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My first tube amp - Dynaco st 70!

seems like i have much to learn about how to handle my tubes right... i just hope i didnt create any serious damage with my clear lack of knowledge.

it is at least good to know that it was my fault and not the amp.. i sold my old amp because it gave me too much trouble and i bought this one hoping for some piece of mind, not to get into another restoration advernture.
 
Try giving All the Tubes a little Twist each way...That would Tell you if you have a Socket Problem...
 
If you had issues with no preamp hooked up it could be that the input impedance resistor is open. Sounds like it was oscillating maybe. Does it always work with the preamp? Tube amps are very, very resilient. Much more than SS. I think people think they're super delicate because they're made out of glass! They can take a lot of abuse. Not saying you should be stupid but unless you're sticking a screwdriver in the circuit you're probably not going to make anything worse than it already was!

good luck!
 
NOSValves said:
Hard to say...how long was it off from hot state and then turned back on? If not more then a few minutes you made a huge no no with tube gear. You should always allow at least 5 minutes before hot off then on. Also why were you unhooking the preamp to bias??? all you need to do is turn the volume down. Also always bias with the amplifier good and hot like a couple hours after turn on, unless swapping output tubes then right away then again in the couple hours.
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Can you elaborate on this 5 minute rule? It will serve very useful on the basis. Thank you.
 
just cane back home.. turned it on and it works fine right now. lets hope it wont happen again, altough im gonna have my tech give it a look soon.
 
well.. i spoke with the previous owner who is also an audio tech and he assured me that i get a warrenty from him. he also said what you guys said - it was the off and the on that i did which caused the sound. im much more relaxed now.

now i keep enjoying some music :) and oh boy does this amp sound wonderful!

now here's a question - what tubes should i get?! right now it has svetlanas el 34 and GE 6gh8, can i use kt66 instead of the el34? which brand do you guys reccomend?
 
TankPopper said:
well.. i spoke with the previous owner who is also an audio tech and he assured me that i get a warrenty from him. he also said what you guys said - it was the off and the on that i did which caused the sound. im much more relaxed now.

now i keep enjoying some music :) and oh boy does this amp sound wonderful!

now here's a question - what tubes should i get?! right now it has svetlanas el 34 and GE 6gh8, can i use kt66 instead of the el34? which brand do you guys reccomend?
Click to expand...
As it has dynaco main transformer there is only one tube : EL34
Nothing wrong with them ..
 
TankPopper said:
well.. i spoke with the previous owner who is also an audio tech and he assured me that i get a warrenty from him. he also said what you guys said - it was the off and the on that i did which caused the sound. im much more relaxed now.

now i keep enjoying some music :) and oh boy does this amp sound wonderful!

now here's a question - what tubes should i get?! right now it has svetlanas el 34 and GE 6gh8, can i use kt66 instead of the el34? which brand do you guys reccomend?
Click to expand...

I'd suggest slowing down.. If all the tubes are working properly as is I'd just sit back and enjoy the music for weeks... then decide what you don't like about the sound. Then us that have traveled this road before "might" be able to guide into tubes that "might" help. At this point everything is a crap shoot. One persons favorite tube could be the one you absolutely hate. All things audio are personal preference based no absolutes exist especially in tube rolling. Realize that most folks on these forums love to help you spend your money...
 
I've been running the same Quad of JJ KT77's for Years now in my ST-70...They Sound Great...And they are Reasonable $$$...Way better than EL34s...
 
Yes. If you get JJ just make sure you get them from someone that thoroughly tests them and weeds the bad ones out.
 
I'm in a similar circumstance as the OP: http://www.audiokarma.org/forums/showthread.php?t=541800

I however am lucky enough to have a whopping $0 in this.

I hooked up the 70 and the preamp this past weekend with a cd player. As I suspected, the sound was not too good. Buzzing, volume level differences between channels, drop-out, harsh sound, etc. However this is before any cleaning at all. My point was to just make sure that it worked at all.

My next step will be to familiarize myself with what's what on this thing, remove the tubes and have them tested (without damaging or wiping off the lettering, which is excellent), then formulate a plan to begin a renovation. I'm thinking that I'll keep the original PC and use the original 7199's while replacing all stuff that needs replacing, same for the pre-amp.

But I've got a lot of learning to do. :headscrat
 
The Dynaco ST-70 is one amp that I've overlooked as far as powering my Wharfedales. I was concerned that it would be a bit more power than I need for my W90's (mainly due to me having less control over low-volume settings), but it would be okay for my W60's and would probably sound awesome. The classic Dynaco sound-signature should be a good match for the Wharfedale sound-signature.
 
Recently I built a very interesting W90 and altec Hybrid. it was the drivers from a W90 on an open baffle (plans from something called SFB) sitting ontop altec 15' woofers in a 300 liter cab. it was connected to DIY tube amp that had 50 wpc. that was, hands down, the best setup i have ever heard in my life. i was blown away by the fact the i BUILT those speakers:

IMAG0459.jpg


knowing what those w90 drivers can do (regardlles of the altec right now), im sure the dynaco would be magic with it.
 
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