My new to me ST70

I have been a fan of Dynaco equipment since the early 70's when I put together my first hi-fi set with a kit PAT4 and Stereo 80, A-25's, and an
AR XA turntable with a de rigeur Shure M91ED cartridge. That system was the envy of my friends and travelled with me to all the places I lived at in my pursuit of higher education and served me well into the late 70's when I sold it to buy Japanese made gear which was sexier and more impressive looking although no better performing than my Dynaco's... Oh boy, I think I inadvertently had a hand in the destruction of the American hi-fi industry, but I digress...

Dynaco's combination of performance at an economical price really appealed to me then, and it still does today. I have a stable of recently acquired vintage Dynaco components upgraded to current performance levels with kits designed by circuit designers who like me appreciate the qualities that make Dynaco gear so special, yet wish to improve their performance characteristics. I have systems set up in rooms throughout my house using these components, PAT4's, Stereo 120's, a PAT5, an FM5, A-25, and A-25XL speakers. All have been, as you can see, solid state, and until now I have not owned a piece of their tube gear, and naturally, I wanted an ST70, an as you all know, a landmark piece of audio engineering, and maybe Dynaco's best known product.

I attach pics of my amp, a factory built unit, not sure of the date of manufacture, but the serial number begins with 6921. I'll upgrade it with the VTA70 board and other bits, but first I intend to run it stock for a while so I can have a benchmark to compare the upgrades to.

Oh well, no success with attaching pics, will try later!

In regard to your "upgrade" to Japanese gear, I'm sure many of us have been there and done that, only to much regret it later. It's good that you held on to the speakers and the AR XA. Sure wish I had.

billinrio wrote:In regard to your "upgrade" to Japanese gear, I'm sure many of us have been there and done that, only to much regret it later. It's good that you held on to the speakers and the AR XA.  Sure wish I had.

Unfortunately I didn't! My original Dynaco equipment I sold to a friend back in the 70's, same for my original pair of A-25's and the AR XA to a different friend.

All my vintage gear I've acquired recently.

I'm still looking for an AR XA in decent restorable shape, but it's low on the priority scale for now. The AR tonearm was horrible, I saw one in my college days at Auburn University where the owner had installed a Shure/SME arm. Now that AR XA sounded great!

It lives! Tubes arrived today, matched JJ EL34 quads, Sovtek 5AR4, 1 NOS GE 6GH8A, 1 NOS Zenith 6GH8A, both in adaptors. Sounds great through Vandersteen 2CE Signatures on the 8 ohm tap. My line voltage

My plan is to update the amp with the VTA70 board and larger quad cap. But until the parts arrive and I load up the VTA board I plan to carefully listen to this stock unit and get a baseline of its performance. Already it sounds really great!

Finished the upgrade to VTA70 this morning, with the extra capacitance and PIO cap upgrades, 80-40-30-20 quad cap and a new C354 sealed choke from Dynakit parts. My first impression is how utterly quiet the amp is. Sounds very good, I sense extended highs, wider and deeper soundstage and tighter, lower bass than the standard vintage unit. Very impressed and very happy with the upgrades!

replacing that choke makes a huge difference, When I ordered the SP-14 I saw that there was an option to use a choke in the power supply and I glad I did it. great looking amp.

Frankford wrote:replacing that choke makes a huge difference, When I ordered the SP-14 I saw that there was an option to use a choke in the power supply and I glad I did it. great looking amp.

Thanks! The old choke had leaked its waxy stuff all over the inside of the unit, so replacing it was a priority. I polished the the chassis, but left plenty of "patina" on it, as I've done with other SS Dynaco amps I've updated, I like to show that they are vintage pieces, with some age on their bones!