My modern version of a Dynaco ST70

[Wardsweb]

This is what I came up with for building a modern version of a Dynaco ST-70. The only original parts used were the output transformers. Everything else is new. I upgraded parts and driver board. I drilled and punched a chassis for the new layout and had it chromed. I build a new cabinet out of Baltic birch and veneered it in cocobolo. I was inspired after the Quickie I built with a similar cabinet design.


(https://forum.bottlehead.com/proxy.php?request=http%3A%2F%2Fwardsweb.org%2Faudio%2FST70%2Fbuild%2Fst70_31.jpg&hash=aacfb7c835b4a6b5d24ed1c1a18a16ed24140e62)


(https://forum.bottlehead.com/proxy.php?request=http%3A%2F%2Fwardsweb.org%2Faudio%2FST70%2Fbuild%2Fst70_33.jpg&hash=0ddfeb3c4c60a56497d4af082b834e18c5f9bfd9)

[Paul Joppa]

Sweet!

[Paul Birkeland]

Can you build me one?

That is really pretty, whose driver board did you decide on?

[Grainger49]

WOW !

That is incredible.  What are the two red topped things between the output tubes and the driver tubes?

[Wardsweb]

Can you build me one?

That is really pretty, whose driver board did you decide on?

I used Shannon Park's board. You can see in depth details on my website:

http://wardsweb.org/audio/ST70/

[corndog71]

That is one sexy amp!

[ironbut]

Beautiful work!
How hard was it to do the veneer?

[Wardsweb]

Beautiful work!
How hard was it to do the veneer?

Not hard at all actually. The side you glue and then trim. The top is one piece. I glued it first and then cut out the center.

[Wardsweb]

WOW !

That is incredible.  What are the two red topped things between the output tubes and the driver tubes?

They're several test points on the chassis used for setting bias. The original amp had the tube socket on the front. I opted for a some nicer tip jacks.

[Grainger49]

I take it that the right and left pair of output tubes are still biased together?  I got a schematic some time back that allowed bias for each tube and allowed using non matched tubes.

[Paul Birkeland]

Let's see the inside!

[mrarroyo]

That is sweet indeed! How many watts does it put out? I wonder if I could use it to power my AKG K1000, and if yes how much to build me one?

[Grainger49]

The Stereo 70 is 35 WPC.  That was part of Dynaco's numbering scheme.  The parts are mostly being cloned by a number of companies.  Luther bought his "junker" ST-70 for the old, desirable, cloth insulated  wire output transformers.  

If you use the link he supplied in reply #4, you will find a parts list.

And with a few more pictures of the inside goodies and this MANUAL downloaded you can build your own.

(That is a hot key.)

[Paul Birkeland]

K1000's are very nicely driven by Paramounts, and the DC on the filaments keeps it super quiet. Oddly enough, 2A3's are plenty of power for the K1000. I will test the Stereomour also to see if it is suitable for K1000 duty, but I'm somewheat skeptical.

[mrarroyo]

The Paramount using the 300 tube looks awesome! However, I would not be able to build it due to both poor soldering technique and poor eyesight. Since I would have to have it built I will have to wait until I can come up with $2,000. Thanks.