Voltage Amplifier Tube on VTA

I'm learning as I go and digging it. I've been trying to understand fully the ST120 amp I now own. I've been looking at the schematic and tracing all the parts... what does what. cool stuff

I have the book Beginners Guide to Tube Audio Design... I also have been looking at Booxhound Amp also to learn. This amp is real stripped down. Looking at this and understanding this amp helps as it is real basic. I then can look at the ST120 schematic and I get what most of everything does.

I am not really getting what is going on in the 12AT7 in the center spot. I don't get why only 1 is needed. I would think the amp needs 2 of these. each tube would handle a channel and have the signal run to the grid (assuming 2 tubes)... Then the Cathode and Plate do what they do. I don't get how the center 12at7 handles both R and L channels. Do both channels go to the grid? then the amplified signal is then split to R and L ?

Just trying to learn. This site rocks!


Thanks all!
Andy

mantha3 wrote:
I am not really getting what is going on in the 12AT7 in the center spot. I don't get why only 1 is needed. I would think the amp needs 2 of these. each tube would handle a channel and have the signal run to the grid (assuming 2 tubes)... Then the Cathode and Plate do what they do. I don't get how the center 12at7 handles both R and L channels. Do both channels go to the grid? then the amplified signal is then split to R and L ?

Just trying to learn. This site rocks!


Thanks all!
Andy

Andy,

The short answer is that the 12AT7 is a dual triode. In other words it is basically two triode tubes contained within a single glass envelope. I'll leave further elaboration to those more astute tube experts here on the forum.

Best Regards,
Charlie

Ahhh

I was digging around the net a bit more after I read this from you Ludite. I think I'm getting it a little more from seeing this -



So I'm guessing the right channel is running on one side (say it drives one grid via pin 7)and then the left is running the other (pin 2)...

This helped a lot. I think I'm getting the phase splitters now a little better as well. So you have two signals out of phase... I'm guessing the 12AT7 is having a signal phase handled on each side of the tube... So one phase signal drives the Grid on pin 7 and then the signal out of phase goes to pin 2's grid.

Lots going on in these little 12AT7 tubes! Having fun learning.


Thanks
ATM

mantha3 wrote:I'm learning as I go and digging it. I've been trying to understand fully the ST120 amp I now own. I've been looking at the schematic and tracing all the parts... what does what. cool stuff

I have the book Beginners Guide to Tube Audio Design... I also have been looking at Booxhound Amp also to learn. This amp is real stripped down. Looking at this and understanding this amp helps as it is real basic. I then can look at the ST120 schematic and I get what most of everything does.

Thanks all!
Andy

Andy, thank you for posting the link to Booxhound. I too am learning about tubes, amps, etc. and so your experiences help me. Ken in Calgary.

Nice

Beginners Guide to Tube Audio Design is a decent book. It is written more for push / pull tube amps which is good for us ST70/ST120 etc owners. I think Tubes4hifi have an amazon store selling it so you can support these guys

yes, ANY book or music or anything Amazon sells, if you buy it thru our website we make about 2% on it, not much, but hey . . . .
so if you want something semi-expensive I can add it to the store anytime, or anytime you're buying some music . . . .
http://astore.amazon.com/tub02-20