The Dynaco Tube Audio Forum

Dedicated to the restoration and preservation of all original Dynaco tube audio equipment - Customer support for Dynaco VTA tube amp kits, all Tubes4hifi.com products and all Dynakitparts.com products


    2011 Custom ST-120 Amp

    Share

    jdm

    Posts : 45
    Join date : 2011-04-04

    2011 Custom ST-120 Amp

    Post by jdm on Wed Oct 26, 2011 10:59 pm

    Custom ST-120, April 2011







    Custom Built Dynaco VTA ST-120
    The Dynaco VTA ST-120 is an all-new 60 WATT PER CHANNEL integrated amplifier built on non-magnetic 16 gauge stainless steel chassis with a modern triode designed circuitry.

    The ST-120 uses three large custom wound USA made transformers with 420-0-420 secondary’s outputting 485 volts allowing the use of KT88 or Tung-Sol KT120 output tubes.

    The ST-120 tube set has a GZ34 rectifier; three 12AT7 driver tubes and a matched quad of KT88’s.
    Electrolytic Capacitors include a German Authenticity Cap, Jensen, Elna and Nichicon products.
    Film Capacitors include eight Mundorf 1200V Silver/Gold/Oil connector caps on the Mil Spec PCB.
    Wiring is fine OCC Silver and Copper/Teflon and all solder points are Mundorf Silver lead free.
    Single Line-Stage volume control is provided by a 21 stepped attenuator & machined aluminum knob.
    Triode/Pentode switches allow power output changes between these two modes of operation.
    The VTA board has individual bias controls (DC balance) for each output tube.
    VTA-TDB Time Delay Board eliminates short cycle from external power surge.
    Power output (4 X KT88) 60 watts RMS in ultralinear Pentode mode and 32 watts RMS in Triode.
    IMD .................................. < .38% (19 KHz and 20 KHz) at rated power
    Frequency response ....... 10 Hz to 30 KHz +/- .1 dB at 1 watt
    Power bandwidth ............ 17 Hz to 30 KHz +/- .3 dB at 60 watts
    Distortion…………………..Less than .155thd from 20Hz to 20KHz at rated power
    Sensitivity....................... .1 volt in for 125 watts out
    Feedback .........................13 dB
    Bias setting………………. (.550 volts DC) per each KT88 Output Tube
    Damping factor ................14
    Input Impedance.............. 270,000 ohms
    Hum and noise ................ > 90 dB below 60 watt output
    Dimensions - 13.0" wide X 9.5" deep X 6.5" high
    Weight (each) - 38 pounds

    Prefered Tubes:
    Matched Quad Gold Lion KT88 NEW
    NOS Tungsram 12AT7/ECC81
    NOS 1958 Mullard 5AR4/GZ34 rectifier tube

    Upgraded Capacitors, Resistors, Wire, Fuse/Holder
    ANOTE- 2 Pair AN-SPKR, heavy Silver binding post
    ELNA- RFS 100uF 100V 16x25 RFS-100V
    MUNDORF- 4- 0.10 1200V SUPREME SILVER & OIL
    MUNDORF-4 - 0.33 1200V SUPREME Silver/Gold/Oil
    NEOTECH- 22AWG LIGHT BLUE UP-OCC Solid SILVER WIRE
    NEOTECH- 20-FEET 20 AWG RED UP-OCC COPPER/TEFLON
    SHINKOH- 7K5 1/2 WATT SHINKOH TANT RESISTO
    SHINKOH- 12K 1/2 WATT SHINKOH TANT RESISTO
    SHINKOH- 27K 1/2 WATT SHINKOH TANT RESISTO
    TAKMAN- 1K 0.5 Watt Metal Film 1%
    TAKMAN- 2K2 0.5 Watt Metal Film 1%
    TAKMAN- 10K 0.5 Watt Metal Film 1%
    TAKMAN- 1M 0.5 Watt Metal Film 1%
    TAKMAN- 51K 1/2 WATT CARBON FILM, 2%
    ACME- AGC FUSE HOLDER, CRYO SILVER
    FUSE- HiFi 5A SLOW BLO 1/4"x1 1/4" FUSE
    Satin Gun Blue Transformer covers
    Lorad Power Cord 4’ 3x25 OFC/Silver ends terminated into Wattgate plug



    Sounds Great!



    Sprags

    Posts : 123
    Join date : 2013-02-27

    Re: 2011 Custom ST-120 Amp

    Post by Sprags on Wed Apr 03, 2013 6:57 pm

    Looks great....I'm hoping the one Bob is building for me looks close to yours. It'll inspire me to try my hand at building one myself. I'm a mechanical guy and electrical stuff baffles me because I can't see anything move.

      Current date/time is Mon Dec 05, 2016 2:36 pm