12AX7 vs 12AT7 vs 12AU7
- Thread starter Ice Man
- Start date
Curly
Moe's Bluesman
Quencho092
New member
Re: 12AX7 vs 12AT7 vs 12AU7
would it be safe to put a lower gain tube in V1 in a fender blonde
would it be safe to put a lower gain tube in V1 in a fender blonde
Fresh_Start
New member
Re: 12AX7 vs 12AT7 vs 12AU7
Dumb question time - does "lower gain" mean that the tube would allow more clean headroom in the preamp stage? Or does it mean that the amp will start breaking up earlier?
Ice Man - I know I tried a 12AT7 in one of the slots of my Blues Jr. but can't remember what it did...
Actually here's the answer to my question and a lot of other stuff too: Bill Machrone on pre-amp tubes.
Hope this helps.
Chip
Dumb question time - does "lower gain" mean that the tube would allow more clean headroom in the preamp stage? Or does it mean that the amp will start breaking up earlier?
Ice Man - I know I tried a 12AT7 in one of the slots of my Blues Jr. but can't remember what it did...
Actually here's the answer to my question and a lot of other stuff too: Bill Machrone on pre-amp tubes.
Hope this helps.
Chip
Re: 12AX7 vs 12AT7 vs 12AU7
There are many differences, but the ones that make the biggest difference are the Gain Factor and the Plate Characteristics (including the Grid Voltage Curves).
The Gain Factors for each are as follows...
12AX7 = 100
12AT7 = 60
12AY7 = 40
12AU7 = 17
Keep in mind that this doesn't mean you can put a 12AY7 (40) into a 12AX7 (100) socket just because it has a lower gain. First thing to consider is that the bias circuits for a given socket are designed such that the spec'd tube will operate in the center of the load line - which is based on a given socket's supply voltage and the Plate Load Resistor. If a tube other than spec'd is used, then either the top half of the signal will top out early or the bottom half of the signal will bottom out early. Ya want them to "clip" at the same time to max the level of that stage. The second reason is gain structure. If one stage drives the next with too low of a signal, then some of the dynamic range is being thrown away. In other words, you'll have to turn up the amp to get the same volume and you'll be turning up the noise floor with it.
In summary, stick with the spec'd tubes for a given amp, or have a qualified designer (not a tech) mod it to use a different tube - even then it's a slippery slope. IMO, the older stuff (Fender, Marshall, etc) stuff is so well designed you'd be hard pressed to find a tube tech, or weekend warrior designer that can actually improve it.
I hope this helps.
lovechild
www.lovechildamps.com
There are many differences, but the ones that make the biggest difference are the Gain Factor and the Plate Characteristics (including the Grid Voltage Curves).
The Gain Factors for each are as follows...
12AX7 = 100
12AT7 = 60
12AY7 = 40
12AU7 = 17
Keep in mind that this doesn't mean you can put a 12AY7 (40) into a 12AX7 (100) socket just because it has a lower gain. First thing to consider is that the bias circuits for a given socket are designed such that the spec'd tube will operate in the center of the load line - which is based on a given socket's supply voltage and the Plate Load Resistor. If a tube other than spec'd is used, then either the top half of the signal will top out early or the bottom half of the signal will bottom out early. Ya want them to "clip" at the same time to max the level of that stage. The second reason is gain structure. If one stage drives the next with too low of a signal, then some of the dynamic range is being thrown away. In other words, you'll have to turn up the amp to get the same volume and you'll be turning up the noise floor with it.
In summary, stick with the spec'd tubes for a given amp, or have a qualified designer (not a tech) mod it to use a different tube - even then it's a slippery slope. IMO, the older stuff (Fender, Marshall, etc) stuff is so well designed you'd be hard pressed to find a tube tech, or weekend warrior designer that can actually improve it.
I hope this helps.
lovechild
www.lovechildamps.com
F
Funkfingers
Guest
Re: 12AX7 vs 12AT7 vs 12AU7
Why was this zombie thread ever in TGS?
Why was this zombie thread ever in TGS?
GilmourD
Burritotoneologist
Re: 12AX7 vs 12AT7 vs 12AU7
While they are interchangeable and will function without damaging anything, you may not always like the results, and things may act funny.
For instance, did you know you could design an amp to use a 12AU7 and it will have an actual usable output?
EDIT Wow, just realized the date of the OP. LOL
That's because that's what they originally came equipped with.
While they are interchangeable and will function without damaging anything, you may not always like the results, and things may act funny.
For instance, did you know you could design an amp to use a 12AU7 and it will have an actual usable output?
EDIT Wow, just realized the date of the OP. LOL
IM4Tone
New member
Re: 12AX7 vs 12AT7 vs 12AU7
Besides the answer is "none of the above", but rather 5751.......:joke:
I doubt the Ice Man has been waiting 10 years for the answer.:lmao:It shows up on Google Search, so I figured I'd answer it. Keep calm and carry on
Besides the answer is "none of the above", but rather 5751.......:joke:
Re: 12AX7 vs 12AT7 vs 12AU7
Actually, the reasons you state for not changing the tubes are the very reasons you DO change them. To get those specific results.
Actually, the reasons you state for not changing the tubes are the very reasons you DO change them. To get those specific results.
Re: 12AX7 vs 12AT7 vs 12AU7
For some purposes the 5751 is a great preamp tube. I've been using them in one position or another ever since I've been using tube amps.
For some purposes the 5751 is a great preamp tube. I've been using them in one position or another ever since I've been using tube amps.
Re: 12AX7 vs 12AT7 vs 12AU7
My experience:
Bassman 59' RI (Circa 1992)
Swapped 12AY7 (GT) tube into V1 (in place of the stock 12AX7).
With the 12AY7, the amp had more clean headroom (breakup was not as early as the 12AX7).
Basically, you could turn the volume knob to 3.5 - 4 with the 12AX7's and then start to breakup nicely.
With the 12AY7 you were at 4.5 before any breakup started to occur (so higher volume before breakup).
In theory (please correct me if I am wrong), the advantage of the 12AY7 is: you could gain more clean headroom on the amp -and- if volume wasn't an issue, more of the breakup would come while you were into power tube territory (rather than just preamp tube breakup). So I guess if you were wanting to get to the dirt in a lower volume situation (home, small gigs) then use the standard 12AX7 -but- if you are playing where higher volume is acceptable before you breakup, then the 12AY7 would work well. OR - if you want to get dirt from pedals, then the 12AY7 might be the better way to go. If that makes any sense?
Hope this helps anyone thinking about the swap.
My experience:
Bassman 59' RI (Circa 1992)
Swapped 12AY7 (GT) tube into V1 (in place of the stock 12AX7).
With the 12AY7, the amp had more clean headroom (breakup was not as early as the 12AX7).
Basically, you could turn the volume knob to 3.5 - 4 with the 12AX7's and then start to breakup nicely.
With the 12AY7 you were at 4.5 before any breakup started to occur (so higher volume before breakup).
In theory (please correct me if I am wrong), the advantage of the 12AY7 is: you could gain more clean headroom on the amp -and- if volume wasn't an issue, more of the breakup would come while you were into power tube territory (rather than just preamp tube breakup). So I guess if you were wanting to get to the dirt in a lower volume situation (home, small gigs) then use the standard 12AX7 -but- if you are playing where higher volume is acceptable before you breakup, then the 12AY7 would work well. OR - if you want to get dirt from pedals, then the 12AY7 might be the better way to go. If that makes any sense?
Hope this helps anyone thinking about the swap.
Last edited:
Bob@Montreal
New member
Re: 12AX7 vs 12AT7 vs 12AU7
Just did this morning on my Bugera 5w. Amazing difference!! I'm not a big gain user, so the clean given by the AU7 is perfect for what I want. I aim for clean and would rather use pedals for the crunch, reverb ect, (although this little amp has great reverb). I think it all depends on what amp you're using. Worth a try if you get too much gain in your lower setting, though you will lose a bit of output Volume.. Not much to spend..20$. I may pick up a12AY7 just to see the difference.
BTW, for you cash strapped folks..this amp is worth looking into(200$US from Amazonia).
It's a bit of a crap shoot from what I read, in that some are defective right outta the box and have to be returned for a replacement . I found mine 2nd hand so no worries there. Really sweet tone.
Standard American Tele / Ibanez roadstar (1985 model w/ coil-tapped bridge p/u).
Just did this morning on my Bugera 5w. Amazing difference!! I'm not a big gain user, so the clean given by the AU7 is perfect for what I want. I aim for clean and would rather use pedals for the crunch, reverb ect, (although this little amp has great reverb). I think it all depends on what amp you're using. Worth a try if you get too much gain in your lower setting, though you will lose a bit of output Volume.. Not much to spend..20$. I may pick up a12AY7 just to see the difference.
BTW, for you cash strapped folks..this amp is worth looking into(200$US from Amazonia).
It's a bit of a crap shoot from what I read, in that some are defective right outta the box and have to be returned for a replacement . I found mine 2nd hand so no worries there. Really sweet tone.
Standard American Tele / Ibanez roadstar (1985 model w/ coil-tapped bridge p/u).
Last edited:
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