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Dynakit ST-70 How Difficult?

This past winter I assembled a Bob Latino VTA ST120 tube amplifier. I have not soldered a wire in many years and I had no troubles putting this together. His instructions and accompanying photos/illustrations were a very big help. I too was worried about possibly making a poor solder joint, but it's really not difficult. If anything, it's more an exercise of routing and shaping wires between the transformers, tube sockets and circuit board. Bob's real-time support by email and phone is legendary.

If you set yourself up with a well-equipped work area; soldering iron and stand; good nips and wire stripper; bright light (and a flashlight to get in there) I suspect you will find yourself having a lot of fun and feeling a little sad when it's all done.

Oh yeah...it's sounds great!

Good luck!
 
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I've recently done one of the Bob Latino kits as well. Very good instructions, simple to follow. And a very nice sound at the end of it. Be methodical, double check everything and it should all be fine.
 
Yes, follow the instructions carefully, do neat work, take your time, and you'll be rewarded with long lived musical pleasure for many years to come. My Stereo 70 still sounds terrific, and has been reliable since 1973.
 
Triode Electronics sells a kit version of the ST-35 PCB by Shannon Parks over at diytube.com which uses easier to swap different driver tubes for improved sonics. The Output Transformers were among the first copies along with magnequest.com (he makes handbuilt runs of them , so you have to email him or contact him on his forum @ audioasylum) ) and are highly liked.

The EFB mod by Dave Gillespie of AK and diytube etc. is well worth adding to any ST-35 version or easy to drive 7591 type tube amp. for a really low cost improvement in output tube life and sonics. See it at his site @ tronola.com.

Another maker of Output Transformers that are highly liked which just started Dynaco & other clones is transcendar.com.

If you want to build a more powerful version of the ST-35 (use 7591 type Output Tubes & a higher capacity PS Trans or 2 of the original) ) or a ST-70 type consider the New Output Transformers sold by Triode Electronics that are made by Magnetic Components. They are quite affordable and should be really nice!

Remember the Output Trans on a tube amp defines the sonics and for many that's why they look for the vintage amps or used trans from them.
Interleaving or layering between the primary or secondary coils (more is costlier as it takes a lot more time and really improves the sonics) ) is why some output trans are so expensive in new production or found in the valued vintage ones bringing the prices up in many cases. Some vintage are way overpriced also!

From that another consideration is a rebuilding (replacing mostly old caps and possibly some resistors) a vintage amp of quality as it's not that hard either with info and help on the forms. HH Scott, Fisher, Pilot, & Sherwood & most Heathkit & Eico (they were mostly kits) come to mind as ones to look for.

There are also other great vintage brands that can go for big $ or hidden gems out there.

Never just plug a dormant vintage tube amp in that has been sitting for a year or more as the old caps can suddenly short taking any of the transformers out. They should be recapped, but to test for good transformers etc. they should be brought up on a variac or at least a dim bulb tester or better yet both.

Finally never run a tube amp without a load of speakers or big resistors when testing as a voltage spike can take out the output transformers.

Tube amp's tubes don't like to be short cycled either (wait till the tubes are well cooled off in usually 5-10 min) so watch kids or storms.
 
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Been looking for my next Project...Was also looking at Dynakit ST-70 Kit or Tubes4hifi (Bob Latino VTA ST-70).

Looks like Bob Latino VTA ST-70 will be on my order list...So look for a Thread on this build in a few weeks.
 
a461b74ba45a91b9a95d054ac5cada4f.jpg


If you want a turnkey kit I suggest the dynakitparts ST-35. I built this several years ago. Added the EFB mod (note the small heatsink) and upgraded coupling caps. Two days to build.

It sounds lovely. Looks nice with the stainless chassis. Smaller than the 70.


Sent from my iPad using Tapatalk
 
Rockyhill said:
a461b74ba45a91b9a95d054ac5cada4f.jpg


If you want a turnkey kit I suggest the dynakitparts ST-35. I built this several years ago. Added the EFB mod (note the small heatsink) and upgraded coupling caps. Two days to build.

It sounds lovely. Looks nice with the stainless chassis. Smaller than the 70.


Sent from my iPad using Tapatalk
Click to expand...

Rockyhill,
That looks real nice. I keep waffling back and forth between the 35 and the 70 kit. Does the 35 have enough power?

Thanks
 
st35 has plenty power for most spkrs over 86 or so db spl.
I just ran mine on my new Tekton Lore 2, 96db spl, and it sounds fantastic.
go for it. you wont be sorry.
 
Rockyhill said:
a461b74ba45a91b9a95d054ac5cada4f.jpg


If you want a turnkey kit I suggest the dynakitparts ST-35. I built this several years ago. Added the EFB mod (note the small heatsink) and upgraded coupling caps. Two days to build.

It sounds lovely. Looks nice with the stainless chassis. Smaller than the 70.


Sent from my iPad using Tapatalk
Click to expand...

Hi Rocky,
what EFB bias mod did you use?
thanks.
 
Sir Bakerman said:
Rockyhill,

That looks real nice. I keep waffling back and forth between the 35 and the 70 kit. Does the 35 have enough power?



Thanks
Click to expand...


I drive Infinity RSb's without issue. I've never found a SPL rating for them although they have a reputation for wanting power.


Sent from my iPad using Tapatalk
 
Sir Bakerman…As mentioned in an earlier post Eico made kits. I bought an ST- 40 from a member here and have been very pleased with it. 20 wpc is more than enough to drive my Farzier speakers. In the past the prices for the Eico's have been very reasonable. Good luck to you!
 
Getting back to the original question of "how difficult is it to build". The dynakitparts instructions were excellent. The ST-35 has two circuit boards which makes assembly easy. The trickiest part was installing the socket wires. If you go EFB you undo a few things from the original build and add a few new components. There are some posts about that. I check the bias once or twice a year. Especially after changing tubes.


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Dunno if it has been mentioned, but instructions are downloadable either whole or in part for at least the Triode Electronics ST70 and the Latino ST (VTA?) 70.

Download them and see what you think.
 
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