New to tube amplification

Hello- After a long hiatus (20 plus year) from two channel stereo I have recently purchased a ST 70 which per the documentation provided was rebuilt in 2011 to a : “low output Tubes4hifi VTA board using 2 - bh7 and 1- center 12au7 tubes. The EL34 tubes are East German With Dynaco logo on them. Quad Cap from dynakitparts.com and diode protection for gz34 rectifier tube.” The tubes are: 2- RCA 12bh7, 1- Tungsram 12au7, 1- 5AR4 Electron Tube and the 4 Dynaco EL 34s. Currently, I am using a Marantz 7T pre amp and Klipsch Heresy 1 circa 1981. Currently listening to Relaxin’ with the Miles Davis Quintet. But there are very few types of music I won’t listen too.

I have never owned a tube amp before. All previous amplification was solid state. I am trying to learn about tubes and have spent a lot of time researching my amp/tubes and it led me here. So ... can you give me some insight on my current amp and help me to improve my tube knowledge? What is some good online reading? Books?

My other hobby is antique fans collecting just in case any of you may be members of AFCA.

Thanks
Greg

You should check out Uncle Dougs videos on YouTube, he makes some great videos with a lot of useful information broken down and easy to understand. Many of his videos are for guitar amps but still a ton of useful information.

https://www.youtube.com/watch?v=x5SSKX74DKg

Kramer beat me to it. Uncle Doug’s videos are excellent.  I also learned a ton by reading forums like this one.  If you can find an old RCA Receiving Tube manual, you may find it helpful.

There is a person who has a lot of youtube videos you can watch and learn from, it's Mark and his web page

https://blueglowelectronics.wordpress.com/

On his home page there is a tab called Sketches & Info, when clicked to that page scroll down to Single Ended KT-88  build, there you can find all the build videos especially the walk through video that will explain the whole build and what the components do in the circuits.

TM

http://home.indy.net/~gregdunn/dynaco/components/ST70/index.html

https://en.wikipedia.org/wiki/Dynaco

https://www.hifizine.com/2010/06/restoring-dynaco-st-70/

https://www.audiophilenirvana.com/audiophile-equipment-reviews/dynaco-st-70-timeless-classic/

You certainly picked the workhorse of the hobby, of which some 300,000+ were made, and of which every part and piece is still available, but for tubes, better than OEM in most cases. It also seems that the mods done to it were amongst the better options available.

There are some links above with varying opinions, some evidence-based, some wishful, but all worth a look. For now, focus on what you have and its care-and-feeding. Getting into tubes is a long and slippery slope such that I try to advise taking your time with what you have before embellishing.

Some basics:
a) Tube amps are not solid-state amps, they behave differently and they will give very different sound depending on a number of factors.
b) Tube amps clip softly - not to suggest that they may be driven to clipping with impunity, but that when they clip there is much less danger to speakers, and the sound is not as harsh. A 40-watt SS amp will sound very different than a 35-watt tube amp, especially at the margins.
c) Accordingly, there is a tendency to 'crank' them up. Try to resist.

And, of course, tube amps generally being fairly low-powered as compared to similar (by weight) SS amps, your speakers, listening area, preferred volumes and similar are much more of a factor.

And, the mandatory cautionary notes:

* There are LETHAL voltages within the amp, on the circuit board and exposed below the chassis.
* Tubes get VERY hot with temperatures in excess of 250F being not uncommon. They will burn instantly if touched - by you, by a pet, by a child. For this reason, either run with a cover, or place the amp in an area not easily accessible by children or pets. Along these lines, a visitor to my office yesterday, 47 years old, well-educated and a Canadian-born engineer living in Brooklyn had never seen a vacuum tube in her life. She was entirely fascinated by the little ST35 playing in the background, and shocked at the heat it generates.

Otherwise, Enjoy!

Enjoy!

Kramer- Thanks for the You Tube links- they are very informative.
Corn Dog- Thanks I will look for that reference manual.
10-E-C- thanks for link I will add the You tube videos to my watch list and will read the webpage.
Peter W. - Thanks for the links and your insight. I have not exceeded about 1/4 mark on the volume knob- beyond that it tends to be too loud ( I guess I am too old). I have no plans to do anything else to it at this time. I have always had a healthy respect for Electricity- and while researching tube amps before my purchase your cautionary notes were driven home.

Overall looks like I have some more 'work' to do.

Thanks again
Greg