Can I Build It In 10 Minutes? The Dynaco VTA ST-70 Amp Kit

The ST-70 is a classic amp designed by David Hafler of Dynaco that dates back to 1959. This VTA kit is similar to the original in all the right places, but features some modern updates. Can I build it in ten minutes? Let's find out!

0:00 Introduction
1:02 Painting the transformers
1:40 Building the PC board
2:00 Bias trimmers
2:10 How I organize components
2:55 Cleaning flux from PC board
3:28 Protecting the chassis with masking tape
3:45 Building the chassis
4:25 Reassembling the transformers
4:50 Installing the transformers
5:00 Let’s learn about chokes
5:30 Installing the choke and output transformers
5:42 Installing multi-section capacitor and chassis wiring
7:54 Faulty expensive Russian capacitors
8:20 Finishing PC board and installing it on the chassis
8:53 Installing front panel hardware
9:44 Level control modification
10:12 Rocket Sockets
10:42 Uh oh, there’s a problem
11:19 Installing AC power cord
11:35 Correcting the faulty capacitor
11:44 A new world record!
11:52 Initial startup and tests
12:32 Bench testing
12:44 The finishing touches
12:50 Protective shield modification
13:15 These feet stink
13:30 Crank up the music!

Check out the videos Dave of My Own Devices made about this project:

My Weak-End Update video with info about Rocket Sockets:

Some videos I've made showing amp bench testing in detail:

To learn more about VTA (Tubes for Hifi) kits visit:

To visit my Amazon Shop, please click:

#stereorepair #stereoamplifier

[peterc]

Nothing like music being played by a tube amp. 👍

[tgr]

Welcome back, Flux! I wish I had some insightful thing to say, but really all I've got is "I've missed you, and glad you're back!" I learn a lot from your videos.

[Mrsteve]

So glad you're back. Your attention to detail is what brings me back time after time to watch your videos. That and how succinctly you orate what you do along the way is among the best I've seen. Keep them coming!

[MODAC]

Terrific Chris, you did a great job and it sounds fantastic. I’m very confident it will be rocking for many years to come. I have shelved it until the weather cools down a bit. It gets 🔥🔥🔥

[Geoduck.]

This was a hoot to watch Chris.
Some years ears ago I rebuilt two ST-70's for friends only keeping the original iron and chassis. I used VTA rebuild kits very highly recommended! At the time those PIO USSR caps were like two bucks each. One amp I used KT77's and the other it's original Dynaco Mullard EL34's!
In my case I kept the tube rectifier for my friends as I have a number of Mullard GZ34 tubes. SS rectification is not a bad thing in fact many think it's superior to tube.

[tpock]

Wow! Amazing job! and very entertaining to watch

[Chuek-WaiTai]

Great work and fantastic video. Enjoy very much. Thank you! I don't mind to watch the normal speed video. 🙂

[waynepollard]

Like background music of your videos ! Keep up the great content ! I'm a new subscriber ! Thanks !

[StringPassion.]

After watching your SCA80Q build, I snagged one for parts and repaired it. It just needed new diodes in the power supply. It sounds absolutely wonderful.

[amoruzz]

Very nice 👍
I need to get mine refurbished one of these day's. I also have a cool solo Heathkit tube preamp that could be used for other thing's. 🤔

[sergiogomezphotography]

Great video, I recently bought my ST-70, I’d like to paint the transformer shields as you did but I guess it would take a lot of unsoldering to remove them.

[StringPassion.]

Awesome. I'm going to restore my Stereo 70 shortly.

[KeritechElectronics]

You can build it in 5 minutes! If someone is viewing this video at twice the normal speed, and still understanding everything, haha. That's double craziness indeed.

Nice build, and I like using the masking tape for doing stuff on the chassis, especially when drilling the thing. Learned it the hard way.

I like these Russian caps. The power cord looks really bad to me, an outdated practice that should be preserved only on some vintage devices and that's that.
I'd use an IEC C13 socket or a strain relief cable gland and a round 3-lead cable.

Cool acrylic PCB shield, makes things safe while preserving the look. I like it a lot. The amp looks great indeed.

Nice weak-end update logo BTW :)

[waynemasters]

I can't believe I could smell burnt coffee when I turned it on!

[darthbubba]

You? Build it in 10 minutes? 🤣 You and I both know that both of us take more time than that just checking component values against the schematic. And welcome back! I really missed your videos.

[jago]

Means nothing you don't have schematics, websites to order the schematics, where to buy the parts, I could go on. But you're not the only one I love you do the same thing

[mr.selfdestruct]

2010 Vta st120 here. Is the weber ws1 with thermistor healthy for the amp. If so what are the pros and cons? Thank you. Great vid

[timbuckxxi]

Slick clean amp..Maybe 50 watts a channel of VALVE tone ! Looked like EL34 power tubes..NICE !

[Galova]

these capacitors are 50 years old and they are paper-foil in oil type. there's no surprise it has degraded. who knows in what conditions they've been stocked all these years. they have a guarranteed maximum storage time of about 20 years, maybe 25 in required conditions like temperature and moisture.

[bukeksiansu]

The intro music reminds me to Duran Duran Come Undone.