tubes4hifi VTA ST-120 User manual

VTA ST-120 with CCS driver board amp KIT assembly manual
Congratulations on your pur hase of the VTA ST-120 amp kit. Every effort has been made to give you
the finest sounding, most reliable and best looking 60 watt per hannel tube amplifier kit presently
available. Your VTA amp kit features the following items whi h are all upgrades from the original Dyna o
kits.
1. A new STAINLESS STEEL hassis that is identi al in size, shape and markings to the older original
ni kel plated steel frame. This hassis is NON-MAGNETIC and removes any magneti interferen e effe ts
of a steel hassis on the audio ir uitry.
2. Quality USA made A-260-120 ustom wound output transformers whi h are interleaved/layer-wound
and in orporate high quality M-6 grain oriented laminations.
3. A more robust PA-060-120 power transformer rated at 120 volts, having 410-0-410 se ondaries and a
450 milliamp urrent transfer apability.
4. All stainless steel s rews with zin plated kep nuts
5. Heat resistant Celanex™ o tal tube so kets
6. An 80, 40, 30, 20 uF main power supply ele trolyti ap.
7. An all triode VTA driver board made of mil-spe epoxy fiberglass. This board also ontains an on board
bias supply for the output tubes.
8. Gold plated input and output terminals.
9. A dual hoke system rated at 480 milliamps
10. Triode/pentode swit hes to allow the amp to run in two modes of operation
11. A supplementary ap module (SCM) with an ESL redu tion apa itor
Your KIT omes with a very easy to follow instru tion manual and a lear pi torial spe ifi to the VTA
driver board. All you need to omplete the kit is a soldering pen il, some rosin ore solder, a s rewdriver,
pliers and a wire utter/stripper to build your own VTA ST-120. The kit takes about 10-12 hours to build
depending on your skill level and any previous experien e with kit building.
List of Parts
1 - 16 gauge heavy duty stainless steel hassis frame with bottom over
1 - VTA driver board with parts set
7 – Celanex™ o tal tube so kets
7 - grounding lugs (in with tube so kets)
1 – USA made PA-060-120 power transformer
4 - hard rubber isolation washers for power transformer
2 - USA made A-260-120 ustom interleave/layer wound output transformers
2 - C24-X hokes
1 - multi se tion (80, 40, 30, 20 uF) quadruple apa itor
1 - three lug terminal strip
1 - pair of gold plated RCA input ja k ja ks with mounting board
2 - pair of gold plated 3 post output binding posts with mounting board
1 - rubber grommet
1 - fuse post with 5 amp SLO-BLO fuse (inside the fuse holder)
2 – 11 amp rated SPST slide swit hes
1 - 13 amp rated AC power ord
2 - .022 Mfd 100 volt apa itors
4 - 1000 ohm 1 watt resistors
4 - 10 ohm 2 watt bias resistors
1 - 4.7K ohm 3 watt resistor for quad ap
1 – Supplementary Cap Module (SCM)
1 – ESL redu tion apa itor
1 - hardware kit for amp
1 - 22 foot oil of 20 gauge tinned solid ore opper wire
1 – triode/pentode kit (2 DPDT swit hes, two 2 lug terminal strips, 4 X 100 ohm 1 watt resistors)
OPTIONAL > One tube set – 4 X 6550 output tubes, 3 X 12AU7 (or 12BH7, 5963, 6189, 5814), 1 X 5AR4
re tifier

Optionally painting the transformers
Power and output transformers ome from the fa tory with minor surfa e imperfe tions.
You may, as an option, paint your transformers for a better appearan e. (re ommended)
To most people a semi-gloss paint looks best on transformers. Use a spray an – don’t
brush it on.
Re ommended paints for the transformers are the following paints ..
Krylon # 2421 "Fusion" Satin bla k (my favorite)
Krylon # 51613 Satin bla k indoor/outdoor
Any type of semi-gloss automobile engine enamel in a spray an.
The Krylon paints are arried by Wal-Mart and many other stores. Go to an auto supply
store for engine enamel. Suggestion below on how to paint the transformers.
1. Obtain SIX 8 X 32 ma hine s rews 2 3/4 to 3 in hes long with nuts.
2. Remove one transformer 8 X 32 nut, nylon spa er(s) and s rew and repla e it with
one of the six ma hine s rews and nut. Tighten the nut se urely.
3. Do the same for the transformer s rew on the opposite diagonal orner of the
transformer.
4. Remove the other two 8 X 32 s rews, nylon spa ers and nuts on that transformer.
5. Repeat steps 2 through 4 for the other two transformers.
6. Sand off any imperfe tions in the fa tory finish on the three transformers with
100 grit paper. Usually the “bells” have few to no imperfe tions but the “plates”
have varnish drips whi h should be sanded out. Sand again with 220 grit paper.
7. Remove all sanding dust from the outer surfa e of the transformer. Rubbing
al ohol on a paper towel works well.
8. Cover the transformer wires by pla ing them in a plasti bag. Use some masking
tape near the transformer to hold the bag on the wires.
9. Spray 3 light oats on ea h transformer and allow to dry overnight.
10. Remove the plasti bags that over the wires.
11. Reinstall all the original s rews, spa ers and nuts.

INSTRUCTIONS
NOTE – You may or may not want to onstru t the VTA driver board BEFORE or AFTER you atta h the
hassis parts. If you wish to onstru t the VTA driver board at this time skip ahead to the VTA driver
board instru tions whi h are inside the VTA pa kage and pro eed with its onstru tion. When you are
through ome ba k to this point and begin mounting the hassis parts.
Obtain the hassis. Uns rew the four 6-32 hassis s rews and remove the bottom over. Taped
inside the bottom over are four round bla k rubber “feet”. Remove the paper over from ea h of the
rubber feet to a ess the sti ky bottom of ea h foot. Atta h firmly ea h rubber foot to the outside of the
hassis bottom over dire tly over ea h of the four holes in the bottom over. Orient the hassis with the
power transformer utout fa ing you and mark “V1”, “V2”, “V3”, “V6” and “V7” with a felt tip marker on
the inside of the hassis next to the appropriate tube so ket. (tube so ket numbers shown on the
pi torial) After ompleting ea h assembly instru tion pla e a he k beside the assembly instru tion
number.
1. Mount the FIVE o tal so kets that fit on the hassis TOP from the BOTTOM OF THE CHASSIS with
¼ in h long 4-40 stainless steel s rews and 4-40 kep nuts. Use the pi torial to orient the keyway of
ea h tube properly. On V2, V3 and V6 mount a single GROUND LUG around the outside s rew
losest to the side of the hassis and fa e the lug towards pin 8. On V7 mount ONE ground lug
around the outside s rew and fa e this ground lug towards pin 8. Mount the other ground lug
around the inside s rew and fa e this se ond ground lug towards the ba k of the amp. Tighten all
nuts se urely. Don’t lose the extra two grounding lugs.
2. Disassemble the three gold plated speaker binding posts from ea h of the two mounting
plates. Atta h the LEFT and RIGHT mounting plates to the ba k INSIDE of the amp with 4-40
hardware. Reassemble the three speaker binding posts on ea h of the mounting plates. One of the
round plasti olored spa ers (red or bla k) goes INSIDE the hassis and the other spa er (with
the binding post atta hed) goes OUTSIDE the hassis. Make sure that the BLACK terminal is on
the side that says “G” on the outside of the hassis frame and the two RED terminals are on the
side that says "4 8 16". Ba k off on the red or bla k plasti nut on the OUTSIDE of the hassis on
ea h binding post and rotate ea h post so the hole on the outer binding post fa es UP. Pla e the
flat washer up against the inside spa er, then the star washer, then the two nuts. Tighten the three
studs on the left and right sides with the gold plated nuts. Use a slim s rewdriver through the hole
in the outer post to keep the post fa ing UP as you tighten the nuts. NOTE - The outer plasti
spa er with binding post will lo k up against the hassis and NOT the mounting board.
3. Mount the rubber grommet in the 3/8 in h hole in the ba k CENTER of the hassis.
4. Mount the fuse holder in the "D” shaped hole in the ba k of the hassis. The slim bla k washer
goes on the OUTSIDE of the hassis. Tighten the large nut on the inside of the hassis but do not
over tighten as this may ause the plasti threads to strip. Che k and make sure that the 5 amp
SLO-BLO fuse is inside the fuse holder. (press IN and rotate the ap ounter lo kwise)
5. Mount the SPST on/off swit h on the REAR of the hassis with 4-40 hardware. Make sure that the
two terminals on this swit h are lose to the UNDERSIDE OF THE CHASSIS TOP SURFACE.
Che k the pi torial.
6. Pla e the 4 rubber isolation washers on the ends of ea h of the four bolts of the PA-060-120 power
transformer. Mount the power transformer in the large enter ut out. The wires should fa e the
FRONT of the hassis. Fasten the power transformer to the hassis with four 8-32 kep nuts. In the
original amp a metal able lamp was used on ea h of the two front bolts as seen on the pi torial.
These lamps are not really ne essary as the wires will stay in pla e fine when soldered.
7. Assemble and mount the Supplementary Cap Module (SCM)
A. Obtain the five lug terminal strip from the SCM kit plasti bag

B. Hold the strip with the grounded lug that atta hes to the hassis towards your RIGHT - The
lug losest to you is lug 1 and the next four lugs are lugs 2, 3, 4 and 5.
C. Conne t one 330K 1 watt resistor (found in SCM bag) between lugs 1 and 2 - have the
resistor straight in line with the terminal strip and not on the side of the lug.
D. Conne t a jumper wire between lugs 2 and 4 - have the jumper straight in line with the
terminal strip and not on the side of the lug. Ar h the jumper over the top of lug 3.
E. Conne t one 330K 1 watt resistor between lugs 4 and 5 - have the resistor straight in line
with the terminal strip and not on the side of the lug.
F. Conne t a 6 in h wire to lug 1 on the side of lug 1 whi h fa es the strip's hassis
atta hment hole.
G. Conne t a 3 in h wire to lug 5 on the side of lug 5 whi h fa es the strip's hassis
atta hment hole.
H. Obtain one of the two supplementary aps and onne t the NEGATIVE terminal of this ap
(the terminal with the GRAY STRIPE next to it) to lug 1 of the terminal strip. Conne t it on
the side OPPOSITE the hassis atta hment hole. You an straighten the apa itor pins to
better fit the terminal holes. (S) Fit the other lug of this ap into lug 2 of the terminal strip
(S)
I. Fit the OTHER supplementary ap with the NEGATIVE terminal (the terminal with the
GRAY STRIPE next to it) in lug 4 (S) and the POSITIVE terminal in lug 5. You an straighten
the apa itor pins to better fit the terminal holes (S). Conne t it like the other ap on the
side OPPOSITE the hassis atta hment hole.
8. Mount the RIGHT C24-X hoke and the SCM on the RIGHT side of the hassis with two of the
larger 8-32 s rews and mat hing kep nuts. Pla e the hoke on first and the SCM mount hole on
top of the hoke. When you mount the SCM, have the two SCM apa itors fa e the power
transformer. Tighten the two nuts. The two SCM aps may tou h the hassis. This is OK.
9. Mount the THREE lug terminal strip on the LEFT side of the hassis with a single 4-40 s rew and
kep nut as shown on the pi torial. Use the s rew hole losest to the power transformer. NOTE - If
the OPTIONAL VTA-TDR (Time Delay Relay) was shipped with your kit, you will install the TDR
INSTEAD OF the 3 lug terminal strip. Remove the VTA-TDR instru tion sheets from the TDR parts
bag. Assemble the TDR and install it in pla e of the 3 lug terminal strip as instru ted under the "B"
se tion of the TDR manual.
10. Mount the RIGHT A-260-120 output transformer with 8-32 hardware. The side of the transformer
with the YELLOW-ORANGE-BROWN-BLACK leads must fa e the BACK of the amp. Mount the
LEFT output transformer and fit the SECOND C24-X hoke under the far left nut losest to the
FRONT of the hassis. NOTE – This hoke mounts with just that ONE nut and s rew and may not
sit perfe tly parallel to the side of the hassis as seen in the photo. The two wires on the hoke
should fa e the INSIDE of the hassis. Che k the pi torial and/or photo.
11. Mount the quadruple se tion filter apa itor in the spe ial utout. It is IMPORTANT that the quad
ap be properly oriented. The 80 Mfd SECTION whi h is designated with a HALF CIRCLE symbol
must fa e the BACK of the amp. Fasten by twisting ea h of the four mounting tabs one-quarter
turn with pliers.
12. Mount the two remaining grounding lugs in the single hole just to the left of the quad ap. Mount
them at a slight angle as seen in the pi torial. This will be your main grounding point for the entire
amp.
13. Obtain the two DPDT swit hes from the triode/pentode kit bag. Install the swit hes in the two
hassis holes where the original Dyna o ST-70 bias ontrols use to be. These two 3/8” holes are
not shown on the main pi torial. The swit hes are a loose fit in the holes and must be entered in
the hole before they are tightened.

14. Remove the outside nut and larger flat washer from the swit h. The smaller flat washer goes
against the INSIDE of the hassis. Pla e the larger flat washer on the hassis TOP and nut on top
of the flat washer. On the inside of the hassis make sure that the six terminals on the swit h fa e
from the front to the ba k of the amp so that the swit h toggle on the top may be swit hed from
FRONT to BACK and not side to side. Refer to the triode/pentode pi torial for help if needed.
15. Center the two swit hes in the holes and tighten the nuts lightly with square nosed slip-joint
pliers. Che k alignment of the two swit hes. If alignment is not orre t move the swit hes slightly
until alignment is orre t. Make your final tightening but DO NOT OVERTIGHTEN THIS NUT or you
ould break the swit h.
16. Mount the two TWO lug terminal strips ba k to ba k in the single entral 4-40 hole between the
two triode/pentode swit hes. Try to keep the strips straight and parallel to the sides of the amp as
you tighten the s rew. Che k the olor photo.
17. NOTE – At this time DO NOT MOUNT the two front power takeoff so kets, the front slide swit h (or
stepped attenuator if you have the stepped attenuator option) whi h fits into the stereo/mono slot
or the input ja ks. These three items must be mounted after installation of the VTA driver board.
WIRING – Ea h length of hookup wire spe ified should have approximately ¼ in h of insulation
stripped from ea h end unless otherwise spe ified. Wires from the three transformers should be
shortened appropriately to the orre t length to rea h their terminal point. If you see the
symbol “(S)”, this means to solder that onne tion at that time. If the symbol is not
there DO NOT SOLDER that onne tion at that time. The 20 gauge tin oated solid ore
opper wire supplied with this kit is the re ommended wire to use. Only rosin ore solder is
re ommended for soldering. Always make a solid me hani al onne tion with your pliers to the
terminal point before soldering. Always keep the hassis and transformers on a soft surfa e like
a towel so they won’t get s rat hed. Orient the hassis so that the power transformer is towards
you. Oriented this way the, the LEFT hannel is on your LEFT and the RIGHT hannel is on your
RIGHT.
1. Twist the pair of WHITE leads from the power transformer together and extend the wires to so ket
V1. Conne t one lead to pin #2 of V1 (S) and one lead to pin #8 of V1.
2. Twist the pair of RED leads from the power transformer together and extend the wires to so ket
V1. Conne t one lead to pin # 4 of V1 (S). Conne t the other lead to pin # 6 of V1 (S). NOTE - If you
have the OPTIONAL VTA-TDR (Time Delay Relay) then do steps 5, 6 and 7 on the TDR manual
under "Wiring to the board" instead.
3. Twist the pair of GREEN leads from the power transformer together and extend the wires to
so ket V2. Conne t one green lead to pin # 2 of V2 and one green lead to pin # 7 of V2.
4. Twist the pair of BROWN leads from the power transformer together and extend the wires to
so ket V7. Conne t one brown lead to pin #2 of V7 and the other brown lead to pin #7 of V7.
5. Twist the BROWN/YELLOW and GREEN/YELLOW wires from the power transformer and extend
the wires to the 3 lug terminal strip. Conne t the BROWN/YELLOW lead to lug # 3 - the lug losest
to the power transformer. Conne t the GREEN/YELLOW wire to lug # 1 – the lug furthest from the
power transformer. NOTE - If you have the OPTIONAL VTA-TDB (Time Delay board) onne t these
two wires to the proper eyelets on the TDB board instead - as instru ted in steps 2, 3 and 4 of the
TDB manual under "Wiring to the board".
6. Conne t the RED/YELLOW lead to one of the grounding lugs next to the quad ap filter apa itor.

7. Extend the RED lead from the LEFT OUTPUT TRANSFORMER and the RED lead from the RIGHT
OUTPUT TRANSFORMER to the 80 Mfd terminal on the QUAD CAP having the HALF CIRCLE
symbol. This is the terminal that fa es the REAR of the amp.
8. Shorten (if ne essary) and onne t the 3 in h wire from lug 5 of the Supplementary Cap Module
(SCM) to the same 80 Mfd terminal on the quad ap having the HALF CIRCLE symbol as des ribed
in the step above. Conne t the 6 in h wire oming from lug 1 of the SCM to one of the two main
grounding lugs next to the quad ap.
9. Twist together the two CHOKE leads from right side hoke. Conne t one hoke lead to 80 Mfd
terminal on the quad ap having the HALF CIRCLE symbol and the other hoke lead to the 40 Mfd
terminal on the quad ap having the SQUARE symbol. Lengthen the two leads from the se ond
LEFT SIDE hoke by adding about 4 in hes of wire to ea h of the two leads. After you lengthen
these two leads solder ea h onne tion (S) and be sure to insulate the two onne tions with bla k
ele tri al tape or insulated shrink tubing. (500 Volts DC here!) Twist together and onne t the two
hoke leads from the LEFT side hoke to the same two 80 and 40 Mfd terminals on the quad ap
as you did with the right side hoke.
10. Extend the two BLACK leads from the power transformer around the power transformer as shown
in the pi torial. Conne t one BLACK lead to lug “A” of the fuse post (S) and one BLACK lead to
lug # 1 of the on/off swit h (S).
11. Conne t the BLACK lead from the RIGHT OUTPUT TRANSFORMER to the SMALL GROOVE near
the end of the RIGHT BLACK speaker terminal. Conne t one end of a wire to the right BLACK
speaker terminal’s small groove (S). Conne t the other end of this wire to one of the grounding
lugs next to the quad ap. Conne t the BROWN (4 ohm) wire to the SMALL GROOVE near the end
of red binding post that is losest to the bla k post. (S) Conne t the ORANGE wire (8 ohms) to the
SMALL GROOVE near the end of red binding post that is furthest away from the bla k post. (S)
* The remaining YELLOW wire from the output transformer will be onne ted at a later step in
onstru tion.
12. Repeat step 11 above for the LEFT OUTPUT TRANSFORMER and the LEFT speaker terminal.
13. Conne t the BLUE wire from the LEFT OUTPUT TRANSFORMER to pin 3 of V3. Conne t the
BLUE/WHITE wire from the LEFT OUTPUT TRANSFORMER to pin 3 of V2. Conne t the BLUE wire
from the RIGHT OUTPUT TRANSFORMER to pin 3 of V6. Conne t the BLUE/WHITE wire from the
RIGHT OUTPUT TRANSFORMER to pin 3 of V7.
This is an in omplete VTA ST-120 manual

Triode/Pentode swit h pi torial
NOTE: Disregard any pin number markings on the swit hes themselves
and use the pin numbers listed below.