 17 seconds but may be adjusted for more or less delay at the discretion of the user. There are complete instructions for the assembly and installation of the board. In a stock ST-70 the board replaces lugs 5, 6 and 7 of the 7 lug terminal strip. In a VTA ST-70/ST-120 tube amp kit, the VTA-TDB replaces the 3 lug terminal strip. The VTA-TDB may also be easily retrofitted to any VTA ST-70/ST-120 tube amp kit.

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 primarily intended for those running amps withOUT a tube rectifier. If you have a tube rectifier you already have a slow turn-on. 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.

TDR KIT $35 + $5 shipping (or with amplifier kit) TDR installed into any WIRED ST-70 or ST-120, add $60



Customer Reviews posted on the Internet . . . . . .

Audio Asylum review #1 of the ST-70 kit
Audio Asylum review #1 of the ST-120 kit
Audio Asylum review #2 of the ST-70 kit Audio Asylum review #2 of the ST-120 kit
Audio Asylum review #3 of the ST-70 kit
Audio Asylum review #3 of the ST-120 kit
Audio Asylum review #4 of the ST-70 kit
Audio Asylum review #4 of the ST-120 kit


"What's it like to build Bob's VTA Dynaco ST-70? - check the link below ..." step-by-step photos


here's a link to a partial view of the build manual



It's finally here - the all new VTA M-125 tube amplifier KIT
This is a 125 watt monoblock amp IN KIT FORM that uses four output tubes in a parallel push pull output circuit. 
The amp is built on a 10 inch by 12 inch 16 gauge brushed stainless steel chassis and uses a modified VTA Mark III driver circuit. 
The recommended tube complement is 4 X KT88, 6550, KT90, KT100 or KT120 output tubes, 2 X 12BH7 (recommended) or 12AU7 driver tubes, 
and a Weber WZ68 Copper cap solid state rectifier. 
NOTE - A tube set is not included with this amp KIT. 
On the front face is an on/off switch and three bias test pins. 
One test pin is used in biasing the two left output tubes and one test pin is used in biasing the two right output tubes. 
The bottom center test pin is a ground pin. The rear face contains one RCA input jack, a fuse holder, 
an IEC AC connector, and a pair of output binding posts. 
The output binding posts may be set up for 4, 8 or 16 ohm speakers. 
The amp has a switch which allows operation in pentode/ultralinear mode (125 watts) or triode mode (65 watts). 
The triode/ultralinear switch may be used while the amp is running.

 
Note - Pricing  $869 EACH or $1738 for a PAIR.

You will need a PAIR of M-125 monoblock amps for a two channel stereo system.
 
PA -125M power transformer
   4.50" W X 3.75" D X 3.875" H
   Weight 13.5 pounds
   415-0-415 secondaries @ 450 milliamps
   Two 6.3 VAC @ 5 amp heater lines
   One 5 VAC @ 5 amp rectifier line
   One 55 VAC bias line
 
A-125M output transformer
   4.625" H X 3.875" W X 4.25" D
   Weight 11.5 pounds
   Primary impedance 2200 ohms
   Secondary impedance 4, 8 and 16 ohms
 
List of parts.
1 - 16 gauge heavy duty brushed stainless steel chassis
1 - VTA driver board and parts set with upgraded power supply and Russian PIO main coupling caps included
1 - PA-125M power transformer
1 - A-125M output transformer
5 - Celanex octal tube sockets
4 - ground lugs
1 - 550 volt rated quad cap
2 - C24-X chokes
1 - SCM (supplementary cap module)
1 - set of ESL bypass capacitors
1 - fuse post and 5 amp fuse
1 - 15 amp rated SPST on/off switch
1 - 15 amp rated DPDT triode/ultralinear switch
3 - bias test pins
1 - Bulgin IEC connector
1 - 14 gauge 15 amp rated 6 foot IEC AC power cord
1 - 3 lug terminal strip
1 - 2 lug terminal strip
2 - 10 ohm 5 watt bias resistors
4 - 1000 ohm 1 watt resistors
4 - 100 ohm 1 watt resistors
1 - 20 foot coil of 20 gauge tinned solid core copper wire
1 - gold plated RCA input connector
1 - pair of gold plated output binding posts
1 - amp hardware set with all stainless steel screws
 
NOTE - The amp may also be operated with just TWO OUTPUT TUBES - one left side output tube and one right side output tube. 
The amp just needs to be rebiased when switching to two output tube mode. 
With just two output tubes, the amp will have about 65 watts available in pentode ultralinear mode and about 35 watts in triode mode.
 
Specifications for the VTA M-125 amp KIT ...
 
Power output (4 X KT88) 125 watts from 17 Hz to 32 KHz at less than 1% THD in ultralinear - 65 watts in triode
Power output (2 X KT88) 65 watts from 17 Hz to 34 KHz at less than 1% THD in ultralinear - 35 watts in triode
IMD .................................. < .38% (19 Khz and 20 Khz) at rated power
Frequency response ....... 10 Hz to 35 KHz +/- .1 dB at 1 watt  
Power bandwidth ............ 17 Hz to 37 KHz +/- .3 dB at 125 watts 
Sensitivity ....................... 1 volt in for 125 watts out
Feedback .........................10 dB
Damping factor ................14
Input impedance .............. 270,000 ohms
Hum and noise ................ > 95 dB below 125 watt output
The M-125 does not invert phase
Dimensions - 10.0" wide X 12.0" deep X 7.10" high
Weight (each) - 34 pounds > shipping weight 38 pounds


"Shipping costs will be invoiced separately - 38 pounds each amp from zip code 01566 by UPS ground"

single M-125 KIT with NO TUBES
$869 + shipping
pair of M-125 KITs with NO TUBES
$1738 + shipping
WIRED PAIR OF M-125 amps with NO TUBES
$2495 + shipping
WIRED PAIR OF M-125 amps with ALL TUBES
$2795 + shipping

M-125 FAQs
1. Are there any advantages to the 16 gauge stainless chassis?
Besides the obvious fact that this chassis will never rust, a stainless chassis is non-magnetic and cannot hold a magnetic field.
Amps built on stainless steel chassis tend to be quieter than amps built on standard steel chassis.
The 16 gauge chassis weighs about 1.25 pounds more than if it was made of 18 gauge steel.
The 1.25 pound extra mass better supports the heavy transformers and also acts as a somewhat larger heat sink to help the two transformers run a little cooler.

2. How does the VTA M-125 compare in sound quality to your other two kits - the ST-70 and ST-120?
The M-125 uses the same basic circuit as the ST-70 and ST-120 and sounds very similar to my other amp kits at lower volume levels.
The M-125 will, however, play about 3 dB louder than the ST-120 and about 6 dB louder than the ST-70.
Slight differences are that the M-125 has a somewhat wider bandwidth and a little less gain.

3. What is this 4 output tube or 2 output tube option?
The circuit is arranged so that the amp may be operated with either two left side and two right side output tubes OR just one left side and one right side output tube.
For two output tube operation it doesn't matter which left side tube socket or which right side tube socket is used as long as one of each are used.
The amp must be rebiased when you switch from 4 output tube operation to 2 output tube operation.
The recommended bias setting with four output tubes is 1.20 volts DC FOR EACH SIDE which provides a bias current (using a 10 ohm bias resistor) of 60 milliamps
for each of the four output tubes. For two tube operation the recommended bias setting is .600 volts DC per each side which also provides a bias current of 60 milliamps
for each of the two output tubes.

4. Could a single VTA M-125 be used as a guitar amp?
The amp has a standard RCA input and is designed to be used for home audio. The input jack could be easily modified by any kit builder to accept an electric guitar input.

5. Is the VTA M-125 as easy to assemble as your ST-70 and ST-120 amp kits ?
Actually the M-125 is even EASIER to assemble than either the ST-70 or ST-120 amp kits. The chassis is about the same size as the ST-70/ST-120
but there is only the wiring for ONE channel instead of two channels. As with the ST-70 and ST-120 amp kits, the assembly manual is written in detail for the beginner.
The color pictorial photograph included with the amp kit shows the location and termination point of every wire.

6. Are there any options for the M-125 amp kit ?
No - The amp comes with both power supply upgrade caps and Russian K40-Y PIO main coupling capacitors as standard equipment. Also, I will not be stocking the tube set for the M-125.

7. Is the VTA M-125 amp available in a 220/240 volt version for 240 volt countries and can you ship one to me in (any country with 240 volt AC line voltage)? "The M-125 amps in kit or wired form are available in 240 volt as a special order item only. Email me for more details .."


send us email at: Bob01605@aol.com for any questions about the VTA M-125 amp KIT...


   
 

bottom view of M125 showing wiring

review of the M125 amp on Audio Asylum

check out our tube preamps here . . .


visit our new "Dynaco Tube Audio Forum"

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 tubes 4 hifi
 "the path of least resistance is through a vacuum"