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:
• I Screwed Up Buying a ...
• The Dynaco VTA ST-70 R...
My Weak-End Update video with info about Rocket Sockets:
• Weak-End Update With F...
Some videos I've made showing amp bench testing in detail:
Kenwood Jumbo receiver: • 1971 Kenwood Jumbo Rec...
Eico HF-52 tube amp: • It's Done! 1957 Eico H...
Dynaco SCA-80Q amp: • Dynaco SCA-80Q Amp Kit...
Kenwood KA-76: • Kenwood KA-76 Amp. Let...
Heathkit preamp: • Let’s Test A Heathkit ...
McIntosh MC2105: • McIntosh MC2105 P8: Le...
To learn more about VTA (Tubes for Hifi) kits visit:
www.tubes4hifi.com
To visit my Amazon Shop, please click:
www.amazon.com/shop/fluxconde...
#stereorepair #stereoamplifier

[@peterc3143]

Nothing like music being played by a tube amp. 👍

[@seanmcguire6998]

Except transistors replacing the inefficient and hot tubes, in a better circuit scheme. Still…the dynamics, warmth from 2nd order harmonics, and the REAL wattage that only tubes can give!

[@Mrsteve4761]

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!

[@FluxCondenser]

Thank you!

[@tgr131]

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.

[@FluxCondenser]

Wow! Thank you so much for that.

[@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 🔥🔥🔥

[@FluxCondenser]

I used to pick on Florida for being so hot and sticky. Then I’m moved to Antalya which makes Florida seem like the North Pole!

[@tpock63]

Wow! Amazing job! and very entertaining to watch

[@scrappy7571]

good to see you back

[@jmsbriann]

Great, good job once again!

[@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.

[@FluxCondenser]

Nice to hear your experience with the ST70. Just as so many others have shared, underscoring just how popular these things are. The greatest selling amp of all time, I believe. And yes, in my opinion for this amp solid state is the way to go for the rectifier.

[@michaelmski5421]

Well Done and stunning finish.

[@FluxCondenser]

Many thanks!

[@TeslaTales59]

Nice work!

[@srschhina5295]

Outstanding work. Thanks ! 🇮🇳

[@waynepollard6879]

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

[@FluxCondenser]

Thanks for the sub!

[@Chuek-WaiTai]

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

[@FluxCondenser]

Thanks, one of these days I’ll do just that. Publish a 20+ hour video in real time. I don’t think anyone would really be interested in that, though.

[@bozersgal]

@@FluxCondenser with something this classic and beloved, you might be surprised

[@FluxCondenser]

Hm.

[@phillipkelloway8905]

Excellent job

[@6StringPassion.]

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.

[@zdzisawwodzynski3086]

Pełna profeska gratuluję

[@6StringPassion.]

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

[@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. 🤔

[@anthonysilva5312]

Man! So cool!🇨🇦

[@FluxCondenser]

Glad you liked it.

[@antoniorinaldi784]

Fantastic

[@gilbertlessard4380]

Hi Chris. I am new to your channel. Enjoyed it immensely. Just wondering if you used any shielded cable in the build. Looking forward to watching the rest of your videos.

[@bboehm]

Very nice video! Where can one buy the driver board cover kit? Thank you!

[@mr.selfdestruct2917]

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

[@waynemasters8673]

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

[@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 :)

[@FluxCondenser]

Thanks! And the footage is actually mostly at 20X speed not 2X believe it or not. I agree, the knot for the power cord is not ideal and a strain relief would be better. But yeah, I like to keep the vintage look sometimes. Take care and thanks for the thoughtful comment.

[@KeritechElectronics]

@@FluxCondenser trying my best to make my comments and videos as thoughtful and meaningful as I can :)

[@timbuckxxi9690]

Or go at half speed if you're really bored..

[@user-Limaa]

nice do have some mic tube preamp that can distortion, non-transistor project

[@patricebourdon7880]

Great, what are the 2 empty bulb slots for in front ?

[@jago5300]

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

[@kamertonaudiophileplayer847]

What is a big black thingy you used at wring?

[@crimsonghost6454]

Great job as always. I hope everything works out for you in all aspects. Now whats the hifi and record store situation like in Turkey? That would be cool to see and learn about.

[@FluxCondenser]

Thanks. Yes, hifi and music in Turkey are some subjects I hope to soon explore in upcoming videos. Stay tuned!

[@ggeorge3219]

I've built my share of tuners and amps. Remember Lafayette catalog? So much fun. I did let the smoke out of a couple but replacement is easy. How many watts {rms} ?

[@justinfaso2855]

Do you have a list of the songs used in this video

[@bennettamplification]

What are those sockets on the face used for? Great video by the way 🙌🏼🤝🏻

[@timbuckxxi9690]

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

[@FluxCondenser]

It’s a beauty.

[@darthbubba866]

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.

[@FluxCondenser]

Ha! You got that right. This was really a pretty solid week of work from beginning to end. And videotaping the whole thing adds a lot of time and complication as well. What’s really difficult is taking the 20+ hours of video and editing it down to quickly tell a story. My eyes are bleary for days after editing these things. But, it’s well worth it when fans like you show your appreciation. As always, thanks!

[@joossejoosse509]

Hola excelente video, el kit se puede comprar?

[@johnnytheg]

Good to see the build videos are back. One thing, is that a solid state rectifier on this amp? Did it come with the kit that way or did you swap out the tube on your own?

[@FluxCondenser]

Thanks, John. Good observation. The amp came with a tube rectifier, but it blew during testing. It wasn’t a cheap tube, either. I prefer to run these things with solid state tube replacements.

[@paulbathe1130]

Where can you order the dyna kit and how much does it cost

[@chuckmcgillis8160]

I've got an at70 case that's chromed. But need all the parts to the amp . How much would you charge to build it for me if I send you the case

[@darrellgenejeremiah8111]

Beautiful!

[@engelbertodelapena9526]

hello nice build can you post the schematic

[@brianhartline1197]

Where do i get in touch for one and how much for a fender twin type clean single channel with 6CA7 power amp

[@giulioluzzardi7632]

Great job, are the output valves 5881's ?

[@bukeksiansu2112]

The intro music reminds me to Duran Duran Come Undone.

[@marioduarte7658]

Cheers from Brazil! Nice vídeo. Would you recommend that amp to me since I am struggling to build my first high end?

[@FluxCondenser]

Greetings. Tell me about your experience level and what you’re struggling with and perhaps I can guide you.

[@pietjanssen4734]

Where can i order the kit (In Europe) ?

[@didioentoro7575]

Dynaco ST-70 KIT where could you buy it now ? Is it complete KIT including chassis?

[@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.

[@charlesufpa]

Hello. Very cool your video and equipment. How can I acquire it? Grateful.

[@charlesufpa]

@o'o I ASKED WHERE TO BUY IT... I DON'T WANT IT FOR FREE, CRAZY I ALREADY WORK.

[@danhorton6182]

Nice work, new subscriber. What station are you using? The hand piece looks a lot like the hand piece my Hakko FX-100 uses. Are you pleased with your station? Edit: I see at the end of the video you post a pick of the FX-100, so that must be it. Your honest thoughts of it?

[@FluxCondenser]

Thanks, I have a mini review of the FX-100 here you can check out: kzbin.info/www/bejne/a3m9dYeJa8eGmLM

[@danhorton6182]

@@FluxCondenser awesome, thank you for the response. I’d have to agree, easily the best I’ve used. I enjoy using it more than the JBC I paid nearly 1-1/2 times more for. Anyways, just curious as I really don’t see many people using it and I think it’s kind of a hidden gem. Don’t know if you are, but if you’re considering upgrading to a better vacuum I have the FR-410 which is a matching unit in looks at least. I didn’t think it was going to be, but it’s a HUGE improvement over the FR-301 hand vacuum. To me at least it was well worth the money for the upgrade. They also make an FR-400 which is a heavy duty version for quite a bit more, but I’ve found the FR-410 more than sufficient.

[@szeleungtam6647]

Only one 5U4 isThet. enough ?

[@Soundbrigade]

Can I send my half built tube amps to you so you can help me finish building them? I’ve got a KMQ60 clone, a simple EL84-PP, a GU50-SE and some SE and PP-amps built on pen-size tubes and finally a mega-project with GU72 SE-monoblocks…. If you fixed a Dynaco in 10 minutes, my un-finished projects would take a day at max. PS. Having worked at a capacitor plant for 10 years I would never ever use PIO, tubes. They are simply inferior when it comes to using them for sound equipment due to their high amount of distortion.

[@hansivarlie9125]

Nice music

[@michaelsingh7529]

How can i access the kit.Thanks.

[@FluxCondenser]

www.tubes4hifi.com/amps.htm

[@megaheadbanger]

I buying american caps Mojo Dijon for my amps, think old soviet caps is not cool (but I have lot of them). You using old soviets caps... It blow my mind

[@FluxCondenser]

They were new Soviet caps. Not old.

[@basspig]

I've got an original ST-70 in good condition. I wonder how much it is worth?

[@FluxCondenser]

Check ebay.

[@basspig]

@@FluxCondenser I have. Their listings are all over the place from $500 for a non working one to $1900 for a customized restored one.

[@PartySpock]

Mullard el 34 👍👍

[@geoffreyharbinson2488]

Im old I cant think fast anymore . Ive built smaller sruff I so wish I could slow the video down for the wiring parts

[@MichaelB-xi1hk]

Tap the gear symbol in the upper right hand corner of the video to bring up settings. Select playback speed. You can speed up, or slow down playback at your will.

[@antonalemaskin9563]

💯👍

[@marcusfountain1694]

This just makes me wana take mind apart ,lol's

[@JustinRoofCentral]

Can you build me one like this?

[@squarrl]

How is this thing legal? I see a two wire power cord and a metal chassis.

[@FluxCondenser]

It could easily be wired with a grounded cord, so that’s an easy addition to make, and yes that would add a margin of safety. Given that everything is powered from the transformer, though, the only potential for that being of benefit would be if the power cord became frayed and somehow came in contact with the chassis. I mean, it could happen, but it’s unlikely. Also, there is a fuse which adds a margin of safety. Again, I’m not disagreeing. A grounded cord will add some safety, but this thing isn’t exactly a death trap, either. And I have no hesitation leaving it on in my home. Then again, I know who built it. Trusting someone else’s work with a kit is another story. And you pose a good question about the legality. I’m really not sure what the laws are on that for America. If anyone knows, please chime in.

[@cletusberkeley9441]

I hate those little feet. I used four hockey pucks when I built mine. Looks great and very stable. Gives good clearance under the amp too.

[@FluxCondenser]

Hockey pucks? Yuck. Use the type I installed. Much better looking and stable.

[@jackwalton1975]

Those Bourns trimmers will eventually die. Pete Millett uses PIHER available from Mouser.

[@FluxCondenser]

They seem like quality trimmers to me and Bourns has a good reputation. Do you have any real world data to support that they are more prone to failure with real world comparisons in the same application?

[@TimTam770]

$995 for the kit with no tubes

[@johto]

video sped up and over 14 minutes, so no...you did not build this under 10 minutes LOL

[@IgorSPopovich]

You did NOT assemble this amp in 10 minutes! More like a few hours, 10 minutes in the video maybe 🤣 Just taking transformers apart, sanding and painting the end bells would take more than 10 minutes!!!

[@FluxCondenser]

Well, yes. In fact I shot over 20 hours of footage to build the amp, a lot more than a few hours.

[@KeritechElectronics]

@@FluxCondenser and that's just stuffing a ready-made chassis, of course. Manual fabrication would take another few well-packed days of work.

[@user-yb5gy7qs5j]

no you can not build it ten minutes you cant count all the parts in that time? gkl

[@MrFat.]

More like, 10 hours. 🤣

[@szeleungtam6647]

Ignore the important thing. Only to the nonsense

[@francisigooch5269]

WOW that wiring is such a mess. Unbelievable. Russian capacitors? You never heard of Nichicon capacitors??

[@user-yb5gy7qs5j]

no sir mister you can not build a dynco st 70 in ten min. you cant gather together all the parts in ten

[@maikl6920]

....усилитель-дерьмо полное, только красота .........

[@darrellgenejeremiah8111]

Better make sure the transformer bolts are tight