12at7 in V1 and Grandma.........

[Gsxrbusa]

I went to my Grandmothers 90th birthday party last week. (so what does this have to do with tubes? I will tell you) I spent 4 days with her, I figure she does not have that much time left. We were talking about her belongings and who gets them when she goes. I did not bring this subject up, she did. I told her how much I liked this specific lamp she had. The lamp is in pictures, in various locations through out the house, over the past 30-40 years. She said if you want it, put your name on it. ?????? That way there is no question who gets it among the family. Anyway, she said take anything that was my Grandfathers. He was an electrical engineer and was in radio/tv repair. I go searching and find a kick ass analog volt/ohm meter and a couple small boxes of tubes. To my point. There was 20, or so, 12AT7 tubes. Ranging from german, japanese and USA made. Brought them home and tested them out, half of them were microphonic or didn't work at all. The rest fired up and worked great. Brands like GE, RCA and more I never heard of. I put one in the V1 spot of the Framus. Shit it sounds great. Lost a little head room and gain but kinda tamed the Dragon a bit. Fuck, I like it. Any you guys do this? Maybe my ears were shot from testing so many tubes. Try it again tomorrow and see if I still hold the same opinion. Either way, my Grandma kicks ass.

 

[JakeAC5253]

Cool story. If you aren't using the tube as sentimental value, I wouldn't put a 12at where a 12ax is meant to go. I would try a 12ay instead if you like that sound.

 

[truthhurts318]

good story...

when i had a 5150...i used a EH 12AT7 in V4 to tame the beast a littlebit. it really cut back on the fizzy sound that am had.

 

[Gsxrbusa]

What is the difference between the 12at7 and 12au7? I tried an AU7 and it did not sound the same to me.

 

[JakeAC5253]

What is the difference between the 12at7 and 12au7? I tried an AU7 and it did not sound the same to me.

I suggested 12ay7, not 12au7.

Here, read this thread

http://www.tdpri.com/forum/archive/inde ... 77987.html

A quote from the thread:

The 12AT7 and 12AU7 are driver tubes. They were not designed for audio amplification, as the X, Y and 5751 were, and are said to sound kinda muddy used in guitar amps, but there's virtually no risk of trying them out in a guitar preamp, so have at it. They ARE useful as Phase inverters and Reverb drivers, though--a common practice to try and tone down really gainy amps (eg-find some more headroom) is to substitute a 12AT7 as the PI and back off the gain hitting the power tubes a bit.

 

[Gsxrbusa]

What is the difference between the 12at7 and 12au7? I tried an AU7 and it did not sound the same to me.

I suggested 12ay7, not 12au7.

Here, read this thread

http://www.tdpri.com/forum/archive/inde ... 77987.html

A quote from the thread:

The 12AT7 and 12AU7 are driver tubes. They were not designed for audio amplification, as the X, Y and 5751 were, and are said to sound kinda muddy used in guitar amps, but there's virtually no risk of trying them out in a guitar preamp, so have at it. They ARE useful as Phase inverters and Reverb drivers, though--a common practice to try and tone down really gainy amps (eg-find some more headroom) is to substitute a 12AT7 as the PI and back off the gain hitting the power tubes a bit.

Thanks for the link bro, good info there. I am going to do some more experimenting now!

 

[Primakurtz]

Not to be overly skeptical, but were does this info come from "designed to be driver tubes"? Just curious.

And... does it really matter what they were designed for? All tubes amplify signals. Different circuits use them in different ways, and respond differently to tube changes a s a result.
I've had amps that sound great with AT's in V1 and AX's in the PI spot, and vice versa. Tube rolling is good, clean, harmless fun - enjoy, and congrats on the score!

 

[sled]

Not to be overly skeptical, but were does this info come from "designed to be driver tubes"? Just curious.

Basically, the 12ax7 is a voltage amplification (low current) device. As the the gain decreases (12at7, 12ay7, 12au7) the current capability goes up (lower internal resistance) and thus the tube can be described as a driver. If one understands tube biasing and the tube's intended function, one would see that depending, the tubes are hardly interchangeable.

 

[JakeAC5253]

Not to be overly skeptical, but were does this info come from "designed to be driver tubes"? Just curious.

And... does it really matter what they were designed for? All tubes amplify signals. Different circuits use them in different ways, and respond differently to tube changes a s a result.
I've had amps that sound great with AT's in V1 and AX's in the PI spot, and vice versa. Tube rolling is good, clean, harmless fun - enjoy, and congrats on the score!

The way that I understand it is that the pins are different on the t7 as opposed to the x7 or y7. The pins route signal through the tube and if you change the positions of the pins you are changing what the tube will do. As far as I know that is the main difference. It is not to be thought of simply as levels of gain where one has more than the other, it's more complex than that.

 

[Gsxrbusa]

So, Am I ok running the 12AT7 or wtf? You guys are kinda freaking me out

 

[titanamps]

you can use an AT anywhere, some people just don't like how they make the amp sound. you won't hurt the amp if that's your concern.

also, FWIW i supply my amps with AT PI tubes :thu:

 

[Gsxrbusa]

you can use an AT anywhere, some people just don't like how they make the amp sound. you won't hurt the amp if that's your concern.

also, FWIW i supply my amps with AT PI tubes :thu:

Thank you sir I tried it at practice tonight and switched back and forth between AT and AX. It really is not as big of a difference in a mix. Just takes a little hair off the top. More noticable playing alone.

 

[titanamps]

the AT has 70% as much gain as the AX, so it's really nothing that bumping the gain knob won't replicate. most of the difference you hear is because the AT has different characteristic curves than the AX and isn't biased the same, which puts it closer to saturation or cutoff (depending on the design) than the AX.