Dynaco "ST-120" kit or wired amp new with warranty | | Asking Price: | $795.00 | | Original Price: | $0.00 | | Condition: | NewItem Condition Descriptions- New
Brand new and factory sealed in the box. - Excellent
Perfect in every way. Indistinguishable from a new product but not factory sealed. - Very Good
Used but with no major damage anywhere. Item works as new and has no visible damage. - Good
Used with 1-2 minor scratches anywhere on the item. Item works as new. - Fair
Well used with minor scratches anywhere on the item. May have minor functional issues. - Parts Only
Does not work, use for parts only.
| | Location: | | | Included Items: | Owner's Manual
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| Description: | Up for sale is an all NEW Dynaco "ST-120" power amplifier KIT or WIRED. It is built on the same stainless steel chassis that I use for the ST-70 and contains all new parts. There are no recycled parts from any original Dynaco tube amplifier. It differs from the ST-70 kit in the following ways ..
1. The VTA driver board, as used on the ST-70, has a number of modifications for use on the ST-120 to better drive 6550 or KT88 output tubes.
2. The ST-120 power transformer has the same footprint as the PA-060 transformer found on the original Dynaco ST-70 amplifier but has a 2.7 inch stack lamination and puts out 420-0-420 volts on the secondaries @ 425 milliamps. This transformer weighs about 5 pounds more than an original PA-060 power transformer and 2 pounds more than the upgraded PA-060 power transformer that I use on the ST-70 kit. Over 490 volts DC are seen on pin 3 (plate) and pin 4 (the ultralinear screen tap) of the output tubes.
3. The two output transformers used on the ST-120 are USA made and feature interleaved/layer windings with M6 silicon steel grain oriented laminations. They have 4200 ohm primaries and 40% ultralinear screen taps. They 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. See comparison photos ..
4. The amp uses TWO C-354 chokes which together can handle 400 milliamps of current flow.
5. This ST-120 features a Supplementary Cap Module or "SCM" which adds another 195 Mfd (800 volt rated) of power storage. The power supply also uses a set of wideband bypass capacitors for ESL reduction.
6. The fuse is a 5 amp slo-blo fuse instead of a 3 amp slo-blo as on the ST-70
NOTE - The tubes are OPTIONAL on this amp kit. 6550 or KT88 or KT90 output tubes are recommended. Recommended bias voltage is .550 volts DC for each output tube which provides a bias current of 55 milliamps per tube. The other tubes are 3 X 12AT7 and one GZ34 OR Weber WZ68 Copper Cap rectifier.
The kit or wired amp contains ...
1 - Assembly manual with pictorial and full color interior wiring photo
1 - Stainless Steel chassis frame with all original Dynaco markings
1 - VTA driver board with parts set
7 - Micanol octal tube sockets with cadmium plated pins
1 - PA-060-120 power transformer with bottom plate
4 - hard rubber isolation washers for power transformer
2 - A-260-120 USA made custom interleave/layer wound output transformers
2 - C-354 chokes
1 - multi section (80, 40, 30, 20 Mfd) quadruple electrolytic capacitor
1 - three lug terminal strip
1 - one lug terminal strip
1 - pair of gold plated RCA input jack jacks with mounting board
2 - pair of gold plated output binding posts with mounting board
1 - rubber grommet
1 - fuse post with 5 amp SLO-BLO fuse
2 - SPST 16 amp rated slide switches
1 - 13 amp rated AC power cord
2 - .022 Mfd 600 volt capacitors
4 - 1000 ohm 1 watt resistors
4 - 10 ohm 2 watt bias resistors
1 - 6800 ohm 2 watt resistor
1 - Supplementary Cap Module (SCM)
1 - set of wideband ESL reduction capacitors
1 - hardware kit for amp with all stainless steel screws
1 - 22 foot coil of 20 gauge tinned solid core copper wire
1 - 600 volt rated triode/pentode kit for both channels
$795 + shipping for the complete kit LESS TUBES - One year warranty on all parts
OPTIONAL tube set for this amp > 4 X 6550 OR KT88 (matched quad), 3 X 12AT7, 1 WZ68 Weber Copper Cap rectifier > + $144
OTHER OPTIONS available
1. Hand matched set of 4 Russian PIO K40-Y .22 Mfd @ 1000 volts coupling caps + $30
2. Driver board upgrade power supply caps + $15
The KIT comes with an easy to follow instruction manual and a clear pictorial specific to the VTA driver board. All you need is a soldering pencil, rosin core solder, a screwdriver, pliers, and a wire stripper/cutter to build your own Dynaco ST-120. This very easy to build kit takes about 10-12 hours to complete depending on your skill level and any previous experience with kit building. Over 75 kit and wired ST-70 and ST-120 amps have been sold in the past two years > many satisfied customers - check my feedback on Ebay and Audiogon on > Bob01605
FAQ on the ST-120 tube amp kit ....
1. Tell me more about the Weber WZ68 Copper Cap rectifier that’s in the optional tube set.
The Weber WZ68 Copper Cap Rectifier is a solid state rectifier which emulates the forward conduction resistance curve of a rectifier tube. It also has linear in-rush current limiting to simulate the warm-up of a tube rectifier. It is equal to TWO GZ34 rectifier tubes and can flow up to 450 milliamps of current.
2. Why two chokes ?
The obvious thing to do in this amp, which has higher current demands than the ST-70, would be to use a larger choke than on the ST-70 - one that can handle more current. Larger chokes, however, won't fit inside the 1 5/8" depth of the standard ST-70 chassis so TWO chokes share the duties.
3. Will the standard ST-70 tube cage from my original ST-70 amp fit your chassis?
Yes - Since this chassis is identical to the original chassis except made of stainless steel, your original ST-70 tube cage will fit either the ST-70 or ST-120
4. What is this "SCM"?
The SCM or Supplementary Cap Module is the name given to two extra storage caps on a 4 lug terminal strip. The terminal strip is bolted to one of the right side choke screws and adds an extra 195 Mfd of power storage. The SCM allows the amp to play with more ease at higher volume levels. In conjunction with the 88 Mfd on the driver board, this amp has over 450 Mfd of power storage - more than 2 1/2 times what a PAIR of 60 WPC Dynaco Mark III monoblocks had.
5. What is ESL and ESL reduction?
ESL stands for Equivalent Series Induction. All capacitors have inductive properties whose impedance rises with the frequency and causes the effective capacitance to vary with frequency. ESL reduction is the use of a carefully chosen set of bypass capacitors that will create a low-impedance path to ground for the entire power supply over a wide band of frequencies.
6. Bob, How does the ST-120 sound in comparison to your VTA ST-70 ?
Both amps sound virtually identical but the ST-120 does have noticeably more power. If you listen at moderate volumes on fairly efficient speakers in an average sized room the ST-70 may have enough power for your music system. If you listen at higher volume levels on relatively inefficient speakers in a larger room then probably the ST-120 would better suit your needs.
7. I live in Europe which has 240 volt AC voltage. Do you have a 240 volt transformer for your ST-120 ?
Presently there is no 120/240 dual primary power transformer available for for the ST-120 kit. The amp may be operated in Europe, however, if you can get an external transformer drop device used for operating USA 120 volt AC devices on 240 volt European voltage. These external transformers, which are available online, should be capable of supplying 600 to 800 watts of power.
Specifications for the ST-120 amp
Power output ................... 60 watts RMS per channel from 17 Hz to 30 KHz at less than 1% THD with both channels driven in PENTODE - 32 watts RMS in TRIODE.
Frequency response ....... 10 Hz to 30 KHz +/- .1 dB at 1 watt
Power bandwidth ............ 17 Hz to 30 KHz +/- .3 dB at 60 watts
Feedback .........................13 dB
Hum and noise ................ > 90 dB below 60 watt output
Weight - 40 pounds > shipping weight 45 pounds
Unsolicited ST-120 Email comments from some of the first few ST-120 customers ....
"Bob, I finished the assembly of my ST-120 kit last night (6/10/08). Everything went together without a hitch. Your instructions were quite clear and complete. The amp powered up without any issues whatsoever; no blown fuses, no hum or other spurious noises, and the output tubes biased perfectly. More to the point the amp performs great in my vintage system, sounding exceptionally clean and solid with my AR3a's, providing more than enough of the bottom end punch that these speakers love to produce and a very smooth and open mid-range and top end. Plus it looks great, especially glowing in the dark! A very nice quality piece." M. B., California
"Bob, the ST-120 sounds great! Not a hint of noise. Very full sound, more low end than I expected (or perhaps I’m used to). Certainly no comparison to my old Stereo 70 and just a whole lot cleaner than my Lafayette 550 ... " D. C., Illinois
"Bob, SUCCESS! As I am writing this email I am listening to the amp! ... The output tubes biased easily ... I am using the headphone output from my CD player to drive the amp. My wife has conceded that the semi-gloss black (on the three transformers) does look good ... I am enjoying the sound quality of the ST-120 amp immensely. The sound is amazing. The output tubes I purchased are matched JJ KT88's and the driver board tubes are new old stock JAN Phillips that I purchased with balanced elements so all would start out on equal footing. Everything is so crystal clear. I am hearing subtle sounds/noises in the recordings that were not evident previously. It seems as though you are there in the concert hall. This has been a rewarding experience that has brought back the enjoyment to true Hi Fi listening. "A. B., California
"Hi Bob, The ST-120 amp sounds wonderful upon first fire up, and only gets better with a little run in!! ... The amp performs very well in both modes of operation depending on speaker arrangement. I would highly recommend the ST-120 to anybody interested ... far superior to the original ST-70 which was very tough to beat!" T. W., Florida
"Bob, finished the ST-120 kit three days ago ... It worked great right from the first turn-on with nooooo problems ... Very quiet amp - no hum at all ... It sounds more powerful and much more detailed than my old Dynaco Mark III's. Glad I didn't rebuild the Mark III's. They will be going up on Ebay soon ..." R. B., Connecticut
The KIT amp is also available COMPLETELY WIRED AND TESTED with all tubes and a one year parts and labor warranty (90 days on the tubes) - for $1139 + shipping. A wired and tested amp WITHOUT TUBES is $995 + shipping. Email me for this option ...
You won't find a better looking, better sounding or more reliable 60 watt per channel tube amp KIT anywhere.
USA and Canada sales only unless a foreign buyer is willing to accept delivery by USPS Express Mail which has a tracking number to assure confirmation of delivery. Approximately $180 - $190 for delivery to most of Europe.
Thanks for looking ...
Payment Terms: Paypal, Money Order
Shipping Terms: United States, Canada
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