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Wardsweb does a Dynaco ST-70 his way

Wardsweb

Wardsweb

Behind The Curtain
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I am building a custom modern version of an ST-70 from scratch. The only original parts I'm using from a ST-70 are the output transformers. Everything else will be new. You may follow the build here:

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

st70_13.jpg
 
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Redboy said:
Very nice.

What's your favorite way to cut holes in aluminum, Wardsweb?
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My favorite would be using a Uni-Bit. It cuts clean and is quick. For items larger than 7/8" I typically use a chassis punch. The picture below shows the 9 pin socket holes done with a Uni-Bit and the larger 8 pin socket holes done with a chassis punch. The chassis punch holes usually require a little clean up on the edges.

st70_16.jpg
 
I haven't mastered the art of the chassis punch but I do like my step bits! :yes:

I don't suppose you could do it on this chassis, but did you give any thought to building an ST-70 where the driver board could be swapped out fairly easily for a different flavor/ brand/ model? That's the only tube amp that comes to mind that has so many different options available - it could be a tweaker's delight! I guess the original chassis design is pretty good for that... :scratch2:

Looking good so far!
 
FWIW, Take a look at Dynacos original specs for the 420 iron. It will perform very well way past 35 watts. Last time I had my 70 on the test bench the outputs "finally" saturated with a 25Hz signal at 65 watts. That was with KT 90s and a very beefed up power supply of course. That Triode repro of the POA 60 is dynamite.:yes:
 
OK, Luther, we need to get together when you get it done and run in for a while...I want to bring over my tweaked VTA-70i and compare them...I've also got two more ST-70's that sometimes call out for new driver boards and I'd like to hear Shannon's to see if I want to pick up a couple...

Shannon and I made a trade a few years back when he was starting his Eiclone boards...I traded a well worn HF-89 to him and got a pair of Eiclone boards and two of his 35 WPC boards...still have them and never did anything with them...
 
RickB said:
OK, Luther, we need to get together when you get it done and run in for a while...I want to bring over my tweaked VTA-70i and compare them...I've also got two more ST-70's that sometimes call out for new driver boards and I'd like to hear Shannon's to see if I want to pick up a couple...

Shannon and I made a trade a few years back when he was starting his Eiclone boards...I traded a well worn HF-89 to him and got a pair of Eiclone boards and two of his 35 WPC boards...still have them and never did anything with them...
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Sure thing Rick. It will give me another chance to hit you up for "the" speaker cabinets. :D
 
I've had very good luck using the bigger unibits that go up to an inch or more. I can punch holes at work but have found out the unibits actually do a nicer job in aluminum. Don't buy the cheap bits as they don't last.

One nice thing about the unibits also is you can debur the hole if you bring the next step down to the hole slightly. Flip your plate and do the same thing on the bottom to finish it off and you will come up with about as professional looking hole as you can get.
 
DENNYDOG said:
I've had very good luck using the bigger unibits that go up to an inch or more. I can punch holes at work but have found out the unibits actually do a nicer job in aluminum. Don't buy the cheap bits as they don't last.

One nice thing about the unibits also is you can debur the hole if you bring the next step down to the hole slightly. Flip your plate and do the same thing on the bottom to finish it off and you will come up with about as professional looking hole as you can get.
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Yes and when I use my drill press they're even better.
 
JonL said:
Looks great! Are there any reviews or comments on that driver board?
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I used that board for my diy triode amp that I built for AKFEST 2007. That is an excellent board, with a solid circuit design that includes constant current sources on the drivers. This should sound (and look) excellent Luther!

Markus
 
Chassis is drilled, cut and punched. Now a lot of time trial fitting and working out wire routing. I will have it all in my head much like all the moves in a chess match before I solder the first wire.

st70_17.jpg
 
WW,

You're a personal inspiration to me in terms of building. It's like being able to sit back at a favorite concert and enjoy the show.:thmbsp:

Stay thirsty, my friend.

Best,

John
 
Wardsweb said:
Chassis is drilled, cut and punched. Now a lot of time trial fitting and working out wire routing. I will have it all in my head much like all the moves in a chess match before I solder the first wire.

st70_17.jpg
Click to expand...

Ain't that the truth! There are so many ways of wiring and routing, it makes me nut because I keep forgetting what I though was good two minutes after I thought about it.
 
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