They are readily available on ebay and from vintage equipment suppliers. Replacement parts are also readily available. They sound nice in stock, refurbished form, but they also respond to every upgrade you make, because the basic circuit is so simple. If you have speakers with 89 DB, or higher effeciency, you should have no problems, powerwise, especially if you run them in pairs.

They do sound a little soft in the highs without parts upgrades, when one compares them to the best modern gear.

I am old enough to remember these amps when they were new. My first amp was a Dyna Mark IV I built from a kit when I was 14. When I grew up, I went the solid-state route,like so many others. While transistor amps can be great, many of them have a "That sounds really good. Turn it down!" quality, especially with CDs. I decided to try a pair of ST 70s, after a retired electical engineer friend of mine told me that he thought they made very, very good monoblocks, if set up properly. Of course, they must be serviced and updated to some degree. The old selenium rectifier stack has to go. The big caps on the circuit boards, and noisy, carbon resistors also need to be replaced, for sound quality and reliablity. I also installed modern, fiberglass driver boards that reproduce the original circuit. The boards have MIT caps and Vishay resistors in the signal path. Strapping these amps is easy. There is a switch on the front that parallels the inputs. Then, you just connect the output terminals, following the instructions in the owner's manual. (Having a manual is very important.)Doing this changes the characteristics of the amps dramatically. They are much more assertive, and dynamic, without being harsh. Tube selection is critical. I am currently using Svetlana EL34s, Mullard 7-notch GZ34s, and RCA, or Sylvania 7199s. THESE MUST BE CLOSELY MATCHED IN STRAPPED AMPS!If they are not, the tubes fight each other, and fail sooner than they would otherwise.The sound also suffers. I am using the amps to drive a moderately effecient pair of custom-built monitors. The bass under 100 cycles is handled by a McCormack DNA.5, and subwoofers designed to match the monitors. In this configuration, the ST 70s sing. They image very nicely, with great location and depth. Their legendary midrange is only enhanced by the increased headroom, and their highs are also more pronounced. Other Equipment used in this system: McCormack Signature CD player, Rega Planar 3 turntable, Sansui TU-719 tuner, and a pair of Dyna PAM-1 preamps, that have also been given massive parts upgrades, and individual, stand-alone power supplies, (Dyna PS-1s) Parts and tubes are not much of an issue. Many suppliers sell parts for these amps, and the quality of modern EL34s is steadily improving. Do not let that fear stop you from trying out these units. They sold more units than any other tube stereo amp for good reasons. If you have any curiosity about tubes, this is where to start. PS. I think an earlier reviewer mentioned Variacs. You need one for these amps,or any other vintage tube units. Get one, and the bigger it is, the better.

Similar Products Used:

Hafler 200, 220, Hafler 500, McCormick DNA .5, DNA 1, and some big, solid state Kenwood monoblocks.

fluid, silk and all synonyms, pick the song you love best and try to deny it...

Many homes I go to don''t own one!

I bought it (1992)and it is a Dynakit 100% stock. Most tubes were shot so in the closet it went. I am an "AUDIOHOLIC" I continue to buy sell trade and look for the sound that is just never there. I have listened to so many solid state amps that I can''t remember....a few I still enjoy and keep in fact an old Dynaco 150 is my all time favorite. anyway...... new Svetlana''s and a couple of used others and I made it. I don''t have to look any further... It may get better but I can''t imagine how much that would cost, nor do I care. I am telling you I made it. Completely stock, paired with a Rotel Preamp that also is my home theatre.... In fact it would be my dedicated pre today if I never got to HT. Anyway, how do you explain the sound..... I can''t but I am listening to Van Morrison right now and have the CD player on repeat. If the sound can make you cry..... then you have made it. The amps pushes ACI Emeralds, Analysis Plus Cables, DIY interconnects, a Klipsch sub that is not in the use most of the time for music.....The bells tend to linger.... it is all there.... Just buy one..... don''t worry there are plenty of us out there that will buy it from you if you don''t like and use it. Just get the vinyl out with voices, Ray Chales Sweet Geogia Brown, my old buddy got married a hundred years ago and that was there song..... I cried then..... I cried the other night when I played it again.... I will buy tubes and more tubes.... it doens''t matter..... email with questions..it''s that good..

Similar Products Used:

Old McIntosh Integrated (Tubes) Eico

Very sweet mid range sound, love this aspect of the amp. Very smooth non jagged sound.

Runs hot

I picked up this machine with a Pas2 preamp, Dual 1229 turntable at a yard sale about 2 years ago for $10.00. I never have been a beleiver in tube stuff. About 1 month ago my NAD Power amp fried and I thought what the heck why not hook it up and give it try. The first thing I had to was track down a Rectifier tube and put it in. I also had replace some cut power cords on the power and pre amp. I tied this into Nakamichi Cd player, Kef speakers (Vintage Crestas and 103.2''s) and turned it on. At first I cranked it and it sounded like crap ( knew nothing about varacs and capacitors and gradually bringing them up). However after about a half hour it actually started to sound pretty good. I have been running it for about a month now and I can truthfully say that it does not compare to my Nad power in some areas ( the highs are a little more flat, the bass is not even close). Also have a passive Infinity Sub tied into this. The one area where it really shines is in the area of mid-range, I really enjoy the smoothness of the sound. I have ran other integrated amps with more power through my Kefs (very inefficient but oh so sweet sounding) and some would not even push these. So Maybe it does take less to get more with tube equipment. I have used an endless list of integrated stuff like Carver, Hafler, Marantz, HK, Yamaha, etc, and this damm relic is starting to grow on me. When i get my Nad back I''m not sure which I''m going to keep, I''m actually thinking of getting another one and running them mono in hopes that it gives me the bottom end that I''m missing. For what I spent on it and what I had to spend to get it going its a great deal. When I''m considering buying a second one for more power that should tell you something, I''m quite impressed by the sound produced by this old relic. As to date other than the rectifier tube and cords I have not done a thing to this amp which is amazing for something that is 30 plus years old. If I do keep it I will try to keep it as original as possible. If they only built anything like this nowadays

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never anything tube before this

I guess I mentioned it''s strengths already. but price, availability of parts, and it''s responce to be modified without high $ cost is it''s mainstay, long live the st70,

the ST 70 is only weak in the point where one is not able to couple it with equipment that will work well with this honey of an amp

I must first give an over all background for the basis of this critique, I have been an avid enthusiast for too long to mention, and have experimented with many types of combinations, types, being solidstate, tube combos preamp to amp and visa versa, the dynaco ST 70 in my oppinion is one of the most forgiving amps ever made responds well to modification, I have two of the babies, one has been extensively reworked, and the other stock, to be quite honest the stock amp is possibly more real, to me any way, the stock amp is pushed by a bryston.5b preamp and the receiving end is handled by a very revealing SABA speaker monitor sattelite system, this system is so entransing, to listen to, womens voices seem to just stand out, play some Diana Krull, she might as well be singing right in front of you, every nuance of music is revealed, that is a stock amp, the one that is reworked, I don''t think there is that much appreciable difference worth noting, if you change the preamp to one with tone control, such as a marantz 7t I own, all that is not there seemingly,is gained. I worked in a high end audio store where I got to experiment with names like thiel, audioquest, mirage, conrad johnson, harman kardon, NHT,audio research, Adcom, and more and have put together every combo you could think of, that was at my disposal, I tried a test with a cd that most people can get their hands on, and that is to play a cut off an Enya cd, watermark and the first cut. at 56 on the clock and again at about 106 there is a kettle drum that most systems will not create, this little amp in stock form with no help from gain control will produce, I was shown that test by a mirage salesman, and i have used it ever since, putting a lot of wanted to be high end systems to shame, I am using a very nice pair of sansui, yes I said sansui, SP 20000''s pretty rare speaker, built in 1978 most likely conceived in 77. but anyway, that is the speaker I am using, very very efficient. I have used magnapan, advent, and a few older types by marantz, for vintage comparison, and my sansui''s stay on top, to hear someone say that efficient speakers in the middle late sixties didn''t exist, is to think that they didn''t look, but you have to have your system tweeked, good interconnects, good speaker wire, and ends.over all I would rate this little amp worth 10 times it price.

Similar Products Used:

scott, the dyna sca 35 (not real equal)conrad johnson.

I agree with the good doctor. I use the amp to drive a set of Accoustat's and the stage is warm and forward. The current for bass is abundant and solid. Electro static speakers are hard to drive, and fussy with electronics. (Just try driving an electrostatic with a Japanese poor-fi amp like a Kenwood M-1 basic. the sound is utterly vulgar as if the speakers were stowed in a closet!!!) This is an amp a collector , enthusiast, or audiophile can love for it's unique character.
I do not hesitate with a five star rating. Simply top drawer transparency!

Unbelievable sound output, great range of sound

I have blown a lot of fuses

I got my ST-70 from my father when he gave up the hobby. I am using a Carver Model C-1 Sonic Holography Preamp and a McIntosh MR71 FM tuner. I use a simple SONY discman as a CD player and I also have my computer hooked up to it for MP3s. I am using huge Bozak Symphony speakers in a custom-made case. This amp sounds great with this equipment, well beyond any transistor amp.

Unbelievable sound output, great range of sound

I have blown a lot of fuses

I got my ST-70 from my father when he gave up the hobby. I am using a Carver Model C-1 Sonic Holography Preamp and a McIntosh MR71 FM tuner. I use a simple SONY discman as a CD player and I also have my computer hooked up to it for MP3s. I am using huge Bozak Symphony speakers in a custom-made case. This amp sounds great with this equipment, well beyond any transistor amp.

excellent control over music dynamics

was too hot to use in a warm climate

This is a report being written from my last use of the 70 and a Pas 3x about 20 years ago. I must have got the last kit on earth at that time. It did use the twin 7199s. On my Marantz Imperial 6g speakers, this combo was outstanding in overall sound reproduction of LPs and FM radio. I found it was just too hot in S. Fla. to use any kind of tube equipment so I sold everything I had. David Hafler defintely was a leader in the audio field with his tube products.

Similar Products Used:

Fisher and Harmon Kardon int. tube amps

Soundstage wider that the Mighty Mississippi, buttery midrange, hefty bass, smoooooth highs.

Hotter that a two-bit hooker and heavy as a small sedan

I bought (some would say stole) this amp for a mere $200 along with a Dynaco PAT-4 preamp, and a Dynaco FM-3 tuner. All three of these were dirty and old, as can be expected of 35+ year old equipment. This was an older version of the ST-70 with the A460 power x-former. It came filled with Mullards, and the FM-3 was filled with old Telefunkens. What a find!

I totally gutted the amp, until I ended up with a completele empty chassis and some rusty irons. I threw away nearly everything else besides six resistors and a capacitor. Next I sanded and re-painted the transformers flat black, and polished the chassis till my arm hurt (not till it was a mirror finish like I had hoped to do). Then I waited for the replacement parts to roll in.

I upgraded the board with the Van Alistine Super 70i kit, which replaced the bigh quad cap with a bank of littler ones, and introduced an imput bandwidth filter to help the output and power transformers from overloading (check out his website for more details http://www.avahifi.com/70rebuild.htm) The new tube sockets are gold and ceramic. New gold plated input and output connections, and of course a new grounded power cord.

Now that it is done, and the Sylvetna EL34s are warmed up, I am being treated, for the first time, to pure musical ecstacy. A virtual orgasm in my ears. Previously I had been feeding my beautiful, and very revealing, Dunlavy SCII s with solid state amps like Marantz of various types, NADs, Carvers, even some Pioneer and Sony junk. The highs were always sybillant and harsh, and the mids somewhat scooped out. Now, however, the highs are smooth and celestial; and the midrange is like REAL maple syrup or a velvet quilt. The amp is very revealing -- several times I have heard parts of records I have never heard before. The sound is very balanced and beautiful. It matches well with traditionally bright, and accurate speakers like the Dunlavys. (Although I bet it would mate well with about anything...) And the amp gets LOUD!!!

Anyway I am finally in love with my stereo. The $400 I spent on this ugly little amp is a small price to pay to reach Amplifier Heaven. Some people pay many thousands of dollars more and never reach it. Now all I need is a good preamp -- factory wired or a kit. I am open to suggestions...

My equipment...

Marantz CD-46 cd player
Music Hall MMF turntable
NHT SW2pi subwoofer
Dunlavy SCII speakers
Dynaco FM-3 tuner
Carver C-2 preamp
Synergistic Research speaker cables

Similar Products Used:

None yet.

Value. Great tube sound! Incredible looks, especially at night!

None, except possibly the rusty, pitted chassis.

My first venture into vintage tube equipment has been an enjoyable success. I can't believe the sound this old machine puts out! Sounds like real music is coming out of my Polk 10Bs. Selling my Sony STR-DB930 and replacing it with the ST-70 coupled with the Dynaco PAS-2. I am VERY happy with the sound I'm getting out of these two old vitage pieces. I don't think I'll ever be able to go back to solid state.