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dynaco st 70 what tubes to replace first

Ive just bought a rebuilt st 70 and am very happy with imaging and sound quality Ive checked the tubes that are with it and they are run of the mill. WANT TO UPGRADE !!

Suggestions please on what order to replace first and if you can; recomendations, Im looking for a creamy thick sound.

Im an old guy and this is my first tube amp and limited knowledge but a fast learner and very excited to go back to non-ordinary reality via sound.
Larry
lawrenceaudio
rodman99999
6,206 posts
 
It's important to note that there are many variables that will determine, or limit, a listener's ability to discern improvements/changes in presentation. ie: A system(source/pre/speakers/cables) that does not present or pass the info on the recording, poor recordings, room acoustics, aural acuity(actually; the lack there-of), the untrained ear, and the ubiquitous mental block(a refusal to hear what is obvious to others, because it doesn't agree with your mindset). Don't let the opinion of another stop you from experimenting with your own system. There are numerous simple/inexpensive mods and tube upgrades for the ST-70, that will yield much musical pleasure, if you ignore the naysayers(again- providing the rest of your system, and your ears, support them). Besides- It's just fun to experiment! Happy listening, all.
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dav65mus
41 posts
 
I will agree that *most* st 70's will bias 6l6 or kt66 tubes properly, but some will not without a resistor change in the circuit.

My amp has new much higher quality bias pots with a wider adjustment range than stock.... some stock bias pots may not turn the bias low enough without a resistor change in the circuit for the 6l6, kt66 tubes... while this may not seem like a big deal to most people here, the reason some may buy a rebuilt amp is they have no desire, expertise, tools, etc. to change anything in the circuit.

I have been in this hobby for almost 35 years and have owned countless speakers, seperates, recievers,etc.You are on the right track going with a rebuilt st70. It is the best sounding amp I have ever owned and cost much less than many of them. I will never go back to solid state amps again!

As mentioned by a previous poster don't let anyone's personal experience be the end all to your decision.
What works in my listening room may sound horrible in yours.

Power tubes for a dynaco st70 are cheap enough to play around and have fun with....
hifitime
715 posts
 
A Dynaco brought up to spec's is ok done right.A repainted one hides the transformers.There are transformers with cloth leads that sound totally different that the early ones.I went through about 20 or more of them.When everybody went to SS,there wasn't much choice for someone who wanted tube amps.You had to buy vintage amps.Some say they started out sourcing the transformers without the employees knowing about it.You could make them bias up for a 6L6 family tube,but any tech knows it is not made for them! At 4300 ohms for the A470 vs. the over 6000 ohms compatible for the 6L6 family.It's easy to buy a rusted Dynaco cheap and repaint it.There are people out there putting different transformers in the old Mac amps too.If there is a buck to be made,somebody ruthless out there sure will jump in.The early Dynaco 70 that has transformers similar in shine to the old Mac gear are the best ones.
lawrenceaudio OP
10 posts
 
Gentlemen: Esp Dave65mus, Rodman99999,& Viridian
I am so gratefull for the time you have taken to respond.

As a novice in this field of audio I appreciate your knowledge and passion.

I"ve got the new NOS ordered and look forward to Listening but also following your opinions on the threads.

Lawrence
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