#1
so i was reading about preamp tubes and i read that 1st, V1 is most important, then V2 does pretty much nothing positive (i suppose negative if its a bad tube) or can color your clean sound, and V3 (or the last one) is the phase inverter if you have multiple channels.

i read that tihs phase inverter is highly recommended to be a matched tube. i also read that a 12at7 has like 5x the power handling current of a 12ax7, and is commonly used as the phase inverter tube.

well that sounds good. but what does that really mean? why is a 12at7 better in the PI stage?
#2
First off, all the tubes do something.

Second, it depends on the amp as to what each tube does.

Third: the Phase Inverter is the final gain stage before the power amp tubes, and if you use a high gain tube there, it can make the amp a little mushy sounding. 12AT7's are much lower gain than a 12AX7, and are used in that position because they clean up the signal before it hits the power amp. This give you more clarity and and overall better tone.
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#3
+1

The higher power handling of the 12AT7 in the PI stage can also make it last longer than a 12AX7 in that position because the PI works harder than any other preamp tube.
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#4
The generalizations you gave aren't really valid. Every circuit is different, and every tube in the signal path contributes substantially to the amp as a whole.

That being said, 12AT7's in the PI position will usually yield different results than 12AX7's. Whether for better or for worse is entirely dependent on the circuit. 12AT7's will not break up as quickly as 12AX7's. This can be a good thing as sometimes PI distortion is not pleasing.

12AY7's and 12AU7's are also good PI tubes.
#5
well i do not want to lower gain, but i dont want too much clipping. i want higher gain with no negative side effects, as well as natural power tube breakup.

so i think im going to keep V2, stock (i see nothing wrong with it), V1 an aftermarket higher gain tube, and V3 a 12at7. and im going ruby tubes aka JJs for the power tubes.
#6
Another great choice for PI is the 5751 (preferably a NOS one like a Jan Phillips of GE Phillips), because it has gain of a 12AX7, without as much output (correct me if I'm wrong, folks!). Essentially, a lower gain PI=less noise, more clarity in many cases.
Then there's this band called Slice The Cake...

Bunch of faggots putting random riffs together and calling it "progressive" deathcore.
Stupid name.
Probably picked "for teh lulz"

Mod in UG's Official Gain Whores
#7
the V1, V2, V3 designation is not valid with every amp. breaking the schematic down to the triodes.


every tube colors the tone to a certain degree. i don't think the first triode colors the most tone either. i think all tubes do anyway. some might sound more different than others, if it makes a difference, then it's a difference to me. not MORE or LESS difference.

as far as distortion goes, first triode of an amp does not clip unless it's being loaded by a gigantic signal ala pedals and other preamps. passive pickups will not distort the first triode unless the cathode resistor is broken. then into more gain stages, they cause distortion. typically in a guitar amp, one to four gain stages are used, one being the most vintage (marshall 18w) and four being high gain (5150) amplifiers. it somewhat controls how much distortion you can get out of the amp.


btw, you don't need a multiple channel amp to have a phase inverter. phase inverter tubes are not recommended to be matched. PI isn't even matched anyway, so there's no real reason to match it so badly.
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#8
Quote by ECistheBest
phase inverter tubes are not recommended to be matched. PI isn't even matched anyway, so there's no real reason to match it so badly.


This is somewhat incorrect. Matching or not matching is a high debated topic. Some people argue like you that the PI isn't matched so there is no reason to do that. But if the PI is designed to be matched then matched tubes would help keep the balance.

But you can always throw a small capacitor between the anodes of both tubes to reduce effects of imbalance.

So the option to match or not to match is purely up to you TS. It does, however, cost more to match so if you see a site that sells tubes telling you to match the sections... well they just might have motives that involve fattening their wallets.
#9
Quote by XgamerGt04
But you can always throw a small capacitor between the anodes of both tubes to reduce effects of imbalance.
I wouldn't. That just cuts down on high frequencies and ultrasonic instabilities.

In a LTPI, having a 82:100 ratio between the anode resistors generally achieves a good balance. 82k on the grid-driven side, 100k on the other.
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#10
Does the phase inverter do anything on the clean channel of a two channel amp? For example a Peavey Classic 30.
#11
Quote by cloudedground
Does the phase inverter do anything on the clean channel of a two channel amp? For example a Peavey Classic 30.


The phase inverter has nothing to do with channel switching. It's purpose is to send two identical but out-of-phase signals to a push-pull output section. It comes after the preamp. Channel switching happens before the signal hits the phase inverter.