#dynaco st70

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Friday Night Vinyl

Got the Green Eyed Monster fired up...

Tonight’s first platter had to be the Nina Simone album from the post a few nights ago, “Little Girl Blue”.

Next up was Joni Mitchell’s self-titled Reprise debut...

Next up an LP of music from Bali.

Talking Heads’ second album, “More Songs About Buildings And Food”.

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The tubes.

Dynaco ST70.

Matched quad of vintage Japanese Raytheon EL34s, Mullard 5AR4 (Britain), Dynaco-branded 7199s.

No mods whatsoever.  Matched with a bone stock PAS-3X, tone controls intact and sounding marvelous.

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The delicious glow of a properly working Dynaco Stereo 70 (ST70) Tube Power Amplifier.  This is one I worked over recently for a good friend.  The Dynaco ST70 is truly “Hi-Fi For Everyman”...read up on the original company...you will learn much.

I bought my first ST70 and PAS3X pair with my very first paycheck from my first job, working in the grocery store at the age of 16, in 1975.  I’ve been a tube-head ever since.

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Moar TubePorn...this is my buddy’s amp after I got done with it.  Brought it up to voltage slowly, over the span of two days.  This enabled all the original capacitors to properly re-form.  The main repair was a solder connection on the bottom of the driver board that was never really properly finished.  It was “tack-soldered”, but was never properly filled/soldered in.  I kept it as original as possible, and thanks to paitence and the variac, It came back to life nicely.  The sound is incredible.  Kept his JJ output tubes and Realistic Lifetime 7199 drivers, and got a vintage GE copper-plate 5AR4 to finish.  It polished up nicely, and I’m guessing it works a little too well...my buddy now has to recone his woofers... ;-)

[audio-luddite]

Everything Old is New again.

Mr Audiophiliac put up his Dynaco ST 70 amp review. As I expected he loves it and even bought it.

The ST 70 is a 1959 era stereo tube amp that puts out 35 Watts per side. It is probably the most common tube amp out in the wild and they number in the many many thousands. It was very good in 1959, when all amps available were tube. It was available as a kit and many were assembled when knowing how to use a soldering iron was quite common. Having assembled and rebuilt Dynaco tube and transistor amplifiers I know the process. Dynaco tube amps are MUCH easier to build.

So yes he loved it. He tested it with some strange speakers including the Chinese knock off LS3 5/A.

To a certain degree if you put a signal into any device like an amp or a speaker you get a facsimile of the real version. How close is the tricky bit. But some things like those knock off speakers will alter the response of the system sometimes dangerously. They are cheap knock offs remember.

Aside from everything else 35 Watts is not enough in my opinion for a good system. My CL60 is almost too small for some music I listen to at 60 Watts per side. (more below)

And as that guy is older and has a thing for tube amps he is predisposed to like some stuff that is questionable. Actually the really interesting thing about his presentation was a link to where he got the amp.

This guy did the restoration work and tested it and a modified version. Look a young guy! His tests are interesting. Note the ASR testing guys did a ST 70 and it did very poorly.

I liked that he did listening tests as well. It would have only been better if they had a control amplifier like a nice MOSFET unit to compare both to. The listening results are particularly good in that the two machines test very different. On the bench one is clearly better, but on the couch with music the experience is totally different.

Distortion is good!?

I need to point out that the test numbers Novalux got were using a lab load. That is usually a straight resistor that can handle many Watts of power. A simple resistor is really easy for an amp to handle. A speaker with a cross over filter is completely different. That can massively change frequency response and distortion.

Regarding power:

I listened to some tunes last night. I have the Mangione "Children of Snachez" sound track LP. It has some amazing Bass. If you play it loud you feel it. Not just in the drums, and bass guitar, but also the horns have impact. You need Watts to get that. You need available current to push the speakers around.

I also listened to Cat Stevens "Catch Bull at 4". I really like that album. It has great range and was well recorded and mastered. There are many layers to the songs both sonically and literally. My favorite is O Caritas which is song in Latin. It is a ballsy song. Again you have to have power behind it.

I have played on both sides of the solid state / vacuum schism. I continue to do so. They are both fun.

The point is to have fun and enjoy music.

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The Glow of my Dynaco Stereo 70.

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The Glow.